Structural equation modeling

Depression influences fatigue in inflammatory bowel disease amongst other factors: a structural modelling approach

Objectives

Fatigue is common in people with inflammatory bowel disease (IBD) and is associated with IBD activity, sleep disturbance, anxiety and depression. The relative contribution of these factors to fatigue is unclear. This study aimed to investigate the relationship between fatigue and these factors through a novel approach using structural equation modelling.

Design

Online questionnaire circulated via three tertiary IBD centres and Crohn's Colitis Australia.

Methods

Fatigue was assessed using the Functional assessment of chronic illness measurement system fatigue subscale. Validated measures of sleep, anxiety, depression and IBD activity were included. Following correlation analyses, a structural equation model was developed for the outcome of the fatigue score. Direct and indirect effects were calculated.

Results

There were 630 complete responses to the online questionnaire. The median age of respondents was 41 with the majority female and over half (52%) on biologic medication. Structural equation models for Crohn's disease and ulcerative colitis demonstrated a good fit. In Crohn's disease, the relationship between IBD activity and fatigue was mostly mediated indirectly through the influence of IBD activity on sleep, anxiety and primarily depression. Sleep quality mediated the influence of IBD activity and the indirect effects of depression on fatigue, but not anxiety. Unlike in Crohn's disease, the direct influence of IBD activity on fatigue in ulcerative colitis was non-negligible, although remained of lesser magnitude than the indirect effect of IBD activity on fatigue. Depression was the primary indirect mediator of the influence of IBD activity on fatigue in ulcerative colitis.

Conclusion

In Crohn's disease, IBD activity leads to fatigue through its influence on sleep quality and mental health. The data suggest treatment of clinically significant depression, in both ulcerative colitis and Crohn's disease, may result in the largest decline in fatigue score compared to other variables. Treatment algorithms for fatigue should consider depression a priority.

A review of common statistical methods for dealing with multiple pollutant mixtures and multiple exposures

Traditional environmental epidemiology has consistently focused on studying the impact of single exposures on specific health outcomes, considering concurrent exposures as variables to be controlled. However, with the continuous changes in environment, humans are increasingly facing more complex exposures to multi-pollutant mixtures. In this context, accurately assessing the impact of multi-pollutant mixtures on health has become a central concern in current environmental research. Simultaneously, the continuous development and optimization of statistical methods offer robust support for handling large datasets, strengthening the capability to conduct in-depth research on the effects of multiple exposures on health. In order to examine complicated exposure mixtures, we introduce commonly used statistical methods and their developments, such as weighted quantile sum, bayesian kernel machine regression, toxic equivalency analysis, and others. Delineating their applications, advantages, weaknesses, and interpretability of results. It also provides guidance for researchers involved in studying multi-pollutant mixtures, aiding them in selecting appropriate statistical methods and utilizing R software for more accurate and comprehensive assessments of the impact of multi-pollutant mixtures on human health.

Effects of road width, radii and speeds on collisions at three-arm priority intersections

Simulation and observational studies have identified the importance of intersection geometries and vehicle speeds in collisions. However, the causal mechanisms of such collisions in low-speed areas and for different collision types remain unclear. This observational study investigates the complex relationships between geometries, speeds, visibilities, and road traffic collisions in the context of low-speed urban areas.Data were collected from 120 three-arm priority intersections in Portsmouth, UK. In 2007, Portsmouth became the first city in the UK to adopt a 20mph speed limit on all residential streets. The city has also adopted the UK's Manual for Streets (MfS) as the design standard for all new priority intersections in low-speed residential areas.Piecewise structural equation models (pSEM) were developed to represent the causal mechanisms that relate to geometries, speeds, speed limits and collisions. Findings indicate the role of combinations of approach lane width, corner radii, speed limit, and type of collision. The interaction of wider approach lanes on the minor arm and larger radii of turns for left-turning vehicles (left-hand driving perspective) was associated with higher numbers of road traffic collisions for right-turning vehicles. It is posited here that this is due to the orientation of the left-turning vehicle blocking the left visibility of the right-turning vehicle. These results give weight to the introduction of the 20mph speed limit zone in Portsmouth and some of the changes brought about by MfS. However, the combined effect of approach width and radii on collisions is novel and could form the basis of further guidance on reducing specific types of collisions at three-arm priority intersections.

Exploring influential factors in the self-assessment of life satisfaction among Chinese elderly: a structural equation modeling analysis

The aging problem is becoming more and more prominent globally. Attention to the quality of life and related health improvement among the elderly has become an important issue in modern society. This study utilized a tracking survey conducted in 2017-2018, involving 9,327 Chinese older adults, to examine health influencing factors, and applied structural equation modeling to analyze the influencing factors on the self-assessment of life satisfaction among older adults in different regions (cities, counties, and villages) in China. This study revealed that economic status, psychological status, personal situation, life behaviors, and child care are important influences on older people's self- assessed life satisfaction. There is a positive correlation between economic status, psychological status, child care and the results of the self-assessment of life satisfaction of the elderly. Psychological status and child care have a greater impact on the self-assessment of life satisfaction among the elderly in urban areas compared to villages and towns. The influence of economic status on the self-assessment of life satisfaction of the elderly is lower in urban areas than in rural areas. There is a significant difference in the influence of personal situations on the self-assessment of life satisfaction among the elderly. Additionally, older individuals tend to report higher levels of self-assessment of life satisfaction. Furthermore, female elderly individuals tend to report higher levels of satisfaction compared to males. Findings from this study indicate that improving health self-assessment in older adults requires targeted efforts based on different geographic areas of life and the age stages of older adults, and more attention needs to be paid to men who are just entering old age.

Structural equation modeling for identifying the drivers of health-related quality of life improvement experienced by patients with migraine receiving eptinezumab

BACKGROUND

As new migraine therapies emerge, it is crucial for measures to capture the complexities of health-related quality of life (HRQoL) improvement beyond improvements in monthly migraine day (MMD) reduction. Investigations into the correlations between MMD reduction, symptom management, and HRQoL are lacking, particularly those that focus on improvements in canonical symptoms and improvement in patient-identified most-bothersome symptoms (PI-MBS), in patients treated with eptinezumab. This exploratory analysis identified efficacy measures mediating the effect of eptinezumab on HRQoL improvements in patients with migraine.

