The outbreak of the COVID-19 epidemic intensified the volatility of commodity markets , which created a significant negative impact on the volatility spillovers among these markets. It may also have triggered a new volatility risk contagion. In this paper, we introduce the DCC-GARCH-CONNECTEDNESS approach to explore the volatility spillover level and multi-level spillover structure characteristics among the commodity markets before and during the COVID-19 epidemic in order to clarify the new volatility risk contagion patterns across the markets. The results implied several conclusions. (i) The COVID-19 epidemic has significantly improved the total volatility spillover level of the energy and precious metals markets and has enhanced the risk connectivity among the markets. (ii) The COVID-19 epidemic has amplified the volatility of the crude oil market, making it the main volatility spillover market, namely the source of volatility risk contagion. (iii) The COVID-19 epidemic outbreak enhanced the external risk absorption capacity of the natural gas and silver markets, and the absorption level of the external volatility spillover improved significantly. Furthermore, the risk absorption capacity of the gold market weakened, while the gold market has remained the endpoint of external volatility risk during the epidemic and has acted as a risk stabilizer. (iv) The volatility spillover among markets has clear time-varying characteristics and a positive connectedness with the severity of the COVID-19 epidemic. As the severity of the COVID-19 epidemic increases, the volatility risk connectivity among the markets rapidly increases. The COVID-19 epidemic has spread rapidly around the world since the beginning of 2020, affecting the global economy and deeply and dramatically impacting global commodity markets. As the benchmark of global commodities, the energy and precious metals markets have suffered a particularly prominent loss.The spread of COVID-19 has caused the international energy market, which was involved in the U.S.-Iraq conflict, to experience a new round of disturbances. These have mainly presented through a sharp decline in industrial and commercial energy demand due to the COVID-19 outbreak. The isolation measures for continued epidemic spread have further reduced fuel demand in the transportation industry. At the same time, the supply-side producers have not taken collective action to restrict production and ensure price. COVID-19 has created a both-way instability between energy supply and demand, and its consequences have been particularly prevalent in the international crude oil and gas markets. As a commodity with dual economic and political attributes, the economic and strategic significance of crude oil is undeniable. In statistics and empirical studies, international crude oil prices have also been confirmed to closely relate to the global economy , the indCOVID-19 has directly impacted the supply and demand of the global capital market, and its igniting of investor panic should be considered. COVID-19 has influenced the precious metals market, characterized by the dual attributes of goods and finance, to attract a large amount of capital. This is striking when compared to the decline in global risk asset prices. As traditional hedging commodities, gold and silver are fully representative of the panic-driven turmoil in precious metals markets. As a recognized hard currency in precious metals, gold is a reserve asset during periods of economic stability and a hedging tool during periods of economic anomalies. In other words, it is sensitive to the impact of external emergencies . During This paper applies a DCC-GARCH-CONNECTEDNESS approach employed by Gabauer  and KariThis study makes several contributions to the existing literature. Given the complexity of the COVID-19 epidemic and its impact, we applied a DCC-GARCH-CONNECTEDNESS approach to describe the time-varying volatility spillover between the energy and precious metals markets from a dynamic perspective. The DCC-GARCH-CONNECTEDNESS approach combines the dynamic conditional correlation-generalized autoregressive conditional heteroscedasticity (DCC-GARCH) model, the volatility impulse response functions (VIRF), and the connectedness approach of Diebold and Yilmaz . FurtherThe remainder of this paper is organized as follows. Literature review reviews the literature pertaining to the shock of the COVID-19 epidemic on commodity markets. Methodology and data introduces the methodology applied in this paper and describes the data. Empirical results and disscussion presents the empirical results, and conclusion concludes the paper.Research into COVID-19's impact on global markets has burgeoned. Regardless of the theoretical or empirical point of view taken, most scholars' results have shown that the COVID-19 epidemic will increase volatility in global markets and strengthen the risk spillover effect among markets , 13. WhiResearch has made some progress in assessing COVID-19's impact on the commodity market. However, it has an increasingly sensitive position in the international economy to connect the commodity and financial markets. Consequently, the academic community's focus on the commodity market remains insufficient, especially compared to the traditional capital market. The existing literature largely focuses on the link between the stock and commodity markets under the COVID-19 epidemic or only the single commodity market. Studies have paid less attention to the dynamic relationships among different markets within the commodity market. However, as an energy-intensive industry, the precious metals market is sensitive to volatility in the energy market . The epiIn terms of research methods, existing studies on the risk spillover between financial markets under the COVID-19 epidemic have largely applied the VAR family model, mainly including TVPVAR , 30, PVAIn summary, the research methods used to depict financial market volatility caused by external shocks have been correspondingly solid. Based on the classical VAR and GARCH models, scholars have expanded the models according to their research directions, using the Diebold and Yilmaz , 31, 32 Based on the above discussion, this paper aims to solve the following problems: (1) What is the dynamic impact of the COVID-19 epidemic on the energy and precious metals markets? (2) What is the level and status of risk spillovers among the energy and precious metals markets under the impact of the COVID-19 epidemic? (3) What dynamic volatility spillover connections and risk transfer paths between energy and precious metals markets were caused by the COVID-19 epidemic? This paper selects crude oil, natural gas, gold, and silver as the representative industries of the two markets and constructs a DCC-GARCH-CONNECTEDNESS approach to examine the volatility spillover of their price returns and to estimate the impact of the COVID-19 epidemic. Furthermore, we analyze the changes in directional dynamic connectedness within commodity markets. Our research expands the existing literature, enriches research on the volatility spillover characteristics of the commodity market under the spread of the COVID-19, and accounts for the deficiency of research perspectives and methods.The time-varying volatility spillover indexes were constructed using the following three aspects of the DCC-GARCH-CONNECTEDNESS approach: (1) time-varying total connectedness, (2) time-varying directional connectedness, and (3) time-varying net pairwise directional connectedness. The specific construction process of various volatility spillover indexes was as follows:First, the DCC-GARCH model was constructed. The two-step DCC-GARCH model employed by Engle  was utilFt−1 represents all available information up to t−1. yt, μt, ϵt, and ut are N × 1-dimensional vectors that represent the analyzed time series, conditional mean, errors, and standardized errors, respectively. Moreover, Rt, and N × N-dimensional matrices that represented the dynamic conditional correlations, time-varying conditional variance-covariance matrices, and time-varying conditional variances, respectively.where Dtwas constructed using the GARCH model constructed by Bollerslev  and b(β) are non-negative shock and persistency parameters that satisfy the a+b < 1(α+β ≤ 1) condition. If condition a+b < 1 is fulfilled, Qt and Rt will vary over time. Alternatively, the model will converge to the CCC-GARCH model, where Rt does not change with time.where Subsequently, we calculated the volatility impulse response functions (VIRF), which has the same meaning as the generalized impulse response functions (GIRFs) introduced by Koop et al.  and Pesaj, t represents the selection vector with one on the jth position and zero otherwise.where δIt is worth noting that forecasting the conditional variance-covariances utilizing the DCC-GARCH model is the heart version of the VIRF and can be accomplished iteratively in the three steps.Dt+h|Ft). The specific process was as follows:First, GARCH  was used to predict conditional volatility (E(Dt+h|Ft) could be predicted:Second, where+h-1|Ft) , which hThird, the conditional variance-covariances could be expressed asi. This was calculated as follows:Finally, the generalized forecast error variance decomposition (GFEVD), which can be interpreted as the variance share one market has on others, was calculated based on the VIRF. These shares were then normalized so that each row summed up to one, meaning that all markets together explained 100% of the forecast error variance of market where, Thus, the total connectedness index (TCI) could be constructed asi to market j and the mean level  and (17) and defined the net pairwise volatility spillover among the energy and precious metals markets as formulas (16) minus formulas (17). This was calculated asi (FROMit volatility spillover). The expressions are as follows:Subsequently, we constructed the time-varying directional connectedness index and calculated the volatility spillover from market to all other markets ( volatility spillover) and the volatility spillover index from all other markets to market Subtracting formulas (19) and formulas (20) from each other led to the net total directional connectedness:NETit is positive (negative), it means that market is a net transmitter (receiver) of volatility risk.If investment.com (https://cn.investing.com/indices/).In this paper, we represent precious metals markets through the gold and silver markets and represent energy markets through the crude oil and natural gas markets. Four active foreign exchange trading funds (ETFS) were selected to represent the gold, silver, crude oil, and natural gas markets; in other words, we recorded the closing price of the fund as the asset price and then used the logarithmic difference of the fund's closing price to represent the compound return of this kind of asset. Doing so reflected the market performance, providing real and reasonable data information for the fluctuation correlation analysis among commodity markets. The specific selection of funds is shown in To clarify COVID-19's impact on the volatility spillover connectedness between commodity markets—in other words, the market risk contagion structure—the sample intervals selected in this paper included the periods before and during the COVID-19 epidemic. In addition, considering the availability of sample data and the