Invited commentary: structural equation models and epidemiologic analysis

The mediating role of behavioral risk factors in the pathway between childhood disadvantage and adult psychological distress in a Finnish employee cohort

Childhood disadvantage is associated with increased adult psychological distress, but the role of behavioral risk factors in the pathway remains unclear. We examined whether behavioral risk factors mediate the effects of childhood disadvantage on adult psychological distress. We used the Helsinki Health Study data of employees of the City of Helsinki, Finland, aged 19-39 (mean age 32.0) years at baseline (2017). We included women (n = 2397) and men (n = 586) who responded to both baseline and follow-up (2022) surveys. At baseline, eight types of childhood disadvantage were asked retrospectively, and six adult behavioral risk factors were included. Psychological distress was measured by the DASS-21 at follow-up. We conducted mediation analyses using generalized structural equation modeling. Among women, we found indirect path effects of childhood disadvantage on adult psychological distress through behavioral risk factors (symptoms of depression: β = 0.68, 95% CI 0.20-1.17; anxiety: β = 0.54, 95% CI 0.13-0.95; and stress: β = 0.69, 95% CI 0.20-1.09). Among men, childhood disadvantage contributed only directly to adult depressive (β = 0.71, 95% CI 0.16-1.26) and stress (β = 0.61, 95% CI 0.10-1.13) symptoms. Our findings suggest that behavioral risk factors can mediate some of the adverse effects of childhood disadvantage on adult psychological distress among women.

Going beyond the comparison: toward experimental instructional design research with impact

To design effective instruction, educators need to know what design strategies are generally effective and why these strategies work, based on the mechanisms through which they operate. Experimental comparison studies, which compare one instructional design against another, can generate much needed evidence in support of effective design strategies. However, experimental comparison studies are often not equipped to generate evidence regarding the mechanisms through which strategies operate. Therefore, simply conducting experimental comparison studies may not provide educators with all the information they need to design more effective instruction. To generate evidence for the what and the why of design strategies, we advocate for researchers to conduct experimental comparison studies that include mediation or moderation analyses, which can illuminate the mechanisms through which design strategies operate. The purpose of this article is to provide a conceptual overview of mediation and moderation analyses for researchers who conduct experimental comparison studies in instructional design. While these statistical techniques add complexity to study design and analysis, they hold great promise for providing educators with more powerful information upon which to base their instructional design decisions. Using two real-world examples from our own work, we describe the structure of mediation and moderation analyses, emphasizing the need to control for confounding even in the context of experimental studies. We also discuss the importance of using learning theories to help identify mediating or moderating variables to test.

Effects of aircraft noise exposure on self-reported health through aircraft noise annoyance: Causal mediation analysis in the DEBATS longitudinal study in France

BACKGROUND

Previous studies reported an association between transportation noise and self-reported health status (SRHS). They also suggested a mediating role of noise annoyance using conventional statistical methods. These methods are subject to bias in longitudinal studies with time-dependent exposure, mediator and confounding factors. This study aims to investigate the mediating role of aircraft noise annoyance in the effect of aircraft noise on SRHS using a causal inference approach to address time-dependent variables issues.

METHODS

We used data from 881 participants in all three visits in the DEBATS longitudinal study conducted around three French airports. Participants over 18 years of age reported their self-perceived health status, aircraft noise annoyance, and noise sensitivity by completing a questionnaire at three visits in 2013, 2015 and 2017. Noise maps were used to estimate aircraft noise levels outside their homes. Marginal structural models with inverse probability weighting were used to estimate the total effect of aircraft noise levels on SRHS and its decomposition into direct and indirect effect through aircraft noise annoyance.

RESULTS

This study showed a deleterious effect of aircraft noise on SRHS. The odds ratio (OR) corresponding to the total effect and comparing the highest aircraft noise category (≥60 dBA) to the reference category (<50 dBA) was significant (ORpoor/fair_SHRS = 1.25 (95%CI: 1.06 to 2.08)). It also showed no direct effect of aircraft noise levels on SRHS, but an indirect effect through annoyance. This indirect effect increased as aircraft noise levels increased, with a statistically significant OR when comparing the highest noise category (≥60 dBA) to the lowest (<50 dBA) (ORpoor/fair_SHRS = 1.16 (95%CI: 1.03 to 1.52)). Nearly 66% of aircraft noise's effect on SRHS was mediated by aircraft noise annoyance.

CONCLUSION

This study supports the deleterious causal effect of aircraft noise on SRHS. The results highlight the important mediating role of aircraft noise annoyance in the causal pathway from exposure to aircraft noise to poor/fair SRHS.

Underlying pathways of social inequality in tooth loss: The mediating role of sugary beverages and diabetes

BACKGROUND

Previous studies show social inequality in tooth loss, but the underlying pathways are not well understood. The aim was to investigate the mediated proportion of sugary beverages (SBs) and diabetes and the association between educational level and tooth loss, and to investigate whether the indirect effect of SBs and diabetes varied between educational groups in relation to tooth loss.

METHODS

Data from 47,109 Danish men and women aged 50 years or older included in the Danish Diet, Cancer and Health Study was combined with data from Danish registers. Using natural effect models, SBs and diabetes were considered as mediators, and tooth loss was defined as having <15 teeth present.

RESULTS

In total, 10,648 participants had tooth loss. The analyses showed that 3% (95% confidence interval 2-4%) of the social inequality in tooth loss was mediated through SBs and diabetes. The mediated proportion was mainly due to differential exposure to SBs and diabetes among lower educational groups.

CONCLUSIONS

The findings show that SBs and diabetes to a minor degree contribute to tooth-loss inequalities. The explanation indicates that individuals in lower educational groups have higher consumption of SBs and more often suffer from diabetes than higher educational groups.

Deworming and micronutrient status by community open defecation prevalence: An observational study using nationally representative data from India, 2016-2018

BACKGROUND

Micronutrient deficiencies are widespread in India. Soil-transmitted helminth (STH) infections are acquired by interaction with soil and water contaminated by human feces and lead to blood loss and poor micronutrient absorption. The current recommendation for control of STH-related morbidity is targeted deworming, yet little is known about the effectiveness of deworming on micronutrient status in varying sanitation contexts. Ranging between 1% and 40% prevalence across Indian states, open defecation (OD) remains high despite India's investments at elimination by promoting community-wide sanitation. This variation provides an opportunity to study the relationship between deworming, micronutrient status, and OD at-scale.

METHODS AND FINDINGS

Cross-sectional datasets that were representative for India were obtained the Comprehensive National Nutrition Survey in 2016 to 2018 (n = 105,060 individuals aged 1 to 19 years). Consumption of deworming medication was described by age and community OD level. Logistic regression models were used to examine the relationship between deworming, cluster OD, and their interactions, with anemia and micronutrient deficiencies (iron, zinc, vitamin A, folate, and vitamin B12), controlling for age, sex, wealth, diet, and seasonality. These regression models further allowed us to identify a minimum OD rate after which deworming becomes ineffective. In sensitivity analyses, the association between deworming and deficiencies were tested in subsamples of communities classified into 3 OD levels based on statistical tertiles: OD free (0% of households in the community practicing OD), moderate OD (>0% and <30%), or high OD (at least 30%). Average deworming coverage and OD prevalence in the sample were 43.4% [IQR 26.0, 59.0] and 19.1% [IQR 0, 28.5], respectively. Controlling for other determinants of nutritional status, adolescents living in communities with higher OD levels had lower coverage of deworming and higher prevalence of anemia, zinc, vitamin A, and B12 deficiencies. Compared to those who were not dewormed, dewormed children and adolescents had lower odds of anemia (adjusted odds ratio 0.72, (95% CI [0.67, 0.78], p < 0.001) and deficiencies of iron 0.78, (95% CI [0.74, 0.82], p < 0.001) and folate 0.69, (95% CI [0.64,0.74], p<0.001)) in OD free communities. These protective effects remained significant for anemia but diminished for other micronutrient deficiencies in communities with moderate or high OD. Analysis of community OD indicated a threshold range of 30% to 60%, above which targeted deworming was no longer significantly associated with lower anemia, iron, and folate deficiency. The primary limitations of the study included potential for omitted variables bias and inability to capture longitudinal effects.

CONCLUSIONS

Moderate to high rates of OD significantly modify the association between deworming and micronutrient status in India. Public health policy could involve sequencing interventions, with focus on improving deworming coverage in communities that have achieved minimum thresholds of OD and re- triggering sanitation interventions in high OD communities prior to deworming days, ensuring high coverage for both. The efficacy of micronutrient supplementation as a complementary strategy to improve nutritional outcomes alongside deworming and OD elimination in this age group needs further study.