METHODS

Data from the DELIVER study of patients with 2-4 prior preventive migraine treatment failures (NCT04418765) were inputted to two structural equation models describing sources of HRQoL improvement via Migraine-Specific Quality-of-Life Questionnaire (MSQ) scores. A single latent variable was defined to represent HRQoL and describe the sources of HRQoL in DELIVER. One model included all migraine symptoms while the second model included the PI-MBS as the only migraine symptom. Mediating variables capturing different aspects of efficacy included MMDs, other canonical symptoms, and PI-MBS.

RESULTS

In the first model, reductions in MMDs and other canonical symptoms accounted for 35% (standardized effect size [SES] - 0.11) and 25% (SES - 0.08) of HRQoL improvement, respectively, with 41% (SES - 0.13) of improvement comprising "direct treatment effect," i.e., unexplained by mediators. In the second model, substantial HRQoL improvement with eptinezumab (86%; SES - 0.26) is due to MMD reduction (17%; SES - 0.05) and change in PI-MBS (69%; SES - 0.21).

CONCLUSIONS

Improvements in HRQoL experienced by patients treated with eptinezumab can be substantially explained by its effect on migraine frequency and PI-MBS. Therefore, in addition to MMD reduction, healthcare providers should discuss PI-MBS improvements, since this may impact HRQoL. Health technology policymakers should consider implications of these findings in economic evaluation, as they point to alternative measurement of quality-adjusted life years to capture fully treatment benefits in cost-utility analyses.

TRIAL REGISTRATION

ClinicalTrials.gov (Identifier: NCT04418765 ; EudraCT (Identifier: 2019-004497-25; URL: https://www.clinicaltrialsregister.eu/ctr-search/search?query=2019-004497-25 ).

Evaluating use of web-based interventions: an example of a Dutch sexual health intervention

With the current increase in web-based interventions, the question of how to measure, and consequently improve engagement in such interventions is gaining more importance. Modern day web analytics tools make it easy to monitor use of web-based interventions. However, in this article, we propose that it would be more meaningful to first examine how the developers envisioned the use of the intervention to establish behavior change (i.e. intended use), before looking into how the intervention is ultimately used with web analytics (i.e. actual use). Such an approach responds to the regularly expressed concern that behavioral interventions are often poorly described, leading to less meaningful evaluations as it is not clear what exactly is being evaluated. Using a page on chlamydia prevention (104 557 pageviews in 2020) from a Dutch sexual health intervention (Sense), we demonstrate the value of acyclic behavior change diagrams (ABCDs) as a method to visualize intended use of an intervention. ABCDs show at a glance how behavior change principles are applied in an intervention and target determinants of behavior. Based on this ABCD, we investigate actual use of the intervention, using web analytics tool Matomo. Despite being intended to stimulate STI-testing, only 14% of the 35 347 transfers from this page led to the STI-testing page and a high bounce rate (79%) and relatively high exit rate were reported (69%). Recommendations to further interpret the data are given. This real-life example demonstrates the potential of combining ABCDs and Matomo as methods to gain insight into use of web-based interventions.

A structural equation model linking health literacy, self-efficacy, and quality of life in patients with polycystic ovary syndrome

BACKGROUND

Health literacy is a crucial factor that affects health outcomes. Understanding the current status of health literacy among patients with polycystic ovary syndrome (PCOS) is the basis for helping patients better manage risk factors and improve their health outcomes. This study aimed to explore the status of and factors influencing health literacy in patients with PCOS, and to validate the pathway between health literacy, quality of life, and self-efficacy for these patients.

METHODS

A cross-sectional study was conducted using a convenience sample of 300 patients with PCOS in the gynecology outpatient clinic of a tertiary hospital in Zunyi from March to September 2022. Data on health literacy, demographic features, quality of life, and self-efficacy were collected. Multiple stepwise linear regression was conducted to assess the risk factors associated with health literacy for the study participants. A structural equation model was used to construct and validate the pathways.

RESULTS

Most participants exhibited low health literacy (3.61 ± 0.72), and only 25.70% had adequate health literacy. Multiple regression analysis revealed that the main factors associated with health literacy among participants included Body Mass Index (BMI) (B = -0.95, p < 0.01), education (B = 3.44, p < 0.01), duration of PCOS (B = 4.66, p < 0.01), quality of life (B = 0.25, p < 0.01), and self-efficacy (B = 0.76, p < 0.01). Multiple fit values indicated that the model fit the data effectively. The direct effect of health literacy on self-efficacy and quality of life was 0.06 and 0.32, respectively. The indirect effect of health literacy on quality of life was -0.053, and the total effect of health literacy on quality of life was 0.265.

CONCLUSIONS

Health literacy was low among patients with PCOS. Healthcare providers should pay more attention to health literacy and to developing the corresponding intervention strategies urgently needed to improve the quality of life and health behavior of patients with PCOS.

Emotional Exhaustion, a Proxy for Burnout, Is Associated with Sleep Health in French Healthcare Workers without Anxiety or Depressive Symptoms: A Cross-Sectional Study

Burnout is frequent among healthcare workers, and sleep problems are suspected risk factors. The sleep health framework provides a new approach to the promotion of sleep as a health benefit. The aim of this study was to assess good sleep health in a large sample of healthcare workers and to investigate its relationship with the absence of burnout among healthcare workers while considering anxiety and depressive symptoms. A cross-sectional Internet-based survey of French healthcare workers was conducted in summer 2020, at the end of the first COVID-19 lockdown in France (March to May 2020). Sleep health was assessed using the RU-SATED v2.0 scale (RegUlarity, Satisfaction, Alertness, Timing, Efficiency, Duration). Emotional exhaustion was used as a proxy for overall burnout. Of 1069 participating French healthcare workers, 474 (44.3%) reported good sleep health (RU-SATED > 8) and 143 (13.4%) reported emotional exhaustion. Males and nurses had a lower likelihood of emotional exhaustion than females and physicians, respectively. Good sleep health was associated with a 2.5-fold lower likelihood of emotional exhaustion and associations persisted among healthcare workers without significant anxiety and depressive symptoms. Longitudinal studies are needed to explore the preventive role of sleep health promotion in terms of the reduction in burnout risk.