comparability of the estimated results of the sub-samples, the sub-samples selected in this paper were drawn between October 18, 2017 and January 22, 2020 and between January 23, 2020 to March 18, 2022, respectively. We used the start date of the COVID-19 epidemic data published by Johns Hopkins University as the virus's outbreak date. The sample data was the daily frequency information. The two sample intervals contained 568 trading days, and the full sample had a total of 4,544 daily frequency data. The descriptive statistics of each variable are shown in In addition, the sample data used in this paper were time series data, and the stability test of each sequence data was an important prerequisite to ensure the accuracy and rationality of the estimation results. Consequently, the ADF unit root test was performed on the price compound return sequences of energy and precious metals before and during the COVID-19 epidemic. Moreover, to ensure the robustness of the test results, a PP test was also applied to verify the results of the ADF unit root test, as shown in Based on the VIRF and GFEVD, this paper calculated the volatility spillover connectedness among the energy and precious metals markets before and during the epidemic, as shown in The outbreak of the COVID-19 epidemic also increased the closeness of volatility spillover connectedness among the gold, silver, crude oil, and natural gas markets and enhanced risk connectedness among commodity markets. It is worth noting as well that, before the COVID-19 epidemic broke out, silver was the main volatility spillover market with strong risk contagion capacity. In turn, the gold market was the main receiver of the external volatility spillover, and the risk transfer of the precious metal market was significantly stronger than that of the energy market. During the COVID-19 epidemic, the volatility spillover level of the silver market decreased rapidly, and the precious metals markets showed their risk absorption capacities under the shock of major emergencies which verified that the precious metals market could play the role of risk shock absorber in the case of increasing external economic uncertainty. The crude oil market became the main spillover of risk.The COVID-19 epidemic has placed enormous pressure on global economic growth, creating a negative impact on financial systems that cannot be ignored. As In addition, it is worth noting that the volatility of the commodity price compound return had time-varying characteristics and showed clear differences over time.From the dynamic perspective, we conducted an in-depth study on the volatility spillover connectedness structure and its changes among the markets before and during the COVID-19 epidemic. We aimed to rectify the dynamic changes of the total volatility spillover level, the level of volatility spillover between the commodity markets, and the risk spillover status of the energy and precious metal markets. In so doing, we attempted to identify the spillover path and tendency of commodity markets' volatility risk under the continuous impact of the COVID-19 epidemic. We further clarified the COVID-19 epidemic's dynamic impact on the energy and precious metals markets in order to provide theoretical support and decision-making reference for the formulation of the COVID-19 epidemic control policies and the establishment of risk prevention and control mechanisms.The dynamic changes in the total volatility spillover level among the energy and precious metals markets before and during the COVID-19 epidemic are shown in Additionally, The COVID-19 epidemic has made significant heterogeneous impacts on the energy and precious metals markets and has significantly changed their volatility spillover ability and risk spillover status. This is exemplified in The TO volatility spillover level of the silver market was found to have decreased, and the FROM volatility spillover level of the silver market was found to have increased. The volatility spillover level of the natural gas market also had the same characteristics, meaning the NET volatility spillover level of the silver and natural gas markets transitioned from positive to negative. We found that the silver and natural gas markets have become receivers of external volatility spillover under the COVID-19 epidemic. Furthermore, their risk absorption capacity has improved significantly, which mainly relates to the demands of economic recovery and excess earnings opportunities in certain countries. For example, under the COVID-19 epidemic, countries have sought the optimal path to recover their economies. They have preferred to accelerate economic transformation and replace the old kinetic energy driven by resources with the new kinetic energy brought by technological innovation. New energy technologies, such as 5G and solar energy, belong to silver-intensive fields, which enhance the anti-risk value of silver. Simultaneously, manufacturers' production reduction strategy during COVID-19 has been effective, reducing the price sensitivity of natural gas and increasing investment income. Consequently, its risk absorption capacity improved. Under the shock of the epidemic, the magnitude of TO volatility spillover and FROM volatility spillover of crude oil market has increased simultaneously, while the hoist scope of the TO volatility spillover level was decidedly higher than the FROM volatility spillover. Thus, the level of the crude oil market's NET volatility spillover has risen rapidly throughout the COVID-19 epidemic. The crude oil market changed from the receiver of the external volatility risk to the spillover of the volatility risk and became the source of risk contagion among commodity markets in the post-epidemic era. This may have occurred because the COVID-19 epidemic cut production supply chains around the world and weakened market demand expectations for oil, which undoubtedly exacerbated the volatility of international oil prices and improved its risk spillover levels. It is noteworthy that during the COVID-19 epidemic, the TO and FROM volatility spillover levels of the gold market showed reverse changes, and the net volatility spillover level of the gold market improved. This reveals that the negative impact of the COVID-19 epidemic weakened the risk absorption capacity of the gold market and mainly related to the enhanced risk reception capacity of the silver and natural gas markets. However, we found that the net volatility spillover level of the gold market before and during the COVID-19 epidemic was below the 0-scale line, and its absorption capacity of external volatility spillover was the strongest. This proves that gold with the property of hedging continues to stably play the role of risk damper, which is consistent with the research conclusion of Junttila et al. . OverallAdditionally, the spillover ability and status of commodity markets showed clear time-varying characteristics. As the COVID-19 epidemic increases in severity, the volatility spillover level of each market will enlarge. For example, in the early stages of the outbreak in 2020, the net volatility spillover levels of the silver, gold, and natural gas markets decreased significantly. Furthermore, all showed strong risk reception ability, whereas the level of risk spillover in the crude oil market rose rapidly. As countries paid more attention to the prevention and control of the epidemic, investors' preference gradually decreased, the frequency of capital flow decreased, and the stability of capital increased. Thus, the level of risk spillover and risk absorption of each market decreased. This point was mutually corroborated with the conclusions of our previous study.The in-depth exploration of the time-varying volatility spillover connectedness among the energy and precious metals markets was the key point for clarifying the price risk spillover path and spillover tendency among those markets amid the COVID-19 epidemic. We further found that the COVID-19 epidemic has intensified the volatility of the crude oil market. Under the shock of the epidemic, the crude oil market has become the source of risk spillover for all other markets, and the risk transmission of the crude oil market has been directional. The silver market was found to be the main transmission object, and the market risk was found to have finally been digested by the gold market, indicating that the silver market plays a major role in the risk transfer station of the gold market. It is worth noting that the outbreak of the COVID-19 epidemic enhanced the risk absorption capacity of the natural gas market and magnified its role in stabilizing the risk of price volatility. Therefore, the natural gas market has also become the main gathering place for risks during the COVID-19 epidemic and is mainly connected with the risk spillover from the crude oil market. It must be emphasized that the stability of the above risk transmission path also showed to have time-varying characteristics, and this stability improved as the epidemic became more severe. In the early stages of the COVID-19 outbreak in 2020 and in the middle and early periods of 2021, the stability of the risk connection, spillover path, and tendency among markets significantly improved, indicating that our above conclusions are robust.In this article, we utilized the DCC-GARCH-CONNECTEDNESS approach to explore the volatility spillover connectedness before and during the COVID-19 epidemic. Based on existing literature, relevant research conclusions were enriched and expanded. The main conclusions of this paper are as follows.First, the outbreak of the COVID-19 epidemic strengthened the volatility correlations among the gold, silver, crude oil, and natural gas markets and enhanced the risk connection among them. Second, the COVID-19 epidemic has intensified the price risk of the crude oil market and increased its volatility risk spillover level. Therefore, under the shock of the epidemic, the crude oil market has transitioned from the receiver of market volatility risk to the spillover. It has also become the source of the risk transmission of commodity markets in the post-epidemic era. Third, the outbreak of the epidemic enhanced the risk reception capacity of the natural gas and silver markets, as well as amplified its role in stabilizing the risk of price volatility. It also weakened the risk absorption capacity of the gold market, though the gold market remains the terminus of external volatility risk as the risk stabilizer. In addition, the COVID-19 epidemic has weakened the volatility spillover level within the precious metals market and enhanced the spillover connection between the precious metals and energy markets, which fully highlights the risk mitigation function of the precious metals markets. Fourth, the volatility spillover level between markets showed clear time-varying characteristics and positively correlated with the severity of the COVID-19 epidemic. This means that increases in the severity of the COVID-19 epidemic will amplify the volatility spillover level of each market in the same direction.Some policy implications can be drawn from the above conclusions. First, because the COVID-19 epidemic was shown to have intensified the risk volatility spillover among commodity markets, governments should attempt to prevent and control the epidemic, restore consumer confidence, and improve the industrial chain