Does adult socioeconomic status mediate the relationship between adolescent socioeconomic status and adult quality of life?

Objective

This study aimed to determine the association between adolescent socioeconomic status (father's education and adolescent subjective socioeconomic status) and adult quality of life and the mediation roles of adult socioeconomic status, social capital and lifestyle (physical activity and exposure to smoke) among the "Tehran University of Medical Sciences Employees Cohort (TEC) Study" participants.

Method

Data of 4455 participants were derived from the Tehran University of Medical Sciences Employees Cohort (TEC) Study. In this study, the World Health Organization quality of life-BREF, the World Bank's Integrated and the International Physical Activity Questionnaire were used. Data were analyzed with structural equation modeling using SPSS Amos 24.0 program.

Results

The mean age of the participants was 42.31 years (SD: 8.37) and most of the subjects were female (60.7%). Correlation analysis results revealed that, quality of life had a significant and positive association with adolescent subjective socioeconomic status (r = 0.169, p < 0.01) and father's education (r = 0.091, p < 0.01). A mediation model testing the direct relationship between adolescent socioeconomic status and adult socioeconomic status and quality of life, showed a positive relationship between adolescent subjective socioeconomic status (β = 0.229, p < 0.001) and father's education (β = 0.443, p < 0.001) with adult socioeconomic status. Adult socioeconomic status was positively related to quality of life (β = 0.205, p < 0.001). Adult socioeconomic status mediated the relationship between adolescent subjective socioeconomic status (β = 0.047, p < 0.01) and father's education (β = 0.091, p < 0.01) with quality of life. While adult socioeconomic status fully mediated the relationship between the father's education and quality of life, it partially mediated the adolescent subjective socioeconomic status-quality of life association. Other variables such as social capital and lifestyle did not have mediator role in a mediation model.

Conclusion

This study provides the evidence for the role of adult socioeconomic status as a partial mediator between adolescent subjective socioeconomic status and quality of life. Therefore, there are several unknown mediators other than adult socioeconomic status that need to be explored in future studies.

The Impact of Biological and Social Factors on Mortality in Older Adults Living in Rural Communities

BACKGROUND

Information on factors that increase mortality in remote settings is limited. This study aims to estimate the independent and joint role of several factors on mortality risk among older adults living in rural Ecuador.

METHODS

Participants were selected from community-dwelling older adults who were included in previous studies targeting mortality risk factors in the study population. Generalized structural equation modeling (GSEM) was utilized to evaluate prior causal assumptions, to redraw causal links, and to introduce latent variables that may help to explain how the independently significant variables are associated with mortality.

RESULTS

The study included 590 individuals (mean age: 67.9 ± 7.3 years; 57% women), followed for a median of 8.2 years. Mortality rate was 3.4 per 100 person-years. Prior work on separate multivariate Poisson and Cox models was used to build a tentative causal construct. A GSEM containing all variables showed that age, symptoms of depression, high social risk, high fasting glucose, a history of overt stroke, and neck circumference were directly associated with mortality. Two latent variables were introduced, 1 representing the impact of biological factors and another, the impact of social factors on mortality. The social variable significantly influenced the biological variable which carried most of the direct effect on mortality.

CONCLUSIONS

Several factors contributed to mortality risk in the study population, the most significant being biological factors which are highly influenced by social factors. High social risk interact with biological variables and play an important role in mortality risk.

Association Between Child Maltreatment and Aggression in Chinese Early Adolescents: The Mediating Role of Irritability

Child maltreatment (CM) is a major global public health issue, and a strong association exists between CM and aggression. However, the underlying mechanism of this association has not been understood to date. The objective of this study was to explore the mediating role of irritability in the association between CM and aggression in Chinese early adolescents. A cross-sectional study was conducted using a self-report questionnaire to evaluate the levels of CM, aggression, and irritability in 5,724 middle school students from the Anhui Province, China. Structural equation modeling was used to test the hypothesis of the mediating effect of irritability on the relationship between CM and aggression. We further investigated gender differences in this association using multiple group analyses. CM was positively related to both irritability and aggression, and irritability was positively associated with aggression (p < .01). The mediating effects of irritability between CM and aggression were significant (β = .107, 95% confidence intervals [CI]: 0.077-0.133, p < .05). Males had a higher indirect effect size of the pathway from CM to aggression via irritability compared with females. Overall, irritability was a crucial mediator in the relationship between CM and aggression in Chinese adolescents, and males were more prone to engage in aggression compared with females through the pathway of irritability. Therefore, early irritability characteristics should be carefully monitored in adolescents, and they should be provided adequate support to acquire critical emotion regulation skills.

Psychosocial factors, dentist-patient relationships, and oral health-related quality of life: a structural equation modelling

BACKGROUND

Psychosocial factors and dentist-patient relationships (DPR) have been suggested to be associated with oral health outcomes. This study aimed to test a conceptual model which hypothesised relationships among psychosocial factors, DPR variables, and oral health-related quality of life (OHRQoL) in the 'distal-to-proximal' framework.

METHODS

A total of 12,245 adults aged 18 years or over living in South Australia were randomly sampled for the study. Data were collected from self-complete questionnaires in 2015-2016. The outcome variable of Oral Health Impact Profile was used to measure OHRQoL. Psychosocial domain consisted of psychological well-being, social support, and health self-efficacy. DPR domain included trust in dentists, satisfaction with dental care, and dental fear. The hypothesised model was tested using the two-step approach in structural equation modelling.

RESULTS

Data were analysed from 3767 respondents after the screening/preparing process (adjusted valid response rate 37.4%). In the first step of the analysis, confirmatory factor analyses produced acceptable measurement models for each of the six latent variables (GFI = 0.95, CFI = 0.98, RMSEA = 0.04). The final structural model indicated that better well-being, higher self-efficacy, and more satisfaction were associated with lower oral health impact (β = - 0.12, - 0.07, - 0.14, respectively) whereas fear was positively associated (β = 0.19). Among intermediates, support was positively associated with satisfaction within a small effect size (β = 0.06) as compared to self-efficacy with trust (β = 0.22). The invariance of the final model was also confirmed on participants' SES and dental service characteristics except the variable of 'last dental visit'.

CONCLUSIONS

Psychosocial factors and DPR variables were associated with oral health impact in both direct and indirect paths. The framework of 'distal-to-proximal' actions is empirically supported from psychosocial factors via DPR variables to OHRQoL.

Can cognitive inflexibility reduce symptoms of anxiety and depression? Promoting the structural nested mean model in psychotherapy research

OBJECTIVE

To estimate the causal effect of executive functioning on the remission of depression and anxiety symptoms in an observational dataset from a vocational rehabilitation program. It is also an aim to promote a method from the causal inference literature and to illustrate its value in this setting.

METHOD

With longitudinal (four-time points over 13 months) data from four independent sites, we compiled a dataset with 390 participants. At each time point, participants were tested on executive function and self-reported symptoms of anxiety and depression. We used g-estimation to evaluate whether objectively tested cognitive flexibility affected depressive/anxious symptoms and tested for moderation. Multiple imputations were used to handle missing data.

RESULTS

The g-estimation showed a strong causal effect of cognitive inflexibility reducing depression and anxiety and modified by education level. In a counterfactual framework, a hypothetical intervention that could lower cognitive flexibility seemed to cause improvement in mental distress at the subsequent time-point (negative sign) for low education. The less flexibility, the larger improvement. For high education, the same but weaker effect was found, with a change in sign, negative during the intervention and positive during follow-up.

DISCUSSION

An unexpected and strong effect was found from cognitive inflexibility on symptom improvement. This study demonstrates how to estimate causal psychological effects with standard software in an observational dataset with substantial missing and shows the value of such methods.

Use of Tenofovir Alafenamide Fumarate for HIV Pre-Exposure Prophylaxis and Incidence of Hypertension and Initiation of Statins

Importance

Pre-exposure prophylaxis (PrEP) is an important tool for preventing HIV infection. However, PrEP's impact on cardiometabolic health is understudied.

Objective

To examine the risk of incident hypertension and statin initiation among adult (age ≥18 years) health plan members starting PrEP with tenofovir alafenamide fumarate (TAF) compared with propensity score-matched adults taking tenofovir disoproxil fumarate (TDF).

Design, Setting, and Participants

This retrospective cohort study used electronic health records (EHRs) from Kaiser Permanente Southern California. Adult members starting PrEP in Kaiser Permanente Southern California between October 2019 and May 2022 were included. Propensity score matching with multiple imputation (50 matched data sets) was conducted to generate 1 TAF:4 TDF matched data sets with balanced baseline covariates.

