Does increasing physical activity reduce the excess risk of work disability among overweight individuals?

OBJECTIVES: We examined the extent to which an increase in physical activity would reduce the excess risk of work disability among overweight and obese people (body mass index ≥ 25kg/m^2). METHODS: We used counterfactual modelling approaches to analyze longitudinal data from two Finnish prospective cohort studies (total N=38 744). Weight, height and physical activity were obtained from surveys and assessed twice and linked to electronic records of two indicators of long-term work disability (≥90-day sickness absence and disability pension) for a 7-year follow-up after the latter survey. The models were adjusted for age, sex, socioeconomic status, smoking, and alcohol consumption. RESULTS: The confounder-adjusted hazard ratio (HR) of long-term sickness absence for overweight compared to normal-weight participants was 1.43 [95% confidence interval (CI) 1.35–1.53]. An increase in physical activity among overweight compared to normal-weight individuals was estimated to reduce this HR to 1.40 (95% CI 1.31–1.48). In pseudo-trial analysis including only the persistently overweight, initially physically inactive participants, the HR for long-term sickness absence was 0.82 (95% CI 0.70–0.94) for individuals with increased physical activity compared to those who remained physically inactive. The results for disability pension as an outcome were similar. CONCLUSIONS: These findings suggest that the excess risk of work disability among overweight individuals would drop by 3–4% if they increased their average physical activity to the average level of normal-weight people. However, overweight individuals who are physically inactive would reduce their risk of work disability by about 20% by becoming physically active.