A). We aimed to use non-invasive measurements to estimate the SA in extremely preterm infants.The main pathophysiologic characteristic of chronic respiratory disease following extremely premature birth is arrested alveolar growth, which translates to a smaller alveolar surface area  cm2. The adjusted SA was lower in the infants who required home oxygen [637.7 (323.5–837.5) cm2] compared to those who did not . In predicting the need for supplemental home oxygen, the adjusted SA had an area under the receiver operator characteristic curve of 0.815 (p = 0.017). An adjusted SA ≥688.6 cm2 had 86% sensitivity and 77% specificity in predicting the need for supplemental home oxygen.Thirty infants with a median (range) gestational age of 26.3 (22.9–27.9) weeks were studied. The median (range) adjusted SThe alveolar surface area can be estimated non-invasively in extremely preterm infants. The adjusted alveolar surface area has the potential to predict the subsequent need for discharge home on supplemental oxygen.We describe a novel biomarker of respiratory disease following extremely preterm birth.The adjusted alveolar surface area index was derived by non-invasive measurements of the ventilation/perfusion ratio and adjusted by concurrent measurements of volumetric capnography.The adjusted alveolar surface area was markedly reduced in extremely preterm infants studied at 7 days of life and could predict the need for discharge home on supplemental oxygen.This method could be used at the bedside to estimate the alveolar surface area and provide an index of the severity of lung disease, and assist in monitoring, clinical management and prognosis. Respiratory services are now providing care to the new patient population of ‘BPD adults’ who have severe persistent respiratory complications, associated abnormal neurodevelopment and impaired quality of life.5 Despite the clinical significance, BPD has been historically diagnosed as a binary condition,6 was then categorised to mild, moderate and severe7 and more recently classified into four categories of severity.8 This binary or categorical classification, however, fails to capture the granularity of the disease spectrum.9 There is, thus, a pressing clinical need for reliable biomarkers of BPD that could assist in quantifying severity, personalised monitoring, early decision making and family counselling.Extremely preterm birth, occurring before 28 completed weeks of gestation, is almost universally associated with respiratory disease,10 This translates to a smaller alveolar surface area (SA) which, in later life, can become a limiting factor, manifesting as decreased respiratory reserves, limited exercise capacity and functional limitations affecting everyday life.11 Although the SA would be an ideal biomarker to quantify and monitor BPD, it cannot be measured in newborn infants as the gold standard measurement method of stereological morphometry can only be performed post-mortem, or using functional tests such as the diffusing capacity for carbon monoxide which require volitional manoeuvres, reliably performed only by older children.The cardinal pathological process in BPD is the arrest of alveolar development which leads to a simplification of the lung structure with fewer and larger alveolar sacs.A in living individuals by functional morphometry, which is the non-invasive estimation of the SA based on paired measurements of the fraction of inspired oxygen and transcutaneous oxygen saturation based on Fick’s first law of diffusion12 and we validated the method using gold standard stereology in a model of extreme prematurity using non-human primates, preterm baboons.13We have recently described an alternative method to measure the SA in extremely preterm human infants. We also aimed to explore whether the SA was related to respiratory outcomes of extreme prematurity such as the need for supplemental home oxygen and hence had the potential to predict chronic respiratory morbidity.In this study, we aimed to use functional morphometry to measure the S14 Infants were ventilated by volume-targeted ventilation using the SLE 6000 neonatal ventilator  and were intubated with Cole’s shouldered endotracheal tubes, which minimise the expiratory leak.15 The study was approved by the Brighton and Sussex Research Ethics Committee, UK [REC 20/PR/0299]. Parents of eligible infants were approached and the infants were recruited after written informed consent. The study was registered on clinicaltrials.gov [NCT 04936477].Extremely preterm infants (born before 28 completed weeks of gestation) were recruited between 1 October 2020 and 31 January 2022 at the Neonatal Intensive Care Unit, King’s College Hospital NHS Foundation Trust, London, UK. Recruited infants were studied at 1 week after birth and the study continued for 6 months after the recruitment of the last infant to allow for the collection of the outcome data. The time point was selected as it has been demonstrated that positive pressure ventilation at 7 days after birth was 99% sensitive in predicting the later development of BPD.A can only be applied post-mortem,16 estimation of the SA was undertaken by functional morphometry. This method utilises non-invasive measurements of the ventilation-perfusion ratio (VA/Q) and Fick’s First law of diffusion, after adjusting for pulmonary perfusion, thickness of the respiratory membrane and the alveolar-arterial gradient (AaG).12 We have previously used traditional stereological morphometry to validate this method, using a non-human primate facility of preterm baboons.13 The predictive equation that was utilised to estimate the SA was:13A = surface area in cm2, and VA/Q = ventilation/perfusion ratio.As the gold standard method of stereological morphometry to measure the SA/Q ratios and the resulting effect on oxygenation can be measured non-invasively using the oxyhaemoglobin dissociation curve.18 All infants were nursed supine for consistency, as regional pulmonary blood flow and the delivery of ventilation to different zones of the lungs can vary depending on position.19 To calculate the VA/Q,20 three to five paired measurements of transcutaneous oxygen saturation (SpO2) and fraction of inspired oxygen (FiO2) were recorded by altering the provided FiO2 so that the SpO2 varied within a predefined range of 86–100% for 5–10 min. A Nellcor neonatal pulse oximetry probe  was used. A previously published computer software was used.22 The sigmoid oxyhaemoglobin dissociation curve depicts the partial pressure of oxygen (PIO2) in kPa on the x-axis and the oxygen saturation of haemoglobin (%) on the y-axis; with the shifting of the curve to the right equating to a lower VA/Q.20 The computer software superimposed a best-fit oxyhaemoglobin dissociation reference curve to individual infant data, thus giving a calculated value of VA/Q.23 The software used the fetal curve as a reference and incorporated the concurrent haemoglobin value (mg/dL) measured by blood gas analysis.Inequalities of ventilation and perfusion in non-homogenous lung disease can contribute low, normal or high V13 The ECHO was also performed to confirm that the direction of the ductal flow was left-to-right, as a predominantly right-to-left ductal flow would cause hypoxaemia and affect the calculation of the VA/Q. The AaG was also calculated to demonstrate that the regression equation was transferable to human data.24Targeted echocardiography (ECHO) was concurrently performed by a certified neonatal clinician utilising the Philips Affiniti 50G ultrasound system . The following parameters were measured: presence and direction of any intracardiac shunting, any patent ductus arteriosus (PDA) , pulmonary to systemic flow ratio (Qp/Qs) and left atrial (LA) to aortic ratio. All ECHO findings were reviewed by an external paediatric cardiology consultant for quality control. The ECHO measurements were performed to demonstrate that the pulmonary blood flow (Qp) and cardiac output (CO) were comparable to the parameters of the baboon model and confirm that the regression equation was transferable to human data.25 was incorporated into the ventilator circuit between the endotracheal tube and the ventilator circuit for 10 min to collect expired carbon dioxide (CO2) and volume data used for the construction of volumetric capnograms and the calculation of the physiological and alveolar dead space.26 The measurement of exhaled CO2 was only performed in the infants who were invasively ventilated at the time of the study. For consistency, only ventilator inflations as opposed to spontaneous infant breaths were analysed. The start of expiration was defined as the start of negative flow with the end of expiration corresponding to the end of negative flow. No time delay was observed between the CO2 and flow signals, with the maximal end-tidal CO2 aligning with the end of expiration as determined by the flow wave.An NM3 mainstream capnograph with a combined flow sensor  and a dead space of less than 1 mL2 was combined to calculate the mean CO2 of mixed expired air:emeanCO2 is the mean CO2 of the mixed expired air in mmHg, Vte is the expired tidal volume in mL, PCO2 is the partial pressure of CO2 in the blood in mmHg, Vendexp is the volume at the end of expiration and Vendinsp is the volume at the end of inspiration.27Flow was integrated over time to calculate the expiratory tidal volume for each expiration. The expiratory tidal volume with the corresponding CO28 The modified Bohr–Enghoff equation was chosen as it has been shown that it can provide dead space measurements regardless of the shape of the volumetric capnogram and the presence of an alveolar plateau.30The dead space was calculated from the Enghoff modification of the Bohr equation.Dphys) (mL) was calculated as follows:The physiological dead space (VDana) (mL) was calculated as follows:The anatomical dead space  (mL) was calculated as follows:The alveolar dead space (VALV) (mL) was calculated as follows:te is the expired tidal volume in mL, PaCO2 is the partial arterial pressure of CO2 in mmHg, PEtCO2 is the maximal end-tidal CO2 in mmHg.27Finally, the alveolar tidal volume .13 To give a more precise index of the functioning SA