Realist evaluations (RE) are increasingly popular in assessing health programmes in low- and middle-income countries (LMICs). This article reflects on processes of gleaning, developing, testing, consolidating and refining two programme theories (PTs) from a longitudinal mixed-methods RE of a national maternal and child health programme in Nigeria. The two PTs, facility security and patient–provider trust, represent complex and diverse issues: trust is all encompassing although less tangible, while security is more visible. Neither PT was explicit in the original programme design but emerged from the data and was supported by substantive theories. For security, we used theories of fear of crime, which perceive security as progressing from structural, political and socio-economic factors. Some facilities with the support of communities erected fences, improved lighting and employed guards, which altogether contributed to reduced fear of crime from staff and patients and improved provision and uptake of health care. The social theories for the trust PT were progressively selected to disentangle trust-related micro, meso and macro factors from the deployment and training of staff and conditional cash transfers to women for service uptake. We used taxonomies of trust factors such as safety, benevolent concerns and capability. We used social capital theory to interpret the sustainability of ‘residual’ trust after the funding for the programme ceased. Our overarching lesson is that REs are important though time-consuming ways of generating context-specific implications for policy and practice within ever-changing contexts of health systems in LMICs. It is important to ensure that PTs are ‘pitched at the right level’ of abstraction. The resource-constrained context of LMICs with insufficient documentation poses challenges for the timely convergence of nuggets of evidence to inform PTs. A retroductive approach to REs requires iterative data collection and analysis against the literature, which require continuity, coherence and shared understanding of the analytical processes within collaborative REs. Key MessagesRealist evaluations (REs) are important, though time-consuming approaches to generating context-specific and practical implications for policy and practice within the ever-changing low- and middle-income countries (LMICs) health policy context. As such, REs reflect an applied nature of health policy and systems research.Theories in REs span across the continuum of middle-range theories—programme theories (PTs)—specific context, mechanism and outcome configurations. Realist researchers need to be cognizant of these levels of abstraction, including different interdependencies and overlaps between them, and need to ensure that PTs are ‘pitched at the right level’ to maintain methodological rigour alongside the policy relevance.Theory gleaning, development and testing require different nuggets of evidence. This is a challenge in REs, particularly in the context of LMICs where programme design and implementation are often insufficiently documented and researchers face difficulties in accessing relevant literature.The retroductive approach in REs requires continuous, iterative and flexible data collection and analysis against the current literature. Collaborative REs need to maintain the continuity, coherence and shared understanding of the analytical processes, though researchers also need to be cognizant of the need to maintain the momentum and focus within longitudinal studies.Theory-driven evaluations, especially realist evaluations (REs), are increasingly popular in assessing health programmes and policies in low- and middle-income countries (LMICs) . REs invREs are method-neutral and involve the retroductive analytical approach of moving between inductive and deductive reasoning to examine the causal powers of the policy or programme evaluated . DiffereIn this article, we report and reflect upon experiences of ‘tracing’  two specific PTs - patient–provider trust and health facility security - within an RE of a national health programme in Nigeria. This article should be of relevance to researchers and practitioners who are interested in understanding specific theory-tracing processes within, and perhaps wider utility of, REs for policy and practice. Following a brief background of the programme, we document the processes of tracing each PT through identifying and comparing their analytical processes. We then discuss our experiences and outline key lessons learned.During 2012–15, the Government of Nigeria implemented the Subsidy Reinvestment and Empowerment Programme (SURE-P), which aimed to support the social sector through reinvesting savings from the removal of fuel subsidies. One component focused on improving maternal and child health (MCH) outcomes (SURE-P/MCH), which was implemented in selected local government areas in the 36 states of Nigeria and in the Federal Capital Territory through clusters of four (4) Primary Health Care facilities plus one (1) general (secondary) referral hospital. SURE-P/MCH comprised supply and demand components. The supply component included recruitment and training of staff , infrastructure development, improving availability of supplies and activation of Ward Development Committees, which through membership of local authorities and community leaders oversee performance of all public services including local health facilities. The demand component aimed to increase the utilization of MCH services through conditional cash transfers to pregnant women , had three phases:Our RE study, REVAMP (DeteDuring phase 1 (June–October 2015), we developed a logic map of the SURE-P/MCH (During phase 2 (November 2015–September 2017), we developed PTs based on insights from more primary data alongside analysis of literature.During phase 3 (September 2017–December 2019), we conducted several rounds of theory testing, refinement and consolidation through iterative data collection/analysis and literature review.The study followed the RAMESES II quality and reporting standards and the recommended mixed-method approach for REs  and implemented within a favourable environment at individual, organisational and system levels, will improve: equitable access to quality maternal and child health services and ultimately the MCH health outcomes in Nigeria (As shown in Our focus in this article on two specific PTs (trust and security) is based on two broad reasons. First, the patient–provider trust and health facility security PTs represent issues of complex and diverse nature. Trust is all encompassing, though it is not always a tangible phenomenon, whereas health facility security is more visible, and both go beyond the funded programme implementation period (2012–15), which relates to the sustainability of programme effects. Second, the importance of both trust and security emerged during the first phase, but each only became distinct PTs subsequently. This, combined with differences in their analytical trajectories, allowed us to compare and contrast our methodological experiences with tracing theories in REs throughout all three project phases.During phase 1, we conducted preliminary discussions with programme architects, reviewed programme documentation, assessed data quality from the national HMIS and reviewed literature on health systems strengthening to improve MCH in LMICs. All these were discussed in-depth at a project meeting in the University of Leeds in September 2015. A major part of that meeting involved face-to-face capacity building on RE. This was followed by step-down capacity-building workshops at the University of Nigeria, facilitated by staff who attended the Leeds meeting for research staff who did not travel to that project meeting.In the first version of our IWTs, we split our theory of change into the supply and demand parts, corresponding to the SURE-P/MCH programme logic  and improved staff availability and training to enhance their performance (trust) . SecuritGleaning of PTs at this point was done through understanding the programme design and logic model, iterative discussions within research team and with programme architects and literature review as described in full elsewhere . Data analysis happened in five groups over 4 weeks, followed by a 2-day data harmonization and theory-building workshop in February 2017 in the University of Nigeria during which 15 themes were identified inductively  and thesRetroductive reasoning was used to develop PTs anchored in those 15 themes, which now were operationalized in tentative causality propositions. In subsequent months, these PTs were extensively peer-reviewed, contrasted with empirical and theoretical literature and informed iterative data collection and analysis. At this point, we included separate questions on trust and security in the data collection tools, and the interview data were coded by the Cs, Ms and Os for each theory. Theories were retroductively fine-tuned to guide their consolidation in phase 3. This process included structured analysis workshops, capacity-building webinars on RE and continuous formal (monthly teleconferences) and informal (email/Skype) exchange within and between the two collaborating teams. The outputs from this phase were eight theories in which we articulated causality through ‘in the context of.if.when.’ propositions. Each proposition acted as magnifying glasses that both augmented and focused our knowledge. A distinctive feature of this phase was our increased in-depth command of the literature, which became more focused on each PT. These eight theories are available elsewhere (Security was a clear first theme identified inductively during the workshop in February 2017 (Box 1), and deductive reasoning was then used to put this theory to the test through iterative engagements with the literature, data and discussions within research team. As shown in Trust, however, did not feature prominently at this stage as a distinct PT but cut across some of the initial 15 themes shown in Box 1, such as those associated with relationship building (theme 10) and different types of financial and non-monetary incentives to improve staff performance in providing MCH services (themes 2–9). During this phase, trust became a component of several PTs shown in Following on from the magnifying glass metaphor, during this phase, specific literatures acted as lenses that framed our analysis. On reflection, our theoretical engagements with the literature were still too close to the level of the empirical with lesser engagements with substantive social science theories, which are necessary to fully establish causality in REs  and infoDuring phase 3, we iteratively tested, refined and consolidated the PTs. At a meeting in September 2017, we developed a detailed fieldwork work plan, which included a wider range of methods—all summarized along with detailed guidance in our methodology handbook. During phase 1 and parts of phase 2, separate fieldwork staff collected and transcribed data under the guidance of more senior core project team who then subsequently analysed the data. Each SURE-P/MCH cluster evaluated was assigned eight fieldworkers. Subsequently, in phases 2 and 3, both data collection and analysis were conducted by the core researchers at the University of Nigeria comprising 10 members. All these raised the importance of having a clear and dynamic (modified for each phase) handbook with step-down capacity-building workshops in the University of Nigeria.While we used methods that were