Exposures

PrEP initiation with either TAF or TDF during the study period.

Main Outcomes and Measures

Incident hypertension and statin initiation within 2 years of PrEP initiation were ascertained through blood pressure and outpatient pharmacy records, respectively. Risk differences and odds ratios (ORs) were estimated using logistic regression and g-computation.

Results

A total of 6824 eligible individuals were identified (mean [SD] age, 33.9 [10.3] years; 6618 [97%] male). This pool was used to generate 2 cohorts without baseline hypertension or statin use for matching (hypertension: n = 5523; statin: n = 6149) In both cohorts, those starting PrEP with TAF were older and were more likely to be non-Hispanic White compared with those starting with TDF. In matched analysis adjusting for baseline covariates, TAF use was associated with elevated risk of incident hypertension (TAF: n = 371; risk difference, 0.81 [95% CI, 0.12-1.50]; OR, 1.64 [95% CI, 1.05-2.56]). TAF use was also associated with elevated risk of statin initiation (TAF: n = 382; risk difference, 0.85 [95% CI, 0.37-1.33]; OR, 2.33 [95% CI, 1.41-3.85]). Subgroup analyses restricted to individuals 40 years and older at PrEP initiation showed similar results with larger risk difference in statin initiation (risk difference, 4.24 [95% CI, 1.82-6.26]; OR, 3.05 [95% CI, 1.64-5.67]).

Conclusions and Relevance

In this study of people taking PrEP, TAF use was found to be associated with higher incident hypertension and statin initiation compared with TDF use, especially in those 40 years or older. Continued monitoring of blood pressure and lipids for TAF users is warranted.

Mediation Analysis of Waist Circumference in the Association of Gut Microbiota with Insulin Resistance in Children

BACKGROUND

Persistent gut microbiota (GM) imbalance has been associated with metabolic disease development. This study evaluated the mediating role of waist circumference in the association between GM and insulin resistance (IR) in children.

METHODS

This cross-sectional study included 533 children aged between 6 and 12. The anthropometry, metabolic markers, and relative abundance (RA) of five intestinal bacterial species were measured. Path coefficients were estimated using path analysis to assess direct, indirect (mediated by waist circumference), and total effects on the association between GM and IR.

RESULTS

The results indicated a positive association mediated by waist circumference between the medium and high RA of S. aureus with homeostatic model assessments for insulin resistance (HOMA-IR) and for insulin resistance adiponectin-corrected (HOMA-AD). We found a negative association mediated by waist circumference between the low and medium RA of A. muciniphila and HOMA-IR and HOMA-AD. Finally, when we evaluated the joint effect of S. aureus, L. casei, and A. muciniphila, we found a waist circumference-mediated negative association with HOMA-IR and HOMA-AD.

CONCLUSIONS

Waist circumference is a crucial mediator in the association between S. aureus and A. muciniphila RA and changes in HOMA-IR and HOMA-AD scores in children.

Longitudinal association between periodontal condition and glycaemic status in middle-aged adults: A cross-lagged panel analysis

AIM

To investigate the existence of a bidirectional temporal relationship between periodontal condition and glycaemic status.

MATERIALS AND METHODS

This longitudinal study included 2198 participants with mean age 43.4 ± 7.7 years, who underwent dental examinations in Yokohama, Japan, at two time points, 2003-2004 and 2008-2009, at an interval of 5 years. Periodontal condition was assessed by the mean value of probing pocket depth (PPD) and clinical attachment level (CAL). Glycaemic status was assessed by fasting glucose and glycated haemoglobin (HbA1c).

RESULTS

The cross-lagged panel models showed the effect of HbA1c at baseline on mean PPD at follow-up (β = 0.044, p = .039). There was a marginal effect of fasting glucose on the mean PPD (β = 0.037, p = .059). It was similar to the effect of fasting glucose or HbAlc on mean CAL. However, in the opposite direction, no effect of mean PPD or CAL at baseline on fasting glucose or HbAlc at follow-up was identified.

CONCLUSIONS

This study demonstrated a unidirectional relationship between glycaemic status and periodontal condition. The study population, however, had mostly mild periodontitis. Future studies are needed to investigate the effect of periodontal condition on glycaemic status in patients with severe periodontitis.

A structural equation modelling approach to understanding the determinants of childhood vaccination in Nigeria, Uganda and Guinea

Vaccines have contributed to reductions in morbidity and mortality from preventable diseases globally, but low demand for vaccination threatens to reverse these gains. Explorations of the determinants of vaccination uptake may rely on proxy variables to describe complex phenomena and construct models without reference to underlying theories of vaccine demand. This study aimed to use the results of a formative qualitative study (described elsewhere) to construct and test a model to explain the determinants of vaccination uptake. Using the results of a survey among more than 3,000 primary caregivers of young children in Nigeria, Uganda and Guinea, factor analysis produced six explanatory factors. We then estimated the effects of each of these factors on uptake of immunization using a structural equation model. The results showed that the probability that a child is fully vaccinated increases if a caregiver has support from others to vaccinate them (B = 0.33, β = 0.21, p<0.001) and if caregivers had poor experiences with the healthcare system (B = 0.09, β = 0.09, p = 0.007). Conversely, the probability of full vaccination decreases if the caregiver's husband exerts control over her decision-making ability (B = -0.29, β = -0.20, p<0.001), or if the caregiver perceives vaccines to be of low importance (B = -0.37, β = -0.27, p<0.001). Belief in religious protection (B = -0.07, β = -0.05, p = 0.118) and a belief that vaccines are harmful (B = -0.12, β = -0.04, p = 0.320) did not have an observed effect on vaccination status. This research suggests that interventions may benefit from that including entire families and communities in their design.

The Causes and Factors Associated with Infant Mortality Rate in Ethiopia: The Application of Structural Equation Modelling

Infant mortality rate is a proxy measure of population health. Previous studies on the infant mortality rate in Ethiopia did not consider measurement errors in the measured variables and had a one-directional effect; little emphasis was placed on testing multiple causal paths at the same time. We used structural equation modelling for a better understanding of the direct, indirect, and total effects among causal variables in a single model. A path analysis was part of an algorithm providing equations that were relating the variances and covariances of the indicators. From the results, the maternal mortality ratio (MMR) was significantly mediating the influence of out-of-pocket expenditure (OOP) on infant mortality rate (IMR), and the fertility rate (FR) was significantly mediating the influence of GDP to IMR (β = 1.168, p < 0.001). The GDP affects the IMR directly and indirectly while the OOP affects IMR indirectly. This study showed that there was a causal linkage between the World Bank Health and Population Variables for causing IMR in Ethiopia. The MMR and FR were found to be the intermediate indicators in this study. Through the indicators, FR had the highest standardised coefficients for increasing the IMR. We recommended that the existing interventions to reduce IMR be strengthened.

Structural equation modelling the impact of antimicrobials on the human microbiome. Colonization resistance versus colonization susceptibility as case studies

The impact of antimicrobials on the human microbiome and its relationship to human health are of great interest. How antimicrobial exposure might drive change within specific constituents of the microbiome to effect clinically relevant endpoints is difficult to study. Clinical investigation of each step within a network of causation would be challenging if done 'step-by-step'. An analytic tool of great potential to clinical microbiome research is structural equation modelling (SEM), which has a long history of applications to research questions arising within subject areas as diverse as psychology and econometrics. SEM enables postulated models based on a network of causation to be tested en bloc by confrontation with data derived from the literature. Case studies for the potential application of SEM techniques are colonization resistance (CR) and its counterpart, colonization susceptibility (CS), wherein specific microbes within the microbiome are postulated to either impede (CR) or facilitate (CS) invasive infection with pathogenic bacteria. These postulated networks have three causation steps: exposure to specific antimicrobials are key drivers, clinically relevant infection endpoints are the measurable observables and the activity of key microbiome constituents mediating CR or CS, which may be unobservable, appear as latent variables in the model. SEM methods have potential application towards evaluating the activity of specific antimicrobial agents within postulated networks of causation using clinically derived data.