which is taking part in gas exchange, the alveolar dead space was deducted from the SA to derive an adjusted SA index  compared to infants with severe BPD who did not (VA/Q = 0.59),9 and using a standard deviation in VA/Q of 0.21,33 a sample of 30 infants was required to detect such a difference in VA/Q with 80% power at a significance level of 5%.Since only a small case series of stereological morphometry has been published reporting the SA in infants that were discharged on supplemental oxygen versus the ones that did not and in infants with severe BPD versus the ones with mild/moderate BPD were statistically significant. Spearman’s Rho correlation analysis was utilised to assess the strength of relationships between the SA and the gestational age, birth weight, birth weight z-score, duration of mechanical ventilation and duration of inpatient oxygen therapy. The relationship of the SA with the duration of inpatient supplemental oxygen was graphically depicted with linear regression analysis. The ability of the adjusted SA index to predict the need for supplemental home oxygen at discharge was assessed with receiver operating characteristic (ROC) curve analysis. Statistical analysis was performed using SPSS software version 27 .The data were tested for normality using the Shapiro–Wilk test and found to be non-normally distributed. Data were presented as median and range. The Mann–Whitney U test was performed to determine if differences in SThirty infants were recruited with a median (range) gestational age of 26.3 (22.9–27.9) weeks, a birth weight of 805 515–1165) g and were studied at a postnatal age of 7 (5–9) days. Twenty infants had a complete course of antenatal corticosteroids and all infants received at least one dose of surfactant. Twenty-six infants received invasive ventilation during the study. The targeted tidal volume was 6.0 (5.0–6.8) mL/kg  and infants on non-invasive support . The adjusted SA in the one infant with bidirectional flow through the PDA was 785.0 cm2 and in the infant with a right-to-left shunt was 444.2 cm2.The median (range) Hb at the time of the study was 12.5 (10.7–15.2) g/dL. The VTwo infants died prior to discharge from the neonatal intensive care unit. All infants surviving to 36 weeks postmenstrual age were diagnosed with BPD: two infants had mild, eight infants had moderate and the remaining 18 infants had severe BPD. The median duration of inpatient supplemental oxygen was 101 (40–171) days. Eighteen infants were discharged home from neonatal care requiring supplemental oxygen with an oxygen flow of 100 (10–500) mL/min.A was negatively correlated with the duration of mechanical ventilation  and the duration of inpatient supplemental oxygen , birth weight  or birth weight z-score . The SA did not differ significantly between infants who required supplemental home oxygen [983.8 (823.4–1208.4) cm2] and the ones who did not .The SA index had a negative correlation with the duration of supplemental oxygen as inpatient . There were no significant correlations of the adjusted SA index with gestational age , birth weight  or birth weight z-score . The adjusted SA index was not significantly different in infants with severe compared to mild or moderate BPD (p = 0.417), nor was it associated with the duration of invasive mechanical ventilation .The adjusted Sp = 0.515), birth weight (p = 0.428), birth weight z-score (p = 0.083), antenatal corticosteroid exposure (p = 0.839), postnatal corticosteroid therapy (p = 0.061), VA/Q (p = 0.111) or alveolar dead space (p = 0.804).Home oxygen requirement at discharge was not significantly associated with gestational age  cm2] compared to the ones who did not [799.1(444.2–902.7) cm2, p = 0.016) . An adjusted SA index greater or equal to 688.6 cm2 had 86% sensitivity and 77% specificity in predicting the need for supplemental home oxygen. The positive predictive value was 92% and the negative predictive value was 55%.The adjusted SA predicted the requirement for supplemental home oxygen on discharge from neonatal care with moderate sensitivity and specificity.We have demonstrated that the non-invasive method of functional morphometry can be used to estimate the alveolar surface area in extremely preterm infants. The derived biomarker of the adjusted SA/Q have been reported to have a moderate ability to predict disease severity in infants with BPD at 36 weeks postmenstrual age with an area under the curve of 0.83.34 In addition, VA/Q has been utilised to differentiate infants with severe BPD who require supplemental oxygen at 36 weeks PMA against those who do not—suggesting that VA/Q is a sensitive marker for describing the impairment in oxygenation associated with lung disease of prematurity.9 A longer duration of oxygen therapy during neonatal care in the current study was associated with a reduced alveolar surface area. This finding is in agreement with a study that used high-resolution computed tomography and reported that prolonged oxygen therapy during neonatal care was associated with long-term abnormalities in the lung parenchyma.35 In the current study, the VA/Q was further corrected by deducting the alveolar dead space to more accurately include areas of the gas-exchanging membrane which are both aerated and perfused and the derived new index was measured as early as at 1 week of postnatal life.Non-invasive measurements of V2 has been demonstrated in eight infants with BPD studied between 2 and 28 months of age compared to 1.7–5.8 m2 in term-born controls.36 Our study reports values which are lower than previously described; however, the infants included in our cohort were all born extremely preterm, including some born at 22 weeks of gestation, and their alveolar surface area was calculated at an earlier time point (7 days). Since it is known that the lung volume and total alveolar number increase with advancing maturity, the lower values of the alveolar surface area in our study are not an unexpected finding.37 It should also be noted that the alveolar surface area was calculated based on a regression model which used the results only from the left lung in the premature baboon model;13 the adjusted SA thus cannot be seen as a true measurement of the total alveolar surface area but rather as a sensitive approximating index.Previous studies have used post-mortem stereological morphometry to calculate the alveolar surface area in infants born prematurely but have included very few infants and with a wide range of postnatal ages. A smaller alveolar surface area at 0.3–1.0 m38 If our results were replicated in an independent cohort, the development of our index may provide useful grading information in this population of extremely preterm infants, and thus subsequently assist in identifying efficacious therapies, and better predict and prioritise those who require focused follow-up.39Based on the pathophysiology of BPD and the corresponding decrease in the alveolar surface area, our methodology for the estimation of the alveolar surface area during the neonatal period might be useful to describe and monitor the pulmonary morbidity in those born extremely prematurely and could hold the potential to guide prognosis and clinical management.40 The use of capnography to calculate dead space in premature ventilated infants has been recognised to have some technical limitations arising from high respiratory rates and small tidal volumes, which might cut short the expiration before the formation of an alveolar plateau.27 In our study, however, the CO2 sensor had a low apparatus dead space and its mainstream position in the respiratory circuit allowed for a faster response time even at high respiratory rates.In our study, we report very small alveolar tidal volumes (median 1.9 mL/kg), which might be inadequate for gas exchange according to traditional respiratory physiology. Recent studies have reported that effective carbon dioxide elimination might be possible with tidal volumes smaller that the dead space, possibly via spikes of fresh gas which penetrate through the dead space and create an interface of gas exchange in the conducting airways.A in our study. From a clinical perspective, ventilation was deemed adequate as it achieved the target range of transcutaneous oxygen saturation and arterial carbon dioxide, and volume-targeted ventilation might have helped to avoid extremes of under- or overventilation. If, however, lung inflation and the level of respiratory support are not optimised, this might affect the reliability of the calculations. In this sense, the effect of the level of respiratory support on the SA and the repeatability of the measurements over time should ideally be assessed in a separate future study.The adequacy of respiratory support could theoretically affect the aeration of the lungs and the subsequent calculations of the S13 This high level of agreement between the human and the baboon studies highlights that the utilised regression equation is indeed transferable to human data. The baboon equation was derived from a group of baboons with a median weight of 0.37 kg compared to 0.805 kg in our included infants, and this size discrepancy might have an impact on the transferability of the baboon equation to the human infants. As our index, however, is meant to be an estimate rather than a true measurement of the SA, the size difference would not have affected the ability of the index to discriminate the pathological state of a need for home oxygen from not needing home oxygen. We have also reported that the adjusted SA predicted the need for supplemental home oxygen with moderate accuracy and an area under the curve of 0.815. We have to consider, however, that this prediction happens very early in postnatal life (7 days) and discharge from neonatal care takes place at a much later age (the median age at discharge was 131 days in our cohort). The majority of this period is spent in intensive care with numerous possible further complications such as episodes of severe infection or life-threatening non-respiratory complications such as necrotising enterocolitis. Considering the above, we believe that the predictive ability of the adjusted SA was remarkably