Association between ambulatory blood pressure and alternative formulations of job strain

OBJECTIVES - The goal of the study was to determine whether alternative formulations of Karasek and Theorell's job-strain construct are associated with ambulatory blood pressure and the risk of hypertension. METHODS - Full-time male employees (N = 262) in eight worksites completed a casual blood pressure screening, medical examinations, and questionnaires and wore an ambulatory blood pressure monitor for 24 h on a workday. Cases of hypertension were ascertained from casual- blood pressure readings for a case-referent analysis. A cross-sectional analysis was also conducted, ambulatory (continuous) blood pressure measurements being used as the outcome. RESULTS - All formulations of job strain exhibited significant associations with systolic blood pressure at work and home, but not with diastolic blood pressure. Employees experiencing job strain had a systolic blood pressure that was 6.7 mm Hg (≃0.89 kPa) higher and a diastolic blood pressure that was 2.7 mm Hg (≃ 0.36 kPa) higher at work than other employees, and the odds of hypertension were increased [odds ratio (OR) 2.9, 95% confidence interval (95% CI) 1.3-6.6]. Using national means for decision latitude and demands to define job strain increased the systolic and diastolic blood pressure associations to 11.5 mm Hg (≃ 1.53 kPa) and 4.1 mm Hg (≃ 0.54 kPa), respectively. Adding organizational influence to the task-level decision latitude variable produced a stronger association for hypertension with job strain (OR 3.7, 95% CI 1.6-8.5). Adding social support to the job-strain model also slightly increased the hypertension risk. CONCLUSIONS - The impact of job strain, at least on systolic blood pressure, is consistent and robust across alternative formulations, more restrictive cut points tending to produce stronger effects.