Do overweight/obesity and low levels of leisure-time vigorous physical activity moderate the effect of occupational physical activity on self-rated health of construction workers?

PURPOSE To investigate the combined effects of occupational physical activity (OPA) and either overweight/obesity or low levels of leisure-time vigorous physical activity (LTVPA) on self-rated health. METHODS A longitudinal study was performed among 29,987 construction workers with complete data on 2 Workers' Health Surveillance Programs during 2010-2018. Self-reported OPA involved strenuous work postures and manual material handling. Low level of LTVPA was defined as self-reported vigorous activity for less than three times per week lasting at least 20 min per session. Overweight and obesity were based on Body Mass Index (BMI) (25.0 ≤ BMI < 30.0 kg/m2 and BMI ≥ 30.0 kg/m2, respectively) using measured body height and weight. Self-rated health was measured using a single item question. Logistic regression analysis was used to investigate the associations between the separate risk factors at baseline and self-rated health at follow-up. The combined effects of demanding OPA and either overweight/obesity or low level of LTVPA on self-rated health were analyzed using the relative excess risk due to interaction (RERI). RESULTS Mean follow-up duration was 31.7 (SD = 14.9) months. Construction workers with strenuous work postures (OR 1.35 95% CI 1.25-1.46), manual material handling (OR 1.29 95% CI 1.19-1.40), obesity (OR 1.31 95% CI 1.17-1.47) and low LTVPA (OR 1.13 95% CI 1.01-1.25) were more likely to report poor self-rated health at follow-up. No statistically significant interaction effects were found for OPA and obesity or low LTVPA. CONCLUSIONS OPA, obesity and low level of LTVPA were separate risk factors for poor self-rated health, but did not appear to have a synergistic effect.