similar to previous phases, the data collection instruments were updated for the testing of PTs. For example, interview guides were structured around causal links within PTs rather than separate Cs, Ms and Os . A previThe scale of the data collection during phase 3 was smaller (39 IDIs and 4 Focus Group Discussions (FGDs) as compared with 96 IDIs during previous phases). However, depth of our engagements with the results was greater as we refined the PTs. At a meeting in February 2019, we extensively discussed, peer-reviewed and further refined the PTs. We also deepened our understanding through visualizing causal links within each PT  in what we call the ‘social laboratory’. The role of substantive social science theories in disentangling the specific mechanisms was operationalized. After substantive social science theories were identified, we did not collect further primary data but applied these new theoretical perspectives to our already rich datasets.For security, we drew upon a complementary body of interdisciplinary literature on theories of fear of crime and gender which determine perceived security by health workers and patients . This liSubstantive theories used to approach causality in the trust PT were progressively selected to capture the complex structural relationships that are entangled across trust-related micro, meso and macro factors . We alsoWe faced three conceptual challenges: first, continuous toggling across the levels of abstraction (CMO configurations in testing PTs and broader middle-range theory). This involved balancing between comparing and contrasting our results with empirical findings from health systems literature at the level of CMOs and a more theoretical engagement with substantive theories at the level of middle-range theory. Second, reaching shared understanding on ‘what causes what’. This meant often moving Cs, Ms and sometimes Os around and resolving circular arguments while going beyond the conventional ‘everything leads to everything’ conclusions. Last, the decision as to which substantive social science theories to use in trust and security PTs. This was perhaps one of the most challenging aspect as there is no firm protocol for appropriateness of theories in realist studies, and which reflected different approaches we used for theorizing security (drawing on complementary body of literature) and trust (progressive selection of theories). Ultimately, the iterative nature of dipping in and out of theories and the data helped us to continuously validate our theorization including choice of appropriate theories and empirical backing of PTs.Neither security nor trust was explicitly articulated in the design of the SURE-P/MCH programme but emerged from data and substantive social science theories. Security appeared a more tangible and context-specific PT, so emerged early. However, security literature often focuses on global/national security threats, and fear of crime is used as a proxy for security itself. Furthermore, tangibility does not always ensure attention in policy design. During our feedback workshop in January 2020, Nigerian policymakers reflected that, since security is such a mundane and routinely evident issue, they had never linked it with provision or uptake of health care. This was mirrored by the scarce literature on the security of health facilities. Conversely, trust was a softer and less tangible concept so emerged later in the project. Trust cut across and was reflected in multiple (often opposing) PTs, perhaps reflecting a larger though complex body of literature on the topic and argument that it applies to all national health systems .A significant distinction between the development and testing of the two PTs was the data used. The dataset for the security PT was exclusively qualitative. However, the trust PT used both quantitative  and qualitative interview data. The tangibility of supporting evidence on security  meant that we did not need to collect quantitative data. Given that the trust PT addressed a softer, less tangible concept, we needed insights from multiple quantitative and qualitative methods to sufficiently disentangle this phenomenon.Our processes of theory tracing followed the established guidance on REs , thus hiCollaborative research typically builds on complementary expertise of different research team members across the partner organizations . Our expOur overarching argument, and a lesson, is that REs are important, though time-consuming, approaches to generating practical implications for policy and practice  converge timely and usefully . This isThird, the retroductive approach in REs requires iterative and flexible data collection and analysis against the literature, meaning that different theories need to follow their own (often different) processes of gleaning, development and testing. Social scientists can be useful ‘theory brokers’ when proceeding to the ‘social laboratory’ stage. Collaborative studies involving partners from multiple countries face a challenge of a ‘parachuting’ approach leading to fragmented engagements—and instead need to maintain the continuity, coherence and shared understanding of the analytical processes. Our long-term study allowed for in-depth engagements and studying the sustainability of programme outcomes such as trust. However, as we faced in our project too, it is important to maintain the momentum and focus within longitudinal studies.In this article, we documented experiences of gleaning, developing, testing, refining and consolidating two PTs (security and trust) from a longitudinal RE of a national health programme in Nigeria. Our overarching argument, and a lesson, is that REs are important, though time-consuming, approaches to generating practical implications for policy and practice and that each theory development process is always complex, unique and distinctive. Three practice lessons are proposed for researchers and practitioners who are interested in understanding specific theory-tracing processes and a wider utility of REs. First, PTs need to be at the right level of abstraction to maintain methodological rigour alongside the policy relevance. Second, sourcing relevant nuggets of evidence is essential for theory tracing and is often a challenge in many resource-constrained settings. Third, collaborative REs require social science expertise and continuous theoretical engagements maintain the continuity, coherence and shared understanding of the analytical processes.Box 1 Themes from a workshop in February 2017SecurityStaff AccommodationAvailability of Adequate Number and Skill Mix of Health WorkersAvailability of Drugs and ConsumablesAvailability of EquipmentAvailability of Health Facility Infrastructure (Upgrade/Borehole/Solar Power)TrainingSupervisionSalaries and Incentives (Demand and Supply-Side Incentives)Relationship Building  a.  Health Worker/Health Worker Relationship  b.  Health Worker/Community  c.  Health Worker/Service User11.  Transportation for Community Mobilization12.  Referrals13.  Intersection of Programme Components14.  Political Commitment15.  Others Box 2 Summary of eight PTs from phase 2S1: Prioritization of MCH. In the context of poor health outcomes, interest from policymakers and politicians in MCH care, combined with advocacy and lobbying from key policy actors to prioritize MCH (C), is likely to help generate and maintain political and economic commitment across all tiers of government manifesting as a culture of ownership of MCH programmes (M), eventually leading to timely release of counterpart funds and availability of other resources , ultimately contributing to sustained implementation of and access to MCH services for vulnerable groups (O).S2: Improved staff motivation. In the context of staff shortages and lack of material resources, if adequate numbers and mix of skilled health workers are recruited, deployed to health facilities  and if health workers receive adequate equipment, supplies and consumables for their work and are regularly trained, supervised and rewarded for good performance (C), then health staff will feel motivated (i.e. appreciated and happy) to increase and maintain their performance (M), which is likely to lead to increased provision and utilization of quality MCH services, ultimately contributing to improved service and health outcomes (O).S3: Health workers feeling safer to work. In the context where health facilities or communities ensure employment of security men, erection of perimeter fences and availability of accommodation for health workers in the facility premises (C), then health workers are likely to feel safer and therefore willing to work (i.e. provide MCH services) during night hours (M), thus ensuring the provision of round the clock MCH services, and improved access to MCH services (O)S4: Implications of withdrawal of support. In a context where basic support to health facilities  is dependent on project funding, a sudden withdrawal of political and financial support to previously funded MCH programme will limit the availability of human and material resources (C), making health workers feel unappreciated and unsupported (M), resulting in low morale and distrust among health workers and reduced performance, which can ultimately constrain the sustained provision of MCH services (O).D1: Supporting women to access health care. In the context of pregnant women’s inability to pay for transportation to health facilities, or for medicines and MCH services, if Ward Development Committees (WDCs) are mobilized and trained and pregnant women are provided conditional cash transfer (CCT) and if village health workers (VHWs) encourage and support women to attend MCH services (C), then pregnant women will feel safer and confident to regularly attend health facilities (M), thus leading to increased and sustained utilization of health facility-based MCH services , and ultimately to better MCH service outcomes (O).D2: Motivated and better performing VHWs. In the context where pregnant women are financially incentivised to access MCH care, if VHWs are provided with CCT and means of transportation to enable them mobilize communities and support women to reach hospitals (C), these VHWs will feel more recognized by communities and motivated to encourage and accompany pregnant women to facilities for MCH services (M), thus contributing towards increased and sustained utilization of MCH services by the pregnant women (O).D3: Distrust due to withdrawal of incentives. In the context of on-going targeted programme to improve access to MCH services to vulnerable pregnant women from remote rural areas, the sudden withdrawal of monetary and non-monetary incentives to support pregnant women to attend the continuum of MCH care (C) will help generate distrust from these women of health workers and wider system and demotivate pregnant women from attending health facilities (M), eventually leading to the reduced utilization of available facility-based MCH services (O).D4: Sustainability of trust in the health system. In the context of improved staff attitude, upgraded health facilities and functioning WDCs achieved during implementation of the SURE-P programme, pregnant women who receive sustained financial and non-financial incentives to use MCH services (C) are likely to develop and maintain a sense of improved trust (including confidence and satisfaction) with health facilities and staff (M), ultimately leading to improved likelihood of repeated and regular utilization of MCH services from these health facilities (O).


