Longitudinal association between chronic diseases and fall risk among middle-aged and older adults in China: the mediating role of activity limitations.

Background: Falls are a major public health issue for middle-aged and older adults, especially those with chronic diseases. While a correlation is known, the longitudinal relationship and the underlying mechanisms between chronic diseases and falls remain unclear. This study investigates the longitudinal association and examines the mediating role of activity limitations. Methods: A total of 2400 middle-aged and older adults who completed all three waves (2013, 2015, and 2018) of the China Health and Retirement Longitudinal Study (CHARLS) were included. Mixed-effects logit models with time-fixed effects were employed to examine the longitudinal association between chronic diseases and fall risk. The association pattern between the number of chronic diseases and the probability of falling was assessed by incorporating quadratic terms, constructing restricted cubic splines, and plotting dose-response relationships. Mediation analysis was conducted to evaluate the role of activity limitations as a mediator. Results: The incidence of falls and multimorbidity increased over the study period. The number of chronic diseases was significantly associated with a higher fall risk (β = 0.138, P < 0.01), exhibiting a linear dose-response relationship. Mediation analysis based on the disablement process model indicated that activity limitations accounted for 21.08% of this association. Conclusions: The risk of falls among Chinese middle-aged and older adults increases linearly with the number of chronic diseases, an association partly mediated by activity limitations. Fall prevention strategies should prioritise managing activity limitations through targeted assessments and interventions, such as physical exercise, to mitigate fall risk in this population.