Exposures to work stress
Psychosocial stress at work was measured and defined in all studies as job strain—a combination of high demands and low control at work. Job strain was ascertained with sets of questions from the validated Job Content Questionnaire (JCQ) and Demand-Control Questionnaire (DCQ),25 46 which were included in the baseline self report questionnaire in all studies. A detailed description of the job strain measure and its validation is provided elsewhere.28 Briefly participants were asked to rate psychosocial demands and control aspects of their job on a Likert-type scale. Mean response scores were calculated for the questions on job demands and job control for each participant. High demands were defined as having a job demands score higher than the study specific median score and low job control was defined as having a job control score lower than the study specific median score. Binary job strain was defined as job strain (high demands and low control) versus no strain (all other categories combined). Job strain categories, or quadrants based on the job strain model, were defined as follows: high strain job (high demands and low control), active job (high demands and high control), passive job (low demands and low control), and low strain job (low demands and high control).