Workplace gender harassment, illegitimate tasks, and poor mental health: Hypothesized associations in a Swedish cohort

Workers exposed to gender harassment and illegitimate tasks may experience adverse mental health outcomes such as depression and burnout. However, the longitudinal effects and the complex interrelationships between these variables remain largely unexplored. We investigated the cross-lagged relationships between gender harassment, illegitimate tasks, and mental health outcomes among working adults in Sweden over a period of two years, as well as the gender differences in the cross-lagged effects. Additionally, the study examined whether illegitimate tasks mediated the relationship between gender harassment and negative mental health outcomes over time. Data were drawn from the Swedish Longitudinal Occupational Survey of Health (SLOSH), covering 2796 working men and 4110 working women in a two-wave analysis from 2018 to 2020. We employed a structural equation model to examine the cross-lagged effects and the mediating effect between gender harassment, illegitimate tasks, and mental health outcomes over time. Furthermore, we applied a multigroup analysis to determine gender differences in the cross-lagged effects. The results showed statistically significant cross-lagged relationships (forward, reverse, and reciprocal) between gender harassment, illegitimate tasks, and mental ill-health. There were statistically significant gender differences in these cross-lagged relationships (burnout: △χ²(47)=106.21, p < 0.01; depression: △χ²(47)=80.5, p < 0.01). Initial illegitimate tasks mediated the relationship between gender harassment and mental ill-health outcomes over time. The gender differences in the interrelationships between gender harassment, illegitimate tasks, and mental ill-health outcomes among workers in Sweden indicate that policies, regulations, and interventions that address these exposures in organisations must be tailored to benefit both men and women.

Candida and the Gram-positive trio: testing the vibe in the ICU patient microbiome using structural equation modelling of literature derived data

Background

Whether Candida interacts with Gram-positive bacteria, such as Staphylococcus aureus, coagulase negative Staphylococci (CNS) and Enterococci, to enhance their invasive potential from the microbiome of ICU patients remains unclear. Several effective anti-septic, antibiotic, anti-fungal, and non-decontamination based interventions studied for prevention of ventilator associated pneumonia (VAP) and other ICU acquired infections among patients receiving prolonged mechanical ventilation (MV) are known to variably impact Candida colonization. The collective observations within control and intervention groups from numerous ICU infection prevention studies enables tests of these postulated microbial interactions in the clinical context.

Methods

Four candidate generalized structural equation models (GSEM), each with Staphylococcus aureus, CNS and Enterococci colonization, defined as latent variables, were confronted with blood culture and respiratory tract isolate data derived from 460 groups of ICU patients receiving prolonged MV from 283 infection prevention studies.

Results

Introducing interaction terms between Candida colonization and each of S aureus (coefficient + 0.40; 95% confidence interval + 0.24 to + 0.55), CNS (+ 0.68; + 0.34 to + 1.0) and Enterococcal (+ 0.56; + 0.33 to + 0.79) colonization (all as latent variables) improved the fit for each model. The magnitude and significance level of the interaction terms were similar to the positive associations between exposure to topical antibiotic prophylaxis (TAP) on Enterococcal (+ 0.51; + 0.12 to + 0.89) and Candida colonization (+ 0.98; + 0.35 to + 1.61) versus the negative association of TAP with S aureus (− 0.45; − 0.70 to − 0.20) colonization and the negative association of anti-fungal exposure and Candida colonization (− 1.41; − 1.6 to − 0.72).

Conclusions

GSEM modelling of published ICU infection prevention data enables the postulated interactions between Candida and Gram-positive bacteria to be tested using clinically derived data. The optimal model implies interactions occurring in the human microbiome facilitating bacterial invasion and infection. This interaction might also account for the paradoxically high bacteremia incidences among studies of TAP in ICU patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12982-022-00116-9.

GSEM modelling of published ICU infection prevention data from > 250 studies enables a test of and provides support to the interaction between Candida and Gram-positive bacteria.

The various ICU infection prevention interventions may each broadly impact the patient microbiome.

Impact of caesarean delivery on children's autism-like behaviours: the mediation of exclusive breastfeeding

Background

The rate of autism spectrum disorder (ASD) has been rising worldwide, and therefore it is important to identify potential causes of ASD to facilitate early prevention. This study examined the role of breastfeeding and the association between caesarean delivery (CD) and children’s autism spectrum disorder.

Methods

The data were from the Ma’anshan birth cohort (MABC) in China, that was set up between May 2013 and September 2014. Women within 14 gestational weeks were recruited. The delivery mode was extracted from medical notes and infant feeding was obtained from questionnaire surveys. Autism-like behaviour was assessed using the Checklist for Autism in Toddlers (CHAT-23) when children were 18 months old, and 3 years of age. At 5 years of age, autism-like behaviour was assessed using the Clancy Autism Behavior Scale behavior. Structural equation models tested the mediation effects of breastfeeding between CD and children’s autism spectrum disorder.

Results

In all, 1520 (48.89%) women gave birth via CD, and 406 (13.86%) children were identified with autism-like behaviours at 18 months. Compared with women giving birth via vaginal delivery, those giving birth via CD were more likely to experience a higher proportion of delayed initiation of breastfeeding (p < 0.01), and delayed onset of lactogenesis (p < 0.01). CD was associated with a lower proportion of exclusive breastfeeding at 4 months after delivery (p = 0.02). Autism-like behaviour was less likely amongst infants with exclusively breastfeeding at 4 months than amongst those not exclusively breastfeeding at 4 months (p < 0.01). SEM indicated that women who gave birth by CD were more likely to stop exclusive breastfeeding in the first 4 months (standard estimations = − 0.04, p = 0.02), and those children who were not exclusively breastfed at 4 months were more likely to have autism-like behaviours (standard estimations = − 0.05, p < 0.01). The associations persisted at 3 years, but not at 5 years.

Conclusions

Exclusive breastfeeding at 4 months of age mediated the association between caesarean delivery and children’s autism-like behaviours.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13006-022-00493-6.

How to apply structural equation modelling to infectious diseases concepts

BACKGROUND

Structural equation modelling (SEM) can address causation questions of great interest to infectious disease physicians and infection control practitioners that would elude techniques based on tests of association. Questions such as the size of intervention effects mediated on entities that cannot be easily measured, questions that cannot be studied in randomized controlled trials and question arising from 'big data'.

OBJECTIVES

To outline the computational and, moreover conceptual, differences between SEM methods versus the traditional tests of association.

SOURCES

Google scholar search for "structural equation modelling" and " Infection" CONTENT: Several examples of SEM applications to infectious diseases topics are used to illustrate. The SEM technique enables postulated causation models to be confronted with data. With this, the candidate models emerge as either 'importantly wrong', or potentially useful for enabling empiric predictions from the one identified as optimal.

IMPLICATIONS

Applications of SEM techniques and related modelling techniques to infectious diseases research will likely continue to emerge, especially so with the availability of 'big data'. ''Since all models are wrong the scientist must be alert to what is importantly wrong. It is inappropriate to be concerned about mice when there are tigers abroad.'' [George Box; 1].

Child diet and mother-child interactions mediate intervention effects on child growth and development

This study examined whether child diet and mother-child interactions mediated the effects of a responsive stimulation and nutrition intervention delivered from 2009 to 2012 to 1324 children aged 0-24 months living in rural Pakistan. Results showed that the intervention improved children's cognitive, language and motor development through child diet and mother-child interactions. Although the intervention did not improve child growth or socio-emotional development, we observed positive indirect effects on child growth via child diet and on socio-emotional development via both child diet and mother-child interactions. In addition, child diet emerged as a shared mechanism to improve both child growth and development, whereas mother-child interactions emerged as a distinct mechanism to improve child development. Nevertheless, our results suggest the two mechanisms were mutually reinforcing and that interventions leveraging both mechanisms are likely to be more effective at improving child outcomes than interventions leveraging only one of these mechanisms.

Not all types of nature have an equal effect on urban residents' well-being: A structural equation model approach

A growing amount of research shows a positive association between urban nature and urban residents' psychological and physical well-being and quality of life. With its focus on specific dimensions of well-being and reliance either on large-scale objective data sets or experimental and comparative designs, prior research does not explicitly address the relationships between the various types of urban nature as experienced by citizens and their overall well-being. The present research proposes a model for the potential influence of the perceptions of the type and characteristics of nature close to urban residences and citizens' well-being via their frequency of exposure to, and their activities in, nature. Using WHOQOL-26 as a measure of well-being and constructing or adapting measurements for the other variables, a questionnaire was designed and administered among a sample of 2500 French urban residents. Psychometric tests, structural equation modeling, and mediation analyses were conducted on the collected data. The results show that: (1) The perceived characteristics of nature near urban residences have both direct and indirect influences on the psychological, physical, environmental, and resources-related dimensions of citizens' well-being; (2) Less domesticated nature-forests, fields, and scrubland-contributes to psychological well-being by favoring light or calm activities in nature, and to physical well-being by supporting exposure to nature. Such wilder nature is also positively associated with the perceived quality of urban residences; (3) Small spots of nature, located close to one's residence-a balcony, a patio, or a roof garden-make a similar but smaller contribution to well-being; (4) Domesticated nature-city gardens and parks-contribute marginally to the physical and resources-related dimensions of well-being. These results complement past research on the perceived characteristics of nature by showing how nature, as experienced by urban citizens, refers to different vegetation spaces. They also invite urban planners and policymakers to acknowledge the positive association between "wilder" natural spaces and well-being.