Rain, snow, or ice may discourage older adults from leaving their homes with potential consequences for social isolation, decreased physical activity, and cognitive decline. This study is the first to examine potential links between annual precipitation exposure and cognitive function in a large population-based cohort of older Americans. We examined the association between precipitation (percent of days with snow or rain in the past year) and cognitive function in 25,320 individuals aged 45+ from the Reasons for Geographic and Racial Differences in Stroke Study. Linear mixed models assessed the relationship between precipitation and cognitive function, as well as rates of change in cognitive function with age. We found a non-linear relationship between precipitation and cognitive function. Compared to those exposed to infrequent precipitation (less than 20% of days with rain/snow in the past year), cognitive function was higher among older adults experiencing moderately frequent precipitation . However, beyond more than about 45% of days with precipitation in the past year, there was a negative association between precipitation and cognitive function, with faster rates of cognitive decline with age. These exploratory findings motivate further research to better understand the complex role of precipitation for late-life cognitive function. Weather and climate are important determinants of everyday mood, behavior, and health. There is an emerging body of literature seeking to better understand the role of the natural environment on cognitive health and potential environmental risk factors for Alzheimer’s Disease and Related Dementias (ADRD). Population-based studies have found an association between cumulative exposure to air pollution and poor cognitive health ,2,3, andThere is currently a lack of research examining how exposure to everyday weather conditions may affect cognitive function and trajectories of cognitive decline. It is critical to investigate the climate and weather contexts in which individuals develop and navigate cognitive decline as they age. Older adults in major American cities such as Cleveland, Detroit, Miami, Seattle, Pittsburgh, Portland, and Buffalo experience more than 135 wet days per year . WintersOlder adults are particularly vulnerable to climatic conditions given physiological and social factors associated with later life function, such as comorbid health conditions, social isolation, and lack of transportation ,14. ThesSnowy and icy winter conditions in Finland significantly increased odds for loneliness among community-dwelling older people, even after adjusting for restricted mobility, living alone, and health . In fiveIn summary, there are multiple pathways by which precipitation could be related to cognitive function in older adults, including affecting physical/general activity levels and social engagement. Precipitation can moderate hot temperatures, which may motivate physical activity and boost opportunities for social engagement and support. However, the absence of research on the relationship between precipitation and cognition prevents an understanding of these pathways, and hampers the ability to identify which older adults are at greatest risk for cognitive decline due to differences in exposure to rainy and snowy conditions. This study is the first to examine potential links between annual precipitation and cognitive function using data from the Reasons for Geographic and Racial Differences in Stroke (REGARDS) study. We tested the relationship between annual exposure to precipitation and age-based trajectories of cognitive function in this national cohort of older Americans followed since 2003. We hypothesized that greater exposure to precipitation would be negatively associated with cognitive functioning and with faster rates of cognitive decline with age.The REGARDS study is an ongoing national cohort study examining regional and racial differences in stroke and cognitive function (described in detail by Howard and colleagues ). Using The present study used data from participants who completed at least one cognitive assessment between 2006 and 2017. Individuals without georeferenced address information were excluded. We also excluded participants who reported stroke prior to the first cognitive assessment, due to the known impact of stroke on cognitive function . Our finGlobal Cognitive Function. Measures of verbal learning, memory, and executive function were administered biannually beginning in 2006 using the Consortium to Establish a Registry for Alzheimer’s Disease (CERAD) Word List Learning (WLL) and Word List Delayed Recall (WLD), Animal Fluency Test (AFT) and Letter Fluency Test (LFT) ,26. The We did not have a hypothesis for which specific cognitive function domains may be associated with precipitation. Therefore, to capture global cognitive function and use multiple sources of information from the REGARDS cognitive assessment with minimal measurement error, we created a composite index ,30. CompPrecipitation. We obtained data on daily precipitation for 2006–2017 from the National Oceanic and Atmospheric Administration ((NOAA), ). We creCovariates. We adjusted models for individual demographic characteristics (collected at baseline) known to be associated with cognitive function, including gender, race (Black or White), highest level of attained education , and year of entry into the study (baseline year). To account for geographically varying precipitation patterns, we adjusted for climate regions using the Köppen climate classification system, which groups climates based on a region’s seasonal precipitation type and temperature . As illuWe used linear mixed models  to examiAll models included random effects for both intercepts and slopes to allow cognitive trajectories to vary by person. Nested models were compared according to two goodness-of-fit indices: the Akaike Information Criterion (AIC) and Bayesian Information Criterion (BIC), which make adjustments for model parsimony . IncreasDue to the known non-linear relationship between climate and health , we modThere was no significant interaction between precipitation and the quadratic form of age, so models included only the interaction between the precipitation splines and the linear form of age. Again, because natural cubic splines cannot be interpreted directly, the association between precipitation and the linear age slope is presented in Predicted values become more precise when precipitation ranges from 20–40% of days in the past year, which is typical for most of the study population. At this frequency of precipitation there is a positive association with cognitive function. A greater percentage of days with rain/snow over this moderate range of precipitation is associated with higher cognitive function among older adults, net of climate region and demographic characteristics. This is counter to our hypothesis, but may reflect the cognitive benefits of precipitation through more green space  or the cognitive stimulation afforded by changing seasons and weather.However, beyond more than about 45% of days with annual precipitation, the association with cognitive function is no longer positive. The relationship is relatively flat across 50–60% of days with precipitation, and exposure to a very high frequency of annual precipitation (between 50–66% of days in the past year) is negatively associated with cognitive function. The relatively wide confidence bands around these predicted values reflect the rarity of these exposures, but for older adults who experience these heavy rainy/snowy conditions, cognitive function is lower with progressively more precipitation exposure.The current study is the first to explore the association between precipitation and cognitive function using longitudinal survey data on a community-dwelling nationwide cohort of older adults. A growing body of literature looks beyond individual risk factors to consider the role of the social and physical environment for cognitive health ,45,46,47We found complex relationships where the frequency of exposure to precipitation had both positive and negative consequences for later life cognitive function depending on the magnitude of the exposure. In very dry conditions with infrequent precipitation (less than 20% of days in the past year), we observed a negative association with cognitive function. Increasing precipitation in this dry range may have negative consequences for cognition if rain or snow is unexpected or uncommon, leading to stress, physical inactivity, and isolation among older adults. Community infrastructure may also not be sufficiently equipped to manage rare precipitation events  resulting in disrupted transportation systems and store closings that may adversely impact older residents. Older adults living in communities with fewer climate-resilient characteristics may be much more vulnerable to precipitation impacts on cognition. For example, in Vancouver (Canada) snow-associated reductions in walking were strong in car-dependent neighborhoods . HoweverMost older adults in this study experienced, on average, 20–40% of days of annual precipitation. Contrary to our expectations, this was positively associated with cognitive function net of sociodemographic and geographic covariates. Perhaps precipitation in these areas contributes to more lush and green spaces, which can encourage older adults to be more physically active. Rain may help moderate hot temperatures, such as the cooling effect of a thunderstorm on a hot summer day. Precipitation may improve air quality and reduce resident exposure to atmospheric pollution ,51,52. QHowever, we also found that exposure to very frequent annual precipitation has potential negative consequences for cognitive function among older adults. At the high extremes of precipitation exposure  cognitive function was negatively associated with precipitation. Exposure to higher rates of annual precipitation was also associated with faster rates of decline in cognitive function with age. There are potential lifestyle pathways by which frequent precipitation could have negative effects on the wellbeing of older adults and their cognitive function. Rainy, icy, and snowy conditions can pose barriers to mobility, reduce physical and general activity levels, and increase social isolation and loneliness ,20,22. TThe strengths of this study include a diverse national sample with repeat measures of global cognitive function across later adulthood. Study participants lived across multiple climate regions of the United States, allowing us to examine a broad spectrum of exposures to precipitation among Americans aging in different geographic locations. However, a number of limitations should be noted. First, we do not differentiate between the specific type of precipitation , nor quantity, which the existing literature  suggestDespite these limitations, the complexity of our findings motivates further research to better understand the role of precipitation for late-life cognitive function, including research on potential mediators such as mobility and social engagement during inclement weather. With climate change, extreme weather events are increasing . Under aBetter understanding of how repeated and long-term exposure to rainy, icy, and snowy conditions may affect the cognitive health of aging individuals can generate novel opportunities to intervene in health and wellbeing. While we cannot change the weather, healthcare providers can take the natural environment into consideration when treating patients to consider those at-risk. They can ask targeted questions about behavior and lifestyle during inclement weather and help develop strategies to overcome potentially-reduced mobility, decreased physical activity levels, and social isolation and loneliness. Older adults may join an indoor mall walking program during the winter, for example, set up ridesharing to appointments and social gatherings with services or friends/family more comfortable driving in inclement weather, take fall prevention classes, and acquire mobility aids to help navigate difficult conditions. Public health officials, community service organizations, and urban planners can take steps to ameliorate the built and social environments in which older adults navigate frequent and prolonged wet and snowy weather, such as programs to check in on homebound and isolated older adults; investment in sidewalk plowing, salting, and maintenance; pedestrian infrastructure improvements to facilitate safer mobility in rainy, snowy, and icy conditions; and indoor winter recreation programs. A better understanding of the mediators and modifiers of this precipitation–cognition association can inform a range of possible mobility, physical activity, and social engagement interventions during inclement weather that could potentially maintain and improve cognitive health as people age.