high. A future study could measure the adjusted SA before discharge or at 36 weeks postmenstrual age to predict later morbidity; this time point, however, would be more an assessment of severity rather than a prediction of neonatal outcomes.Our study has strengths and some limitations. We reported a median pulmonary perfusion of 350 mL/min (compared to 314 mL/min in the baboon paper) and a median AaG of 599 mmHg (compared to 591 mmHg in the baboon paper).A/Q, but does not strictly describe a decrease of the alveolar surface area. The relative contribution of this phenomenon, however, might not be particularly significant in this population, as the slope of the second phase of volumetric capnography , has been reported to be similar in healthy term and ventilated preterm infants.41Methodologically, we should also note that a certain degree of distorted lung architecture in BPD would cause diffusion limitation within the airway lumen rather than at the alveolar membrane level. This would be captured by a decrease in VA/Q, respiratory dead space and focused echocardiography26 were combined with a recently validated animal model.26 We should acknowledge that the current cohort included only infants born extremely prematurely and all infants developed BPD; hence, the adjusted SA index was unable to differentiate between those preterm infants who did and did not develop BPD. In our study, there was no association of the alveolar surface area (adjusted or unadjusted) with demographics at birth, such as gestational age and birth weight. This was an unexpected finding as lung growth would be expected to follow somatic growth and overall development. This lack of association might be explained by the narrow range of our included subjects . We selected this range, however, in order to focus on the ability of the biomarker to quantify clinical outcomes and to minimise the dilutional effect from the inclusion of larger and more mature infants in whom arrested alveolar growth would be less profound.We performed a comprehensive physiological assessment in a vulnerable cohort of infants. Previously described methods of calculating the VA/Q were, thus, not significantly affected by hypoxaemia resulting from cardiac right-to-left shunting. It is plausible that in the presence of significant pulmonary hypertension, some degree of atrial right-to-left shunting could have affected our calculations, but the diagnosis of pulmonary hypertension in premature infants would not be made before 28 days of life42 and our subjects were studied at 7 days. Finally, a significant proportion of our infants received medical or surgical treatment for PDA while recent literature has highlighted that expectant management is not inferior to PDA treatment with regard to the development of BPD.43 Furthermore, a multi-centre randomised trial of early treatment versus expectant management in extreme preterms,44 which was published very recently, also highlighted that expectant management was non-inferior to early treatment with respect to BPD.45The echocardiographic findings in our study included a left-to-right direction of ductal shunt in all but one infants and a bidirectional shunt in the remaining one. Our calculations of VIn conclusion, we have described a new, early biomarker of chronic respiratory disease in extreme prematurity, which was based on the pathophysiological mechanisms that explain gas exchange impairment in these infants. The adjusted alveolar surface area index predicted the need for the discharge of supplemental oxygen.


Achieving the weekly physical activity recommendations of at least 150-300 minutes of moderate-intensity or 75-150 minutes of vigorous-intensity aerobic exercise is important for reducing cardiometabolic risk, but evidence shows that most people struggle to meet these goals, particularly in the mid to long term.The Messages Improving Resting Heart Health (MIRTH) study aims to determine if (1) sending daily motivational messages through a research app is effective in improving motivation and in promoting adherence to physical activity recommendations in men and women with coronary heart disease randomized to a 12-month intensive lifestyle intervention, and (2) the time of the day when the message is delivered impacts compliance with exercise training.We will conduct a single-center, microrandomized trial. Participants will be randomized daily to either receive or not receive motivational messages over two 90-day periods at the beginning (phase 1: months 4-6) and at the end (phase 2: months 10-12) of the Lifestyle Vulnerable Plaque Study. Wrist-worn devices (Fitbit Inspire 2) and Bluetooth pairing with smartphones will be used to passively collect data for proximal  and distal  outcomes. Participants will be recruited from a large academic cardiology office practice  and the Royal Prince Alfred Hospital Departments of Cardiology and Radiology. All clinical investigations will be undertaken at the Charles Perkins Centre Royal Prince Alfred clinic. Individuals aged 18-80 years (n=58) with stable coronary heart disease who have low attenuation plaques based on a coronary computed tomography angiography within the past 3 months and have been randomized to an intensive lifestyle intervention program will be included in MIRTH.The Lifestyle Vulnerable Plaque Study was funded in 2020 and started enrolling participants in February 2022. Recruitment for MIRTH commenced in November 2022. As of September 2023, 2 participants were enrolled in the MIRTH study and provided baseline data.This MIRTH microrandomized trial will represent the single most detailed and integrated analysis of the effects of a comprehensive lifestyle intervention delivered through a customized mobile health app on smart devices on time-based motivational messaging for patients with coronary heart disease. This study will also help inform future studies optimizing for just-in-time adaptive interventions.Australian New Zealand Clinical Trials Registry ACTRN12622000731796; https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=382861DERR1-10.2196/46082 Physical activity has been widely recognized as an effective intervention for improving cardiometabolic health ,2. RegulThe emergence of new technologies and digital products such as wearable devices, mobile apps, and mobile health  platforms offers the potential for the delivery of customized educational and motivational material, which may increase compliance with physical activity interventions . SmartphPassive monitoring of health parameters can be accomplished using wearable devices, which allow for nonintrusive data collection . These tAn MRT is a cutting-edge trial design for mHealth research. A unique feature of an MRT is that an individual can be repeatedly randomized multiple times throughout the duration of the study ,15. The Microrandomized trials (MRTs) are unique clinical trial designs suitable for studying interventions using mobile health technologies. They randomize interventions at multiple time points, allowing for dynamic treatment investigation. Key features include fine-grained granularity, personalization, and sequential decision-making. MRTs provide additional information such as temporal dynamics, contextual effects, individual response patterns, and treatment adaptation. These trials offer insights into personalized and effective interventions in the mobile health context.The unique experimental design of an MRT allows for capturing data with the aim of developing sharp decision-making tools or rules for fine-tuning the sending of messages as notifications. The ability to randomize a participant multiple times in an MRT gives it its distinctive characteristic, which is not present in a traditional parallel-group randomized control trial, thereby allowing us to study:the effects of the intervention multiple times over a given time period;if the motivational messages sent as notifications have any near-term effect on engagement with the intervention components over the duration of the study;if this near-term effect changes over the two 90-day study periods; andif the effects of the motivational messages in phase 1 are similar to those in phase 2, thereby having a long-term effect.Through analyzing the data from above, researchers will be able to optimize just-in-time adaptive interventions more effectively for notification delivery through apps encouraging physical activity in patients with coronary heart disease.The main purpose of the Messages Improving Resting Heart Health (MIRTH) study is to determine if (1) sending daily customized motivational messages through a research app improves motivation and engagement with physical activity recommendations in men and women with coronary heart disease randomized to a 12-month intensive lifestyle intervention, and (2) the time of the day when the message is delivered impacts compliance with exercise training. This trial will be a crucial step in determining the potential of technology to support people in their efforts to maintain a physically active lifestyle, which can have a significant impact on the prevention and management of cardiometabolic abnormalities and atherosclerotic cardiovascular disease.The primary objective of this study is to evaluate the immediate effectiveness of motivational messages aimed at promoting physical activity in adults with stable atherosclerotic cardiovascular disease. The secondary objectives include assessing the impact of message delivery time  on the immediate effectiveness of the intervention and investigating its long-term effectiveness over a 12-month period by comparing results at the midpoint and end of the study.The primary hypothesis is (1) that participants will demonstrate an increase in steps taken within 180 minutes of receiving motivational messages compared to those who do not receive the messages. The secondary hypotheses are (2) that participants will exhibit an increase in physical activity duration and heart rate within 180 minutes of receiving motivational messages compared to those who do not receive the messages; (3) the proximal effect sizes of message are different at different times of a day ; and (4) that