structure. International organizations should also play an active role. They can smooth the price volatility of financial assets through control measures such as open-market operations and maintain the stable trend of commodity prices by improving the liquidity of commodity markets. Doing so could prevent the internal risk volatility connection among commodity markets. Moreover, considering the precious metals market as the reception of risk spillover, the government should guide investors to effectively utilize the risk aversion performance of gold and silver and bring precious metals and commodities with large risk spillover into the portfolio basket to realize risk hedging. This could allow them to improve overall investment efficiency and weaken the turbulence caused by external risk shocks as well as give full play to the role of gold as a risk stabilizer in the COVID-19 epidemic. In addition, the prevention and control of crude oil market risk volatility spillover deserves greater attention. At the macro level, governments should improve commodity markets and play a positive role in the global value chain of energy and trade networks. At the micro level, they should guide arbitrage transactions, which can effectively reduce risk exposure, to enrich crude oil price risk management tools, and prevent the negative impact of speculative factors under the shadow of the epidemic. Furthermore, based on the increasingly prominent risk transmission position of the natural gas market, there is an opportunity to build the power of natural gas demand and promote the establishment of a joint bargaining mechanism, which can fundamentally weaken the risk transmission function of the natural gas market and ensure market and financial stability. Finally, as the energy market becomes a risk spillover center, governments should increase the development and utilization of renewable energy. Grasping the opportunity for energy transformation partly granted by the epidemic and actively introducing clean energy, such as solar and wind energy and their related commodities, into financial markets are also important measures. In particular, they are helpful for hedging the instability of traditional energy with the sustainability of renewable energy and for strengthening the risk prevention of international financial markets.The original contributions presented in the study are included in the article/supplementary material, further inquiries can be directed to the corresponding author.XT: conceptualization, validation, writing original draft, supervision, and funding acquisition. XW: methodology and writing—review and editing. SM: writing—review and editing and visualization. ZW: software, visualization, and formal analysis. YZ: validation, resources, and data curation. LX: software, data curation, project administration, and visualization. All authors contributed to the article and approved the submitted version.We acknowledge the financial support from Youth Foundation of Humanities and Social Sciences of the Ministry of Education in China (20YJC790122).The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.


Viewed broadly, discourse analysis is the study of ways in which naturally occurring language is used between people, both in written and spoken contexts. In a learning context, discourse analysis of written and spoken texts is useful for making visible how educators, learners, and others engage in an educational activity to achieve learning goals.By reviewing and discussing a sample of discourse-oriented studies in medical education, this article aims to revisit and argue for the relevance of discourse analysis approaches for medical education research. We also aim to highlight how such discourse-oriented research can inform teaching and learning in medicine.Discourse analysis is a methodological approach to describe people's lived experiences through interaction from a language-in-use perspective, such as what the written or spoken text is about, who is involved, and how the text is organised and functions in a specific context, such as a problem-based learning classroom, or a bedside tutorial.Discourse-oriented studies range from a macro-level analysis of societal institutions (e.g. curriculum documents in policies for selection), meso-level analysis of discourse practice  to micro-level analysis of texts in a specific context (e.g. patient-provider interactions), influenced by various disciplines, including anthropology, cultural studies, linguistics, psychology, and sociology.,A macro-level analysis of discourse is a critical discourse analysis focusing on relationships between language, ideology, and power. Here, language is seen as a form of social practice; the focus is on studying the way social power abuse, dominance, and inequality are enacted, reproduced, and resisted by text and talk in the social and political context.,,Critical discourse analysis is increasingly employed as a research methodology in medical education. For example, it has been used to identify dominant ultrasound discourses,Specifically, we elaborate on one study to show how critical discourse analysis has been applied and the new knowledge is identified. Chen and colleagues conducted a critical discourse analysis of compassionate care within texts of undergraduate medical education accreditation standards in North America in effect since 1957.,Further, these researchers have provided accessible analytical steps to undertaking Foucauldian critical discourse analysis; that is, (i) a familiarisation phase; (ii) assembly of an appropriately comprehensive archive of texts; (iii) analysis of the assembled archive to identify prominent keywords and statements; (iv) analysis of links between the identified dominant discourses and the values of compassionate care, and (v) description of the effects and implications of the dominant discourses on the potential to advance educational practices related to compassionate care.Context is a key conception in the analysis of discourse practice. For example, ethnography of speaking is concerned with understanding the social contexts of linguistic interactions.;19 its notion is to capture what people think they are doing when they talk to each other. Hence, frame analysis is a useful approach which explores different idea elements between people in a communicative event. For example, Sundberg, Reeves, Josephson and Nordquist adopted frame analysis to explore the meanings of interprofessional education by comparing educational leaders' perceptions with educational policy documents.Similarly, interactional sociolinguistics, which evolved through Gumperz's linguistics and anthropologyThe other primary aim of the meso-level analysis of discourse practice is to reveal the underlying meaning of a text and communicative behaviour. Speech act theory and pragmatics focus on the interpretation of utterances in discourse and the relation of speech to action during the conversation. Speech act theory attempts to conceptualise the speaker's intent to achieve a particular purpose through a linguistic lens. Austin argues that the performance of a statement which delivers textual information is a certain kind of action in and of itself and that a single utterance can produce three kinds of acts concomitantly.A micro-level analysis of discourse explores how text is linguistically and functionally organised in specific communicative contexts. In other words, this approach aims to uncover the structural-functional aspects of discourse. Specifically, the Birmingham School of Linguistics and Systemic Functional Linguistics are major schools of this approach and aim to describe the structure of written and spoken texts and relate them to social contexts and other linguistic features.,Regarding the discourse structure, Sinclair and Coulthard from the Birmingham School systematically describe discourse units in a pedagogic context.,As to discourse function, Systemic Functional Linguistics views language as a resource for making multiple strands of meaning simultaneously, including representational meanings about the world and experiences, interpersonal meanings about roles and relationships, and textual meanings about the message., ,Genre theory, developed by systemic functional linguists particularly interested in school education, is an accessible approach to discourse analysis for medical education researchers.For example, taking a structural-functional discourse analysis approach, two of the present authors and their colleagues investigate interactions among interdisciplinary groups of medical, dentistry, pharmaceutical sciences, nursing occupational therapy, and physiotherapy students working together in problem-based learning tutorials.In addition to discourse structure and function, studies on interactions using a more fine-grained perspective are gradually becoming more established in medical education research. This approach to discourse analysis aims to identify the distinctive interaction patterns resulting from negotiation of meaning-making in the phenomenon investigated. In a few these studies from this perspective, the research contexts are generally classified into communicative events with multiple participants or dyadic encounters.-,,,Learning encounters among multiple participants in medical education has been a rich source of interest to the discourse analyst with an educational lens, for example, verbal interactions in group learning settings in the context of problem-based learning,italic)). Detailed transcription helps researchers analyse beyond the literal meaning of transcribed texts and capture the nuanced meaning  of social interaction in its given context.Methodologically, the use of transcription conventions is pivotal when presenting recorded spoken data in a written format for micro-level analysis of discourse. Particularly, the Jefferson transcription system is used by many discourse analysts and conversation analysts.Discourse analysis is a useful methodological approach for researching medical education, which affords several viewpoints, including the relationship between language and power in society (macro), discursive practice in a social context (meso), and discourse structure and function (micro). Particularly, discourse-oriented studies at micro-and meso-levels focus on contextual interaction, which entails looking beyond the literal meaning of language and relating it to the social, cultural, and psychological dimensions of communicative events. Thus, it can help us unpack the black box of the learning process facilitated through interactions in medical education. Detailed analyses of interactions can add novel perspectives on education practices and present not only new avenues for researchers' theoretical contributions but also practical pedagogical implications for the medical education field.Discourse analysis might be challenging for medical educators. Echoing Woodward-Kron, Stevens, and Flynn,The recent COVID-19 pandemic has driven the development of online education and training in synchronous and asynchronous settings, making researching online discourse increasingly important. Discourse analysis can be a key methodology to investigate this at macro-, meso-, and micro-levels.This work was supported by the JSPS KAKENHI Grant-in-Aid for Scientific Research (C) Number 20K10374.The authors declare that they have no conflict of interest.