Social environment and brain structure in adolescent mental health: A cross-sectional structural equation modelling study using IMAGEN data

Adolescent mental health is impacted by a myriad of factors, including the developing brain, socioeconomic conditions and changing social relationships. Studies to date have neglected investigating those factors simultaneously, despite evidence of their interacting effects and distinct profiles for males and females. The current study addressed that gap by applying structural equation modelling to IMAGEN data from adolescents aged 14 years (n = 1950). A multi-group model split by sex was tested with the variables of socioeconomic stress, family support, peer problems, and brain structure as predictors, and emotional symptoms as the main outcome. Findings indicated that, for both sexes, peer problems were positively associated with emotional symptoms, and socioeconomic stress was negatively associated with family support. Additionally, there were sex-specific findings within the full models: ventromedial prefrontal cortex grey matter volume was negatively associated with emotional symptoms for males when corrected for whole brain volume, and socioeconomic stress was negatively associated with whole brain volume for females. This study underscores the importance of the peer environment for early adolescent emotional symptoms in both boys and girls, but goes further to suggest distinct gender associations with socioeconomic factors and brain structure which provides a multi-level view of risk and resilience. Future research could exploit existing IMAGEN longitudinal data to strengthen causal claims and to determine the potential longstanding impact of social environment and brain development on adolescent mental health.

Acyclic behavior change diagrams: a tool to report and analyze interventions

Background

Behavior change interventions have a vital role in enhancing human health and well-being. Nevertheless, concerns have been raised about suboptimal reporting of behavior change interventions, making analyses, replications, and intervention re-use hard or impossible to conduct.

Objective

This paper introduces acyclic behavior change diagrams (ABCDs) to achieve more transparent development, evaluation, and reporting of behavior change interventions. ABCDs are a visual representation of the assumptions regarding causal-structural chains that underlie putative active ingredients of behavior change interventions. These causal-structural chains link the behavior change principles that are applied in an intervention to the (determinants of) behavior targeted in that intervention.

Conclusions

ABCDs are helpful in making implicit assumptions explicit and help communicate assumptions with team members and other stakeholders. Moreover, we believe they make evaluation easier, and their machine-readability allows for ABCDs to be imported directly into (systematic review) databases with negligible costs while disclosing complete and accurate data. Finally, the ABCD approach fits well with other initiatives to gain a deeper understanding and synthesis of the literature on active intervention elements.

When the influencer says jump! How influencer signaling affects engagement with COVID-19 misinformation

With signaling theory, credibility, and social media engagement (SME) as guiding frameworks, this study used an experiment to examine how social media influencers (SMIs) affect how people engage with COVID-19 misinformation. SMI-promoted information elicited more SME, credibility, and purchase likelihood than non-SMI promoted information. The most effective message was a post promoted by an SMI that contained detailed information about an authentic product. However, data indicated nuance regarding the effect of SMIs. The authenticity of the information as well as the amount of detail in the post played a role. Additionally, mediated effects analysis showed that the impact of SME on purchase likelihood was higher among non-SMI followers. Data suggests that using a multi-signal messaging approach is suitable regardless of promotion by an SMI. This has important implications to public health messaging and the author discusses how health agencies may effectively signal information to the public.

Bacterial Keystone Taxa Regulate Carbon Metabolism in the Earthworm Gut

As important ecosystem engineers in soils, earthworms strongly influence carbon cycling through their burrowing and feeding activities. Earthworms do not perform these roles in isolation, because their intestines create a special habitat favorable for complex bacterial communities. However, how the ecological functioning of these earthworm-microbe interactions regulates carbon cycling remains largely unknown. To fill this knowledge gap, we investigated the bacterial community structure and carbon metabolic activities in the intestinal contents of earthworms and compared them to those of the adjacent soils in a long-term fertilization experiment. We discovered that earthworms harbored distinct bacterial communities compared to the surrounding soil under different fertilization conditions. The bacterial diversity was significantly larger in the adjacent soils than that in the earthworm gut. Three statistically identified keystone taxa in the bacterial networks, namely, Solirubrobacterales, Ktedonobacteraceae, and Jatrophihabitans, were shared across the earthworm gut and adjacent soil. Environmental factors (pH and organic matter) and keystone taxa were important determinants of the bacterial community composition in the earthworm gut. Both PICRUSt2 (Phylogenetic Investigation of Communities by Reconstruction of Unobserved States) and FAPROTAX (Functional Annotation of Prokaryotic Taxa) predicted that carbon metabolism was significantly higher in adjacent soil than in the earthworm gut, which was consistent with the average well color development obtained by the Biolog assay. Structural equation modeling combined with correlation analysis suggested that pH, organic matter, and potential keystone taxa exhibited significant relationships with carbon metabolism. This study deepens our understanding of the mechanisms underlying keystone taxa regulating carbon cycling in the earthworm gut. IMPORTANCE The intestinal microbiome of earthworms is a crucial component of the soil microbial community and nutrient cycling processes. If we could elucidate the role of this microbiome in regulating soil carbon metabolism, we would make a crucial contribution to understanding the ecological role of these gut bacterial taxa and to promoting sustainable agricultural development. However, the ecological functioning of these earthworm-microbe interactions in regulating carbon cycling has so far not been fully investigated. In this study, we revealed, first, that the bacterial groups of Solirubrobacterales, Ktedonobacteraceae, and Jatrophihabitans were core keystone taxa across the earthworm gut and adjacent soil and, second, that the environmental factors (pH and organic carbon) and keystone taxa strongly affected the bacterial community composition and exhibited close correlations with microbial carbon metabolism. Our results provide new insights into the community assembly of the earthworm gut microbiome and the ecological importance of potential keystone taxa in regulating carbon cycling dynamics.

Public utility vehicle service quality and customer satisfaction in the Philippines during the COVID-19 pandemic

The implementation of lockdown due to the COVID-19 pandemic has affected most businesses worldwide. The transportation business, specifically in the Philippines, has been heavily affected since only the healthcare and essential workers were allowed to leave their homes during the early stage of the pandemic. This paper aimed to explore the service quality of Public Utility Vehicles (PUV) in the Philippines during the COVID-19 pandemic utilizing the SERVQUAL dimensions. A total of 564 participants answered an online questionnaire using the convenience sampling approach, consisting of 58 questions. Structural equation modelling (SEM) was applied to derive the causal relationships between SERVQUAL dimensions, COVID-19 safety protocol, and customer satisfaction simultaneously. Out of the six dimensions, the SEM indicated that COVID-19 protocols, tangibility, and assurance variables were found to significantly affect PUV service quality and thus, customer satisfaction. This study is one of the first complete studies that analyzed the PUV service quality during the COVID-19 pandemic. The findings could provide the government with an evaluation of the compliance of PUVs to the imposed COVID-19 protocols. Furthermore, the framework of this study could also be applied and extended in evaluating PUV worldwide.