Educational level and colorectal cancer risk: the mediating roles of lifestyle and dietary factors

OBJECTIVE

The association between the educational level and colorectal cancer risk was controversial in developed countries and evidence was limited in Chinese population. This study aimed to investigate the association between the educational level and colorectal cancer risk in Guangdong Province, China.

METHODS

From July 2010 to April 2019, 2502 newly diagnosed colorectal cancer patients and 2538 sex- and age-matched controls were recruited in this case-control study. Multivariable logistic regression models were used to examine the association between the educational level and colorectal cancer risk. Path analysis was used to investigate whether behavioral risk factors potentially mediated the association between the educational level and colorectal cancer risk.

RESULTS

Educational level was inversely associated with the colorectal cancer risk. People who graduated from the college or above had a lower risk of colorectal cancer than those from the primary school or below, with an adjusted odds ratio of 0.42 [95% confidence intervals (CI), 0.34-0.52]. The total, direct and indirect effects of the educational level for the colorectal cancer risk were statistically significant in the path diagram. Path analysis showed that lower red and processed meat intake and higher tea and coffee drinking among high educational participants contributed to the inverse association between the educational level and colorectal cancer risk.

CONCLUSION

The findings suggested that the educational level was inversely associated with the colorectal cancer risk. The association might be mediated by red and processed meat intake, household and leisure-time activities, and tea and coffee drinking.

Healthy diet associated with better asthma outcomes in elderly women of the French Asthma-E3N study

Purpose

The impact of a healthy diet on asthma prevention and management, particularly among elderly women, remains poorly understood. We investigated whether a healthy diet would be associated with fewer asthma symptoms, and, among women with asthma, with reduced uncontrolled asthma and metabolic-related multimorbidity.

Methods

We included 12,991 elderly women (mean age = 63 years) from the Asthma-E3N study, a nested case–control study within the French E3N cohort. Negative binomial regressions were used to analyse associations between a healthy diet [evaluated by the Alternate Healthy Eating Index-2010 (AHEI-2010)] and a validated asthma symptom score, and logistic regressions to analyse associations between the AHEI-2010 with the asthma control test and multimorbidity profiles previously identified by clustering methods on medications used.

Results

After adjustment for potential confounders, a linear inverse association was found between the AHEI-2010 score and the asthma symptom score [mean score ratio (95% CI) = 0.82 (0.75–0.90) for the highest versus lowest quintile; p for trend < 0.0001]. In addition, women in the highest versus lowest AHEI-2010 tertile were at a lower risk to belong to the “Predominantly metabolic multimorbidity-related medications profile” compared to the “Few multimorbidity-related medications" profile [OR 0.80 (0.63–1.00) for tertile 3; p for trend = 0.05; n = 3474].

Conclusion

Our results show that a healthy dietary intake could play an important role in the prevention and management of asthma over the life course.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00394-022-02815-0.

DNA methylation as a mediator of associations between the environment and chronic diseases: A scoping review on application of mediation analysis

DNA methylation (DNAm) is one of the most studied epigenetic modifications. DNAm has emerged as a key biological mechanism and biomarkers to test associations between environmental exposure and outcomes in epidemiological studies. Although previous studies have focused on associations between DNAm and either exposure/outcomes, it is useful to test for mediation of the association between exposure and outcome by DNAm. The purpose of this scoping review is to introduce the methodological essence of statistical mediation analysis and to examine emerging epidemiological research applying mediation analyses. We conducted this scoping review for published peer-reviewed journals on this topic using online databases (PubMed, Scopus, Cochrane, and CINAHL) ending in December 2020. We extracted a total of 219 articles by initial screening. After reviewing titles, abstracts, and full texts, a total of 69 articles were eligible for this review. The breakdown of studies assigned to each category was 13 for smoking (18.8%), 8 for dietary intake and famine (11.6%), 6 for other lifestyle factors (8.7%), 8 for clinical endpoints (11.6%), 22 for environmental chemical exposures (31.9%), 2 for socioeconomic status (SES) (2.9%), and 10 for genetic factors and race (14.5%). In this review, we provide an exposure-wide summary for the mediation analysis using DNAm levels. However, we found heterogenous methods and interpretations in mediation analysis with typical issues such as different cell compositions and tissue-specificity. Further accumulation of evidence with diverse exposures, populations and with rigorous methodology will be expected to provide further insight in the role of DNAm in disease susceptibility.

Understanding the relationship between features associated with pain-related disability in people with painful temporomandibular disorder: an exploratory structural equation modeling approach

Pain-related disability is a multifaceted construct that refers to the impact of pain on an individual's capacity to fulfill their self-defined and social roles. This research examined the relationship between clinical, psychological, and pain sensitivity factors and pain-related disability among adults with chronic temporomandibular disorder (TMD). We analyzed data from a cross-sectional community-based sample of 1088 men and women with chronic TMD. We first constructed and tested a measure of pain-related disability (ie, pain impact), including a variable assessing presenteeism, created measurement models of jaw limitation, psychological unease (negative affect, somatic symptoms, and catastrophizing), and experimental pain sensitivity (eg, pressure pain threshold, thermal tolerance, and mechanical pressure pain threshold). Subsequently, latent variables were combined in a structural equation model. Participants (n = 1088) were 18 to 44 years old (mean 29.2, SD ± 7.8) whose chronic TMD had persisted, on average, for 6.9 years (SD ± 6.4). A model of pain-related disability, jaw limitation, and psychological unease was created and refined with exploratory model revisions to account for correlation among variables. Estimation of the final model indicated excellent fit with the data (root-mean-square error of approximation = 0.048, root-mean-square error of approximation 90% confidence interval [CI] 0.043-0.053, comparative fit index = 0.956, standardized root-mean-square residual = 0.040). Jaw functional limitation and psychological unease was strongly related to pain-related disability. Experimental pain sensitivity was removed from our model because of weak direct effect and the burden of performing experimental pain sensitivity testing in a clinical setting. The final model explained 78% of the variance in pain-related disability.

Trait Emotional Intelligence and Wellbeing During the Pandemic: The Mediating Role of Meaning-Centered Coping

Studies investigating the COVID-19 pandemic from a psychological point of view have mostly focused on psychological distress. This study adopts the framework of existential positive psychology, a second wave of positive psychology that emphasizes the importance of effective coping with the negative aspects of living in order to achieve greater wellbeing. Trait emotional intelligence (trait EI) can be crucial in this context as it refers to emotion-related personality dispositions concerning the understanding and regulation of one's emotions and those of others. The present study investigated the relationship between trait EI and both wellbeing and psychological distress (i.e., depression, anxiety, and stress), while exploring the mediating role of meaning-centered coping (proactive transformative strategies based on meaning in life) and maladaptive coping (i.e., behavioral disengagement and self-blame) during the first few months of the COVID-19 pandemic. A sample of 326 Lebanese adults completed measures of trait EI, wellbeing, psychological distress, coping, and meaning-centered coping. Results showed a strong positive correlation between trait EI and meaning-centered coping. Trait EI also correlated positively with wellbeing and negatively with psychological distress. Structural equation modeling showed that meaning-centered coping partially mediated the relationship between trait EI and wellbeing. Maladaptive coping fully mediated the relationship between trait EI and psychological distress. Findings indicate that trait EI is positively related to dealing with a stressful situation such as the pandemic in positive ways at both the cognitive level, by reformulating the situation to see something valuable in it, and behavioral level, by being proactive about it. Trait EI was positively linked to seeing the situation as an opportunity for personal growth, finding personal meaning in this situation, maintaining an attitude of hope and courage, and acting more responsibly with one's self and others during the current crisis. In turn, this coping formula was related to lower psychological distress and improved mental health. These results are consistent with the existential positive psychology framework and can inform implementation programs and policies aiming at raising awareness and promoting healthy and successful coping during the pandemic.

Reducing socio-economic inequalities in all-cause mortality: a counterfactual mediation approach

Background

Socio-economic inequalities in mortality are well established, yet the contribution of intermediate risk factors that may underlie these relationships remains unclear. We evaluated the role of multiple modifiable intermediate risk factors underlying socio-economic-associated mortality and quantified the potential impact of reducing early all-cause mortality by hypothetically altering socio-economic risk factors.