In the United States, obesity is a major risk factor for chronic disease, and related medical costs are estimated to increase by at least $48 billion annually through 2030 . InterveThe Centers for Disease Control and Prevention (CDC) is committed to improving the health of Americans through evidence-based public health programs; the agency supports these programs through funding mechanisms called cooperative agreements that are awarded to state and local public health entities. A cooperative agreement provides for substantial involvement between a federal awarding agency and a nonfederal entity in carrying out defined activities. This editorial describes activities designed to strengthen partnerships to improve health through PSE approaches.In 2014, CDC’s Division of Nutrition, Physical Activity, and Obesity launched a program called Programs to Reduce Obesity in High Obesity Areas, also referred to as HOP. The program was a result of congressional funding authorization for land-grant universities (LGUs) to work with the US Department of Agriculture’s Cooperative Extension Services (CES) to launch an outreach program to combat obesity where obesity rates are the highest.From 2014 through 2018, CDC’s HOP provided funding to 11 LGUs in states with counties in which the prevalence of adult obesity was greater than 40% according to data from the 2013 Behavioral Risk Factor Surveillance System. CDC staff members provided substantive guidance to the LGUs through program support from CDC project officers and evaluators. These CDC staff members have expertise in HOP areas and provided technical assistance and guidance to LGUs on evidence-based nutrition and physical activity interventions, community-based participatory approaches, community needs assessments, coalition development, performance measures, and leveraged resources . CDC provided this expertise and technical assistance through monthly calls, work plan reviews, and community site visits. LGUs provided direct support and guidance to their respective CES to conduct evidence-based nutrition and physical activity interventions in eligible counties.HOP uses the knowledge and relationships of CES and communities to improve the nutrition and physical activity environments in primarily rural counties. CES aims to “advance agriculture, the environment, human health and well-being, and communities”  by suppoHOP recipients used a community-based participatory approach during the first 6 months to 1 year of the cooperative agreement to engage community coalitions and conduct community needs assessments. HOP recipients worked on the following 3 strategy approaches:1. Providing education and promotional support for environmental approaches.2. Implementing evidence-based practices to increase consumption of healthy foods and beverages.3. Implementing evidence-based strategies to increase opportunities for physical activity.On the basis of CDC guidance, HOP recipients elected to work in either the community or the early care and education setting.Preventing Chronic Disease is to highlight the program’s approach and describe both overarching and program-specific evaluation findings. The collection comprises 8 articles, 7 that highlight the work of LGUs (The purpose of this collection of articles related to HOP in  of LGUs –10, and  of LGUs . Powers and colleagues described a 9-week, multilevel, faith-based health promotion initiative that used PSE approaches in 14 Alabama faith communities (Carter and colleagues summarized findings from a community-based obesity reduction and prevention initiative implemented to increase opportunities for physical activity among residents in rural Alabama . This inGustafson and colleagues examined the effectiveness of community-based interventions implemented in rural Kentucky . They reKendall and colleagues described findings from a community-based project implemented in 3 rural Louisiana parishes that focused on promoting healthy eating and physical activity through PSE approaches . After cStluka and colleagues examined collaborations with residents of rural communities in South Dakota to implement and evaluate garden-based interventions . The autWallace and colleagues described an initiative implemented in 4 rural western counties in Tennessee that engaged community residents in activities to reduce obesity and used a PSE framework and a community-based participatory approach . EvaluatCastillo and colleagues described how needs assessments were used to identify components of a PSE-centered initiative implemented in 4 communities in Hidalgo County, Texas, to increase access to physical activity and healthy foods . The neePreventing Chronic Disease describes approaches to improve the nutrition and physical activity environments in rural areas that have a high prevalence of adult obesity. Articles in this collection support the approaches of previous studies on interventions to improve health outcomes, such as the use of tailored community-based participatory approaches and a focus on using PSE when improving the nutrition environment and opportunities for physical activity in communities. The collection provides examples of community interventions that aim to increase the healthfulness of food and access to physical activity, such as improving healthy food options in retail outlets (This special collection in  outlets , creatin outlets , and col outlets –10. The The findings from HOP influenced the approach and expectations of the subsequent HOP funding period, which began in 2018, and other cooperative agreements funded by CDC. CDC used the emerging approach of collaboration with CES in its current cooperative agreements. CDC continues in its expectation that state and local recipients engage coalitions through community-based participatory approaches, use the results of community needs assessments to drive the selection of interventions, and tailor approaches to meet the unique needs of priority populations and communities. Other funding organizations addressing obesity may consider these approaches for implementation of future community-level work.


Quantifying aging is crucial for addressing aging and related issues. This study aimed to: 1) develop two composite aging measures in the Chinese population using two recent advanced algorithms ; and 2) validate the two measures by examining their associations with mortality and disease counts. Based on data from the China Nutrition and Health Survey 2009 wave , a nationwide prospective cohort study of the Chinese population, we developed Klemera and Doubal method-biological age (KDM-BA) and physiological dysregulation  using 12 routine clinical biomarkers. For the validation analysis, we used Cox proportional hazard regression models  and linear, Poisson, and logistic regression models (for disease counts) to examine the associations. We replicated the validation analysis in the China Health and Retirement Longitudinal Study . We found that both aging measures were predictive of mortality after accounting for age and gender . With few exceptions, these mortality predictions were robust across stratifications by age, gender, education, and health behaviors. The two aging measures were associated with disease counts both cross-sectionally and longitudinally. These results were generally replicable in CHARLS although four biomarkers were not available. In summary, we successfully developed and validated two composite aging measures‒‒KDM-BA and PD, which have great potentials for applications in early identifications and preventions of aging and aging related diseases in China.


This article was originally published with the following error:An error appeared in the initial publication of this article [den Heijer CDJ, Hoebe CJPA, Driessen JHM, et al. Chlamydia trachomatis and the Risk of Pelvic Inflammatory Disease, Ectopic Pregnancy, and Female Infertility: A Retrospective Cohort Study Among Primary Care Patients. Clin Infect Dis In the financial support section, it currently states the following:“This study was supported by the Netherlands Organisation for Health Research and Development .”It should state:“This study was supported by the Netherlands Organisation for Health Research and Development ”.The author regrets this error.


People living with human immunodeficiency virus (PLHIV) struggle with the challenges of living with a chronic disease and integrating antiretroviral treatment (ART) and care into their daily lives. The aims of this study were as follows: (1) to undertake the first mega-aggregation of qualitative evidence syntheses using the methods of framework synthesis and (2) make sense of existing qualitative evidence syntheses that explore the barriers and facilitators of adherence to antiretroviral treatment, linkage to care and retention in care for PLHIV to identify research gaps.We conducted a comprehensive search and did all screening, data extraction and critical appraisal independently and in duplicate. We used the Kaufman HIV Behaviour Change model  as a framework to synthesise the findings using the mega-aggregative framework synthesis approach, which consists of 8 steps: (1) identify a clearly defined review question and objectives, (2) identify a theoretical framework or model, (3) decide on criteria for considering reviews for inclusion, (4) conduct searching and screening, (5) conduct quality appraisal of the included studies, (6) data extraction and categorisation, (7) present and synthesise the findings, and (8) transparent reporting. We evaluated systematic reviews up to July 2018 and assessed methodological quality, across reviews, using the Joanna Briggs Institute Critical Appraisal Checklist for Systematic Reviews.We included 33 systematic reviews from low, middle- and high-income countries, which reported on 1,111,964 PLHIV. The methodological quality of included reviews varied considerably. We identified 544 unique third-order concepts from the included systematic reviews, which were reclassified into 45 fourth-order themes within the individual, interpersonal, community, institutional and structural levels of the Kaufman HIV Behaviour Change model. We found that the main influencers of linkage, adherence and retention behaviours were psychosocial and personal characteristics—perceptions of ART, desires, fears, experiences of HIV and ART, coping strategies and mental health issues—interwoven with other factors on the interpersonal, community, institutional and structural level. Using this approach, we found interdependence between factors influencing ART linkage, retention and adherence and identified the need for qualitative evidence that explores, in greater depth, the complex relationships between structural factors and adherence, sociodemographic factors such as community violence and retention, and the experiences of growing up with HIV in low- and middle-income countries—specifically in children, youth, women and key populations.This is the first mega-aggregation framework synthesis, or synthesis of qualitative evidence syntheses using the methods of framework synthesis at the overview level. We found the novel method to be a transparent and efficient method for assessing the quality and making sense of existing qualitative systematic reviews.CRD42017078155) on 17 December 2017.The protocol of this overview was registered on PROSPERO (The online version contains supplementary material available at 10.1186/s13643-021-01582-z. Qualitative evidence syntheses (QES) aggregate, integrate and interpret results from primary qualitative studies . Like quAlthough access to HIV care has improved significantly over the past few years, people living with HIV (PLHIV) still face numerous challenges when it comes to initiating care and staying on treatment. Human immunodeficiency virus (HIV) represents one of the greatest global public health challenge in history, and since the beginning of the epidemic, approximately 78 million people worldwide have been infected with HIV and 35 million people have died . The JoiPLHIV continue to be challenged by the complexities related to being HIV positive and integrating ART treatment and care into their daily lives. Unsuccessful interventions and the target driven 90-90-90 goals have increased researchers’ commitment to understanding the human experience of living with HIV and engaging in the HIV treatment cascade. Some reviews have focused only on prevention, adherence, linkage to care or retention in care. This can lead to an abundance of research in one area on the cascade and neglect of others. With the growing body of existing systematic reviews , 18, theOverviews of reviews aim to provide