Posttraumatic Stress Disorder and Relationship Satisfaction among Firefighters: The Role of Emotion Regulation Difficulties

Firefighters are exposed to potentially traumatic events throughout their careers, placing them at heightened risk for the development of posttraumatic stress disorder (PTSD). Individuals experiencing PTSD symptoms often experience interpersonal problems and relationship stress, and this may be due to emotion regulation difficulties. The current study examined the association between PTSD symptoms, couple relationship satisfaction, and emotion regulation difficulties among firefighters. Participants were comprised of 188 firefighters (M _age = 41.32, SD = 9.25, 97.3% male) who completed an online questionnaire. Results indicated that PTSD symptom severity was negatively associated with relationship satisfaction and positively associated with emotion regulation difficulties. Additionally, there was a significant negative indirect effect of PTSD symptom severity on relationship satisfaction through heightened emotion regulation difficulties. Negative alterations in cognition and mood were especially relevant to emotion regulation difficulties and relationship satisfaction. Findings highlight the importance of understanding associations between PTSD and interpersonal functioning among firefighters. Emotion regulation difficulties may offer a clinically relevant transdiagnostic factor for targeting PTSD symptoms and relationship functioning among firefighters.

Testing the moderating role of trade openness on the environmental Kuznets curve hypothesis: a novel approach

We explore the moderating role of trade openness (TO) by gauging its main and interaction effects on the economic growth and environmental quality nexus. In this direction, we implement a novel approach by using three different measures of pollution emissions (CO2-CH4-PM2.5) in the environmental Kuznets curve hypothesis and applying a structural equation modelling methodology to 115 countries, grouped into low-, middle- and high-income countries, spanning the period 1992-2018. The evidence suggests that energy consumption has a positive impact on CO2 emissions for all income panels whilst the moderating effect of TO appears to be a key degrading factor of environmental quality in low- and middle-income countries. In addition, TO's interaction with GDP growth is found to negatively affect environmental quality across all income groups. Given that global economies are on the verge of returning to pre-pandemic levels of industrial operations along with emissions in the wake of the failure of COP26 and that COVID-19 has reminded the world the urgency of developing sustainable approaches in fostering 'green economic growth' models; a host of policy measures are proposed in support of this whilst their likely implications are discussed with reference to different income level countries.

Relationship between Braden Scale scores and acute kidney injury among patients with acute coronary syndrome: a multicentre retrospective cohort study

OBJECTIVES

To evaluate the impact of pressure ulcer events assessed by the Braden Scale (BS) on acute kidney injury (AKI) in patients with acute coronary syndrome (ACS).

DESIGN

A multicentre retrospective cohort study.

SETTING

Chest pain centres from seven tertiary hospitals in China.

PARTICIPANTS

We analysed 3185 patients with ACS from the Retrospective Evaluation of Acute Chest Pain study. The patients were divided into three groups (B1, B2 and B3) according to their BS scores (≤12 vs 13-14 vs ≥15, respectively) at admission.

OUTCOME MEASURES

AKI was defined according to the criteria of the 2012 Kidney Disease: Improving Global Outcomes. Multivariate logistic analysis was used to evaluate the relationship between the BS score and AKI.

RESULTS

There were 461 patients (14.5%) with ACS who had the complication of AKI. Patients with a lower score on the BS had a higher incidence of AKI (p<0.001). Multivariate logistic regression analysis showed that adjusted ORs of the BS score for AKI were 2.242 (B1 vs B3: 95% CI: 1.643 to 3.060, p<0.001) and 1.566 (B2 vs B3: 95% CI: 1.186 to 2.069, p=0.002). The receiver operating characteristic curve analysis showed that the area under the curve of the BS score was 0.719 (95% CI: 0.702 to 0.736; p<0.001) for AKI.

CONCLUSIONS

The BS score was independently associated with AKI. It may be a useful tool to identify those who may benefit from further prediction and prevention of AKI in patients with ACS.

TRAIL REGISTRATION NUMBER

ChiCTR1900024657 (http://www.chictr.org.cn/). The satge rekates to results.

Adaptive and maladaptive coping strategies in older adults with chronic pain after lumbar surgery

This study investigated whether adaptive and maladaptive coping strategies mediate the association between chronic pain and health-related quality of life among older adults experiencing chronic pain after lumbar surgery. Participants were 103 older adults with either or both of chronic lower back pain and leg pain after lumbar surgery (median age = 75 years, men = 44, women = 59). Intensity of chronic lower back and leg pain (11-point numerical rating scale), physical activities (Physical Activity Scale for the Elderly) as an adaptive coping strategy, maladaptive coping strategies (e.g. guarding, resting; Chronic Pain Coping Inventory), and health-related quality of life (12-item Short-Form Health Survey) were measured. Hypothetical models with adaptive and maladaptive coping strategies as mediators of pain intensity and health-related quality of life were tested using structural equation modeling. Model fitness was acceptable (adjusted goodness of fit index: 0.94-0.98, comparative fit index: 1.00, root mean square error of approximation: 0.00). The results showed that (1) the adaptive coping strategy of physical activity positively mediated the association between lower back and leg pain, and physical health but not mental and social health; (2) maladaptive coping strategies negatively mediated the association between pain and physical, mental, and social health; (3) physical activities were negatively associated with maladaptive coping strategies. This study demonstrated that adaptive and maladaptive coping strategies serve as mediators of the relationship between chronic pain and health-related quality of life in older adults after lumbar surgery.

Structural equation modeling to detect predictors of breast self-examination behavior: Implications for intervention planning

AIM

Breast cancer is the most frequent malignant tumor among Chinese women. Breast self-examination (BSE) is a simple, effective method for early detection of screening and it is essential for the prevention and control of breast cancer. The aim of this study was to create a hypothetical model to determine the factors influencing women's BSE behavior in Eastern China.

METHODS

A survey was conducted using an online questionnaire and targeting 1200 women aged 18-70 years in Eastern China. Collected data were analyzed using ibm spss 25.0 and amos 24.0 software.

RESULTS

The final model showed a desirable fitness to sample data. A direct positive relationship exists between knowledge on risk factors and BSE. A direct positive association was found between positive attitudes and BSE, while negative attitudes have a direct negative impact on BSE. Objective factors not only had a significant direct impact on BSE, but also directly affected the positive attitudes. Positive attitudes play an intermediary role between objective factors and BSE.

CONCLUSION

Knowledge on risk factors about breast cancer, attitudes toward BSE and objective factors are new predictors which may influence BSE by using the structural equation modeling method.

