Job strain and ambulatory blood pressure: A meta-analysis

Introduction
Studies have indicated that jobs combining high psychological demands and low control (job strain) increase blood pressure when blood pressure is measured by an ambulatory (portable) monitor. However, studies have employed a variety of designs and vary in quality. Thus, we conducted a meta-analysis of published study results along with a systematic assessment of study validity.

Methods
22 cross-sectional studies published between 1985 and May 2011 met inclusion criteria and provided data appropriate for meta-analysis. Authors were queried for additional relevant data when not available in the published article. 19 cross-sectional studies used a single measure of exposure to job strain, while 3 studies provided a measure of cumulative exposure. 3 longitudinal studies also met inclusion criteria, however, differences in exposure measures and length of follow-up precluded a summary estimate of their results. Data were analyzed based on a random effects model using Comprehensive Meta-Analysis 2.

Results
Single exposure to job strain was associated with work ambulatory systolic (4.2 mm Hg, p<.001) and diastolic (2.4 mm Hg, p<.001) blood pressure. Stronger associations were observed in population-based than in single-occupation studies. Biases towards the null were common, suggesting that these results underestimate the effect of job strain on blood pressure. Additional analyses will be presented of cumulative exposure to job strain, forms of exposure assessment (self-report, job exposure matrix, expert rater), range of blood pressure included in studies, study validity score, and potential publication bias. Findings from the 3 longitudinal studies will be discussed.

Discussion
Results suggest that job strain is a substantial risk factor for blood pressure elevation, a potential mechanism by which job strain increases risk of cardiovascular disease. Therefore, workplace surveillance programs need to assess job strain (and other job stressors) and blood pressure. Workplace interventions are needed to reduce job strain and associated health risks.