In non-well differentiated thyroid cancer, the rate of nodal involvement is variable and depends on the histology of the tumor. We aim to highlight the opinions of several experts from different parts of the world on the current management of the less common types of thyroid cancer to provide a consensus on the treatment of regional lymphatics for these entities. The rate of lymph node involvement is variable and depends on the histology of the tumor. Within undifferentiated tumors’, there is an established consensus on the treatment of anaplastic carcinoma, medullary carcinoma and poorly differentiated carcinoma of the thyroid. However, treatment of other rarer tumors must be individualized, taking into account both the aggressiveness of the histology and the anatomical distribution of the disease. In general, prophylactic treatment of the neck is not indicated.Lymph node metastases in non-well differentiated thyroid cancer (non-WDTC) are common, both in the central compartment (levels VI and VII) and in the lateral neck (Levels II to V). Nodal metastases negatively affect prognosis and should be treated to maximize locoregional control while minimizing morbidity. In non-WDTC, the rate of nodal involvement is variable and depends on the histology of the tumor. For medullary thyroid carcinomas, poorly differentiated thyroid carcinomas, and anaplastic thyroid carcinomas, the high frequency of lymph node metastases makes central compartment dissection generally necessary. In mucoepidermoid carcinomas, malignant peripheral nerve sheath tumors, sarcomas, and malignant thyroid teratomas or thyroblastomas, central compartment dissection is less often necessary, as clinical lymphnode involvement is less common. We aim to summarize the medical literature and the opinions of several experts from different parts of the world on the current philosophy for managing the neck in less common types of thyroid cancer. Globally, thyroid cancer is the most common malignant endocrine tumor and accounts for more than 90% of the endocrine cancers . Rather The propensity for lymphatic metastases is variable based on the specific thyroid cancer type, the knowledge of which is an essential part of cancer treatment. It enables a more accurate staging and thus, a more precise estimation of prognosis, data-directed patient counseling, tailored treatment planning, and a more efficient follow-up. Generally, the presence of nodal disease tends to lead to a poorer long-term prognosis but varies depending on the histology of the cancer.Not all thyroid cancers have the same predisposition for lymphatic metastasis. Within the broad spectrum of thyroid carcinoma, even within WDTC, there is the typical different mode of metastasis when comparing follicular thyroid carcinoma (FTC) (mainly hematogeneous route of metastasis)  to papilIn this review, we aim to summarize the medical literature and views of several experts from different parts of the world about the current data on lymphatic drainage pathways of the less common thyroid cancer types, discussing non-WDTC , malignant peripheral nerve sheath tumors (PNSTs), angiosarcoma, leiomyosarcoma, and primary malignant thyroid teratoma or thyroblastoma) to provide a unified philosophy on surgical approaches to nodal disease in these entities. The lymphatic drainage characteristics of WDTC have been described elsewhere and will not be outlined in this review . Although the thyroid lymphatic network forms macroscopic structures, these are hard to visualize pre-operatively and intraoperatively without special techniques. Knowledge of the thyroid lymphatic drainage pathways is a fundamental part of cancer treatment. It enables a more accurate staging and assessment of prognosis, improved patient counseling, tailored treatment planning, and a more specific follow-up analysis.The Italian anatomist Gaspare Aselli, in the early 17th century, takes credit for the first discovery and description of the lymphatic system . MarcellThe central compartment of the neck, which contains level VI-VII lymph nodes, is bounded superiorly by the hyoid bone, laterally by the carotid arteries, inferiorly by the sternal notch and brachiocephalic artery, anteriorly by the superficial layer of the cervical fascia, and posteriorly by the deep layer of the cervical fascia . The cenThe lymphatic pathways also extend into the upper mediastinum, also designated as level VII, as well as laterally into level IV, in the trachea-esophageal groove . While mIn an earlier study, Rouvière reported another lymphatic pathway of the thyroid gland to retropharyngeal nodes in 20% of cadavers. These are rarely observed but parapharyngeal and/or retropharyngeal lymph node metastasis from thyroid cancer are occasionally reported in primary tumors with extensive nodal disease or recurrences after previous neck dissection and where axial imaging beyond ultrasound alone is used to detect them ,27,28.Among patients with thyroid cancer, it may be necessary to perform a neck dissection. A detailed description of the surgical procedure is beyond the scope of this publication and can be found in many publications .If indicated, dissection of the central lymph node compartments (Level VI) should be performed at the same time as the primary thyroid surgery. It involves removal of lymphatic tissue from the prelaryngeal, pre- and paratracheal, and tracheoesophageal nodal basins ,31. DuriThe presence of metastatic disease in the lateral neck should be assessed pre-operatively. Ideally, neck surgery should be performed at the same time as the procedure for the primary disease. The goal of neck dissection is to remove all macroscopic lymph node metastases while preserving the neurovascular structures. The detection of nodal disease focuses on that which is “clinically apparent” and should be defined by pre-operative US and CT nodal mapping studies ,33,34,35PDTC, according to Turin consensus, arises from follicular epithelial cells and accounts for less than 15% of malignant thyroid tumors ,38 Figu. PDTCs hThe management of PDTC has not been standardized due to the rarity of the disease and heterogeneity of inclusion criteria. Surgery with removal of all macroscopic disease can achieve satisfactory locoregional control. Central and/or lateral neck dissection should be performed if there is clinical or radiological evidence of pathological lymph nodes . Some auThe prognosis for these patients, when complete clearance of all gross disease is achieved, is favorable with a 5-year locoregional control of 81% . HoweverATCs are undifferentiated tumors of the thyroid follicular epithelium . The so-The best opportunity for a cure of ATC is comprehensive surgery, essentially one that effectively removes all clinical disease in the neck including the thyroid gland. However, due to the aggressiveness of the tumor and the fact that most patients present with masses infiltrating nearby vital cervical structures , surgery is generally not indicated given the potential morbidity and poor prognosis. Indeed, the majority of ATC successfully treated surgically are in fact only formally diagnosed on post-operative histopathology. Fortunately, new targeted treatment options are emerging with promising results, after which some of the inoperable patients treated with these options become surgical candidates again .In considering surgical treatment, it is important to determine the extent of the disease and the possibility of complete resection. Total or near-total thyroidectomy would only be considered in patients with resectable tumors that can be removed with acceptable morbidity. After surgery, treatment with adjuvant (chemo) RT would be appropriate. For the most advanced and unresectable