Implicit adaptation compensates for erratic explicit strategy in human motor learning

Sports are replete with strategies, yet coaching lore often emphasizes 'quieting the mind', 'trusting the body' and 'avoiding overthinking' in referring to the importance of relying less on high-level explicit strategies in favor of low-level implicit motor learning. We investigated the interactions between explicit strategy and implicit motor adaptation by designing a sensorimotor learning paradigm that drives adaptive changes in some dimensions but not others. We find that strategy and implicit adaptation synergize in driven dimensions, but effectively cancel each other in undriven dimensions. Independent analyses-based on time lags, the correlational structure in the data and computational modeling-demonstrate that this cancellation occurs because implicit adaptation effectively compensates for noise in explicit strategy rather than the converse, acting to clean up the motor noise resulting from low-fidelity explicit strategy during motor learning. These results provide new insight into why implicit learning increasingly takes over from explicit strategy as skill learning proceeds.

Influencing factors of physicians' prescription behavior in selecting essential medicines: a cross-sectional survey in Chinese county hospitals

Background

To explore the key factors affecting prescription practices of essential medicines in Chinese county hospital. National essential medicine policy (NEMP) plays important roles in health care system, especially in developing countries. As a fundamental component in the Chinese health system reform, NEMP was implemented in primary health care institutions during the first stage of reform. As it is rolled out, priority usage and zero-mark-up policy of essential medicines are to be applied in every government-run healthcare institution. However, the intention and influence factors of physicians on priority selecting essential medicine remains unclear.

Methods

Based on the theory of planned behavior, a cross-sectional questionnaire survey was conducted to analyze physicians’ intention, attitude, subjective norms (SNs) and perceived behavioral control (PBC) on prescrictions and their actual behavior on selection of essential medicines.

Results

Two hundred eighty-two physicians participated in the structural questionnaire interview. The final structural equation model reflected influencing factors affecting physicians’ prescribing behavior (χ²/df = 1.32, GFI = 0.99, IFI = 0.99). Structural equation model analysis showed that attitude, other influencers and institutional environment, and PBC significantly affected behavioral intention. However, the control extent of cognition behavior of physicians prescribing had no significant positive effect on the priority usage of essential medicines.

Conclusion

Investigation results demonstrate physicians are unaware of NEMP design and implementation plans. To help enhance rational use of essential medicines we suggest educating physicians on the value of NEMP, and integrating the drug shortage report into the essential medicine (EM) bidding system seamless communication with pharmaceutical manufacturers’ credit information system.

Structural equation modeling for hypertension and type 2 diabetes based on multiple SNPs and multiple phenotypes

Genome-wide association studies (GWAS) have been successful in identifying genetic variants associated with complex diseases. However, association analyses between genotypes and phenotypes are not straightforward due to the complex relationships between genetic and environmental factors. Moreover, multiple correlated phenotypes further complicate such analyses. To resolve this complexity, we present an analysis using structural equation modeling (SEM). Unlike current methods that focus only on identifying direct associations between diseases and genetic variants such as single-nucleotide polymorphisms (SNPs), our method introduces the effects of intermediate phenotypes, which are related phenotypes distinct from the target, into the systematic genetic study of diseases. Moreover, we consider multiple diseases simultaneously in a single model. The procedure can be summarized in four steps: 1) selection of informative SNPs, 2) extraction of latent variables from the selected SNPs, 3) investigation of the relationships among intermediate phenotypes and diseases, and 4) construction of an SEM. As a result, a quantitative map can be drawn that simultaneously shows the relationship among multiple SNPs, phenotypes, and diseases. In this study, we considered two correlated diseases, hypertension and type 2 diabetes (T2D), which are known to have a substantial overlap in their disease mechanism and have significant public health implications. As intermediate phenotypes for these diseases, we considered three obesity-related phenotypes-subscapular skin fold thickness, body mass index, and waist circumference-as traits representing subcutaneous adiposity, overall adiposity, and abdominal adiposity, respectively. Using GWAS data collected from the Korea Association Resource (KARE) project, we applied the proposed SEM process. Among 327,872 SNPs, 24 informative SNPs were selected in the first step (p<1.0E-05). Ten latent variables were generated in step 2. After an exploratory analysis, we established a path diagram among phenotypes and diseases in step 3. Finally, in step 4, we produced a quantitative map with paths moving from specific SNPs to hypertension through intermediate phenotypes and T2D. The resulting model had high goodness-of-fit measures (χ2 = 536.52, NFI = 0.997, CFI = 0.998, GFI = 0.995, AGFI = 0.993, RMSEA = 0.012).

Who self-medicates? Results from structural equation modeling in the Greater Paris area, France

OBJECTIVES

Our study aimed to describe the prevalence of self-medication among the Paris adult population and to identify the factors associated with self-medication.

MATERIALS AND METHODS

This cross-sectional study was based on data collected from the SIRS cohort (a French acronym for "Health, inequalities and social ruptures") in 2005 in the Paris metropolitan area using a face-to-face administration questionnaire among a representative sample of 3,023 French-speaking adults. Structural equation models were used to investigate the factors associated with self-medication in the overall population and according to income.

RESULTS

The prevalence of self-medication in the past four weeks was 53.5% in the Paris metropolitan area. Seven factors were directly associated with self-medication in the structural equation model. Self-medication was found more common among women, young people, in active employment or student, with a high income, but also among people with a health information seeking behavior, with a high daily mobility, and/or with a history of unmet healthcare needs due to economic reasons. When looking at these coefficients according to income, the association between self-medication and daily mobility appeared stronger in the bottom quartile of income whereas it was no longer significant in the rest of the survey population.

CONCLUSION

Self-medication is a frequent practice in the Paris metropolitan area. This study confirms the role of some factors found to be associated with self-medication in the literature such as age or gender and draws attention to other factors rarely explored such as daily mobility, especially among people with a low income, or health information seeking behavior.

Dietary manganese and type 2 diabetes mellitus: two prospective cohort studies in China

AIMS/HYPOTHESIS

The association between dietary Mn and type 2 diabetes is unclear. We aimed to elucidate whether dietary Mn is associated with type 2 diabetes, to investigate whether this association is independent of dietary total antioxidant capacity (TAC) and to explore the underlying mechanisms in their association.

METHODS

Two prospective cohorts of 3350 and 7133 Chinese adults (20-74 years old) were enrolled including, respectively, 244 and 578 individuals newly diagnosed with type 2 diabetes, with mean values of 4.2 and 5.3 years of follow-up. Cox's proportional-hazards regression and linear regression were performed to investigate the association between dietary Mn and type 2 diabetes (diagnosed by OGTT) or HbA_lc and to analyse the joint association between dietary Mn and TAC. Restricted cubic spline (RCS) regression was applied to the non-linear association between dietary Mn and incidence of type 2 diabetes. Mediation analysis was applied to explore potential mediators in their association in a subgroup of 500 participants.

