Urban-rural differences in the association between occupational physical activity and mortality in Chinese working population: evidence from a nationwide cohort study

Background Despite emerging studies suggesting that occupational physical activity (OPA) might be harmful to health, the available evidence is not definitive. Most of these research studies were conducted in high-income Western countries or in urbanized setting. In China, where over one-third of the population resides in rural area, the impact of OPA on health is not well understood. The goal of this study is to investigate how the association between OPA and mortality vary by urban-rural settings. Methods Baseline data on OPA was gathered using the Global Physical Activity Questionnaire from 30,650 urban and 49,674 rural working adults as part of the 2013–2014 China Chronic Disease and Risk Factor Surveillance. Participants were followed for a median of 6.2 years, and death records were retrieved from the National Mortality Surveillance System until December 31, 2019. The multivariable Cox proportional hazard model was used to examine urban-rural differences in the association between OPA and all-cause and cardiovascular disease (CVD) mortality. Subgroup analyses were performed by sex, socioeconomic status, leisure time, transportation, and non-occupational physical activity. Findings During the study period, 1342 deaths were recorded, of which 426 were caused by CVD. In rural area, working adults engaging in occupational moderate-to-vigorous physical activity (MVPA) for ≥40 h per week, compared to those without any, had an adjusted hazard ratio of 0.60 (95% CI: 0.49–0.73) for all-cause mortality and 0.55 (95% CI: 0.37–0.83) for CVD mortality. However, no significant association was found in urban area (0.84 [0.61–1.15] for all-cause mortality, Pinteraction = 0.036; and 0.94 [0.53–1.66] for CVD mortality, Pinteraction = 0.098). The negative associations of occupational MVPA with mortality were more pronounced in women, non-smokers, and those with less non-occupational physical activities. Hypertension, heart rate, and diabetes were important contributors to the relationship between occupational MVPA and mortality. Interpretation The findings from the current study did not support the notion that high levels of OPA would induce harm. On the contrary, in rural setting, higher levels of OPA were associated with lower mortality risks. Furthermore, the observed urban-rural differences in the association between OPA and mortality underscored the need for context-specific public health guidelines on physical activities. Funding R&D Program of Beijing Municipal Education Commission (KM202210025026), National Key Research and Development Program of China (2021YFC2500201), and Young Elite Scientist Sponsorship Program by BAST (BYESS2023385).