Effort-reward imbalance at work and 5-year changes in blood pressure: the mediating effect of changes in body mass index among 1400 white-collar workers

Longitudinal plasmode algorithms to evaluate statistical methods in realistic scenarios: an illustration applied to occupational epidemiology

INTRODUCTION

Plasmode simulations are a type of simulations that use real data to determine the synthetic data-generating equations. Such simulations thus allow evaluating statistical methods under realistic conditions. As far as we know, no plasmode algorithm has been proposed for simulating longitudinal data. In this paper, we propose a longitudinal plasmode framework to generate realistic data with both a time-varying exposure and time-varying covariates. This work was motivated by the objective of comparing different methods for estimating the causal effect of a cumulative exposure to psychosocial stressors at work over time.

METHODS

We developed two longitudinal plasmode algorithms: a parametric and a nonparametric algorithms. Data from the PROspective Québec (PROQ) Study on Work and Health were used as an input to generate data with the proposed plasmode algorithms. We evaluated the performance of multiple estimators of the parameters of marginal structural models (MSMs): inverse probability of treatment weighting, g-computation and targeted maximum likelihood estimation. These estimators were also compared to standard regression approaches with either adjustment for baseline covariates only or with adjustment for both baseline and time-varying covariates.

RESULTS

Standard regression methods were susceptible to yield biased estimates with confidence intervals having coverage probability lower than their nominal level. The bias was much lower and coverage of confidence intervals was much closer to the nominal level when considering MSMs. Among MSM estimators, g-computation overall produced the best results relative to bias, root mean squared error and coverage of confidence intervals. No method produced unbiased estimates with adequate coverage for all parameters in the more realistic nonparametric plasmode simulation.

CONCLUSION

The proposed longitudinal plasmode algorithms can be important methodological tools for evaluating and comparing analytical methods in realistic simulation scenarios. To facilitate the use of these algorithms, we provide R functions on GitHub. We also recommend using MSMs when estimating the effect of cumulative exposure to psychosocial stressors at work.

A test for the correct specification of marginal structural models

Marginal structural models (MSMs) allow estimating the causal effect of a time-varying exposure on an outcome in the presence of time-dependent confounding. The parameters of MSMs can be estimated utilizing an inverse probability of treatment weight estimator under certain assumptions. One of these assumptions is that the proposed causal model relating the outcome to exposure history is correctly specified. However, in practice, the true model is unknown. We propose a test that employs the observed data to attempt validating the assumption that the model is correctly specified. The performance of the proposed test is investigated with a simulation study. We illustrate our approach by estimating the effect of repeated exposure to psychosocial stressors at work on ambulatory blood pressure in a large cohort of white-collar workers in Québec City, Canada. Code examples in SAS and R are provided to facilitate the implementation of the test.

Influence of Work on Elevated Blood Pressure in Hispanic Adolescents in South Texas

Literature supports an association between work and cardiovascular disease in adults. The objective of this study was to examine the relationship between current work status and elevated blood pressure in Hispanic adolescents. Participants were students in Hidalgo County, located along the Texas-Mexico border. Participants enrolled in the cohort study in ninth grade with assessments completed once a year for up to three years. Participants completed a self-report survey, while staff measured height, weight, waist circumference, blood pressure, and were screened for acanthosis nigricans. A generalized linear regression model with a logit link function was constructed to assess current work status and elevated blood pressure. Of the 508 participants, 29% had elevated blood pressure, which was associated with being male and other chronic disease indicators (e.g., acanthosis nigricans, overweight/obesity). The mean probability for elevated blood pressure was higher among currently working adolescents compared to those who were not. Findings were statistically significant (p < 0.05) at baseline. The findings illustrate that a large proportion of adolescents along the Texas-Mexico border may have elevated blood pressure and that working may be associated with it. Subsequent research is needed to confirm these findings, as well as to identify the mechanism for how work may increase hypertension in adolescents.

Psychosocial Stressors at Work and Ambulatory Blood Pressure

PURPOSE OF REVIEW

Psychosocial stressors at work from the demand-latitude and effort-reward imbalance models are adverse exposures affecting about 20-25% of workers in industrialized countries. This review aims to summarize evidence on the effect of these stressors on blood pressure (BP).

RECENT FINDINGS

Three systematic reviews have recently documented the effect of these psychosocial stressors at work on BP. Among exposed workers, statistically significant BP increases ranging from 1.5 to 11 mmHg have been observed in prospective studies using ambulatory BP (ABP). Recent studies using ABP have shown a deleterious effect of these psychosocial stressors at work on masked hypertension as well as on blood pressure control in pharmacologically treated patients. Evidence on the effect of these psychosocial stressors on BP supports the relevance to tackle these upstream factors for primary prevention and to reduce the burden of poor BP control. There is a need for increased public health and clinical awareness of the occupational etiology of high BP, hypertension, and poor BP control.

Effects of psychosocial work characteristics on hair cortisol - findings from a post-trial study

Prolonged work stress, as indicated by the effort-reward imbalance (ERI) model, jeopardizes health. Cortisol represents a candidate mechanism connecting stress to ill health. However, previous findings appear inconclusive, and recommendations were made to assess work stress at multiple time points and also to investigate ERI (sub-)components. This study therefore examines the effects of two single time points, as well as the mean and change scores between time points of ERI and its components on hair cortisol concentration (HCC), a long-term cortisol measurement. Participants were 66 male factory workers (age: 40.68 ± 6.74 years; HCC: 9.00 ± 7.11 pg/mg), who were followed up after a stress management intervention (2006-2008). In 2008 (T1) and 2015 (T2), participants completed a 23-item ERI questionnaire, assessing effort, the three reward components (esteem, job security, job promotion) and over-commitment. In 2015, participants also provided a 3-cm hair segment close to the scalp for HCC analysis, as well as information on relevant confounders (i.e. medication intake, age, work characteristics, socioeconomic and lifestyle factors, number of stressful life events). Linear regressions revealed hardly any cross-sectional or longitudinal effect of ERI and its components on HCC. Only the change scores between T1 and T2 of job security were negatively associated with lower HCC in unadjusted (β = -.320; p = .009) and adjusted (β = -.288; p = .044) models. In this study, only a decrease of perceived job security over time was significantly associated with higher HCC, and other predictors were not related to this outcome. Especially after correction for multiple testing, this study revealed just a weak association of different psychosocial work measurements with HCC. Lay summary This study showed that an increase in perceived job insecurity is correlated with higher levels of the stress hormone cortisol. The higher levels of cortisol might represent a biological explanation for the negative health effects of job insecurity. The association was, however, relatively low, and more and more voices are questioning whether cortisol in hair is a reliable marker for perceived work stress.