RESULTS

Dietary Mn intakes were 4.58 ± 1.04 and 4.61 ± 1.08 (mean ± SD) mg/day in the two cohorts. Dietary Mn was inversely associated with type 2 diabetes incidence and HbA_lc concentration in both cohorts (p_trend < 0.01 and <0.01 for type 2 diabetes, and p_trend < 0.01 and =0.02 for HbA_lc, respectively, in each cohort) independent of TAC, adjusted for age, sex, BMI, tobacco use, alcohol consumption, physical activity, diabetes inheritance, total energy, carbohydrate, total fatty acids, fibre, calcium, Mg, hypertension, hyperlipidaemia, and impaired glucose tolerance or FBG (all at baseline). Their inverse association was stronger in the presence of diets with high, compared with low, TAC. In RCS, intakes of >6.01 and 6.10-6.97 mg/day were associated with a significantly lower type 2 diabetes incidence in the two respective cohorts. Mediation analysis showed that high plasma Mn and low oxidative stress (increased Mn superoxide dismutase and decreased 8-hydroxydeoxyguanosine) contributed to the association between dietary Mn and both type 2 diabetes and HbA_lc.

CONCLUSIONS/INTERPRETATION

Dietary Mn was inversely associated with type 2 diabetes independently of TAC. In addition, this association was stronger in a high- rather than low-TAC diet. Plasma Mn and oxidative stress were mediators in the association between dietary Mn and type 2 diabetes. Future studies on absolute Mn intake should be conducted to study the potential non-linearity and optimal levels of dietary Mn and type 2 diabetes.

Access to primary care for socio-economically disadvantaged older people in rural areas: exploring realist theory using structural equation modelling in a linked dataset

Background

Realist approaches seek to answer questions such as ‘how?’, ‘why?’, ‘for whom?’, ‘in what circumstances?’ and ‘to what extent?’ interventions ‘work’ using context-mechanism-outcome (CMO) configurations. Quantitative methods are not well-established in realist approaches, but structural equation modelling (SEM) may be useful to explore CMO configurations. Our aim was to assess the feasibility and appropriateness of SEM to explore CMO configurations and, if appropriate, make recommendations based on our access to primary care research. Our specific objectives were to map variables from two large population datasets to CMO configurations from our realist review looking at access to primary care, generate latent variables where needed, and use SEM to quantitatively test the CMO configurations.

Methods

A linked dataset was created by merging individual patient data from the English Longitudinal Study of Ageing and practice data from the GP Patient Survey. Patients registered in rural practices and who were in the highest deprivation tertile were included. Three latent variables were defined using confirmatory factor analysis. SEM was used to explore the nine full CMOs. All models were estimated using robust maximum likelihoods and accounted for clustering at practice level. Ordinal variables were treated as continuous to ensure convergence.

Results

We successfully explored our CMO configurations, but analysis was limited because of data availability. Two hundred seventy-six participants were included. We found a statistically significant direct (context to outcome) or indirect effect (context to outcome via mechanism) for two of nine CMOs. The strongest association was between ‘ease of getting through to the surgery’ and ‘being able to get an appointment’ with an indirect mediated effect through convenience (proportion of the indirect effect of the total was 21%). Healthcare experience was not directly associated with getting an appointment, but there was a statistically significant indirect effect through convenience (53% mediated effect). Model fit indices showed adequate fit.

Conclusions

SEM allowed quantification of CMO configurations and could complement other qualitative and quantitative techniques in realist evaluations to support inferences about strengths of relationships. Future research exploring CMO configurations with SEM should aim to collect, preferably continuous, primary data.

Electronic supplementary material

The online version of this article (10.1186/s12874-018-0514-x) contains supplementary material, which is available to authorized users.

Impact of patient characteristics and treatment procedures on hospitalization cost and length of stay in Japanese patients with influenza: A structural equation modelling approach

OBJECTIVES

Little is known about the economic burden of influenza-related hospitalizations in Japan. This study sought to identify the factors that contribute to the total healthcare costs (THCs) associated with hospitalizations due to influenza in the Japanese population.

STUDY DESIGN

A retrospective cross-sectional database analysis study.

METHODS

A structural equation modelling approach was used to analyse a nationwide Japanese hospital claims data. This study included inpatients with at least 1 confirmed diagnosis of influenza and with a hospital stay of at least 2 days, who were admitted between April 2014 and March 2015.

RESULTS

A total of 5261 Japanese inpatients with a diagnosis of influenza were included in the final analysis. The elderly (≥65 years) and the young (≤15 years) comprised more than 85% of patients. The average length of stay (LOS) was 12.5 days, and the mean THC was 5402 US dollars (US$) per hospitalization. One additional hospital day increased the THC by 314 US$. Intensive care unit hospitalizations were linked to higher costs (+4957 US$) compared to regular hospitalizations. The biggest procedure-related cost drivers, which were also impacted by LOS, were blood transfusions (+6477 US$), tube feedings (+3501 US$) and dialysis (+2992 US$).

CONCLUSIONS

In Japan, the economic burden due to influenza-related hospitalizations for both children and the elderly is considerable and is further impacted by associated comorbidities, diagnostic tests and procedures that prolong the LOS.

Structural equation modeling with latent variables for longitudinal blood pressure traits using general pedigrees

Structural equation modeling (SEM) has been used in a wide range of applied sciences including genetic analysis. The recently developed R package, strum, implements a framework for SEM for general pedigree data. We explored different SEM techniques using strum to analyze the multivariate longitudinal data and to ultimately test the association of genotypes on blood pressure traits. The quantitative blood pressure (BP) traits, systolic BP (SBP) and diastolic BP (DBP) were analyzed as the main traits of interest with age, sex, and smoking status as covariates. The single nucleotide polymorphism (SNP) genotype information from genome-wide association studies (GWAS) data was used for the test of association. The adjustment for hypertension treatment effect was done by the censored regression approach. Two different longitudinal data models, autoregressive model and latent growth curve model, were used to fit the longitudinal BP traits. The test of association for SNP was done using a novel score test within the SEM framework of strum. We found the 10 SNPs within the GWAS suggestive P value level, and among those 10, the most significant top 3 SNPs agreed in rank in both analysis models. The general SEM framework in strum is very useful to model and test for the association with massive genotype data and complex systems of multiple phenotypes with general pedigree data.