there will be no difference in long-term outcomes between phase 1 (months 4-6 of the Lifestyle Vulnerable Plaque Study [LIVEPLUS]) and phase 2 (months 10-12 of the LIVEPLUS) of the study.In the HeartSteps MRT study, research volunteers randomly received, through an app, contextually tailored physical activity notifications delivered up to 5 times per day at user-selected times . During The study will recruit adults aged 18-80 years with stable heart disease who have undergone a clinically indicated coronary computed tomography angiography scan at Royal Prince Alfred Hospital in Sydney, New South Wales, Australia, as previously described . Only inThe criteria listed in Inclusion criteria:Intervention group participants from the Lifestyle Vulnerable Plaque Study Adults who have access to and can competently use a smartphone (running iOS or Android)Presence of low-attenuation plaque on coronary computed tomography angiographyaged 18-80 years2BMI≥22.0 kg/mHave no contraindications for the Lifestyle Vulnerable Plaque StudyAble to provide full, informed consentExclusion criteria:History or clinical manifestation of any other significant metabolic, hematologic, pulmonary, cardiovascular, gastrointestinal, neurologic, immune, hepatic, renal, or urologic disorders, or cancer that, in the opinion of the investigator, would make the candidate ineligible for the studyNon–magnetic resonance imaging–compatible implanted devices or implants2Estimated glomerular filtration rate less than 30 mL/kg/1.73 mInability to exercise through a supine ergometerClaustrophobiaContraindications for adenosine: sinus node disease , second- or third-degree heart blocks, unstable angina, bronchospasm , heart transplant recipient, and history of seizure disorderContraindications for glyceryl trinitrate: known nitrate hypersensitivity, severe anemia, severe aortic or mitral stenosis, and hypotension defined as resting systolic blood pressure equal to 89 mm HgNot suitable for computerized tomography coronary angiography due to contraindicationsPsychiatric or behavioral problems Breastfeeding or pregnant women, or those intending to become pregnant before the scheduled end of the interventionConcurrent participation in any other interventional studyThe subsample for this study will be recruited from the intervention group of the LIVEPLUS . Participants will be recruited from Central Sydney Cardiology and the Departments of Cardiology and Radiology at the Royal Prince Alfred Hospital in Camperdown, New South Wales, Australia. Eligible patients will be introduced to the study by their cardiologist. The research team will conduct a 30-minute informal web-based (Zoom) call to illustrate the study, which will include a presentation and an opportunity for participants to ask questions.The collection of participants’ physical activity data will occur in a free-living setting, reflecting their daily life activities. The baseline assessment for enrollment into the MIRTH study will be conducted based on the baseline assessment previously described for the LIVEPLUS .In contrast to traditional randomized controlled trials, the MRT approach in this study enables each participant to serve as their own control. As a result, there is a single group of research participants who are randomly assigned on a daily basis to either the intervention group (receive message) or the control group (no message) in order to provide data.Participants in the study will receive messages as app notifications based on a random schedule. Each day during the intervention period, participants will be randomized to either receive or not receive the messages at a designated time point. Some of the messages included in the intervention have been previously used in the DIAMANTE study . AdditioExamples of MIRTH messages include the following:“Physical activity is a great way to feel better overall, improve your cardiometabolic health, and lift your mood. Aim for at least 30 minutes of walking each day at a medium pace to see the benefits.”“Going for a walk can improve your mood and clear your mind.”“Can you find 30 minutes in your day to go for a walk? That is less time than it takes to watch one episode of a TV show.”“Do not worry if you are not as physically active as others. Focus on you and your own goals. Everyone is different.”We will track participants’ activity using the Fitbit Inspire 2 wrist-worn device, which connects to a smartphone through Bluetooth and collect the data using our custom-built LivePulse research app, available only in Australia on the App Store  (Apple) The participant time line consists of 2 intervention periods lasting for 90 continuous days, spanning 4-6 months and 10-12 months . ThroughMotivational messages will be randomly delivered to participants allocated to receive the intervention for that day at 3 different time points: 6 AM, 11 AM, or 3 PM . In the The number of steps walked within 180 minutes after either the message or no-message intervention is sent randomly at each decision-making time point .The secondary outcomes are as follows: (1) the duration of time spent engaged in physical activity within 180 minutes after randomization at each decision-making time point ; (2) the change in heart rate within the next 180 minutes after receiving either the intervention or no intervention randomly ; (3) the average change values of resting heart rate within and across both phases 1 and 2 ; and (4) the total number of steps walked within and across both phases 1 and 2 periods .For the proximal analysis, which is based on an MRT design where each participant receives either control or intervention randomly at each selected decision time point over the study period, the proximal effect size of intervention (with-intervention vs without-intervention) is estimated. For the distal analysis, there is no control group; we only observe the total step count  difference between phases 1 and 2 for each participant.The effect sizes of the proximal outcome variables will be determined based on improvements in the number of steps (hypothesis 1), physical activity duration, and heart rate (hypothesis 2) observed within 180 minutes following the randomization of messages at each decision time point. To estimate these effect sizes, we will use the weighted and centered least-squares method as proposed by Boruvka et al . This apThe regression model used in this study includes several covariates: days in study (ranging from 1 to 90 days), message type (intervention messages versus control), and an interaction term between days and message type. The message variable will be converted into a binary variable (0 for control and 1 for intervention), and it will be centered using the corresponding randomization probabilities . Different trends over days, such as constant, linear, or quadratic, can be considered to assess the proximal effect of intervention messages in the regression models.6AM, (A-0.5)I11AM, and (A-0.5)I3PM in the regression model. Here, I6AM=1 indicates that the participant is randomized to the 6 AM time point, and 0 indicates otherwise.To estimate the proximal effect sizes of messages at different time points (hypothesis 3), we will replace (A-0.5) by (A-0.5)IOur goal is to examine the effect of messages at these specific time points , considering that messages are only received at 1 of the 3 time points. Therefore, assuming a constant trend, we can model the daily steps using the following equation:0 is the expected number of steps; and β1, β2, and β3 are the proximal effects of messages on steps at 6 AM, 11 AM, and 3 PM, respectively.Where Y=steps; βt test, assuming that there will be no significant difference in the long-term outcomes between phase 1 and phase 2 of the study (hypothesis 4).The effect size of the distal outcome variables will be assessed using a 2-tailed paired Sensitivity analyses will be conducted for hypotheses 1-3, considering the following factors:The intervention’s proximal effect size will be estimated by adjusting for additional baseline characteristics such as age, gender, and physical activity history. These characteristics can be included as covariates in the regression models.The regression model estimating the proximal effect of the intervention will be based on participants who have at least 45 (50%) out of 90 days of data available.In the case of positively skewed distributions of the primary outcome variables, the data will be transformed using logarithm or square root transformations. Before the transformations, a small decimal number  will be added to the zero values. This is done to address the issue of zero values in the data . Missingt test.Sample size calculations were conducted using Liao et al  as a refFor activity suggestions, the interventional messages aim to promote physical activity, that is, walking. The primary outcome measure for each participant at each decision-making time point is the step count recorded within the subsequent 180 minutes after receiving a message. With 1 decision-making time point per day, this step count serves as the key data point for analysis. Detailed data management procedures have been outlined in the study’s protocol to ensure proper handling, processing, and analysis of the collected data .Fitbit data will be collected during participant visits, specifically scheduled to align with the 6th and 12th months of the LIVEPLUS. During these visits, the data from Fitbit devices will be downloaded and collated for further analysis  Zone of the Sydney Local Health District . The original informed consent allows for secondary data analysis without additional consent. Before baseline testing, the research team will conduct a video call with potential participants to provide an overview of the study and address any questions or concerns. Any identifiable data obtained will remain confidential and encrypted on secure RPAH servers. Participants will be assigned a unique study ID number, and nonidentifiable data will be stored for at least 15 years. All deidentified data will be stored on university servers and only accessible by research staff through password-protected computers. The mobile app backs up data on both the smartphone