Introduction Recommendations regarding physical activity typically include both leisure time and occupational physical activity. However, the results of research on occupational physical activity and the association to myocardial infarction are inconsistent. The aim of this study was to investigate if occupational physical activity affects the risk of myocardial infarction.

Method In this prospective cohort study, data from the WOLF study are analysed. In total, 9,961 employees having no history of myocardial infarction were followed from inclusion to their first incidence of myocardial infarction. Hazard ratios (HR) were estimated using Cox proportional hazard regression, for different levels of occupational physical activity in relation to the risk of myocardial infarction.

Results A follow-up with a mean of 13.1 years found 249 cases of myocardial infarction. In analyses adjusted for age, sex and socio-economic status, participants standing and walking more than 50% of their working day had HR of 1.13 (95% CI: 0.83–1.54), compared to participants seated more than 50% of their working day. The corresponding HR for participants whose work included lifting or carrying was 0.86 (95% CI: 0.59–1.24). Stratified analyses resulted in a significantly decreased risk for young people whose work included lifting or carrying, HR 0.37 (95% CI: 0.17–0.84), compared with younger persons who sat most of their working day.

Conclusion Only weak associations between occupational physical activity and the risk of myocardial infarction were observed in this study. A significant reduced risk were seen for young participants with work including lifting and carrying, but this result must be interpreted with caution due to few participants in the stratified analyses. Based on the results from this study, occupational physical activity does not seem to be enough for reducing the risk of myocardial infarction, which is an important message to people with high levels of occupational physical activity.