Improving access to high-quality primary care for socioeconomically disadvantaged older people in rural areas: a mixed method study protocol

INTRODUCTION

The UK has an ageing population, especially in rural areas, where deprivation is high among older people. Previous research has identified this group as at high risk of poor access to healthcare. The aim of this study is to generate a theory of how socioeconomically disadvantaged older people from rural areas access primary care, to develop an intervention based on this theory and test it in a feasibility trial.

METHODS AND ANALYSIS

On the basis of the MRC Framework for Developing and Evaluating Complex Interventions, three methods will be used to generate the theory. First, a realist review will elucidate the patient pathway based on existing literature. Second, an analysis of the English Longitudinal Study of Ageing will be completed using structural equation modelling. Third, 15 semistructured interviews will be undertaken with patients and four focus groups with health professionals. A triangulation protocol will be used to allow each of these methods to inform and be informed by each other, and to integrate data into one overall realist theory. Based on this theory, an intervention will be developed in discussion with stakeholders to ensure that the intervention is feasible and practical. The intervention will be tested within a feasibility trial, the design of which will depend on the intervention. Lessons from the feasibility trial will be used to refine the intervention and gather the information needed for a definitive trial.

ETHICS AND DISSEMINATION

Ethics approval from the regional ethics committee has been granted for the focus groups with health professionals and interviews with patients. Ethics approval will be sought for the feasibility trial after the intervention has been designed. Findings will be disseminated to the key stakeholders involved in intervention development, to researchers, clinicians and health planners through peer-reviewed journal articles and conference publications, and locally through a dissemination event.

Increased hemoglobin A1c threshold for prediabetes remarkably improving the agreement between A1c and oral glucose tolerance test criteria in obese population

CONTEXT

It is unclear why the prevalence of diabetes and prediabetes, especially prediabetes, between diagnosed by oral glucose tolerance test (OGTT) and hemoglobin A1c (HbA1c) criteria, is substantially discordant.

OBJECTIVE

We aimed to evaluate the effects of obesity on the agreement between HbA1c and OGTT for diagnosing diabetes and prediabetes and identify the optimal HbA1c cutoff values in different body mass index (BMI) classifications.

DESIGN SETTING AND PARTICIPANTS

In a population-based, cross-sectional study in Harbin, China, 4325 individuals aged 20-74 years without a prior diagnosed diabetes were involved in this study.

OUTCOME

measure The performance and optimal cutoff points of HbA1c were assessed by receiver-operating characteristic curve. The contribution of BMI to HbA1c was analyzed by structural equational model.

RESULTS

The agreement between HbA1c criteria and OGTT decreased with BMI gain (κ = 0.359, 0.312, and 0.275 in a normal weight, overweight, and obese population, respectively). The structural equational model results showed that BMI was significantly associated with HbA1c in normal glucose tolerance and prediabetes subjects but not in diabetes subjects. At a specificity of 80% for prediabetes and 97.5% for diabetes, the optimal HbA1c cutoff points for prediabetes and diabetes were 5.6% and 6.4% in normal-weight, 5.7% and 6.5% in overweight, and 6.0% and 6.5% in an obese population. When the new HbA1c cutoff values were used, the agreement in obese subjects increased almost to the level in normal-weight subjects.

CONCLUSIONS

The poor agreement between HbA1c and OGTT criteria in an obese population can be significantly improved through increasing the HbA1c threshold for prediabetes.

strum: an R package for structural modeling of latent variables for general pedigrees

BACKGROUND

Structural equation modeling (SEM) is an extremely general and powerful approach to account for measurement error and causal pathways when analyzing data, and it has been used in wide range of applied sciences. There are many commercial and freely available software packages for SEM. However, it is difficult to use any of the packages to analyze general pedigree data, and SEM packages for genetics are limited in their application.

RESULTS

We present the new R package strum to serve the need of a suitable SEM software tool for genetic analysis. It implements a general framework for SEM within the context of general pedigree data. This context requires specialized considerations such as familial correlations and ascertainment. Our package is an extraordinarily flexible tool capable of modeling genetic association, linkage analysis, polygenic effects, shared environment, and ascertainment combined with confirmatory factor analysis and general SEM. It also provides a convenient tool for model visualization, and integrates tools for simulating pedigree data. The various features of this package are tested through a simulation study to evaluate performance, and our results show that strum is very reliable and robust in terms of the accuracy and coverage of parameter estimates.

CONCLUSIONS

strum is a valuable new tool for genetic analysis. It can be easily used with general pedigree data, incorporating both measurement and structural models, giving it some significant advantages over other software packages. It also includes a built-in approach for handling ascertainment, a helpful integrated tool for genetic data simulation, and built-in tools for model visualization, providing a significant addition to biomedical research.

Workplace health promotion and working conditions as determinants of employee health

Purpose

– The purpose of this paper is to investigate general psychosocial work conditions and specific workplace health promotion (WHP) measures in relation to employee health and sickness absence in Swedish municipal social care organizations.

Design/methodology/approach

– In a random sample of 60 out of the 290 municipalities in Sweden, 15,871 municipal social care employees working with elderly and disabled clients were sent a questionnaire concerning psychosocial work environment, WHP, and self-rated health. The responses (response rate 58.4 per cent) were complemented by register data on sickness absence (>14 days). All data were aggregated to employer level.

Findings

– A structural equation modelling analysis using employer-level data demonstrated that employers with more favourable employee ratings of the psychosocial work conditions, as well as of specific health-promoting measures, had better self-rated health and lower sickness absence level among employees.

Practical implications

– The results from this representative nationwide sample of employers within one sector indicate that employers can promote employee health both by offering various health-specific programmes and activities, such as work environment education, fitness activities, and lifestyle guidance, as well as by forming a high-quality work environment in general including developmental and supportive leadership styles, prevention of role conflicts, and a supportive and comfortable social climate.

Originality/value

– This study with a representative nationwide sample demonstrates: results in line with earlier studies and explanations to the challenges in comparing effects from specific and general WHP interventions on health.

Mediation of cardiovascular risk factor effects through subclinical vascular disease: the Multi-Ethnic Study of Atherosclerosis

OBJECTIVE

It is unclear to what extent subclinical cardiovascular disease (CVD) such as coronary artery calcium (CAC), carotid intima-media thickness (CIMT), and brachial flow-mediated dilation (FMD) are mediators of the known associations between traditional cardiovascular risk factors and incident CVD events. We assessed the portion of the effects of risk factors on incident CVD events that are mediated through CAC, CIMT, and FMD.