and a web-based cloud server based in Sydney. While the app does not have a delete function, participants may request to have their data deleted from the cloud server. Access to mobile app data is restricted to the research team. There is no monetary compensation or amount for LIVEPLUS participants; however, participants who complete the 12-month period get to keep the Fitbit device used for physical activity monitoring.The LIVEPLUS trial received funding in 2020 and initiated participant enrollment in February 2022. Recruitment for the MIRTH trial began in November 2022. As of September 2023, two participants have been enrolled in the MIRTH study and provided baseline data.The MIRTH trial aims to conduct a comprehensive analysis of the impact of a customized mHealth app on smart devices, delivering a lifestyle intervention to patients with coronary heart disease. This intervention includes time-based motivational messaging, which can be used to develop a JITAI. The goal of this approach is to provide prompts and cues at the optimal time to enhance motivation and promote increased physical activity behavior among participants. Through this study, we aim to gain insights into the effectiveness of this intervention in improving motivation and achieving the desired objectives of the study.During the 90-day study duration, participants may receive randomized physical activity suggestions at up to 90 time points. Considering both phase 1 and phase 2 of the trial, there is a maximum potential for 180 time points in total (90 days for each phase). Since we anticipate an equal distribution of intervention and control messages among participants (with a randomization probability of 0.5), it is statistically unlikely for any participant to receive the intervention at all 180 time points. However, we can use the two 90-day study phases to examine improvements in distal outcomes. Our analysis will involve comparing resting heart rate and step counts from baseline (months 3 and 9) to the end of each phase. Furthermore, we will assess distal outcomes by comparing monthly changes within a study phase and between the 2 phases. Based on our hypothesis, we anticipate that participants who receive the intervention messages will demonstrate an increase in physical activity behavior aligned with the recommended guidelines. Additionally, we expect to observe improvements in resting heart rate and overall cardiometabolic health at the 12-month time point. This study will serve as a foundation for integrating an MRT design into routine clinical digital health prescriptions, especially for populations where lifestyle behavior change facilitated by digital health interventions can improve or potentially reverse disease states. The physical activity data collected during the baseline time points are more likely to reflect habitual physical activity behavior. In future studies, the incorporation of a reinforcement learning algorithm can consider additional factors such as user location, local weather conditions, and undisclosed calendar information to deliver a personalized and gamified JITAI.This study introduces an innovative strategy to address physical activity behavior in patients diagnosed with coronary heart disease. It examines the timing of messages within each individual and their impact on outcomes. The study implements a layered digital intervention with minimal participant burden. It spans a longer duration of 180 days, divided into two 90-day periods. Furthermore, to our knowledge, this is the first MRT study to use incremental recruitment specifically for this population.The findings of this study may have limited generalizability to the broader population with cardiovascular disease due to the specific characteristics of the study participants. It is important to note that this study is not designed as a double-blind study, as both participants and researchers are aware of the content and frequency of the messages being delivered. However, the lack of blinding does not pose a significant disadvantage since the outcomes are objectively assessed through Fitbit data, minimizing potential bias in outcome evaluation. It should be noted that this study does not incorporate reinforcement learning in the algorithm, which limits our ability to examine time-varying states for potential moderation effects, such as participant activity levels on the intervention day or the preceding day. Given that the intervention component is delivered through personal electronic devices such as smartphones and Fitbit, it is important to acknowledge the potential for technical issues that could impact the reliability of step count records. These challenges may include supporting participants in resolving technical issues with limited in-person assistance. It is worth noting that, in certain instances, Fitbit devices have been known to register hand movements as step counts, which could introduce some measurement inaccuracies . To addrThe outcome of this study will provide preliminary insights into the value and efficacy of motivational messages in promoting physical activity behavior among patients with coronary heart disease in a community setting. The results will provide important data on the effectiveness of delivering physical activity motivational messages through a research study app. If proven effective, this approach could be implemented to enhance personalized care strategies, including the use of digital health interventions, for patients with coronary heart disease.


Children with cerebral palsy (CP) show progressive loss of ambulatory function characterized by kinematic deviations at the hip, knee, and ankle. Functional electrical stimulation (FES) can lead to more typical lower limb kinematics during walking by eliciting appropriately timed muscle contractions. FES-assisted walking interventions have shown mixed to positive results in improving lower limb kinematics through immediate correction of gait during the application of FES, or long-term, persisting effects of non-FES-assisted gait improvements following multi-week FES-assisted gait training, at the absence of stimulation, i.e., neurotherapeutic effects. It is unknown, however, if children with CP will demonstrate a neurotherapeutic response following FES-assisted gait training because of the CP population's heterogeneity in gait deviations and responses to FES. Identifying the neurotherapeutic responders is, therefore, important to optimize the training interventions to those that have higher probability of benefiting from the intervention.The purpose of this case study was to investigate the relationship between immediate and neurotherapeutic effects of FES-assisted walking to identify responders to a FES-assisted gait training protocol.The primary outcome was Gait Deviation Index (GDI) and secondary outcome was root mean squared error (RMSE) of the lower extremity joint angles in the sagittal plane between participants with CP and a typically developing (TD) dataset. Potential indicators were defined as immediate improvements from baseline during FES-assisted walking followed by neurotherapeutic improvements at the end of training.Gait analysis of two adolescent female participants with spastic diplegia (Gross Motor Function Classification System level II and III) was conducted at the start and end of a 12-week FES-assisted treadmill training protocol. Participant 1 had scissoring crouch gait, while participant 2 had jump gait.The GDI showed both immediate (presence of FES) and neurotherapeutic (absence of FES after training period) improvements from baseline in our two participants. Joint angle RMSE showed mixed trends between immediate and neurotherapeutic changes from baseline. The GDI warrants investigation in a larger sample to determine if it can be used to identify responders to FES-assisted gait training. It is the most prevalent childhood neuromotor diagnosis with an estimate of 764,000 cases in United States . While tvia the afferent corticospinal pathways and conveys proprioceptive and somatosensory information  immediate correction in the presence of FES (immediate effect), (2) correction after a period of training in the presence of FES (training effect), and (3) persisting effect without FES, following a multi-session training protocol (neurotherapeutic effects). Note that FES is present when immediate effect is measured, and FES is not present when neurotherapeutic effect is measured. Additionally, neurotherapeutic effects are measured after a period of time following training to demonstrate if FES training can induce lasting corrections, unlike immediate effects which are measured when FES is first applied during walking before practice has taken place (not after first training session). When interpreting the reported results, one should differentiate between training and neurotherapeutic effects as many of the reported outcomes post-training are FES-assisted after a period of training. Whereas we are interested in the non-FES-assisted effects that persist after a period of training with FES.The positive immediate and training effects of FES-assisted walking interventions in children with CP include improved spatiotemporal gait parameters , 17, gaiMost available FES-assisted walking studies in the CP population are focused on the TA muscle; they strongly suggest immediate and training effects of FES on ankle angle improvement at initial contact and during swing. CP gait deficits, however, are complex and occur throughout the gait cycle; the direction of progress points toward the use of multi-channel FES devices to act across multiple joints . For exavia implementing a training intervention, and subject-specific stimulation protocols we may induce neurotherapeutic improvements in gait. We modified their intervention by (1) increasing the dosage of training, (2) devising a subject-specific stimulation protocol, and (3) increasing the number of muscle groups that the system was capable of stimulating. Because the response to FES-assisted walking is influenced by the variation of gait patterns . In an ideal scenario, the effect of FES-assisted gait training creates permanent