Joint effects of job strain and road-traffic and occupational noise on myocardial infarction

OBJECTIVES: The aim of this study was to assess the joint effect of job strain and both road-traffic and occupational noise on myocardial infarction (MI). METHOD: We conducted a population based case–control study on first time MI in Stockholm County during 1992–1994. Participants answered a questionnaire and underwent a physical examination. Residential road-traffic noise exposure was based on residential history combined with information on traffic intensity and distance to nearby roads. Occupational noise exposure was assessed by occupational history combined with a job-exposure matrix derived from measurements. Job strain was based on questions regarding psychological demands and decision latitude. A total of 3050 study participants (1252 cases and 1798 controls) were included in the study. RESULTS: An increased risk of MI was indicated among participants exposed to road-traffic noise [odds ratio (OR) 1.23, 95% confidence interval (95% CI) 1.01–1.51], occupational noise (OR 1.17, 95% CI 0.98–1.41) and job strain (OR 1.39, 95% CI 1.17–1.65). Participants exposed to one, two, or three of these factors showed an increased risk (OR 1.16, 95% CI 0.97–1.40, OR 1.57, 95% CI 1.24–1.98, and OR 2.27, 95% CI 1.41–3.64, respectively). Exposure to two or three of these factors occurred among about 20% of the controls. CONCLUSION: Our results indicate that exposure to a combination of noise exposure and job strain increases the risk of MI substantially. Such exposures affect a considerable part of the population, which has relevance for prioritization of preventative measures.