disease, which is the most common situation, treatment should be individualized according to the patient’s general medical condition and care goals .Nearly all patients with ATC present with a thyroid mass, and regional spread is clinically apparent at the time of diagnosis in about 50% of cases . ATC hasIf lymph node metastases at the central compartment are present, a unilateral or bilateral therapeutic lymph node dissection should be considered when the thyroid gland is removed . HoweverImportantly, approximately 35% of ATC is associated with the BRAF V600E mutations. Given the dramatic response of BRAF-mutated ATC to BRAF/MEK inhibitor, all patients with stage IVB or stage IVC ATC should be quickly tested for this mutation prior to initiation of treatment including surgery . BRAF immunohistochemistry testing can be performed in approximately 48–72 h in many centers, and the presence of this mutation will often shift the treatment paradigm to upfront systemic therapy (BRAF/MEK inhibitor). Under such circumstances, neo-adjuvant treatment with dabrafenib plus trametinib may be indicated to improve the chances of complete tumor resection ,47,50. TMTC is a neuroendocrine carcinoma that arises from thyroid parafollicular C cells and accounts for only 1–2% of thyroid cancer  Figure . About 7While sporadic MTC usually presents with a solitary thyroid nodule, a significant proportion of patients may initially present with lymphadenopathy because of the high propensity for early metastatic spread to the cervical lymph nodes. Central compartment lymph node metastases are observed in approximately 50% of cases, both sporadic and hereditary. The pattern of metastatic distribution in the neck is variable and is not related to the size of the thyroid tumor. Contralateral central lymph node metastases are observed including patients with small primary tumors . The supThe ATA guidelines for the management of medullary thyroid cancer have stated that patients with MTC can be treated by complete primary tumor resection and cervical lymph node dissection ,55. HoweIn patients with MTC without evidence of cervical lymph node involvement on pre-operative ultrasound, bilateral prophylactic central compartment lymph node dissection is indicated ,51. MachFor patients with locoregionally advanced RET-mutated MTC, including patients with invasive nodal disease, a novel strategy of neo-adjuvant RET-specific inhibitor prior to surgical resection has been reported , and thiIn conclusion, in patients with pre-operative evidence of lateral cervical adenopathy, bilateral dissection of the central and affected lateral compartments is indicated . In the MEC is a carcinoma of unknown histogenesis classified as low, intermediate, or high grade according to the histologic features, although most cases are considered to be low grade . TypicalPatients are usually asymptomatic and the tumor usually presents as a unilateral cold nodule in ultrasound. Up to 15% of the cases reported have demonstrated extrathyroidal extension and approximately 42% of the patients have lymph node metastases in the central compartment (level VI) at the time of diagnosis . This hiThe treatment of choice is surgery and consists of total thyroidectomy . NeverthMost of the reported patients show a good outcome and cases of disease-free survival of more than 10 years have been reported. Nevertheless, some with a high-grade tumor expressing adverse features have had a poor outcome .Peripheral nerve sheath tumors can be benign or malignant. MPNST, or malignant “Triton” tumor, is a sarcoma of the cells that form the sheath that covers peripheral nerves . CriteriPrimary MPNSTs of the thyroid gland are rare, accounting for <0.02% of all thyroid tumors worldwide ,72. PrimBecause of the high rate of local recurrence, aggressive surgical resection including total thyroidectomy or extended total thyroidectomy when extrathyroidal extension is observed  to achieve wide free margins, with adjuvant radiation therapy and eventual chemotherapy currently being the mainstay of treatment of these tumors . HoweverGiven the small number of cases described, it is difficult to predict the behavior of the tumor. However, most reported patients have died of their disease.Angiosarcoma is an uncommon soft tissue sarcoma  Figure . AccordiThyroid angiosarcomas is the most common of the mesenchymal thyroid tumors . They usThere is no established consensus on the optimal treatment approach of thyroid angiosarcoma due to its rarity . In reseAlthough the development of cervical metastases is very common, in most cases of angiosarcoma described in the literature, prophylactic treatment of the neck has not been performed ,95,96,97It is important to take this tumor type into account when dealing with a thyroid tumor with aggressive histological features . A correPrimary thyroid leiomyosarcomas are exceedingly rare with less than 40 cases reported in the literature ,100,101 These tumors usually occur in elderly people and are not related to previous thyroid lesions or radiation exposure ,103. TheDue to the limited experience with these rare tumors, there are no evidence-based treatment protocols. If radical resection is possible, surgery is the treatment of choice ,104,108.Teratoma is defined as a neoplasm that consists of tissue derived from more than one primitive germ cell layer, at least some of which is foreign to the anatomic site in which it occurs. Cervical teratomas are rare, and even more rare for those arising in the thyroid gland . CurrentMalignant thyroid teratomas usually begin as a thyroid mass accompanied by lymphadenopathy. These tumors frequently harbor in the lungs ,118.These tumors should be managed aggressively to achieve best results. Surgical excision is the treatment of choice. Neo-adjuvant chemotherapy can reduce the size of the primary tumor and metastases . In caseLocal tumor recurrence or distant metastatic disease determines patient prognosis .The rich lymphatic supply of the thyroid gland, coupled with the high propensity for the development of lymph node metastases in malignant thyroid tumors, warrants the head and neck surgeon to be familiar with the tumor-specific indications and techniques of regional lymph node dissection.Nodal metastases can negatively affect prognosis and locoregional control in all forms of thyroid malignancies and should be considered and treated to reduce regional recurrence rates, with minimal morbidity.In non-WTDC, the rate of nodal involvement is variable and depends on the histology of the tumor. While in MTC, PDTC, and ATC, with high frequency of lymph node metastases, prophylactic central compartment dissection is generally necessary. For mucoepidermoid carcinomas, malignant peripheral nerve sheath tumors, sarcomas, and malignant thyroid teratomas, central compartment dissection is less often necessary, as clinical lymph node involvement is less common.Within non-WDTC there is an established consensus on the treatment of ATC, PDTC, and MTC. However, the management of other rarer tumors needs to be individualized. For the management of neck nodes for these rare tumors, the evidence is lacking due to a paucity in numbers. Clinicians must consider both the aggressiveness of the histology and the anatomical distribution of disease. All these cases merit multidisciplinary involvement to discuss the potential for pre-operative systemic therapy and post-operative adjuvant therapies. By approaching patients with a multidisciplinary individualized approach, a tailored treatment plan can be devised. In all cases, tumor and patient-related factors should be considered to minimize morbidity and maximize clinical impact on a rare and diverse group of diseases.


