CARDIOVASCULAR STRESS REACTIVITY AND JOB STRAIN AS DETERMINANTS OF AMBULATORY BLOOD-PRESSURE AT WORK

Objective: To test the hypothesis that cardiovascular reactivity to la boratory mental stressors interacts with job strain in predicting bloo d pressure at work. Design: Ambulatory monitoring of blood pressure an d heart rate was carried out for an 8-h period on a work day and on an equivalent non-work day in 49 male firefighters. Methods: Participant s were recruited from a larger cohort (n=90) on the basis of showing h igh or low systolic reactions to mental arithmetic 15-24 months previo usly, coupled with high or low ratings of perceived job strain (high d emand-low control). Four groups were tested: low job strain-low systol ic reactors (n=12), low job strain-high systolic reactors (n=12), high job strain-low systolic reactors (n=12) and high job strain-high syst olic reactors (n=13). Results: Systolic blood pressure (SBP) was highe r on work than non-work days, and diastolic blood pressure and heart r ate were higher at work in the morning but not in the afternoon. These effects were due partly to posture and physical activity differences between the two days. Neither job strain nor laboratory reactivity ind ependently predicted ambulatory blood pressure. However, SBP was signi ficantly higher during the afternoon at work in the high job strain-hi gh systolic reactors than in the other groups. This was independent of baseline SBP, and was not due to differences in posture or activity a t the time of recordings. Ambulatory SBP reactivity (difference betwee n ambulatory values and workplace resting levels) in the afternoon at work was also elevated significantly in high job strain-high systolic reactors compared with in the other groups. Conclusions: The results s upport the hypothesis that individual differences in the appraisal of work stress modulate the relationship between stress reactivity and am bulatory blood pressure.