APPROACH AND RESULTS

Six thousand three hundred fifty-five of 6814 Multi-Ethnic Study of Atherosclerosis participants were included. Nonlinear implementation of structural equation modeling (STATA mediation package) was used to assess whether CAC, CIMT, or FMD are mediators of the association between traditional risk factors and incident CVD event. Mean age was 62 years, with 47% men, 12% diabetics, and 13% current smokers. After a mean follow-up of 7.5 years, there were 539 CVD adjudicated events. CAC showed the highest mediation while FMD showed the least. Age had the highest percent of total effect mediated via CAC for CVD outcomes, whereas current cigarette smoking had the least percent of total effect mediated via CAC (percent [95% confidence interval]: 80.2 [58.8-126.7] versus 10.6 [6.1-38.5], respectively). Body mass index showed the highest percent of total effect mediated via CIMT (17.7 [11.6-38.9]); only a negligible amount of the association between traditional risk factors and CVD was mediated via FMD.

CONCLUSIONS

Many of the risk factors for incident CVD (other than age, sex, and body mass index) showed a modest level of mediation via CAC, CIMT, and FMD, suggesting that current subclinical CVD markers may not be optimal intermediaries for gauging upstream risk factor modification.

The relationship between BMI and glycated albumin to glycated hemoglobin (GA/A1c) ratio according to glucose tolerance status

Glycated albumin to glycated hemoglobin (GA/A1c) ratio is known to be inversely related with body mass index (BMI) and insulin secretory capacity. However, the reasons for this association remain unknown. We aimed to investigate whether BMI directly or indirectly influences GA/A1c by exerting effects on insulin secretion or resistance and to confirm whether these associations differ according to glucose tolerance status. We analyzed a total of 807 subjects [242 drug-naïve type 2 diabetes (T2D), 378 prediabetes, and 187 normal glucose tolerance (NGT)]. To assess the direct and indirect effects of BMI on GA/A1c ratio, structural equation modeling (SEM) was performed. GA/A1c ratio was set as a dependent variable, BMI was used as the independent variable, and homeostasis model assessment-pancreatic beta-cell function (HOMA-β), homeostasis model assessment-insulin resistance (HOMA-IR), glucose level were used as mediator variables. The estimates of a direct effect of BMI on GA/A1c to be the strongest in NGT and weakest in T2D (−0.375 in NGT, −0.244 in prediabetes, and −0.189 in T2D). Conversely, the indirect effect of BMI on GA/A1c exerted through HOMA-β and HOMA-IR was not statistically significant in NGT group, but significant in prediabetes and T2D groups (0.089 in prediabetes, −0.003 in T2D). It was found that HOMA-β or HOMA-IR indirectly influences GA/A1c in T2D and prediabetes group through affecting fasting and postprandial glucose level. The relationship between GA/A1c and BMI is due to the direct effect of BMI on GA/A1c in NGT group, while in T2D and prediabetes groups, this association is mostly a result of BMI influencing blood glucose through insulin resistance or secretion.

How Informative are the Vertical Buoyancy and the Prone Gliding Tests to Assess Young Swimmers' Hydrostatic and Hydrodynamic Profiles?

The aim of this research was to develop a path-flow analysis model to highlight the relationships between buoyancy and prone gliding tests and some selected anthropometrical and biomechanical variables. Thirty-eight young male swimmers (12.97 ± 1.05 years old) with several competitive levels were evaluated. It were assessed the body mass, height, fat mass, body surface area, vertical buoyancy, prone gliding after wall push-off, stroke length, stroke frequency and velocity after a maximal 25 [m] swim. The confirmatory model included the body mass, height, fat mass, prone gliding test, stroke length, stroke frequency and velocity. All theoretical paths were verified except for the vertical buoyancy test that did not present any relationship with anthropometrical and biomechanical variables nor with the prone gliding test. The good-of-fit from the confirmatory path-flow model, assessed with the standardized root mean square residuals (SRMR), is considered as being close to the cut-off value, but even so not suitable of the theory (SRMR = 0.11). As a conclusion, vertical buoyancy and prone gliding tests are not the best techniques to assess the swimmer’s hydrostatic and hydrodynamic profile, respectively.

Quantitatively analyze composition principle of Ma Huang Tang by structural equation modeling

ETHNOPHARMACOLOGICAL RELEVANCE

In Chinese classic formulas, Ma Huang Tang (MHT), composed of Ephedra, Cassia twig, Bitter apricot kernel and Prepared licorice, has been widely used to treat cold, influenza, acute bronchitis, bronchial asthma and other pulmonary diseases. However, there is no quantitative interpretation about composition principle of MHT as well as other Chinese compound prescriptions. This study was aimed using structural equation modeling (SEM) to decipher 'monarch, minister, assistant and guide' which is the unique and integrated composition principle of Chinese compound recipes, by taking MHT for instance.

MATERIALS AND METHODS

Sixteen prescriptions of different dose ratios were combined orthogonally from four herbal drugs of MHT, then their diaphoretic, antispasmodic and analgesic effects were assessed by the indicators of the rat sweating point number, the spasmolysis percentage of guinea pig trachea and the murine writhing number, respectively. Basing on SME, the systematology analysis method to complex causality, path diagrams for herbal drugs were drawn with the Amos software and the relationships of the four herbal ingredients and therapeutic effects were measured.

RESULTS

Sixteen recipes induced SD rats sweating, remitted spasm of guinea pig trachea smooth muscle, and relieved ICR mouse pain due to acetic acid in comparison with animal model group or normal control groups. Three different SME models were specified and the relevant relationship was analyzed. According to the results of measured standardized path coefficients, Ephedra exerts the greatest contribution to the integral potency, so it acts as the monarch drug in MHT; Cassia twig is slightly weakly effective than Ephedra, and has the most significant interaction with Ephedra, which shows that it is the minister drug; the direct effects of Bitter apricot kernel and Prepared licorice on the integral potency are non-significant, while these two drugs have very significant synergetic effect with Ephedra or Cassia twig, thus they can be interpreted as subordinate drugs to strengthen the therapeutical effects of the monarch and minister drugs; the higher interaction values of Bitter apricot kernel suggest that it is the assistant drug, and Prepared licorice is the guide drug with lower values.

CONCLUSION

SME can be used to quantitatively analyze the composition principle of Chinese compound prescriptions like MHT, which demystifies the ancient and classical system theory of traditional Chinese medicine from a totally new viewpoint.