a single synthesis or summary from multiple systematic reviews . QES oftmega-aggregation framework synthesis was developed and utilised to identify evidence gaps and to inform future research from the evidence collated within included systematic reviews. The mega-aggregative framework synthesis approach consists of eight distinct steps  care following a positive HIV test is referred to as linkage to care in this overview. While no specific criterion exists with regard to linkage to care, it has been previously defined as one visit or more during the first 6 months of receiving a positive diagnosis and the initiation of antiretroviral treatment . AdherenTypes of contextsReviews synthesising information from high-, middle- and low-income countries were included in this overview. The geographic settings included rural and urban across all global regions.Types of outcomesThe review-level outcomes of interest were self-reported barriers and facilitators to linkage to ART, adherence to ART and retention in care. Outcomes that were measured and reported using statistical associations between various factors and linkage, adherence and retention in care were not included.A comprehensive search for systematic reviews up to 25 July 2018 was conducted in the Cochrane Library , The Campbell Library, MEDLINE via PubMed, SCOPUS and CINAHL EBSCHOhost. PROSPERO was also checked for ongoing systematic reviews. Experts in the field were contacted and reference lists of included reviews were checked to identify further potential reviews for inclusion. An additional search on Google Scholar was conducted to search for reviews not contained within the databases. Key terms included in the search strategy were ‘HIV’, ‘linkage’, ‘adherence’, ‘retention in care’, ‘ART’, ‘qualitative’ and ‘systematic reviews’. Search terms were modified appropriately for the various databases. Detailed search strategies for all databases are reported in Additional file Included systematic reviews were subjected to quality appraisal by the first author (LH) and second author (AR) independently and in duplicate. Discrepancies were resolved through discussion. Risk of bias was assessed using an amended version of the Joanna Briggs Institute Critical Appraisal Checklist for Systematic Reviews  JBI-SR-. The JBIWe assessed the overall quality of systematic reviews as either low, medium or high, by considering items 1–9. Although the area of quality assessment in QES is still being debated in the field and the philosophical underpinning and epistemological reasoning behind conducting or not conducting quality assessment are unique to the rationale and question of the review authors , we inclThe data extraction took place in two phases: (1) data extraction of characteristics of included studies and (2) data extraction of barriers and facilitators for data synthesis.Data extraction of characteristics of included reviews and their primary studiesData was extracted by the first author (LH) and checked and validated by a second author (AR) and third author (IEW) using a pre-specified piloted data extraction form in Microsoft Excel  read the systematic reviews several times to become more familiar with the findings and recommendations made by the review authors. Following this, LH extracted barriers and facilitators verbatim into Excel for each review and categorised them according to the pre-specified dimensions of the Kaufman HIV Behaviour Change Model . The revmega-aggregative framework synthesis’ to this overview. Meta-aggregation is a method of data synthesis used in QES and focuses on aggregating primary-level findings into categories and then further aggregating those categories into synthetic statements that may be used for policy and practice without losing the critical interpretive value of the qualitative findings [The principles of meta-aggregation and framework synthesis were integrated to design and apply the novel approach of ‘findings . Mega-agAs with mega-ethnography , this tyThis overview used guidance from the Johanna Briggs Institute Methodology for Umbrella Reviews  and the n = 10), did not contain qualitative primary studies or data (n = 4) or did not include the target population group (n = 1). We were unable to obtain the full texts for two reviews and are waiting on information from one author and have classified these three reviews as ‘awaiting assessment’. Three ongoing reviews or protocols were found in our search . After the removal of duplicates, 1921 citations were imported into Covidence and the title and abstracts were screened, resulting in 78 retrieved for full text review. Thirty-nine reviews were excluded  synthesised primary studies that were conducted in both high-income countries and low- and middle-income countries with a large concentration of included primary studies being conducted in sub-Saharan Africa  are included in this overview. Some reviews included high-risk populations, such as pregnant and postpartum women, children and adolescents, commercial sex workers, men who have sex with men, transgender persons, prisoners, intravenous drug users and foreign nationals. Two reviews on children and adolescents included data from caregivers. Table We applied the conceptual definitions of the outcomes as per the overview protocol and we found that 13 reviews addressed the outcome of linkage to ART, 29 addressed the outcome of adherence to ART and 11 addressed the outcome of retention in care , such as being younger, whether the participant’s occupation was considered socially acceptable, gender, and not having identification documents in order to enrol in care services. Barriers related to patient fears (9 findings) were the emergent themes. PLHIV expressed fears of the consequences of disclosure, such as job loss, stigma and social isolation, fears of being on lifelong treatment and the negative side effects of ART. PLHIV reported experiencing psychological distress and emotional reactions (9 findings) and some were shocked at the news of their positive status, unsure about how they had contracted the disease, and the possibility of infidelity in their relationships. Feelings of hopelessness and depression were a recurring theme, with women questioning their self-esteem as wives and mothers. For children, two findings of barriers to linkage included negative emotions and self-perception.On the PLHIV doubted their ability to adhere and commit to lifelong treatment and care. Themes for the facilitators of linkage to ART on the individual level included physical health (6 findings) and barriers regarding physical health (8 findings). In the context of participants’ psychological distress, some reviews found that participants could no longer ignore the physical symptoms of the disease or their declining health, while others found that although they tested positive for HIV, they were asymptomatic, and therefore delayed care. The desire to care for family, protect unborn children from the transmission of HIV, as well as the desire for future marriage and children facilitated children’s linkage.interpersonal level, relationships in the household emerged as an important theme, both as barriers (7 findings for adults and 1 finding for children) and facilitators (3 findings for adults and 1 finding for children). PLHIV reported conflicts in the household, threats of domestic violence and abandonment, and the lack of autonomy for women, as barriers to linkage to ART. In contrast, supportive partners and families with mutuality-fostering relationships involving empathy facilitated linkage.On the community level, the main barrier expressed was stigma and discrimination (4 findings), which is linked to community narratives around masculinity, HIV as witchcraft, and hospitals as places of death. Children reported unsupportive teachers (1 finding) as a barrier to linkage. Facilitators reported included peer support and support groups (6 findings) which served as a proxy for family support when it was lacking. One finding for adults included community beliefs and practices as a barrier with negative beliefs about ART, detrimental gender norms, and a preference for traditional healers and medicines.On the institutional level, barriers such as stigma experienced at health care facilities (7 findings), service delivery (24 findings), which includes overcrowding, long queues, high staff turnovers, inconvenient client times, poor resources and participants’ experiences with limited medication availability as well as their experiences of HIV testing were reported. Four findings were related to barriers of institutional models of care. PLHIV identified gaps in the ART cascade referral process, particularly for women who test positive during their antenatal care (ANC) and are not followed-up postpartum, as well as lack of integrated services. PLHIV perceived health care models such as home visiting, as a barrier, as it might contribute to involuntary disclosure. There were fourteen findings for facilitators in the theme models of care, including offering population-specific services for adolescents, the integration of HIV care within ANC, offering mental health assessments and providing multi-level, multi-pronged approaches to care. The facilitators for the theme service delivery (2 findings) included PLHIV having positive experiences of HIV testing and encountering a clinic staff member who welcomed people into the clinic. Counselling practices and principles (6 findings) that respected the place of traditional medicine, incorporated the traditional beliefs of people, and that provided in-depth counselling before and after HIV testing were reported as facilitators on the institutional level. Children reported lack of privacy experiences at the clinic, the physical environment at the clinic and high staff turnover as barriers to linkage (1 finding).At the structural level, reported barriers included the financial cost of care (2 findings), healthcare policies (3 findings), income and food security (4 findings), transport and distance to the clinic (4 findings) and one finding for living conditions and context. Facilitators included income and food security (1 finding), and transport and distance to clinic (2 findings), which includes having an escort to the clinic.On the Only one high-quality review  was founFindings on barriers and facilitators to adherence to ART, and reviews reporting on these are summarised in Additional file individual level, emerging themes related to barriers to adherence were linked to medication (19 findings), sociodemographic factors (18 findings) and fears (12 findings). Reviews reported medication characteristics, negative side effects, pill burden and regimen, travelling away from home and lack of privacy as barriers, and the use of reminders, simpler medication regimens as facilitators, within the medication theme. Several reviews synthesised findings on the self-reported sociodemographic characteristics such as levels of education, age and gender. In some cases, a woman’s positive HIV status was considered a result of her husband’s infidelity and reduced the risk of stigmatisation when disclosing her status. In other cases when women were seen taking their medication they were stigmatised as hypersexual and were discriminated against. Other reported barriers were grouped under the themes psychological distress and emotions (15 findings) and fears (12 findings). Fears were related to the medication toxicities, side effects, unintentional disclosure, that the treatment would harm a pregnant woman’s unborn child and the fears that ART leads to impotency, infertility, and the impossibility of sexual activity.On the The theme of coping strategies (12 findings) and desires (7 findings) were identified as facilitators to mitigate fears, anticipated stigma and negative side effects of ART. Coping strategies included being aware of personal strengths and weakness, learning to manage the HIV diagnosis and interpreting physical signs of the body, drinking liquids, resting and adopting a resilient and positive attitude. People desired to be healthy to care for their families and to maintain their appearance to keep their status a secret. Knowledge and understanding was identified both as a barrier (6 findings), such as receiving conflicting messages from community members, providers, peers and the media; and as a facilitator (7 findings) such as, understanding the need for compliance.interpersonal level, peoples’ relationships within the household emerged as a barrier (15 findings) and facilitator (7 findings) to adherence. Family involvement and emotional, material, and social support were important