improvements; individuals would not have to wear the FES system as an orthotic. Considering time commitment associated with training and the inconsistency in neurotherapeutic effects of FES between participants, it is desirable for the therapists to identify who may respond to a high dosage (multi-session) FES intervention and demonstrate immediate improvements. One intuitive indicator might be the immediate response to FES, i.e., the ability to minimize an individual's gait deviations when FES is applied. The purpose of this case study was to quantify the immediate and neurotherapeutic effects of FES-assisted gait training on lower limb kinematics in two individuals with CP, and thereby, investigate the relationship between immediate and neurotherapeutic effects. Here, we hypothesize that participants, who demonstrate immediate kinematic improvements from baseline towards more typical gait , quantified using metrics such as GDI score, will also have neurotherapeutic improvements towards more typical gait to a high dosage intervention delivered with a multi-channel FES system.2.2.1.A stimulation protocol was developed by three physical therapists (PTs) using videos of each participant's gait to determine the muscles to target  and the timing (gait phase) of stimulation to address the participant's gait deviations. Two PTs  were trained pediatric PTs with expertise in the CP population; the remaining PT had a master's degree in biomechanics and had 8 years of experience as a research PT working with children with CP. The PTs made separate stimulation protocol recommendations based on observations of subject's gait (video) and discussed them. When recommendations differed, a consensus stimulation strategy was defined through discussion by considering the best compromise to improve gait kinematics and walking speed. Stimulation amplitude and pulse duration were set for each muscle group and gait phase, individually, to address subject-specific gait deviations as prescribed by the PTs' evaluation and determined in a procedure called thresholding , 28; the2.2.Two female participants with spastic diplegia took part in our FES training program. Participant 1  had a scissoring crouch gait and used a rollator for ambulation. Scissoring crouch gait is characterized by excessive hip and knee flexion with excessive adduction and/or internal rotation at the hip, leading to the lower limbs crossing over in a scissor-like pattern . Her iniThe study was approved by the University of Delaware and Shriners Hospitals for Children, Philadelphia . Assent and consent were obtained from the participants and their parents, respectively, prior to the study.The worksheet provided by Schwartz et al.  was used2.3.Kinematic (sampling rate 128 Hz) and kinetic  data were collected, for the assessment, using instrumented motion capture  while patients walked at their initial self-selected walking speed on an instrumented treadmill . Kinematic data were averaged over all complete gait cycles (from 15 to 30 cycles) and were analyzed in Visual 3d . Data were normalized to a gait cycle (%) defined by consecutive heel strikes on the treadmill's force plates.Three time points were assessed in children with CP: (1) Participants walking kinematics, at the baseline session, S00 in 2.4.The GDI was the primary outcome measure and compared with the control dataset at baseline, Time1 and Time2 to examine if FES led to a shift towards the gait of typically developing children in each participant.GDI is a comprehensive index of gait pathology based on 15 different kinematic measures , to quantify the similarity of our participants' gait to the that of control individuals measured by the scaled distance of the kinematics measures from those of control subjects . An incr2.5.The secondary outcome measure was root mean square error (RMSE) between the participant's hip, knee, and ankle joint angles  demonstrated clinically relevant improvement at Time2, an increase of about 11 points from baseline. The improvement in CP02 (GMFCS level II) was smaller when compared with CP01, a total of 2.17 points. The right side GDI for CP01 demonstrated similar trends and levels of improvements to the left side; for CP02, although the trends from baseline were positive at both Time1 and Time2, the neurotherapeutic improvement was only 0.42 point at Time2.The 3.2.CP01: Neurotherapeutic improvements were observed in the RMSE of all three joints, i.e., RMSE decreased between baseline and Time2. This decreasing trend, however, was not reflected in the immediate changes of the hip angle between baseline and Time1; the hip RMSE increased 1.5° (from 18.4° to 19.9°) and 2.3° (from 20.6° to 22.9°) from the baseline at Time1 for the left and right sides, respectively. CP02: The immediate effect (baseline to Time1) and the neurotherapeutic effects (baseline to Time2) demonstrated similar decreasing or increasing trends in all of the joints except right knee and ankle. The increase of 4.5° in the right knee RMSE at Time1 was in the opposite direction of neurotherapeutic effect, a decrease of 6.3° from baseline in the knee RMS at Time2; for right ankle RMSE, a decrease of 1.6° from baseline at Time1 was in contrast to 0.4° of increase from baseline at Time2. All these RMSE changes and the joint angles at each time points are demonstrated in 3.3.CP01, the hip was almost unchanged compared to the baseline at Time 1 (green trace), however, it got more extended, typical, at Time2  at Time2. The knee was more flexed during pre-swing, i.e., less typical, at Time1; it returned to its baseline pattern, a more typical pattern, after the training (red trace). Ankle: except for the loading response, the ankle was less typical throughout the gait cycle at Time1; however, its pattern followed the TD pattern (black trace) for most of the gait cycle at Time2 and was substantially more dorsiflexed during the gait cycle.In 4.We explored the potential to use acute kinematic changes measured by RMSE and GDI score, during the first session of applying FES, as indicators of the neurotherapeutic effects following training with FES in two participants with CP. The hypotheses were that the direction of change in the GDI and RMSE were the same for the immediate effect (change between baseline and Time1) and neurotherapeutic effect (change between baseline and Time2). Thereby, one could use the immediate changes (baseline to Time1) to identify individuals who would have neurotherapeutic changes (baseline to Time2). The improvement in GDI scores of both sides at Time1, the immediate effect of FES (Stim), could indicate improvement at Time2 when compared to the baseline, i.e., the neurotherapeutic effect of FES (NoStim). The trend of changes in the joint angles RMSE, on the other hand, was inconsistent. Therefore, GDI was a potential indicator of the neurotherapeutic effect of FES, using its immediate effect. Note that, our hypothesis was regardless of the magnitude of immediate and neurotherapeutic changes; ideally the magnitude of neurotherapeutic improvements would be larger than immediate improvements meaning the trend of improvement would be ascending from baseline to Time1 and continues with further improvements from Time1 to Time2, i.e., basline < Time1 < Time2.GDI has previously been reported to be a reliable measure and was used in many studies , 36–38 fIt is worth noting that the magnitude of the GDI changes might be different from subject to subject, potentially depending on the level of mobility. As can be seen, CP01 (GMFCS III) had more substantial and clinically relevant changes toward TD, more than one standard deviation (11 points). This might be because of lower CP01's GDI score at the baseline 52.14), and thus more capacity for improvement, when compared with that of CP02 (65.84), i.e., CP01 was almost 5 SD away from TD in comparison to 3.5 SD for CP02. Similar discrepancies in the magnitude of improvements were reported previously for these two subjects . These r, and thuWhen joint-by-joint RMSE was used as the indicator, the immediate effects were not necessarily in the same direction as neurotherapeutic effects; therefore, our hypothesis was rejected for this measure. For example, although the knee and ankle RMSEs improved (decreased) at Time2 for more affected side, in both subjects, but they demonstrated detrimental immediate effect at Time1, i.e., RMSE change away from TD and thereby, RMSE increase between baseline and Time1 for CP02's right ankle and knee . Thus, oThe visual inspection of the joint angles in the sagittal plane  further The main limitation of this study was the number of participants in our training protocol. More subjects are needed to find a reliable indicator for identifying the responders for our FES-assisted gait training protocol. Additional comprehensive gait metrics, such as Movement Deviation Profile  and Gait5.As the main objective of this study, we investigated if the acute kinematic changes of FES application during walking can be used as a potential indicator of changes following long-term FES-assisted gait training, and thereby, to identify the responders. To this end, two kinematic-based measures were evaluated. The GDI score changed in the same direction between baseline vs. Time1 and baseline vs. Time2 for both participants; therefore, the direction of changes at Time1 may be an indication of the direction of changes after a period of FES-assisted gait training. The immediate changes from baseline in RMSE did not follow the same trend post-training for all joint angles. Additionally, predicting the neurotherapeutic effects by visual inspection of the immediate changes in joint angles can be complicated, as expected, without a clear indication if FES-assisted gait training is helpful. Regardless, with continued training, FES assistance appears to be beneficial in reducing gait deviations, as indicated by improvements made in the GDI. Therefore, an inclusive measure, GDI, which includes the kinematics from all three lower extremity joints, may be a candidate measure for indicating the neurotherapeutic effect of FES using its immediate effect; more participants, however, are required for any conclusion.