Methods

Data were from seven cohort studies participating in the LIFEPATH Consortium (total n = 179 090). Using both socio-economic position (SEP) (based on occupation) and education, we estimated the natural direct effect on all-cause mortality and the natural indirect effect via the joint mediating role of smoking, alcohol intake, dietary patterns, physical activity, body mass index, hypertension, diabetes and coronary artery disease. Hazard ratios (HRs) were estimated, using counterfactual natural effect models under different hypothetical actions of either lower or higher SEP or education.

Results

Lower SEP and education were associated with an increase in all-cause mortality within an average follow-up time of 17.5 years. Mortality was reduced via modelled hypothetical actions of increasing SEP or education. Through higher education, the HR was 0.85 [95% confidence interval (CI) 0.84, 0.86] for women and 0.71 (95% CI 0.70, 0.74) for men, compared with lower education. In addition, 34% and 38% of the effect was jointly mediated for women and men, respectively. The benefits from altering SEP were slightly more modest.

Conclusions

These observational findings support policies to reduce mortality both through improving socio-economic circumstances and increasing education, and by altering intermediaries, such as lifestyle behaviours and morbidities.

Methods to Account for Uncertainty in Latent Class Assignments When Using Latent Classes as Predictors in Regression Models, with Application to Acculturation Strategy Measures

Latent class models have become a popular means of summarizing survey questionnaires and other large sets of categorical variables. Often these classes are of primary interest to better understand complex patterns in data. Increasingly, these latent classes are reified into predictors of other outcomes of interests, treating the most likely class as the true class to which an individual belongs even though there is uncertainty in class membership. This uncertainty can be viewed as a form of measurement error in predictors, leading to bias in the estimates of the regression parameters associated with the latent classes. Despite this fact, there is very limited literature treating latent class predictors as measurement error models. Most applications ignore this issue and fit a two-stage model that treats the modal class prediction as truth. Here, we develop two approaches-one likelihood-based, the other Bayesian-to implement a joint model for latent class analysis and outcome prediction. We apply these methods to an analysis of how acculturation behaviors predict depression in South Asian immigrants to the United States. A simulation study gives guidance for when a two-stage model can be safely implemented and when the joint model may be required.

Mendelian randomisation approaches to the study of prenatal exposures: A systematic review

BACKGROUND

Mendelian randomisation (MR) designs apply instrumental variable techniques using genetic variants to study causal effects. MR is increasingly used to evaluate the role of maternal exposures during pregnancy on offspring health.

OBJECTIVES

We review the application of MR to prenatal exposures and describe reporting of methodologic challenges in this area.

DATA SOURCES

We searched PubMed, EMBASE, Medline Ovid, Cochrane Central, Web of Science, and Google Scholar.

STUDY SELECTION AND DATA EXTRACTION

Eligible studies met the following criteria: (a) a maternal pregnancy exposure; (b) an outcome assessed in offspring of the pregnancy; and (c) a genetic variant or score proposed as an instrument or proxy for an exposure.

SYNTHESIS

We quantified the frequency of reporting of MR conditions stated, techniques used to examine assumption plausibility, and reported limitations.

RESULTS

Forty-three eligible studies were identified. When discussing challenges or limitations, the most common issues described were known potential biases in the broader MR literature, including population stratification (n = 29), weak instrument bias (n = 18), and certain types of pleiotropy (n = 30). Of 22 studies presenting point estimates for the effect of exposure, four defined their causal estimand. Twenty-four studies discussed issues unique to prenatal MR, including selection on pregnancy (n = 1) and pleiotropy via postnatal exposure (n = 10) or offspring genotype (n = 20).

CONCLUSIONS

Prenatal MR studies frequently discuss issues that affect all MR studies, but rarely discuss problems specific to the prenatal context, including selection on pregnancy and effects of postnatal exposure. Future prenatal MR studies should report and attempt to falsify their assumptions, with particular attention to issues specific to prenatal MR. Further research is needed to evaluate the impacts of biases unique to prenatal MR in practice.

Stigma of persons with disabilities in South Africa: Uncovering pathways from discrimination to depression and low self-esteem

Despite the fact that universal inclusion is a basic principle of the Sustainable Development Goals, the inclusion of persons with disabilities in humanitarian interventions and development policies remains elusive. Persons with disabilities face high risks of poverty, poor nutrition, limited inclusion in labor markets and poor mental health as a result. Stigma is likely to play a negative role in this regard and yet, no study has investigated the impact of stigma on depression and self-esteem of persons with disabilities. To address this gap in the literature, we conducted in June 2017 a random sample disability case control household study in Soweto, a township in Johannesburg, South Africa. Using propensity score analysis and structural equation modeling, we investigated the relationship between disability, stigma, depression and self-esteem controlling for socioeconomic covariates. Our main empirical results showed that stigma significantly mediates the association between disability and higher depression on the one hand and between disability and lower self-esteem on the other. This mediating effect exists even after controlling for age, gender, marital status, education, employment and wealth. We also found strong direct associations between disability and depressive mood, somatic indicators and negative feelings such as unhappiness and low self-esteem. Unemployment aggravates depression and low self-esteem while low education worsens self-esteem only. In addition, depression exacerbates low self-esteem. Both unemployment and low education are more common among persons with disabilities aggravating the disability, depression, poor self-esteem nexus. Similarly, persons with disabilities who are more likely to be depressed are also at higher risk of low self-esteem. These results point to a vicious reinforcing circle of exclusion from society, despair and self-deprecation, which could prove difficult to break. Substantial psycho-social support and anti-stigma policies anchored in local cultural values, engaging persons with disabilities and their communities, are required to break this vicious circle.

Health-Related Behaviors in Adolescents Mediate the Association between Subjective Social Status and Body Mass Index

The aim of this study was to explore the association between adolescent subjective social status (SSS) and body mass index (BMI) at two different time points and to determine whether this association was mediated by health-related behaviors. In 2002 (n = 1596) and 2017 (n = 1534), tenth-grade students (15-16 years old) in schools in the District of Oppland, Norway, completed a survey. Four categories of perceived family economy were measured as SSS, and structural equation modeling was performed, including a latent variable for unhealthy behavior derived from cigarette smoking, snuff-use, and alcohol-drinking as well as dietary and exercise as mediators. No linear association was found between SSS and BMI in 2002 (standardized ß -0.02, (95% confidence interval (CI) -0.07, 0.03)). However, an association was present in 2017 (standardized ß -0.05 (95% CI -0.10, -0.001)), indicating that BMI decreased by 0.05 standard deviations (0.05 × 3.1 = 0.16 BMI unit) for every one-category increase in SSS. This association was mediated by exercise (standardized ß -0.013 (95% CI -0.02, -0.004) and unhealthy behavior (standardized ß -0.009 (95% CI -0.002, -0.04)). In conclusion, a direct association between SSS and BMI was found in 2017 in this repeated cross-sectional survey of 15-16-year-old Norwegian adolescents. This association was mediated through health-related behavior.

Physical activity and lung function-Cause or consequence?

Concerns exist that the positive association of physical activity with better lung function, which has been suggested in previous longitudinal studies in smokers, is due to reverse causation. To investigate this, we applied structural equation modeling (SEM), an exploratory approach, and marginal structural modeling (MSM), an approach from the causal inference framework that corrects for reverse causation and time-dependent confounding and estimates causal effects, on data from participants in the European Community Respiratory Health Survey (ECRHS, a multicentre European cohort study initiated in 1991–1993 with ECRHS I, and with two follow-ups: ECRHS II in 1999–2003, and ECRHS III in 2010–2014). 753 subjects who reported current smoking at ECRHS II, with repeated data on lung function at ECRHS I, II and III, physical activity at ECRHS II and III, and potential confounders at ECRHS I and II, were included in the analyses. SEM showed positive associations between physical activity and lung function in both directions. MSM suggested a protective causal effect of physical activity on lung function (overall difference in mean β (95% CI), comparing active versus non-active individuals: 58 mL (21–95) for forced expiratory volume in one second and 83 mL (36–130) for forced vital capacity). Our results suggest bi-directional causation and support a true protective effect of physical activity on lung function in smokers, after accounting for reverse causation and time-dependent confounding.