factors to PLHIV. Other barriers such as punishment for lack of adherence for children, negative family reactions to disclosure, enacted stigma by family members and lack of autonomy in relationships made it difficult for people to adhere.On the Community level barriers were related to community beliefs and practices (6 findings) such as strong negative community beliefs about HIV and bypassing of clinics and hospitals for traditional healers. Peers and support groups (6 findings) played a mitigating role and helped participants adjust to their new daily routine. Financial and emotional support also facilitated adherence.institutional level of the framework were service delivery (27 findings), which was reported as a barrier; and models of care (15 findings), which was reported as a facilitator. People who may have had the intention of adhering to ART were discouraged by the difficulties of making a scheduled appointment and the long waiting times at the clinic when they did seek care. Negative experiences at the clinic when collecting the refills of medication included the lack of privacy, overcrowding and stigma experienced within the clinic by other patients, community members and staff. People reported spending up to a day waiting to see a health care worker and were presented with additional barriers such as drug stock-outs or limits on the amount of medication that could be dispensed at a time. Models of care, such as integrated mental health care, integrated antenatal care (ANC) and HIV care, and specialised services for adolescents, with highly skilled and trained healthcare workers,The two emergent themes identified at the structural-level themes identified for barriers to ART adherence included the financial cost of ART, healthcare policies, and income and food security, each of which had three findings. PLHIV reported that food insecurity and no access to liquids prevented them from taking their medication. PLHIV felt discouraged by their lack of understanding of healthcare policies and some reported the barrier of access laws at health care facilities that sent patients to their birthplace to seek care. Policies directed at specific populations with criminalising threats for transgender persons, commercial sex workers, drug users and deportation threats for immigrants were reported as barriers. Even with the advent of free ART, the indirect cost of ART is still high in low-income settings with participants expressing the challenge of travelling to clinics in rural areas, the affordability of safe, reliable transport and the indirect cost of childcare when visiting the clinic in order to collect medications. Facilitators at the structural level included financial relief for care (5 findings) and income and food security (2 findings), which included the provision of grants for food supplementation and travel reimbursement.The One high-quality review  found thTen reviews contributed to the findings for retention in care, and the barriers and facilitators as reported in the reviews, by country income level and quality rating, are presented in Additional file individual level were the barriers of sociodemographic factors (5 findings), such as issues around gender, and concerns about not have registered identification documents to access care due to either immigrant status or being transgender; the themes of fears (4 findings); and psychological distress and emotional reactions (7 findings). PLHIV reported experiencing mental fatigue from being retained in care and experiencing psychological suffering as an adult with HIV, which included feeling angry, feeling like they have lost control of their lives and feelings of depression and hopelessness.The prominent themes on the interpersonal level, emergent themes included the barriers (5 findings) and facilitators (3 findings) of disclosure. Disclosure was reported as a barrier either in cases when participants chose not to disclose, and this resulted in sporadic care within health care systems, or due to post-disclosure stigma. Family members who were supportive and relationships in the household (6 findings) were reported as facilitators of retention in care. Partners who were emotionally supportive and encouraged healthy living were considered facilitators of retention in care. In other instances, partners who were not involved in care were considered as barriers, with reviews reporting that women did not have decision-making power in some contexts, and this denied them the opportunity to seek care.On the community level had two emergent themes with one finding each. These included the theme of community beliefs and practices and the theme of peers and support groups, which was also reported as facilitators with six key findings. Facilitator findings included having a treatment companion, identifying a confidante, attending support groups and enlisting the help of supervisors and teachers to facilitate retention in care.The institutional level were reported. Themes included service delivery (20 findings) and models of care (17 findings), followed by stigma in health care and engagement (7 findings) and engagement with health care workers (6 findings). Service delivery barriers included long waiting times and subsequent short consultations with health care workers, drug and test stock outs, lack of privacy, laboratory challenges, negative experiences of testing for HIV, the physical clinic environment and the failure of the health care facility to keep up with rapidly changing treatment protocols. PLHIV reported same-day appointments between services offerings at the clinic, their experiences of HIV testing and the provision of disability accommodations to be facilitators of service delivery (5 findings). The facilitators of models of care (9 findings) included integrated care to reduce patient burden, the treatment of depression and anxiety related to diagnosis, offering male-friendly services without needing to access care through partners’ ANC services and home visiting or mobile care units.For retention in care, many themes that related to the Structural-level barriers were emergent for health care policies (4 findings), financial costs of care (2 findings), transport and distance to clinic (2 findings), and one finding each for income and food security, and living condition and context. PLHIV reported the cost of attending care even while ART was universally free and accessible as a barrier to engaging in care. Indirect costs included the loss of wages when attending the clinic, transportation costs, childcare costs and the possible loss of grants due to their HIV-positive diagnosis. Only one facilitator of having a higher income was reported at the structural level.No high-quality reviews were found for self-reported barriers and facilitators of retention in care for children or adults.We reclassified the third-order concepts into 45 fourth-order themes within the five levels of the Kaufman  HIV behaReview-level evidence : ChecklistAdditional file 6. Differences between protocol and manuscriptAdditional file 7. Tables of excluded studies, ongoing studies, and protocols (N = 45)Additional file 8. Individual summaries and critical appraisal reasonsAdditional file 9. Overlap of included primary studies (n = 826)Additional file 10:. Summary of review level evidence: Linkage to ARTAdditional file 11. Summary of review level evidence: Adherence to ARTAdditional file 12. Summary of review level evidence: Retention in careAdditional file 13. Summary of themes and included reviews linked to outcomes


Bisphenol-A (BPA) has been reported to be associated to female infertility. Indeed, BPA has been found to be more frequently detected in infertile women thus leading to hypothesize a possible effect of BPA on natural conception and spontaneous fecundity. In addition, in procedures of medically assisted reproduction BPA exposure has been found to be negatively associated with peak serum estradiol levels during gonadotropin stimulation, number of retrieved oocytes, number of normally fertilized oocytes and implantation. BPA deleterious effects are more critical during perinatal exposure, causing dysregulation of hypothalamic-pituitary-ovarian axis in pups and adults, with a precocious maturation of the axis through a damage of GnRH pulsatility, gonadotropin signaling and sex steroid hormone production. Further, BPA exposure during early lifestage may have a transgenerational effect predisposing the subsequent generations to the risk of developing BPA related disease. Experimental studies suggested that prenatal, perinatal and postnatal exposure to BPA can impair several steps of ovarian development, induce ovarian morphology rearrangement and impair ovarian function, particularly folliculogenesis, as well as can impair uterus morphology and function, in female adult animal and offspring. Finally, studies carried out in animal models have been reported the occurrence of endometriosis-like lesions after BPA exposure. Moreover, BPA exposure has been described to encourage the genesis of PCOS-like abnormalities through the impairment of the secretion of sex hormones affecting ovarian morphology and functions, particularly folliculogenesis. The current manuscript summarizes the evidence regarding the association between BPA exposure and female infertility, reviewing both clinical and preclinical studies. In the last decades the environmental pollution caused by urbanization and industrialization has been reported to affect human health , 2. EndoBisphenol-A  is one of the most investigated EDCs. BPA is largely found in polycarbonate resin mainly used for plastic bags, bottles and packaging, particularly water and milk bottles, coated tins, particularly food and drink cans, and microwave ovenware –13. The The current review aims to give an overview of the link between BPA exposure and female infertility by reporting the few epidemiological studies available in humans and by providing, in particular, in vitro, ex vivo and in vivo animal-based evidences of BPA implication in the pathogenesis and progression of female infertility. In particular, studies describing the BPA effect observed on regulation of hypothalamus-pituitary-ovary (HPO) axis and on female reproductive organs  morphology and functions  will be focused. Moreover, the current manuscript will critically review the observational studies in humans evaluating the association of serum and/or urinary BPA levels and female infertility mostly focusing on natural conception, in medical assisted reproduction (MAR) outcome and on infertility–related reproductive disorders, particularly endometriosis and polycystic ovary syndrome (PCOS).Articles were individually retrieved by each author up until February 2018, by search in PubMed (MEDLINE) using the following search terms: ‘bisphenol- A’, ‘ovary’, ‘uterus’, ‘HPO axis’, ‘oviduct’, ‘vagina’, ‘PCOS’, ‘endometriosis’, ‘endocrine disruptor’, ‘female fertility’, ‘female infertility’, ‘time to pregnancy’, ‘environment’, ‘endocrine disruptors’. The reference lists of relevant articles and reviews were also searched manually.