This cohort study investigates the association of increased bronchopulmonary dysplasia risk from high-dose docosahexaenoic acid with decreased benefits to IQ among children born preterm. Is the increased risk of bronchopulmonary dysplasia (BPD) from high-dose docosahexaenoic acid (DHA) supplementation in the neonatal period associated with changes in benefits to IQ?In this cohort study involving 656 children born at less than 29 weeks’ gestation, the increased risk of BPD from neonatal DHA supplementation was not associated with a change in the 3.45-point benefit in IQ at 5 years’ corrected age.This finding suggests that if clinicians supplement children born preterm with high-dose DHA, resulting increases in BPD risk would not be associated with meaningful reductions in the benefit to IQ. High-dose omega-3 docosahexaenoic acid (DHA) supplementation of children born at less than 29 weeks’ gestation has been shown to improve IQ despite increasing the risk of bronchopulmonary dysplasia (BPD). Given that BPD is associated with poorer cognitive outcomes, it is unclear whether the increased risk of BPD with DHA supplementation is associated with decreased benefit to IQ.To investigate whether the increased risk of BPD with DHA supplementation was associated with diminished IQ benefit.This cohort study used data collected from a multicenter, blinded, randomized controlled trial of DHA supplementation in children born at less than 29 weeks’ gestation. Participants were recruited from 2012 to 2015 and followed up until 5 years’ corrected age. Data were analyzed from November 2022 to February 2023.Enteral DHA emulsion  or a control emulsion from the first 3 days of enteral feeds until 36 weeks’ postmenstrual age or discharge home.Wechsler Preschool and Primary Scale of Intelligence, 4th Edition; children from the 5 highest-recruiting Australian hospitals were assessed. The total effect of DHA supplementation on IQ was divided into direct and indirect effects using mediation analysis, with BPD as the presumed mediating variable.Physiological BPD was assessed at 36 weeks’ postmenstrual age. IQ was assessed at 5 years’ corrected age using the Among 656 surviving children from hospitals involved in IQ follow-up , there were 323 children with DHA supplementation and 333 children in the control group. Mean IQ was 3.45 points  higher in the DHA group than the control group, despite an increase in the risk of BPD (160 children [49.7%] vs 143 children [42.8%] with BPD). The indirect effect of DHA on IQ via BPD was not statistically significant , with most of the effect of DHA on IQ occurring independently of BPD .This study found that associations of DHA with BPD and IQ were largely independent. This finding suggests that if clinicians supplement children born preterm with high-dose DHA, any resulting increase in BPD risk would not be associated with meaningful reductions in the IQ benefit. Contrary to expectations, in our N-3 Fatty Acids for Improvement in Respiratory Outcomes (N3RO) randomized trial,5 we found that DHA supplementation of children born at less than 29 weeks’ gestation increased the risk of BPD from 43.9% to 49.1%. Although BPD has been found to be associated with poorer cognitive outcomes,9 our assessment at 5 years’ corrected age demonstrated a 3.45-point increase in mean full-scale IQ with DHA supplementation.10 To our knowledge, few other studies have tested the association of in utero DHA dose with the neurodevelopment of infants born earlier than 29 weeks. Those study results were inconsistent possibly because they conducted assessments at younger ages, for which measurements less reliably predict IQ.12Children born at less than 29 weeks’ gestation are at high risk of bronchopulmonary dysplasia (BPD) and have an IQ a mean 12 points lower than children born at term.1Findings from the N3RO trial may create a dilemma for clinicians in the neonatal unit concerning how best to balance perceived risks and benefits associated with high-dose DHA supplementation. BPD occurs among approximately half of children born at less than 29 weeks’ gestation and is a major challenge for clinical practice. However, high-dose DHA supplementation provides one of the few treatments in the neonatal unit found to improve IQ and potentially minimize the longer-term burden facing these children. Such a benefit is particularly compelling given that cognitive outcomes of children born at less than 29 weeks’ gestation have had little improvement over the last 30 years.In this cohort study, we conducted an exploratory mediation analysis of results from the N3RO trial with the aim of untangling the opposing outcomes associated with DHA supplementation for BPD and IQ in children born at less than 29 weeks’ gestation. In particular, we sought to quantify the indirect effect the DHA-related increase in BPD risk had on the IQ benefit and the direct effect of DHA supplementation on IQ independent of earlier effects on BPD risk.16The original N3RO trial and its 5-year follow-up were approved by the Human Research Ethics Committee at each participating hospital . Written informed consent was obtained from guardians prior to randomization and before the appointment at 5 years in the N3RO trial. This cohort study’s mediation analysis was also approved by the WCHN Human Research Ethics Committee as the lead hospital with a waiver of consent based on a public interest case . This study followed the A Guideline for Reporting Mediation Analyses (AGReMA) statement for reporting mediation analyses of randomized trials and observational studies.14 Briefly, 1273 children born at less than 29 weeks’ gestation were randomized in a 1:1 ratio to receive an enteral DHA emulsion (60 mg/kg/d) or a control emulsion without DHA from the first 3 days of enteral feeds until 36 weeks’ postmenstrual age or discharge home, whichever occurred first. Randomization was stratified by gestational age at birth (<27 weeks and 27 to <29 weeks), sex, and hospital , with children from a multiple birth randomized individually. Children were assessed for physiological BPD at 36 weeks’ postmenstrual age , determined by requirements for supplemental oxygen or respiratory support with an assessment of oxygen saturation.15 All randomized and surviving children from the 5 highest-recruiting hospitals in Australia (656 children) were then invited to undergo an assessment using the Wechsler Preschool and Primary Scale of Intelligence, 4th Edition at 5 years’ corrected age to determine full-scale IQ (the primary outcome of the follow-up phase); 5 hospitals participated in this phase of the trial based on statistical power considerations. Recruitment into the N3RO trial was done from June 2012 to September 2015, with 5-year IQ assessments performed between August 2018 and May 2021.This investigation used data collected in the N3RO trial, a multicenter, blinded, parallel-group randomized clinical trial designed to evaluate the effects of DHA supplementation on BPD and IQ in children born extremely preterm. The methods of the trial have been detailed elsewhere.10 into interventional direct and indirect effects,17 with BPD as the presumed mediating variable. The interventional direct effect describes the association between DHA supplementation and IQ that is independent of earlier effects on BPD. Equivalently, it is the estimated benefit to IQ associated with DHA supplementation if hypothetically we could intervene to eliminate the excess risk of BPD with DHA supplementation . The interventional indirect effect describes the amount of change in the IQ benefit that was associated with the DHA-related effect on BPD, or equivalently, the additional benefit to IQ associated with intervening to eliminate the excess risk of BPD under DHA supplementation . In addition to dividing the total effect of DHA supplementation on IQ into these direct and indirect effects, we also sought to describe the association between BPD and IQ in preliminary analyses.In this analysis, we divide the previously reported total effect of DHA supplementation on IQ19 Hospital was included as an indicator of clinical care and demographic and medical characteristics of the children, with the risk of BPD and mean IQ observed to vary substantially across the 5 hospitals involved in the follow-up phase of the N3RO trial. Finally, sex was chosen because males born extremely preterm have been found to have a higher risk of BPD20 and more pronounced cognitive impairment23 than females. Other potential confounders  were considered but were universally used  or not associated with BPD and IQ in the N3RO data set. Included confounders were measured at baseline and used to stratify the randomization in the original study and so were strictly balanced between DHA and control groups. Primary analyses were performed under an assumption of no residual confounding, with the robustness of findings to this assumption explored in sensitivity analyses.The conceptual model guiding the mediation analysis is shown in Owing to the blinded nature of the original trial, proposed confounders in the causal diagram and BPD at 36 weeks’ postmenstrual age were ascertained in a fully blinded manner. The trial statistical team (T.R.S. and J.M.B.) and 9 parents representing 11 children (5 children in the DHA group and 6 children in the control group) were unblinded