Association of physical activity with fracture: a prospective cohort study of 387,307 Chinese participants

Analyzing data from over 387,000 Chinese adults, we found that moderate physical activity was associated with a lower risk of hip fracture. In contrast, high levels of activity driven by manual labor were associated with increased overall fracture risk. These results highlight the need to differentiate between leisure and occupational exertion in health guidelines.

Fractures are a major health burden in ageing populations, but evidence on the association between physical activity and fracture risk in Chinese adults is scarce. We aimed to investigate the relationship between physical activity and incident fracture in a large Chinese cohort.

In this prospective cohort study, we included 387,307 participants aged 40-79 years from the China Kadoorie Biobank. Physical activity was assessed via questionnaire and quantified primarily as total physical activity (TPA, metabolic equivalent of task-hours per day [MET-h/day]), with further disaggregation into occupational (OPA) and non-occupational (non-OPA) domains. Moderate-to-vigorous physical activity (MVPA) duration (min/week) was also analyzed. Incident fractures were ascertained through linkage to health insurance databases. Cox models were used to estimate hazard ratios (HRs) with 95% CIs.

During a median follow-up of 10.1 years, 8964 fractures occurred. Higher levels of TPA were associated with an increased risk of fracture (quartile 3 [16.42-28.19 MET-h/day] HR 1.34, 95% CI 1.25-1.43; quartile 4 [> 28.19 MET-h/day] HR 1.47, 95% CI 1.37-1.58). This elevated risk was primarily driven by OPA. In contrast, non-OPA showed no significant association with fracture risk. A moderate level of TPA (quartile 2 [9.73-16.41 MET-h/day]) was associated with a lower risk of hip fracture (HR 0.82, 95% CI 0.71-0.94). When assessed by duration, MVPA of 300-449 min/week or ≥ 450 min/week was also associated with increased fracture risk.

High levels of physical activity, particularly OPA, are associated with an increased risk of fracture in Chinese middle-aged and older adults, whereas non-OPA shows no such association. Moderate activity was associated with a lower risk of hip fracture. These findings highlight the importance of distinguishing between OPA and OPA in fracture prevention guidance.