−7M for cell culture experiments, corresponding circulating BPA levels in animals after administration of BPA at LOAEL concentration [The proper definition of BPA low-doses or high-doses range has been extensively discussed. In the current review, in accordance with the Chapel Hill BPA expert panel consensus statement , “low BPntration . BPA levntration .BPA is a chemical mainly used as a monomer in the manufacturing of polymers, in particular polycarbonate resins, but also epoxy polyester, polysulfone and polyacrylate resins, and flame retardants –13. SincBPA daily human exposure, assessed by measuring the urinary excretion of BPA, may vary widely worldwide, as well as the daily dietary intake, assessed by measuring BPA levels in food . AccordiBPA is a lipophilic synthetic organic compound that, following oral administration, is absorbed through the gastrointestinal tract and transported to the liver where it is metabolized acquiring characteristics of hydrophilicity , 49. BPABPA active form exerts its primary endocrine disrupting activity mimicking estrogens, but also different hormones, including androgens, such as testosterone (T) and dihydrotestosterone (DHT), and thyroid hormones. Indeed, BPA has a conformational structure that confers the ability to bind both ER alpha (ERα) and beta (ERβ), although, according to in vivo models, the affinity of BPA for ER is 1000-fold to 10,000-fold less than the affinity of 17β-estradiol (E2) . BPA genApproximately 1 to 2.5 ng/mL of active BPA, evaluated by different detection methods , were absorbed mainly through the primary route (diet) and different sources of exposure , and circulates in human blood . The preThe review will be divided in several sections focused on the following topics: 1) the main epidemiological studies evaluating the association between BPA levels and overall female fertility, in both conditions natural conception and MAR, and 2) the main in vitro, ex vivo and in vivo studies concerning: a) BPA effects on HPO axis; b) BPA effects on female reproductive organs morphology and functions; and 3) the main in vitro, ex vivo, and in vivo studies on BPA role in the development of reproductive disorders, mainly endometriosis and PCOS, including epidemiological studies in humans.http://old.iss.it/rpma/). The increase in the prevalence of couple, including female infertility, worldwide has been also related to the increased environmental contaminants registered worldwide [Increasing evidences have been suggested that BPA might affect female fertility and could contribute to the pathogenesis of female infertility. In general, infertility affects 25% of couples in developing countries and is defined as the inability to become pregnant after 12 months of regular unprotected sexual intercourse . Couple orldwide .The current section describes the present evidence in epidemiological studies concerning the impact of BPA in female infertility, including both natural conception and MAR , 61.The hypothetical role of BPA in natural conception has been investigated in several observational studies, evaluating the relationship between BPA levels and spontaneous fecundity –65.In the frame of the Italian project PREVIENI, an observational prospective cross-sectional study was performed in 48 women aged 18–40 years affected by infertility aiming to investigate the role of EDCs, including BPA, on reproductive health . The numTaken together these results suggest that BPA exposure is frequently detected in infertile women and especially in infertile women living in metropolitan area. The level of BPA exposure does not seem to be associated to TTP but the studies investigating this association considering a very low LOD, which was probably one of the main bias preventing to find an association between BPA levels and TTP.The hypothetical role of BPA in MAR has been investigated in several observational studies reporting a negative relationship between BPA levels and MAR outcomes. Recently it has been highlighted a protective role of soy-based foods against the negative effect of BPA on MAR outcomes. Soy-based foods contain a complex mixture of phytoestrogens, many of which are hormonally active that, like BPA, might have estrogenic activity. The soy-based foods related protective mechanism might lay in the ability to interfere with BPA-induced effects on DNA methylation –70.Bloom et al. investigated the association between serum BPA levels and ovarian response to exogenous gonadotropin stimulation in an prospective cross-sectional carried out in 44 women aged 35–40 years undergoing MAR. An inverse association between serum BPA levels and peak E2 levels were found leading to hypothesize that BPA exposure might influence E2 production during gonadotropin stimulation . Mok-LinIn summary, these findings suggest that BPA could have a negative effect on MAR outcomes, particularly BPA exposure was associated to a decrease in E2 production and number of oocytes retrieved after ovarian stimulation and to an increase in implantation failure. The consumption of soy-based foods might have a protective role against BPA effects on MAR outcome, probably interfering with the BPA-induced effects on DNA methylation.Female reproduction in humans and in rodents is closely related to a proper function of HPO axis. Indeed, after sexual maturation, HPO axis coordinates ovarian function and particularly ovarian steroidogenesis and folliculogenesis with the final ovulation and prepares reproductive organs to support a potential pregnancy .Humans and rodents, share the same regulation of reproductive system by the HPO axis, including the regulatory hypothalamic system that releases gonadotropin releasing hormone (GnRH) in rhythmic pulses, the pituitary gland that secretes follicle stimulating hormone (FSH) and luteinizing hormone (LH), and the ovary itself that releases sex hormones, including estrogens, particularly E2, and progesterone (P), which control the function of reproductive system, particularly ovarian and uterine function in the classical cycles , 72. HowNon-primate females, including rodent females, instead, are characterized by an estrus cycle, in which the endometrium is reabsorbed if conception does not occur during the cycle and in which there are recurring periods when the females are fertile and sexually receptive (estrus) interrupted by periods in which the females are not fertile and not sexually receptive (anestrus) . EstrousThe HPO axis plays a critical role in the development and regulation of reproductive system. Fluctuations in this axis cause changes in the hormones produced by each gland and triggering various local and systemic effects. GnRH is secreted from the hypothalamus by GnRH-expressing neurons and activates the anterior portion of the pituitary gland to produce LH and FSH. Both gonadotropins stimulate the ovary to produce E2 and T. The following section describes the available data on the putative effects, and underlying mechanisms, of BPA on HPO axis, obtained in experimental in vitro, ex vivo and in vivo studies. The studies will be described dividing the target of HPO axis, such as hypothalamus, pituitary and ovary. The studies reporting the effects of BPA on HPO axis, with impact on reproductive function, particularly ovarian steroidogenesis, and, therefore, on female fertility are summarized in Tables Few experimental in vitro and ex vivo studies have investigated the effects of BPA exposure on HPO axis regulation , 79, 80.Ex vivo studies conducted on cell primary cultures of POA-anterior hypothalamus-medial basal hypothalamus showed that hypothalamic cells, explanted at PND13 or at adulthood by rat female pups postnatally exposed, from PND1 to PND10, to subcutaneous administrations of low and high BPA doses, exhibited a higher GnRH pulse frequency and decreased GnRH inter-pulse intervals , 80.An ex vivo study conducted on primary cultures of pituitary gland explanted at PND13 by rat female pups postnatally exposed, from PND1 to PND10, to subcutaneous administrations of low and high BPA doses showed a reduced basal and GnRH-stimulated LH release exclusively in cells exposed at high BPA doses . The intIn primary cultures of rat theca-interstitial cells, treatment with low and high BPA doses increased steroid 17 alpha-hydroxylase/17,20 lyase (cytochrome P450c17), cholesterol side-chain cleavage enzyme (P450scc) and steroidogenic acute regulatory (StAR) messenger expression, as well as T secretion. In particular, StAR messenger expression increased only at high BPA doses and T secretion at very high tested BPA dose, suggesting that BPA may induce hyperandrogenism, especially at higher BPA doses . In primSeveral experimental in vivo studies have investigated the effects of BPA exposure on HPO axis regulation , 78–90.The effect of BPA on the hypothalamic hormone secretion, messenger expression and neuronal activity has been investigated in female pups and adult animals during different phases of estrus cycle. Oral administration of low BPA doses markedly increased GnRH messenger expression in POA as well as AVPV-Kiss1, but not ARC-Kiss1, messenger expression, while intracerebroventricular administration increased also ARC-Kiss1 messenger expression, during proestrus, but not during diestrus and estrus, in female adult mice , providiThe effect of BPA on the pituitary hormone secretion and messenger expression has been investigated in female pups and adult animals during different phases of estrus cycle. Oral administration of low BPA doses in female adult mice and rats increased serum FSH and LH levels during proestrus , 86, whiThe effect of BPA on the sex hormone secretion and messenger expression has been investigated in female pups and adult animals during different phases of estrus cycle. Indeed, in rat and mouse female offspring perinatally, prenatally and postnatally exposed to oral, gavage and subcutaneous administration of low and high BPA doses increased circulating E2 levels have been recorded both at PND13 and PND50 in prepubertal or at adulthood, during proestrus and diestrus phases , 80, 81.Although BPA has been found to impair HPO axis in animal studies, no study in humans has been investigated the effect of BPA on HPO axis.Taken together, these findings demonstrate that exposure to low and high BPA doses has harmful effects on the HPO axis causing hormone dysregulation during the different phases of the estrus cycle. However, it is noteworthy that the available data reports discordant results. The different outcome might likely depend on animal model, BPA doses, administration route and window of exposure. Indeed, although BPA deleterious effects have been reported to be more critical with perinatal exposure, during embryonic development, compared to postnatal exposure, BPA exposure during postnatal period or in adulthood can also negatively interfere with HPO axis. Moreover, a different route of administration can differently regulate HPO axis in the same phase of estrus cycle of the same animal model. According to results of ex vivo and in vivo studies on rodent models, postnatal and, particularly, prenatal BPA exposure induces a precocious maturation of the HPO axis by generally increasing GnRH and Kiss1 messenger and protein expression and GnRH pulsatility in the hypothalamus during different estrus cycle phases, whereas according to the results of in vivo studies in monkeys and sheeps, BPA perinatal exposure or BOA exposure during pubertal phase negatively regulate GnRH messenger expression and release, demonstrating that BPA effects on hypothalamus can vary depending on window of exposure and animal models. Similarly, variable results have been found in the analysis of pituitary secretion; since according to the results of ex vivo and in vivo studies in rodent models BPA exposure can cause a different modulation of gonadotropins, that are generally increased, particularly LH, during prepubertal and in adulthood, proestrus and estrus phases, but may also be unchanged or decreased, especially after GnRH stimulation. It is noteworthy that some studies reported different results in the same model and estrus phase but with different route of exposure, suggesting that the administration route of BPA has a key role in the manifestation of the BPA deleterious effects in HPO axis. Finally, according with the results of ex vivo human and rodent models and in vivo rodent models BPA perinatal and postanatal exposure can cause a different modulation of sex hormone secretion, with impairment of ovarian expression of steroidogenic enzymes involved in sex hormone production and consequent increase of T secretion and decrease of P secretion, in diestrus and estrus phases, and generally an increase of E2 secretion in estrus phase, although even unchanged or decreased E2 levels have been reported.The female reproductive system includes the paired ovaries, the oviducts, the uterus, and the vagina. These organs are finely tuned and coordinated to perform the primary functions reproductive system, including folliculogenesis, fertilization, and support of the development of embryo, and to allow the birth of fetus. Morphological and functional changes of reproductive system, particularly the alterations of ovary and uterus, can impair female fertility. In human and rodents, the ovaries are composed by a central highly vascular medulla surrounded by a cortex in which ovarian follicles can be found at different stages of development. The morphological alterations of ovaries can take place during ovarian development or after puberty in fertile-aged females, such as in specific reproductive diseases, like polycystic ovary syndrome (PCOS). In humans and rodents, ovarian development is a dynamic process consisting in the growth of the ovary and establishment of the finite pool of primordial follicles, occurring predominantly during the embryonic period . In partThe following section describes the available data on the putative effects, and underlying mechanisms, of BPA on the morphology and function of female reproductive organs, in particular on ovary and ovarian folliculogenesis and on uterus and embryo implantation, obtained in experimental in vitro, ex vivo and in vivo