Living in temporary housing and later psychological distress after the Great East Japan Earthquake of 2011: A cross-lagged panel model

Living in temporary housing is a risk factor for psychological distress after a natural disaster. As temporary housing is an essential resource for those affected by disasters, investigation of factors which potentially mediate living in temporary housing and psychological distress is needed. This is a cohort study in general population of areas affected by the Great East Japan Earthquake in 2011. Data were obtained from self-report questionnaires in annual health checks between 2014 and 2016 regarding residential situation (e.g., prefabricated or privately-rented temporary housing), psychological distress, sleep disturbances, social support, and covariates. Mediation effects of sleep disturbances and social support on the relationship between temporary housing and psychological distress were evaluated using a cross-lagged panel model during three time points. Among 3,116 participants in 2014, approximately 12% lived in prefabricated or privately-rented temporary housing. Living in prefabricated (β = 0.046, p = 0.031) and privately-rented temporary housing (β = 0.043, p = 0.042) predicted later psychological distress. There was no mediation effect by sleep disturbances (prefabricated temporary housing: β = 0.001, p = 0.620; privately-rented temporary housing: β = −0.001, p = 0.467) or social support (prefabricated temporary housing: β < 0.001, p = 0.748; privately-rented temporary housing: β < 0.001, p = 0.435). CLPM also showed no relationship between living in temporary housing and increased sleep problems or decreased social support. Mental health support may be required for residents who lived in prefabricated or privately-rented temporary housing three years after a natural disaster, whereas support focusing only on sleep disturbances or social support in residents who lived in temporary housing may not be enough to contribute to reducing psychological distress.

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This study investigated mediators on link temporary housing and distress following natural disaster.

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Living in prefabricated and privately-rented temporary housing was associated with distress.

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However, this link was not mediated by sleep disturbances or social support.

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Mental health support may be required for individuals who lived in temporary housing.

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Support focusing only on sleep disturbances or social support may not be enough to contribute to reducing distress.

Pathways between parental and individual determinants of dental caries and dental visit behaviours among children: Validation of a new conceptual model

OBJECTIVES

To delineate the pathways between the parental and individual determinants of dental caries and dental visit behaviours among children, using path analysis.

METHODS

The study employed an observational design; the study sample consisted of 583 parent-child dyads. Data were collected using a sociodemographic and oral health behaviour form, the Parenting Styles and Dimensions Questionnaire, the Corah Dental Anxiety Scale and the Children's Fear Survey Schedule-Dental Subscale. A conceptual model was developed, and it consisted of four endogenous variables (dental caries, children's oral health, dental visit behaviours and children's dental anxiety) and four exogenous ones (parental socioeconomic status, parental dental anxiety, parental oral health behaviours and parenting style). Path analysis was used to test the compatibility of the conceptual model, with a statistical significance at P < .001.

RESULTS

49.1% of participants (n = 286) were male. The mean age of participants was 8.3 (SD = 2.1). The mean DMFT score was 6.0 (SD = 3.0) and the mean Frankl behaviour score 3.0 (SD = 1.0). Parental socioeconomic status showed the strongest association with dental caries (β = .276; P < .001), and children's dental anxiety had the strongest association with dental visit behaviours (β = -.414; P < .001). Parental socioeconomic status and oral health behaviours were directly associated with dental caries (P < .001), and parental socioeconomic status had the most association. Parenting style and parental and children's dental anxiety were associated with dental visit behaviours (P < .001). Further, while all parental variables except prior exposure to training about oral and dental health were significantly correlated with dental caries, only educational level and coverage by health insurance were significantly associated with Frankl behaviour scale score.

CONCLUSIONS

This study developed and validated a conceptual model that delineates the pathways between the parental and individual determinants of children's oral health and dental visit behaviours. The model should help us to understand these pathways to lower the incidence of dental caries and improve dental visit behaviours among children.

Multi-media biomarkers: Integrating information to improve lead exposure assessment

Exposure assessment traditionally relies on biomarkers that measure chemical concentrations in individual biological media (i.e., blood, urine, etc.). However, chemicals distribute unevenly among different biological media; thus, each medium provides incomplete information about body burden. We propose that machine learning and statistical approaches can create integrated exposure estimates from multiple biomarker matrices that better represent the overall body burden, which we term multi-media biomarkers (MMBs). We measured lead (Pb) in blood, urine, hair and nails from 251 Italian adolescents aged 11-14 years from the Public Health Impact of Metals Exposure (PHIME) cohort. We derived aggregated MMBs from the four biomarkers and then tested their association with Wechsler Intelligence Scale for Children (WISC) IQ scores. We used three approaches to derive the Pb MMB: one supervised learning technique, weighted quantile sum regression (WQS), and two unsupervised learning techniques, independent component analysis (ICA) and non-negative matrix factorization (NMF). Overall, the Pb MMB derived using WQS was most consistently associated with IQ scores and was the only method to be statistically significant for Verbal IQ, Performance IQ and Total IQ. A one standard deviation increase in the WQS MMB was associated with lower Verbal IQ (β [95% CI] = -2.2 points [-3.7, -0.6]), Performance IQ (-1.9 points [-3.5, -0.4]) and Total IQ (-2.1 points [-3.8, -0.5]). Blood Pb was negatively associated with only Verbal IQ, with a one standard deviation increase in blood Pb being associated with a -1.7 point (95% CI: [-3.3, -0.1]) decrease in Verbal IQ. Increases of one standard deviation in the ICA MMB were associated with lower Verbal IQ (-1.7 points [-3.3, -0.1]) and lower Total IQ (-1.7 points [-3.3, -0.1]). Similarly, an increase of one standard deviation in the NMF MMB was associated with lower Verbal IQ (-1.8 points [-3.4, -0.2]) and lower Total IQ (-1.8 points [-3.4, -0.2]). Weights highlighting the contributions of each medium to the MMB revealed that blood Pb was the largest contributor to most MMBs, although the weights varied from more than 80% for the ICA and NMF MMBs to between 30% and 54% for the WQS-derived MMBs. Our results suggest that MMBs better reflect the total body burden of a chemical that may be acting on target organs than individual biomarkers. Estimating MMBs improved our ability to estimate the full impact of Pb on IQ. Compared with individual Pb biomarkers, including blood, a Pb MMB derived using WQS was more strongly associated with IQ scores. MMBs may increase statistical power when the choice of exposure medium is unclear or when the sample size is small. Future work will need to validate these methods in other cohorts and for other chemicals.

A Multisectoral Nutrition Program in Nepal Improves Knowledge of Dietary Diversity, Sick Child Feeding, and Handwashing, but Not All Practices: a Program Impact Pathways Mediation Analysis

BACKGROUND

Few intervention studies have focused on how inputs link with outcomes.

OBJECTIVES

This study tested whether Suaahara I program inputs translated into intended outcomes and identified gaps along the theorized program impact pathway to improved nutrition, care, and water, sanitation, and hygiene behaviors.

METHODS

We used household-level, cross-sectional survey data from a process evaluation of Suaahara I conducted in 2014. A total of 480 households with a pregnant woman or child aged <2 y were selected with an equal split between intervention and comparison arms. We used regression models to test associations between exposure to Suaahara I and 3 primary outcomes and 3 parallel knowledge mediators: child minimum dietary diversity, child feeding during illness, and proper handwashing during child care. We used generalized structural equation modeling using full information maximum likelihood to test whether knowledge mediated associations between exposure and outcomes.

RESULTS

In the adjusted regression models between maternal exposure to Suaahara I and 3 behavioral outcomes, we found a small positive association for handwashing (β: 0.21; 95% CI: 0.10, 0.31), but no association with the other 2 outcomes. In the mediation analysis, maternal exposure to Suaahara I, however, was associated with the mediator (knowledge) for all 3 outcomes: handwashing with soap and water (β: 0.05 ± 0.02), child minimum dietary diversity (logit = 0.06; P = 0.03), and child feeding during illness (logit = 0.09 ± 0.02). We found a positive, significant association for the full indirect pathway of program input to output via knowledge for child feeding during illness (logit = 0.07 ± 0.03) only.

CONCLUSIONS

Exposure to Suaahara I behavior change interventions improved knowledge, but this did not always translate into improved practices. It is important to address barriers to optimal practices beyond knowledge in future nutrition programs in Nepal.

