Exploring the 'fit for work' principle: The association between occupational physical activity, cardio-respiratory fitness, and mortality - a meta-analysis of male worker data

Objectives: This individual participant data meta-analysis investigates the association between occupational physical activity (OPA) and both cardiovascular mortality and all-cause mortality across different cardio-respiratory fitness (CRF) groups among male workers. Methods: Data were pooled from five European cohort studies. OPA was categorized into three levels and CRF into low, moderate, and high tertiles. OPA was assessed using self-reports and CRF through objective measurements. Two-stage meta-analyses were conducted. First, we analyzed each cohort using Cox-regression models then we pooled results with random effects model to evaluate the associations between OPA and both cardiovascular and all-cause mortality, stratified by CRF. Models were adjusted for age, body mass index, smoking status, leisure-time physical activity, and educational level. Results: Among 9922 men (mean age 46.8, standard deviation 6.7, years), 55.7% died during an average 25.6-year follow-up, of which 29.3% died from cardiovascular causes. Individuals with low CRF and high levels of OPA showed increased risks of cardiovascular hazard ratio (HR) 1.27, 95% confidence interval (CI) 1.04-1.55 and all-cause mortality (HR 1.22, 95% CI 1.07-1.40) compared to those with low CRF and low levels of OPA. High CRF mitigated cardiovascular mortality risk (HR 1.08, 95% CI 0.79-1.48) but not all-cause mortality (HR 1.27, 95% CI 0.98-1.83) for those with high OPA. Conclusions: Our findings for cardiovascular mortality suggest that high CRF levels may protect workers with physically demanding jobs from adverse cardiovascular outcomes, supporting the 'fit for work' principle. However, this protective effect was not observed for all-cause mortality.