Biomedical incubation platforms make full use of innovation elements, constantly absorbing, integrating, and allocating various resources and innovating the incubation service mode, an important path to improving the performance of innovation incubation. Based on resource-based theory, network theory, and value chain theory, we proposed the conceptual model and research hypothesis for the relationship between innovation elements, incubation capacity, and innovation incubation performance in biomedical incubation platforms, with customized service as a moderating variable. The empirical results show that innovation elements have a significant positive impact on the improvement and transition of incubation capacity. Incubation capacity has a significant positive impact on innovation incubation performance in biomedical incubation platforms. Customized service plays a significant positive regulatory role between incubation capacity and innovation incubation performance in biomedical incubation platforms. The biomedical industry is a typical innovation-driven industry and the development and application of new products and technologies play a key role in the market competitiveness of enterprises. Biomedical incubation platforms incubate incubatees by providing a variety of entrepreneurial supports, including physical space, consulting services, financial support, and network connections , therebyGuided by resource-based theory, transaction cost theory, and social exchange theory, incubation platform research has focused on basic management functions such as basic services, performance evaluation, capacity enhancement, and service innovation as a resource-mediated broker. It has explored the impact mechanism of incubator performance enhancement at the micro level. Most researchers adopt the static perspective of various incubation target plans and incubation practice designs, ignoring the reality of resource mismatch in the innovation incubation process, whereby innovation elements are fragmented and scattered. Researchers have neglected the special characteristics derived from the incubation ecology of double embedding in positive externalities and the integration effect based on transaction costs and relationship values . SchwartResearchers have explored in-depth the mechanism of the influence of absorptive capacity, social capital, incubation platform control, network plurality, and innovation incubation performance from the perspective of power-change theory. However, most studies have explored the causal mechanism or boundary conditions of innovation incubation performance from a single perspective, ignoring the knowledge sourcing of innovation factor flow and allocation in the process of innovation incubation and the reality of organic integration and high synergy between the incubation platform's incubation capacity and external value-based resources. Therefore, this article constructs a conceptual model including innovation elements, incubation capacity, and innovation incubation performance of biomedical incubation platforms. It explores the mediating role of incubation capacity in the relationship between innovation elements and innovation incubation performance by using a structural equation model and examining the moderating role of customized services in the relationship between the incubation capacity and the innovation incubation performance of biomedical incubation platforms by using hierarchical regression analysis. This article aims to reveal the influence mechanism and the effectiveness mechanism of innovation factor focus in promoting advances in incubation capacity and enhancing the innovation incubation performance of biomedical incubation platforms. It aims to provide theoretical support and practical guidance for biomedical incubation platforms to enhance incubation performance and accelerate the growth of incubatees.The composition of innovation factors mainly includes a simple two-dimensional classification taken from the direct factors of technology, capital, and human capital and the indirect factors of infrastructure, social environment, and macropolicies from the production factor perspective . It inclInnovation knowledge source is an important innovation element for science and technology enterprises. The high-tech characteristics of biomedical enterprises provide innovation knowledge source with a technological connotation. This connotation includes high-tech, scientific, and technological leaders, innovative creative thinking, and high-tech advanced medical equipment or instruments. The two main ways to obtain or contact innovative knowledge sources are to acquire external knowledge sources directly and to collaborate with organizations or individuals who have innovative knowledge sources. Zhang and Liu  exploredH1: There is a significant positive correlation between innovative knowledge sources and the incubation capacity of biomedical incubation platforms.The biomedical incubation platform incubation network refers to the organization beyond the nodes constituted by the biomedical incubation platforms through building intra-organizational and cross-organizational cooperation interfaces . These iH2: There is a significant positive correlation between the incubation network environment of biomedical incubation platforms and incubation capacity.The value chain information of biomedical incubation platforms refers to the information resources attached to the value chain activities, the main ways in which biomedical incubation platforms and incubatees break through organizational boundary restrictions to obtain significant external information and knowledge resources. Value chains provide an effective way for enterprises to acquire new knowledge and technology, to extract core knowledge and key technologies through organizational learning, to form strategic alliances, and to engage in other means of enhancing information and innovation capabilities . The amoH3: There is a significant positive correlation between value chain information and the incubation capacity of biomedical incubation platforms.Incubation capability is the core competitiveness of a biomedical incubation platform. It consists of incubatees' self-incubation capabilities, which is the reflection of the comprehensive service capability of a biomedical incubation platform to incubate enterprises and its own growth capability . ColomboH4: There is a significant positive correlation between incubation capacity and innovation incubation performance of biomedical incubation platforms.The term customized service means that the incubation platform provides peer-to-peer professional incubation services in response to the actual conditions and heterogeneous needs of incubatees at the growth stage . ServiceH5: Customized services have a significant positive moderating effect between the incubation capacity and innovation incubation performance of biomedical incubation platforms.In this article, we study the influence of innovation elements and incubation capacity on the innovation incubation performance of biomedical incubation platforms. The sample is selected from incubation platforms such as biomedical industrial parks, incubators, and crowdsourcing spaces at or above provincial level as the survey objects. The Coronavirus disease 2019 (COVID-19) pandemic affected data collection. The data were obtained mainly through online questionnaires and video conference interviews with more than 10 regionally representative biomedical incubation platforms. The quality of data completion was ensured by arranging that the questionnaires were filled out anonymously by incubatee executives who were connected to the incubators and had a good grasp of the companies' innovation incubation. A declaration was made that the survey was intended for academic study and an undertaking was given promising the confidentiality of the questionnaires. From June to October 2021, 500 study questionnaires were distributed through email, WeChat, and other communication methods. A total of 358 questionnaires were collected, of which 38 questionnaires were invalid, leaving 320 valid questionnaires.The variables in this study were measured on a five-point Likert scale, with 1–5 indicating “totally disagree” to “totally agree.” The operationalized definitions and measurements of each variable were developed, designed, and improved based on relevant previous results.Drawing on the study results of Zhou et al.  and JianDrawing on the study results of Li et al. , four scDrawing on the study results of Guo et al. , Lau andDrawing on the study results of Zhao et al.  and Sun Drawing on the study results of Jiang et al. , four scDrawing on the study results of Tang et al. , four scIn this study, the reliability and validity of the sample data were verified using Cronbach's α coefficients, combined reliability (CR), and average variance extracted (AVE) to ensure the authenticity and reliability of data analysis results. Using Amos version 23.0 to perform structural equation modeling (SEM) analysis, as shown in p < 0.01), indicating that the richer the innovation knowledge sources, the stronger the incubation capacity, thereby verifying hypothesis 1; incubation network environment has a significant positive effect on incubation capacity , indicating that the better the incubation network environment, the stronger the incubation capacity, thereby verifying hypothesis 2; value chain information has a significant positive effect on incubation capacity , indicating that the more value chain information is available, the stronger the incubation capacity, thereby verifying hypothesis 3; incubation capacity has a significant positive effect on innovation incubation performance , indicating that the stronger the incubation capacity of the biomedical incubation platform, the more significant the innovation incubation performance, thereby verifying hypothesis 4.Three-step hierarchical regression analysis sets the independent variable as incubation capacity; the dependent variable is set as innovation incubation performance and the interaction term of “incubation capacity × customized service” is added. In the innovation incubation process of biomedical incubation platforms, innovation elements  have a significant positive impact on the innovation incubation performance of biomedical incubation platforms through the mediating role of incubation capacity. Customized services play a significant moderating role between incubation capacity and innovation incubation performance of biomedical incubation platforms. All five hypotheses were verified. The findings of this article have good theoretical reference significance and practical value for the focus of biomedical incubation platforms on the multiple innovation elements and their effective allocation in the incubation process and the improvement of innovation incubation performance of biomedical incubation platforms.(1) Innovation elements  have a significant positive impact on incubation capacity. Incubation capacity as a mediating variable has a significant positive impact on the innovation incubation performance of biomedical incubation platforms. Biomedical incubation platforms directly improve innovation incubation performance by focusing on innovation elements in their operation and management practices. The focus of three innovation elements positively contributes to the survival rate and the growth status of incubatees, the cultivation of incubatees' scientific and technological innovation capabilities, the transformation of scientific and technological achievements, and the graduation rate of incubatees.First, social capital, good entrepreneurial opportunities, and highly cooperative teams were viewed as the most important factors for entrepreneurship in China . BiomediSecond, biomedical incubation platforms grasp the development direction of innovation and entrepreneurship policies, focus on building an ecosystem platform for an incubation network, and build broad open-source incubation platforms by creating a harmonious organizational and cultural atmosphere for biomedical incubation platforms, incubatees, and multiple external subjects. These actions will expand the scale of the incubation network and will attract capital and technology from external subjects to create good incubation platforms. Technology and other factors create a good resource environment for the incubation network, continuously improving the incubation capacity and improving innovation incubation performance.Third, biomedical incubation platforms and incubatees obtain a large number of external information resources through the value chain to help them to break through the organizational boundary restrictions in business management practices and use diverse information resources such as technical information, market information, innovation information, and other kinds of information resources to respond appropriately to the challenges brought by fierce market competition and continuous development. Therefore, during the operation and management of biomedical incubation platforms, managers should strengthen the strategic awareness of innovation element acquisition and continuously strengthen the importance of the innovation element in biomedical incubation platform incubation capacity improvement. This would greatly enhance the incubation capacity and the comprehensive service capacity of incubated enterprises. It would also improve biomedical incubation platforms' own incubation capacity and promote decision-makers' management and innovation resources to compete for strategic awareness. Improvements in these aspects are essentially incubation capacity improvements.(2) Customized services have a significant moderating effect between incubation capacity and innovation incubation performance. The higher level of customization services in the biomedical incubation platform is conducive to improving the range of incubation capacity, implying a greater contribution to innovation incubation performance. With high incubation capacity, a biomedical incubation platform can provide customized services to incubatees according to their growth stages and heterogeneous needs, thereby regulating the relationship between incubation capacity and innovation incubation performance and realizing the path of innovation incubation performance improvement mediated by incubation capacity. Customized services, as a moderating variable between incubation capacity and innovation incubation performance, work in two main ways. First, the biomedical incubation platform uses implicit knowledge and its a priori resource advantages to the full to provide order-based incubation services to meet the real needs of incubatees. Second, the biomedical incubation platform builds an incubation network ecosystem platform with external network subjects through customer interface, market interface, and technology interface activities, attracting multiple subjects to participate in solving incubatees' incubation problems with the incubation platform, motivating incubation parties to use the incubation platform as an interface to achieve knowledge interaction, and realize customized needs and services.The original contributions presented in the study are included in the article/supplementary material, further inquiries can be directed to the corresponding author/s.Approved by the Scientific Research Office of Sanya University, this article named Innovation Elements, Incubation Capacity, and Incubation Performance in Biomedical Incubation Platform: Moderating Role of Customized Services, written by Jiang Qian's research group, aims to illustrate the internal mechanism and effect of how innovation elements, incubation capability, and other variables affect the performance of innovation incubation on biomedical incubation platforms. The research purpose, research plan, research method, research content, and implementation process of this study all meet the relevant ethical requirements of Sanya University. We give our permission for future studies based on our study and please ensure that any follow-up study is in strict accordance with our study plan.QJ: paper design, data analysis, and article writing. DW: paper design and data collection. YFW: paper design and article instruction. BYW: data analysis. All authors contributed to the article and approved the submitted version.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.