after the analysis of BPD data. Except for these individuals, all participants, study personnel, and outcome assessors remained blinded to group allocation through completion of the IQ assessments at 5 years’ corrected age.P < .05 considered to be statistically significant. Data were analyzed from November 2022 to February 2023.Analyses included all randomized and surviving children from 5 Australian hospitals involved in the 5-year follow-up phase of the trial (656 children). Statistical calculations were performed using Stata statistical software version 17 (StataCorp), with a 2-tailed 10 and the association between BPD and IQ under DHA supplementation. Consistent with earlier analyses, the total effect of DHA supplementation on IQ was estimated via linear regression, with adjustment for stratification variables24 and using generalized estimating equations to account for multiple births. An independence working correlation structure was used to produce a treatment effect estimate with a child-level interpretation.25 The association between BPD and IQ under DHA supplementation was estimated using linear regression with adjustment for confounding variables and allowing for 2-way interactions between confounders and BPD for flexibility. However, a BPD by hospital interaction term was not included due to sample size constraints. The mean change in IQ associated with BPD was estimated from the model using g computation.Preliminary analyses were undertaken to describe the total effect of DHA supplementation on IQ, as reported previously,g computation approach to divide the total effect of DHA supplementation on IQ into interventional direct and indirect effects.26 The approach involved simulating BPD values for participants in the DHA group assuming that their risk of BPD was lowered to match that of the control group (1000 Monte Carlo draws each), then simulating IQ values for these participants using updated BPD values. The mean simulated IQ was used to derive direct and indirect effects, with CIs for estimates obtained using bootstrapping . The approach required specification of a regression model for BPD and another for IQ, with both models informed by the directed acyclic graph in For the mediation analysis, we used a simulation-based 27 with linear and logistic models used to impute missing IQ and BPD values, respectively. A rich set of auxiliary variables was incorporated into models for IQ and BPD to minimize the potential for bias under a missing-at-random assumption. Given that children from a multiple birth were randomized individually, all observations were considered independent in the imputation model.28 A total of 100 complete data sets were generated, with results combined across data sets using Rubin rules. Additional details on imputation methods (including auxiliary variables) are provided in the eAppendix in A complicating factor for analysis was the extent of missing data for IQ. As the probability of missing data depended on observed characteristics in the data set, multiple imputation implemented under a missing-at-random assumption was used to address missing data. Imputation was performed separately by randomization group using chained equations,29 Small for gestational age is a known risk factor associated with BPD,19 yet its association with IQ is less compelling.1 Additionally, we were wary of estimation issues with sex and gestational age (measures used in its derivation) that were already included as confounders. Lastly, we performed a sensitivity analysis with BPD defined according to clinical criteria  instead of the physiological definition used in the primary analysis.The robustness of findings to assumptions about the missing data, underlying causal model, and approach to defining BPD was investigated in sensitivity analyses. For missing data, we considered missing not at random mechanisms via pattern mixture models, with IQ scores assumed to be 3 points lower or 3 points higher in children with missing data compared with children who had observed data. This difference was viewed as a very large departure from the 0-point difference expected under a missing-at-random assumption. We did not undertake sensitivity analyses for the imputation of BPD given that this measure had a low level of missing data. For the assumed causal model, we considered a sensitivity analysis with small for gestational age included as an additional confounder of the BPD-IQ association. This confounder was defined as a birthweight less than the 10th percentile given sex and gestational age.P < .001), or 58.7% higher in the DHA group than the control group. In 656 children included in the mediation analysis, the risk of BPD was increased by 6.9 percentage points in those receiving DHA compared with those in the control group (increase from 143 children in the control group [42.8%] to 160 children in the DHA group [49.7%] based on imputed data). This was a similar increase to that observed in all children in the original phase of the N3RO trial (increase from 43.9% to 49.1%).Of 656 children involved in this analysis , 631 children (96.2%) had a physiological BPD assessment and 480 children (73.2%) had an IQ score available . There wMean IQ scores were higher among children in the DHA group and lower in children with a diagnosis of BPD . Childre10 The separation of this total effect of DHA supplementation into direct and indirect effects via the mediation analysis is summarized in As previously reported, mean IQ at 5 years’ corrected age improved from 91.91 points in the control group to 95.36 points in DHA group .10 In this cohort study’s mediation analysis, we found that the increase in BPD risk from neonatal DHA supplementation was not associated with a material decrease in its benefit to IQ. More formally, the nonsignificant interventional indirect effect estimate suggests that if all children received DHA supplementation, a hypothetical intervention to lower the risk of BPD to that seen under control conditions may be associated with little additional improvements to IQ.We previously found that providing the in utero DHA requirement to children born at less than 29 weeks’ gestation was associated with improved IQ at 5 years’ corrected age, despite an increased risk of BPD at 36 weeks’ postmenstrual age.30 On the other hand, the postulated mechanisms of action for DHA on BPD include the reduction of oxidative stress and inflammation underlying the pathogenesis of BPD.31 However intervention trials have not supported the association of high-dose DHA with a beneficial BPD outcome in children born very preterm, with a 2023 meta-analysis31 finding no overall benefit and a moderate increase in BPD risk in findings from trials with a standardized definition of BPD as was used in the N3RO trial. While more work is needed to understand the differential mechanisms by which DHA may be associated negatively with BPD and positively with IQ, our analysis suggests that if clinicians decide to supplement infants born very preterm with high-dose DHA, any resulting increase in BPD risk may not be associated with meaningful reductions in beneficial outcomes for IQ.The limited evidence for an indirect effect on IQ via BPD suggests that the mechanisms by which DHA supplementation was associated with improved IQ may differ from those for BPD. While the exact biological mechanisms by which DHA may be associated with IQ are not known, a substantial body of work indicates that DHA has structural and functional roles in neural tissues, including in synaptogenesis and neurite growth, that may contribute to cognitive benefits.This cohort study’s mediation analysis was based on data from a large, rigorously designed, blinded trial with high levels of compliance and standardized measures of BPD and IQ. However, our study has several limitations. The original trial had higher than expected rates of attrition by 5 years’ corrected age owing to the COVID-19 pandemic; however, reassuringly, the magnitude of the indirect effect of DHA supplementation via BPD appeared robust to specific assumptions made about missing data. The accuracy of indirect and direct effect estimates relied on appropriate specification of the underlying causal model linking DHA supplementation, BPD and IQ together. Given the randomized design of the original trial, our concern was restricted to confounders of the BPD-IQ association, and while effort was made to incorporate key confounders, it is not possible to rule out the effects of residual confounding. Additionally, it should be noted that this analysis did not address the trade-off between an increased risk of BPD and improved IQ associated with high-dose DHA supplementation. Although we did not observe adverse health signals, including for respiratory-related hospitalizations, from parent reports at the 5-year assessment, further investigation is needed to fully assess the association of the modest increase in BPD risk from DHA with long-term pulmonary function.This cohort study found that the increased risk of BPD from neonatal DHA supplementation in children born at less than 29 weeks’ gestation was not associated with a decrease in the positive effect of DHA on IQ. This finding suggests that clinicians may be able to supplement children born preterm with high-dose DHA without meaningful reductions in IQ benefit.