Abstract Body: Background: Leisure-time physical activity (LTPA) is associated with health benefits, but emerging evidence suggests occupational physical activity (OPA) may have paradoxically negative health associations. Limited U.S. data hinders understanding of this phenomenon in the American workforce. This study examined associations between OPA and mortality in a representative U.S. sample.

Methods: Data from 8,041 working adults (baseline age 41.4±0.2, 55.9% female, 80.5% non-Hispanic White) in the 1999-2006 National Health and Nutrition Examination Survey, linked to 2019 National Death Index, were analyzed. Participants worked ≥35 hours/week and had complete data on all included variables. Self-reported jobs were classified into standard occupational classifications and categorized as low, intermediate, or high OPA. Cox proportional hazards models estimated hazard ratios (HR) for all-cause and cardiovascular disease (CVD) mortality across OPA categories, adjusting for age, sex, race-ethnicity, education, smoking status, alcohol consumption, body mass index, self-reported CVD, and LTPA. Effect modification by sex, race-ethnicity, smoking, and LTPA was examined.

Results: In fully adjusted models, intermediate OPA was associated with higher all-cause mortality (HR 1.24, 95% CI 1.00-1.53) compared to low OPA. For CVD mortality, both intermediate (HR 1.79, 95% CI 1.16-2.75) and high OPA (HR 1.71, 95% CI 1.00-2.92) showed increased risk compared to low OPA. Associations varied by subgroups: females with high OPA had higher all-cause mortality risk (HR 1.59, 95% CI 1.05-2.41) compared to low OPA. Among never smokers, high OPA was associated with increased CVD mortality (HR 3.44, 95% CI 1.26-9.37). Surprisingly, among those meeting LTPA guidelines, high OPA was associated with the highest CVD mortality risk (HR 6.21, 95% CI 2.10-18.39).

Conclusion: This analysis supports the OPA health paradox in a U.S. population, with higher OPA levels associated with increased mortality risk, particularly from CVD. Associations varied across subgroups, highlighting the complexity of the OPA-health relationship and potential implications for health disparities. The unexpected finding of heightened risk among those meeting LTPA guidelines warrants further investigation. Results underscore the need for targeted interventions and workplace policies to mitigate health risks for workers in high-OPA occupations, especially among vulnerable populations.