Effects of changes in regular physical activity status on hip fracture: A nationwide population-based cohort study in Korea

Objective Hip fracture incidence is increasing with rapid aging of the population and regular physical activity (RPA) is an important modifiable protective factor for fracture. However, the association between the risk of hip fractures and changes in RPA status in the general population remains unknown. Thus, we explore the association between the risk of hip fracture and changes in RPA status. Methods We studied 4,984,144 individuals without fractures within a year whose data were registered in the Korean National Health Insurance Service database. Baseline physical activity level was assessed using a standardized self-reported questionnaire during two consecutive national health screening surveys performed in Korea from 2009 to 2012. The risk of hip fracture between 2013 and 2016 according to change in RPA was prospectively analyzed. Participants were divided into those who were always inactive, became inactive, became active, and were always active. Results Compared to participants who were always inactive, those who became inactive exhibited a 0.12/1,000 person-years (PY) reduction in hip fracture incidence rate (IR) [aHR: 0.865; 95% confidence interval (CI): 0.824-0.908]. Participants who became active, and those who were always active, exhibited a 0.24/1,000 PY reduction in IR (aHR: 0.827; 95% CI: 0.787- 0.870) and a 0.39/1,000 PY reduction in IR (aHR: 0.691; 95% CI: 0.646-0.740), respectively. Conclusion Changes in RPA status were associated with the risk of hip fracture; consistent RPA was related to the maximum benefit for risk reduction in the general population.