Middle ear abnormalities at age 5 years in relation with early onset otitis media and number of episodes, in the Inuit population of Nunavik, Quebec, Canada

Otitis media (OM) and their sequelae are a major health issue in the Inuit population of Nunavik, Quebec. Hypotheses of the study were: (i) early onset OM leads to repeated OM; (ii) repeated OM episodes leads to middle ear abnormalities (MEA) at age 5 years, (iii) pneumococcal conjugate vaccines (PCVs) may reduce multiple OM and MEA. Immunisation cards, medical records and audiology screening tests at age 5 years in a sample of 610 children born in 1994-2010 in 3 communities were reviewed. Children were classified into three categories using a score based on audiology screening tests: no abnormality, minor, or major MEA. The average number of OM episodes before age 5 years was 5.0 and 30% had minor and 17% major MEA at age 5 years. Community residency predicted both frequent (≥ 8) OM episodes and MEA. Early onset OM (age <6 months) was a predictor of frequent OM (RR = 1.71; 95%CI: 1.50-1.95) whereas PCV (≥1 dose ≥ age 2 months) has no significant effect. Frequent OM episodes were associated with major MEA (RR = 2.16; 95%CI: 1.20-3.85). Although associations were not statistically significant, there was a trend towards a protective effect of PCV administration on frequent OM and minor MEA, but not major MEA. In conclusion, results support an association between early onset OM, frequent OM and MEA that could represent a causal pathway.

Does ethnic-racial identity modify the effects of racism on the social and emotional wellbeing of Aboriginal Australian children?

OBJECTIVES

This study investigates the protective role of ethnic-racial identity (ERI) affirmation on the longitudinal association between racism and Aboriginal Australian children's social and emotional well-being (SEWB).

METHODS

408 children from the K-Cohort of the Longitudinal Study of Indigenous Children were included in the analysis. Data were collected through questionnaire-guided interviews at 7-10 and 9-12 years of age. Children's racism experience, SEWB (Strengths and Difficulties Questionnaire), and confounding were reported by caregivers. ERI was reported by children and dichotomized into high versus low. Generalized linear models with log-Poisson links and robust errors were used to estimate adjusted Risk Ratios (RRa) for the effect of racism on SEWB domains. Effect-measure modification analysis was used to verify differences on effect sizes per strata of ERI affirmation. The presence of modification was indicated by the Relative Excess Risk due to Interaction (RERI).

RESULTS

Slightly above half (51.4%) of the children presented high ERI affirmation. Children exposed to racism and with low ERI affirmation were at increased risk of hyperactive behavior (RRa 2.53, 95% CI 1.17, 5.48), conduct problems (RRa 2.35, 95% CI 1.07, 5.15), and total difficulties (RRa 1.73, 95% CI 0.84, 3.55). Positive RERIs indicated the joint effects of racism and low ERI affirmation surpassed the sum of their separate effects in these domains. Children with high ERI affirmation were at increased risk of peer problems (RRa 1.66, 95% CI 0.78, 3.52).

CONCLUSIONS

These findings suggest that ERI may mitigate the risk of poor SEWB due to racism. Fostering affirmative ERI can be an important strategy in promoting resilience in Aboriginal Australian children.

Statistical Methodology in Studies of Prenatal Exposure to Mixtures of Endocrine-Disrupting Chemicals: A Review of Existing Approaches and New Alternatives

BACKGROUND

Prenatal exposures to endocrine-disrupting chemicals (EDCs) during critical developmental windows have been implicated in the etiologies of a wide array of adverse perinatal and pediatric outcomes. Epidemiological studies have concentrated on the health effects of individual chemicals, despite the understanding that EDCs act together via common mechanisms, that pregnant women are exposed to multiple EDCs simultaneously, and that substantial toxicological evidence of adverse developmental effects has been documented. There is a move toward multipollutant models in environmental epidemiology; however, there is no current consensus on appropriate statistical methods.

OBJECTIVES

We aimed to review the statistical methods used in these studies, to identify additional applicable methods, and to determine the strengths and weaknesses of each method for addressing the salient statistical and epidemiological challenges.

METHODS

We searched Embase, MEDLINE, and Web of Science for epidemiological studies of endocrine-sensitive outcomes in the children of mothers exposed to EDC mixtures during pregnancy and identified alternative statistical methods from the wider literature.

DISCUSSION

We identified 74 studies and analyzed the methods used to estimate mixture health effects, identify important mixture components, account for nonmonotonicity in exposure–response relationships, assess interactions, and identify windows of exposure susceptibility. We identified both frequentist and Bayesian methods that are robust to multicollinearity, performing shrinkage, variable selection, dimension reduction, statistical learning, or smoothing, including methods that were not used by the studies included in our review.

CONCLUSIONS

Compelling motivation exists for analyzing EDCs as mixtures, yet many studies make simplifying assumptions about EDC additivity, relative potency, and linearity, or overlook the potential for bias due to asymmetries in chemical persistence. We discuss the potential impacts of these choices and suggest alternative methods to improve analyses of prenatal exposure to EDC mixtures. https://doi.org/10.1289/EHP2207.

Phthalate exposure during pregnancy and long-term weight gain in women

BACKGROUND

Phthalates are known endocrine disruptors and peroxisome proliferator-activated receptor (PPAR) activators, potentially capable of promoting an obesogenic effect. Pregnant women are especially vulnerable to phthalate exposure due to physiological and metabolic changes during pregnancy, including those related to the metabolism of xenobiotics. Phthalate exposure during pregnancy has been associated with early gestational weight gain, however, its effect on long-term weight gain remains unclear. The aim of the present study was to evaluate the association between phthalate exposure during pregnancy and long-term changes in weight among women.

METHODS

Urinary phthalate concentrations, socioeconomic, anthropometry and information on diet and socioeconomic status were collected during pregnancy from 178 women from the Early Life Exposure in Mexico to Environmental Toxicants (ELEMENT) birth cohort. Maternal body weight and diet information was also collected up to 5 times in the first year postpartum and twice during follow-up visits 5.2-10.7 years later. A path analysis was performed to assess associations between urinary phthalate metabolite levels during pregnancy and change in weight (kg) per year after delivery, including age, education, living with/without partner, parity, daily energy intake and breastfeeding duration.

RESULTS

The mean age at pregnancy was 27.3 ± 5.9 years and mean body mass index during the first postpartum year was 27.07 ± 4.22 kg/m². On average, women gained 3.48 kg (0.52 ± 0.84 kg/year). A unit increase in log-transformed mono-3-carboxypropyl phthalate (MCPP) was associated with 0.33 kg (95% CI: 0.09, 0.56) higher weight gain per year, and mono-benzyl phthalate (MBzP) with 0.21 kg (95% CI: -0.38, -0.03) lower weight gain per year.

CONCLUSION

Exposure to certain phthalates during pregnancy may be associated with long-term weight change in women. More studies on the effects of phthalate exposure during pregnancy on women's long-term health are required.

Ensuring Causal, Not Casual, Inference

With innovation in causal inference methods and a rise in non-experimental data availability, a growing number of prevention researchers and advocates are thinking about causal inference. In this commentary, we discuss the current state of science as it relates to causal inference in prevention research, and reflect on key assumptions of these methods. We review challenges associated with the use of causal inference methodology, as well as considerations for hoping to integrate causal inference methods into their research. In short, this commentary addresses the key concepts of causal inference and suggests a greater emphasis on thoughtfully designed studies (to avoid the need for strong and potentially untestable assumptions) combined with analyses of sensitivity to those assumptions.

Water, sanitation, and hygiene practices mediate the association between women's empowerment and child length-for-age z-scores in Nepal

In Nepal, more than one-third of children are stunted. Prior studies have shown that women's empowerment in agriculture is associated with child (<2 years) length-for-age z-scores (LAZ) in Nepal. This study tests whether child dietary diversity (DD) and household water, sanitation, and hygiene (WASH) facilities and practices mediate the associations between women's empowerment and LAZ. With a cross-sectional dataset of 4,080 households from 240 rural communities across 16 districts of Nepal, we used ordinary least squares regression models to first estimate the associations between women's empowerment and LAZ for children 6 to 24 months (n = 1,402; our previous published analysis included all children <24 months of age), using the Women's Empowerment in Agriculture Index's Five Domains of Empowerment subindex. We used standardized structural equation models to test whether child DD and/or household WASH mediated the association between women's empowerment and child LAZ. Overall, women's empowerment was positively associated with child LAZ (β = 0.24, P = 0.03), as found in our previous analyses. In the mediation analysis, women's empowerment was positively associated with WASH (β = 0.78, P < 0.001), and in turn child LAZ (β = 0.09, P < 0.001). Women's empowerment was not associated with DD, but DD was associated with LAZ (β = 0.06, P = 0.05). Empowered women had better WASH practices than nonempowered women, which translated into higher child LAZ. Child DD was not a mediating factor in the association between women's empowerment and child LAZ. More research is needed to explore other pathways by which women's empowerment may affect child nutrition outcomes.