The contribution of health behaviours to occupational class inequalities in cardiovascular disease: a longitudinal study of Finnish municipal employees

Background: Cardiovascular diseases (CVD) are more common in lower occupational classes, but the mediating role of health behaviours remains unclear. This study aimed to quantify the extent to which health behaviours mediate the association between occupational class and CVD, evaluate their relative contributions to CVD risk, and assess occupational class differences in the effects of health behaviours. Methods: Municipal employees from Helsinki, aged 40-60 at baseline, were followed from 2000-2002 (response rate 67%) to 2022. CVD events were identified from national registers, including hospitalizations, long-term sickness absence, disability pensions, and mortality. Counterfactual mediation analysis using additive survival regression was used to assess the contribution of health behaviours - excessive alcohol consumption, smoking, unhealthy diet, and insufficient physical activity - to the association of occupational class and CVD. Occupational class differences in the effects of health behaviours were assessed with Cox regression. Results: During follow-up, 50% of participants in the low occupational class and 46% in the high occupational class had a CVD event. All unhealthy behaviours except heavy alcohol use were more common in the low occupational class. Health behaviours explained approximately 40% of the excess risk of CVD when moving from high occupational class to low occupational class. Insufficient physical activity (HR 1.44, 95% CI 1.35-1.54) was the strongest predictor of CVD. Unhealthy diet was more strongly associated with CVD in the high occupational class. Conclusion: Health behaviours explained a part of occupational class inequalities in CVD, but most of the inequality remained unexplained, highlighting broader social determinants.