The association between environmental exposure to toxic substances and cardiovascular diseases (CVDs) in humans is widely recognized. However, the analysis of underlying pathophysiological mechanisms is essential to target meaningful endpoints of cardiotoxicity and allow a close-to-real life understanding of the role of chronic and acute exposure to multiple toxicants. The aim of this study is to outline the process for a systematic review of the literature that investigates the relationship between environmental pollution and left ventricular dysfunction. This systematic review and meta-analysis protocol will follow the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA-P) statement. PubMed, Embase, and Web of Science databases will be searched without applying search filters. Two independent reviewers will screen all titles and abstracts and identify the articles to be included in the synthesis. The risk of bias (RoB) will be assessed using an instrument developed for non-randomized  studies (NRS) of environmental exposures. The results of cohort, case-control, cross-sectional, time-series, and case-crossover studies will be extracted and presented in tables considering different population subgroups and length of exposure. This protocol will be expected to provide a sound basis for selecting toxic chemicals and pollutants to contribute with the epidemiological evidence to the in vitro testing protocol within the EU-funded ALTERNATIVE Project. Different sources of potentially harmful substances of anthropogenic origin, including widespread and persistent chemical compounds, e.g., heavy metals, organochlorine pesticides, organic solvents, air pollutants, as well as pharmaceutical drugs and their metabolites, are recognized. Their presence in the environment is a source of great concern as potential causes of multi-organ damage due to their possible additive effects occurring inside the human body. Evidence-based literature, provided by a large number of studies, supports the negative role of environmental contaminants on human health . Air, waCardiovascular diseases (CVDs) are the leading cause of death globally. In 2019, an estimated 17.9 million people died from CVDs, representing 32% of premature deaths mainly due to heart attack and stroke, particularly in the middle- and low-income countries . The risThe associations of CVDs with avoidable exposures, other than those due to behaviors such as tobacco smoke or alcohol consumption, are well established for many categories of toxic by-products from human activities   and manuNowadays, abnormalities of left ventricular contractility due to a direct effect of toxic agents on the heart are not fully understood. Therefore, we aim to systematically review the literature dealing with left ventricular dysfunction in humans due to the environmental exposure to toxic substances. This systematic review will represent an essential part of the knowledge foundation of the ALTERNATIVE project  granted under the European HORIZON 2020 program . The proThe present protocol will allow us to systematically review the effects of exposure to environmental pollutants on left ventricular dysfunction, given the following PECOS question  .What is the existing evidence provided by observational and ecological studies (S) on the effect of exposure to environmental pollutants (E) on left ventricular dysfunction (O) compared to non-exposure, or low-exposure (C) in humans, including the susceptible groups of children and the elderly (P)?PubMed , Embase Moreover, a check of the reference lists of relevant studies will be carried out to detect other studies to be included in the systematic review and inform the interpretation of findings .Cohort, case-control, cross-sectional, time-series, and case-crossover original studies on the association between environmental exposure and cardiovascular diseases will be included. Mortality and hospitalization due to heart failure, hypertensive heart disease, and acute myocarditis will be considered, as well as admission to an outpatient clinic and diagnosis of left ventricular dysfunction. More specifically, we will consider the following specified conditions: combined systolic (congestive) and diastolic (congestive) heart failure (I50.4); systolic (congestive) heart failure (I50.2); hypertensive heart disease with heart failure (I11.0); dilated cardiomyopathy (I42.0); and cardiomyopathy unspecified (I42.9). Respect to exposures, pharmaceuticals, air pollution, metals, POPs including pesticides, industrial chemicals, and organic solvents will be considered. Studies investigating the effects on the general adult population and vulnerable groups  will be included.Randomized clinical trials, reviews, systematic reviews, editorials, commentaries, or other nonoriginal reports will be excluded. Also, in vivo and in vitro studies on cells, tissues, and animals will not be considered. Studies investigating the effects on susceptible groups (pre-existent cardiovascular diseases and/or the presence of documented lifestyle risk factors) and hospital readmission will be excluded.Titles and abstracts will be imported into the Rayyan review management program . After rAfter the full-text articles screening process and identifying the final studies for inclusion in the systematic review, a data collection form will be built. The two investigators will report all the relevant information for each study, and the third investigator will resolve any disagreement. More specifically, for each included study, the following information will be extracted: last name of the first author and year of publication, geographic location of the study area, study design, population type, sample size, environmental risk factor, exposure unit or exposure comparator, exposure temporality, health outcomes, risk estimations and their confidence intervals and p values, and the name of the journal. Regarding risk estimations, we will collect all the estimates reported by different models, e.g., those unadjusted and those adjusted.The two investigators will independently assess the RoB at the study-level using an instrument developed for NRSs  addressing environmental exposures . More spA PRISMA flow diagram  depicts The statistical method and the risk estimations will be reported for each study, and when applicable, the results will be stratified for different subgroups of the populations. The possibility of carrying out a meta-analysis will be evaluated based on the heterogeneity of the study designs in terms of types of chemical exposure, outcomes, and populations investigated. Similarly, across different studies, various types of effect measures are used, mainly odds ratios, risk ratios, and hazard ratios. In this case, before performing the meta-analysis, it will be necessary to conduct a homogenization procedure by converting the various effect measures into a single type of effect estimate. Subsequently, a random-effects model using the REsidual Maximum Likelihood (REML) method will be used to calculate the overall estimate . Forest Moreover, a subgroup analysis will be carried out by pollutant, study design, and location. Using Egger’s test, funnel plot asymmetry will assess the potential publication bias . All staFollowing the Preferred Reporting Items for Systematic reviews and Meta-Analysis protocol (PRISMA-P) guidelines , our sysSystematic reviews and meta-analyses of medical literature have developed rapidly in the past decades, playing a key role in decision making in evidence-based medical practice . Given t3 (PM 2.5). However, little is known about the mechanisms activated by exposure to environmental pollutants that induce damage to the myocardium and the reduction of its normal functionality. If this process is not recognized, it could lead to heart disease. We aim to assess the complex relationship that is modulated by different activation paths, and is exacerbated by high concentrations and cumulative exposures of pollutants with additive effects. Other risk factors and subjective characteristics contribute to the predisposition of or reduction of risk on an individual basis . All those relevant parameters in the exposure–outcome relationship need to be considered appropriately by a stratified analysis for subgroups of variables. However, if the evidence is scarce, the systematic review will identify knowledge gaps [This systematic review protocol was developed specifically to increase the knowledge on harmful environmental pollutants that lead to the cardiovascular diseases as a basis to drive further research. In fact, there is mounting evidence of the positive association between some environmental pollutants and the onset of cardiovascular diseases. The evidence is well documented and some pollutants show a high health hazard, for example particulate matter less than 2.5 µg/mdge gaps  and the In the last 20 years, observational studies have improved our knowledge and awareness of the critical role of environmental pollution in causing damage to exposed populations, in affecting the incidence of cardiovascular diseases, and in mortality . The carWithin the ALTERNATIVE project, the integration of different lines of evidence from toxicology, in vitro tests and -omics will provide wide data to support the identification of the potential candidate Adverse Outcome Pathways (AOPs); in this context, the observational epidemiological studies are instrumental to the definition of the appropriate outcome among the cardiac diseases that can plausibly be traced back to a pollutant showing similar AOPs in the organism. A great part of published reviews provides health evidence on defined diseases and causes of death to advise public health interventions and regulations while little acknowledgement is attributed to preclinical and symptomatic health indicators, which could affect the largest portion of the population . Data prA dedicated article will be drafted to reflect the significance and value of the research stemming from this research protocol application. The findings of the review will extend beyond previous systematic reviews, complementing the evidence on the relationship between environmental exposure and cardiovascular disease. We will review the available epidemiological studies to enlighten the association between contaminants and heart disease starting from the early signs of myocardial damage. The findings from this systematic review will attempt to provide a new insight on the role of environmental pollution and contractile dysfunction.