studies. The studies reporting the effects of BPA on morphology and functions of reproductive system organs and, therefore, on female fertility are summarized in Table .Several experimental in vitro and ex vivo studies have investigated the effects of BPA exposure on ovary and uterus morphology and functions, including ovarian development, folliculogenesis, uterine receptivity and embryo implantation , 95–100.Experimental ex vivo studies on ovary confirmed that exposure to BPA affected folliculogenesis, particularly follicle growth and development, by interfering with multiple mechanisms such as proliferation and apoptosis, beyond steroidogenesis, of ovarian cells. The administration of low BPA doses in ovaries explanted from mouse female pups at PND1 or PND4 inhibited germ cell nest breakdown and enhanced primordial follicle recruitment, by decreasing the expression of Ki-67, Fas, Bac, Bax and caspase 3 and 8, increasing the expression of Bcl2, and activating PI3K/Akt pathway , 96, 100Experimental ex vivo studies on uterus confirmed that exposure to BPA affected uterus morphology and function, particularly interfering with uterine receptivity and embryo implantation. An ex vivo study, conducted on uterus of female adult mice treated with BPA in the first 3 days of pregnancy, demonstrated that high BPA doses delayed the transfer of embryos to the uterus, damaged blastocyst development before implantation, and inhibited embryo implantation. Regarding the putative mechanism, high BPA doses exposure induces a dose-dependent increase of endothelial nitric oxide synthase (eNOS) protein expression in trophoblast cells, the cells forming the outer layer of a blastocyst, with consequent induction of NO excess, which might represent one of the causal factor involved in embryo implantation . MoreoveSeveral experimental in vivo studies have investigated the effects of BPA exposure on ovary and uterus morphology and functions, including ovarian development, folliculogenesis, uterine receptivity and embryo implantation , 101–110The effect of BPA on ovarian morphology and functions has been investigated in female pups and adult animals during different phases of estrus cycle. Prenatal (from GD9 to 16) and postnatal (from PND1 to PND21) exposure to low BPA doses by oral and subcutaneous administration in mouse and rat female pups induced inhibition of germ cell nest breakdown, a decrease of the number of primordial follicles and an increase of their recruitment, as well as an increase of the number of atretic follicles and of ovarian cysts, assessed during first day of life and in adulthood during estrus and diestrus , 109. MoExperimental in vivo studies in mice demonstrated that both prenatal and perinatal exposure to low BPA doses affected oviduct morphology. In particular, in female offspring mice prenatally exposed to low BPA doses an increased number of progressive proliferative lesions in the oviduct was found at adulthood (16 to 18 months of age) . ConsistSeveral experimental in vivo studies in rodent models demonstrated that exposure to BPA from prenatal to adult age, at both low and high doses, affected uterus morphology and functions, in particular uterine receptivity. Mice female offspring prenatally exposed to low BPA doses increased the incidence of proliferative lesions of the uterus, including atypical hyperplasia and stromal polyps of the uterus, as well as sarcoma of the uterine cervix, assessed at 16 to 18 months of age . MoreoveThe effect of BPA on ovarian, oviduct, and uterus morphology and functions has not been investigated in humans although several experimental evidences suggest that BPA could have a detrimental impact on the morphology and functions of female reproductive system.A recent study evaluating the correlation between the urinary BPA levels and ovarian outcomes in a prospective cohort of women undergoing MAR reported that higher urinary BPA levels were associated with lower antral follicle count, raising concern for possible accelerated follicle loss . More epTaken together, these findings demonstrate that exposure to low and high BPA doses has harmful effects on ovarian morphology, in particular in several steps of ovarian development, and functions, in particular folliculogenesis, and on uterus morphology and functions in female adult animal and offspring. The different outcome might likely depend on animal model, BPA doses, administration route and window of exposure. In particular, prenatal, perinatal and postnatal BPA exposure, although with variable results among the studies, to low and high doses mainly regulate: 1) ovarian development, observed in the pups in the first days of birth, reducing the breakdown of germ cell nest, as consequence of deregulated expression of apoptotic genes; 2) oviduct morphology; 3) folliculogenesis, interfering with the growth of antral follicle as consequence of deregulating expression of genes involved in cell cycle and of steroidogenic enzymes, increasing the number of atretic follicles, decreasing the number of corpora lutea and accelerating the transformation of the primordial to primary follicle, this latter mainly due to an ER-dependent hypomethylation of genes involved in oocyte maturation; and 4) uterine morphology, uterine receptivity, and embryo implantation and therefore the establishment of pregnancy. Compromise uterine functions are mainly due to NO excess condition deregulation of P/HAND2 pathway in epithelial and stromal uterine cells.Importantly, disruption of folliculogenesis has been found to be a reversible process depending on the window of BPA exposure. Indeed, damages induced by BPA exposure in adulthood appear to be transient as confirmed by the restoration of physiological condition after the end of BPA exposure, whereas disruption of folliculogenesis persists into adulthood following postnatal exposure, indicating a disruption of ovarian programming in dependence of the window of BPA exposure.A growing body of evidence have been reported that exposure to BPA may contribute to the pathogenesis of female reproductive disorders, due to its ability to disturb endocrine activity in animals and humans. In particular, most of the evidence have been reported a role of BPA in the pathogenesis of endometriosis, a chronic inflammatory disease where cells similar to endometrial cells are found outside the uterine cavity, most commonly in the pelvis . FurtherEndometriosis is a chronic inflammatory disease, characterized by implantation and growth of endometrial tissue outside the uterine cavity . EndometFew experimental in vitro and ex-vivo studies have investigated the relationship between BPA exposure and the occurrence of endometriosis and it has been reported that BPA exposure increases the incidence of endometriosis-like lesions.. These studies are limited by the fact that they have not been carried out in experimental models of endometriotic cells, but they were performed in endometrial cells exposed to BPA in order to investigate if the exposure to BPA could induce the histological pattern of endometriosis.suggesting a hypothetical role of BPA in the pathogenesis of endometriosis , 42. The5type I collagen, and collagen type III alpha 1 chain (Col3a1), which is one of the fibrillar collagens whose proteins have a long, inflexible, triple-helical domain in BPA exposed mice. However, BPA exposure had the opposite effect on collagen degradation through matrix metalloproteinase (MMP), which are enzymes degrading extracellular matrix proteins. In particular, messenger expression levels of Mmp2, protein expression levels of MMP2 and MMP14 and activity of MMP2 were decreased in BPA exposed mice. This decrease in MMP expression and activity may give rise to decreased collagen degradation thus leading to an accumulation of collagen in the stromal and periglandular compartments of the endometrium. All these BPA related changes contribute to the onset of an endometriosis-like phenotype [To investigate the role of BPA in the pathogenesis of endometriosis, two female adult mouse strains (C57Bl/6 N and CD-1 mice) were exposed to low BPA doses or 17α-ethinyl estradiol as control, for 12–15 weeks . These thenotype .Only one experimental in vitro study investigated the effects of BPA on human endometrial cells; in particular, human endometrial stromal cells (ESCs), isolated from the uterus of healthy subjects during the proliferative phase of the menstrual cycle, were exposed to low and high BPA doses, and the effects on cell cycle progression and decidualization markers gene expression were assessed after 24 h, 48 h, 72 h of treatment . The resFew experimental in vivo studies have investigated the relationship between BPA exposure and the occurrence of endometriosis and have been reported that BPA exposure increases the incidence of endometriosis-like lesions , 114.In pelvic organs of BALB-C pregnant mice exposed to low BPA doses, an increase of endometriosis-like structures in the adipose tissue surrounding the genital organs has been found . FurtherSeveral observational studies have been carried out to investigate the possible association between BPA exposure and the occurrence of endometriosis in humans –122. The.PCOS is a multifactorial metabolic-endocrine disorder characterized by the existence of different phenotypes, affecting women of reproductive age . The dia6Only one experimental ex vivo study has investigated the relationship between BPA exposure and the occurrence of PCOS. The wealth of research on PCOS has been provided evidence that genetic, hormonal, metabolic and environmental factors may play a role in the development and clinical manifestations of this complex syndrome. A role of BPA in the pathogenesis of PCOS has been suggested by an experimental ex vivo study in which low BPA doses induced a reduction of cell viability of granulosa-lutein cells isolated from follicular fluid of PCOS women undergoing ART . In the Few experimental in vivo studies have investigated the relationship between BPA exposure and the occurrence of PCOS. BPA exposure has been described to influence the secretion of sex hormones affecting ovarian morphology and functions, particularly folliculogenesis with the genesis of PCOS-like abnormalities , 125. MoA hypothetical relationship between PCOS and BPA has drawn attention in recent years and has been suggested by observational studies, although the underlying mechanisms are poorly understood , 132–135The evidence summarized in the current review suggest that BPA might have a role in the pathogenesis of female infertility. BPA has been often detected in infertile women, thus leading to hypothesize that BPA could interfere with natural conception. BPA exposure has been also associated with negative outcomes of ART and in particular to a decreased E2 production during gonadotropin stimulation, to a decreased number of oocytes retrieved at the end of ovarian stimulation and implantation failure. Findings of studies conducted on animal models pointed out that the deleterious effect of BPA could vary depending on doses, administration route, window of exposure and animal models. In particular, studies on rodent models have demonstrated that the exposure to low BPA doses, but also the high BPA doses, during prenatal and perinatal period, therefore during embryo development, cause dysregulation in HPO axis function and morphological damages to HPO axis organs. Moreover, the BPA exposure in adulthood induces reversible damage in HPO axis function whereas prenatal and perinatal BPA exposure induces irreversible effects in female offsprings. Higher BPA levels have been detected in women with endometriosis and a hypothetical role of BPA in the pathogenesis of endometriosis has been confirmed by experimental animal studies reporting the occurrence of endometriosis-like lesions after BPA exposure. The onset of PCOS-like abnormalities has been found after BPA exposure and this might be induced through the BPA related impairment of the secretion of sex hormones affecting ovarian morphology and functions, particularly folliculogenesis. The several limits of the reported studies prevent to draw final conclusions. This could be due to the fact that most of the studies were retrospective and were not designed aiming to specifically investigate the association between BPA and female fertility. Further, they provide a proxy evaluation of BPA that could not be a parameter to assess the chronic exposure. Therefore, it will be mandatory to perform further studies to investigate the link between BPA and female fertility in order to make the population aware about the health risks related to BPA exposure.