Association between demand–control model components and blood pressure in the ELSA-Brasil study: exploring heterogeneity using quantile regression analyses

Objectives This study aimed to investigate which components of the demand-control model (DCM) are associated with blood pressure (BP) and ascertain whether these associations vary over the BP distribution. Methods We evaluated the baseline date of 11 647 current workers enrolled in the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil) (2008-2010), a multicenter cohort study of 35-74-year-old civil servants. Job demands, skill discretion and decision authority were measured using the Brazilian version of the Demand-Control-Support Questionnaire. The associations between DCM components and systolic and diastolic BP (SBP and DBP, respectively) were examined by gamma regression, indicated for modelling skewed continuous variables, and quantile regression. Tests were conducted for interaction with gender and use of antihypertensives. Results In the adjusted gamma models, no association was observed between DCM components and BP in the total study population. Among non-users of antihypertensives, high decision authority was marginally associated with an increase of 0.59 mmHg (95% CI 0.00-1.18) in SBP. In the quantile models, this association was found to be significant from quantiles 35-60. Further significant but inconsistent positive associations were observed between decision authority and DBP among users of antihypertensives (quantiles 5 and 10) and between skill discretion and SBP in the total study population (quantile 5). The results did not differ by gender. Conclusions Decision authority associates positively with SBP, but only in the central portion of the SBP distribution and among non-users of antihypertensives. No consistent associations were observed for skill discretion or job demands.