Depression is an emotional disorder that is problematic in psychiatry owing to its unclear etiology and unknown pathogenesis. Traditional Chinese medicine formulations such as Xiaoyaosan have been widely used throughout history to treat depression. In this review, we have focused on recent evidences elucidating the links between Xiaoyaosan and the treatment of depression. Data from animal and clinical studies, focusing on the pharmacological mechanisms, clinical applications, and effective materials that form the basis for the treatment of depression are presented and discussed. We found that the antidepressant effects of Xiaoyaosan are related to the effects of monoamine neurotransmitters, regulation of the hypothalamic-pituitary-adrenal axis, neuroplasticity, synaptic plasticity, inflammatory response, neuroprotection, brain-gut axis, regulation of intestinal microbiota, oxidative stress, and autophagy for reducing neuronal apoptosis. This review highlights the current evidence supporting the use of Xiaoyaosan as an antidepressant and provides an overview of the potential mechanisms involved. Hypericum perforatum (St. John’s Wort), Melissa officinalis L. (Melissa leaf), and V. officinalis L.  as plants approved for the treatment of stress and mood disorders  by the Song Dynasty (960–1127 AD) is a classic Chinese medicinal compound. Its functions include reconciling the liver and spleen, soothing the liver, invigorating the spleen, nourishing the blood, and relieving depression. It is mainly used to treat liver stagnation, blood deficiency, and spleen weakness (Radix Bupleuri), Danggui (Radix Angelicae Sinensis), Baishao (Radix Paeoniae Alba), Baizhu , Fuling (Poria), Bohe , Shengjiang (Rhizoma Zingiberis), and Gancao (Radix Glycyrrhizae)], which have been used for centuries to treat mental illnesses, including depression  and self-rating depression scale (SDS) scores of XYS were superior to those of antidepressants alone without significant side effects . Based oDepression is categorized as a mental disorder, and neuroendocrine experiments have found that endocrine hormones are closely related to behavior and mood. From the perspective of neurobiology, the occurrence of depression is closely related to the dysfunction of the HPA axis . When thSynaptic plasticity is an important part of learning and memory from the perspective of neurobiology. It indicates that the structure and function of synapses can change under the influence of the continuous activity of neurons, with adjustable characteristics. Synapses are thus crucial for neuronal networks and information transmission . FurtherNumerous studies have shown that the pathogenesis of depression may be closely related to a disorder in the glutamatergic system . GlutamaGlutamate concentration and action time beyond the physiological range will lead to the production of excitatory neurotoxicity damage to neurons. This is one of the pathological mechanisms of social stress disorders, such as affective disorder. This mechanism is associated with damage to astrocytes (AS) and excitatory amino acid transporters (EAATs) due to long-term stress. Zhou et al. found that XYS exerted antidepressant effects through the NR2B and PI3K/Akt signaling pathways to alleviate hippocampal neuronal damage induced by glutamate-mediated excitotoxicity in rat . Liu et The dysfunction of N-methyl-D-aspartic acid receptor (NMDA) receptors is related to certain neuropsychiatric disorders , and theThe expression of neurotrophic factors in the serum and brain regions of patients with depression are significantly different from those of healthy people, suggesting that neurotrophic factors may become new markers for depression. BDNF is the most abundant neurotrophic protein in the brain tissue, and it is crucial for the growth, proliferation, survival, and synaptic activity of neurons . BDNF prRecent studies have found that neuroinflammation is associated with the occurrence of depression, and that NLRP3 inflammasomes, cytokines, astrocytes, and microglia are all involved. NLRP3 is a regulator of the inflammatory response and can regulate the expression of IL-1β. Microglia are activated during infection or stress, leading to elevated levels of inflammatory factors in the brain that disrupt neuronal structure and function. Astrocytes sense the inflammatory signals activated by microglia. Activated astrocytes are divided into M1 type and M2 type. Those of the M1 type release a variety of pro-inflammatory factors and have neurotoxic effects. Those of the M2 type can up-regulate neurotrophic factors, promote the release of anti-inflammatory factors, and have neuroprotective effects. The secretion of pro-inflammatory cytokines such as IL-1β, IL-6, and TNF-α is increased in patients with depression, while the secretion of anti-inflammatory cytokines such as IL-4 and IL-10, among others, is decreased . Animal Yuan et al. found the antidepressant XYS mechanisms were related to neuroprotection using system-network pharmacological analysis . Yin et The brain-gut axis is a two-way information communication system that integrates the neural, immune, endocrine, and metabolic pathways between the brain and the gastrointestinal tract (GI) . The infIn rodent models, psychological stimuli and stress increase gut permeability and promote bacteria to the systemic circulation and brain, thereby increasing the underlying incidence of depression. The expression of C-type natriuretic peptide (CNP) and natriuretic peptide receptor (NPR)-B in depressed rat decreased after XYS treatment, suggesting XYS may improve the symptoms of depressive gastrointestinal dysfunction by down-regulating the CNP signaling pathway . Ding etIncreasing evidence has shown that the orexin system is related to the pathogenesis of depression, and that its regulation is closely related to the occurrence and development of mental diseases. Hou et al. found XYS could increase the expression of orexin A/Oxidation resistance 1 (OXR1) in the lateral hypothalamus of CIS-induced depression rat model, indicating XYS could improve depression symptoms by regulating orexin A/OXR1 . Ma et aPatients with depression show symptoms of psychological disorders which are often accompanied by symptoms of gastrointestinal dysfunction, such as functional dyspepsia and irritable bowel syndrome . They cain vivo and exhibited mixed apoptotic/autophagy phenotypes in the hippocampus; modified XYS alleviated neuronal apoptosis by regulating autophagy (Autophagy is a lysosomal-dependent protein degradation pathway, which maintains the homeostasis of the intracellular environment through the degradation and recycling of damaged organelles and long-lived proteins; however, excessive autophagy is damaging . Previouutophagy . Chronicutophagy . Ding etutophagy . After XDepression presents an ongoing challenge for modern medicine as the pathogenesis of this disease is not fully understood, and there is no definite treatment method that can successfully stop or reverse depression. XYS is an important and valuable traditional Chinese medicine with a high level of safety and efficacy, and it could be used more widely for the treatment of depression in the future. Previous research into the mechanisms of the effects of XYS have been too broad. In the future, rather than only measuring the observed effects of XYS treatment using commercial products, in-depth research on specific genes or pathways with solid experimental basis should be conducted. It is also necessary to examine the existing hypotheses of depression using gene chip technology to detect whole genome changes and clarify the expression trends of each depression-related gene. Furthermore, there is also a lack of high quality standardized clinical studies that include a large number of patients and multiple centers and are performed as high-quality, randomized, double-blind controlled trials to verify the clinical efficacy of XYS for the treatment of depression. The occurrence of disease involves many aspects of body function, and the study of a single pathogenic factor cannot fundamentally clarify the nature of depression. The metabolic transformation of XYS components after entering the human body must also be considered in future investigations. In future studies, we must comprehensively apply various research techniques and methods to clarify the mechanisms of the action of the XYS antidepressant, and further explain these mechanisms using bioinformatics, network pharmacology, and metabolomics, to provide a basis for the research and development of TCM antidepressant drugs.