Association of falls with risk of dementia and all-cause mortality: a cohort study of Japanese older adults with a 9-year follow-up.

Objective: Many risk factors affect dementia and all-cause mortality. However, whether falls are a risk factor for dementia and all-cause mortality is unclear. The study examines the association of falls with the risk of dementia and all-cause mortality, and whether dementia mediates the association of falls with all-cause mortality.

Methods: Data were taken from the Japanese Gerontological Evaluation Study (JAGES) with a 9-year follow-up. Falls information was collected through a questionnaire and categorized into no falls, single and multiple falls. Dementia and all-cause mortality data were obtained from the long-term care insurance (LTCI) system. The Cox proportional hazard models were used to calculate the hazard ratios (HRs) and 95% confidence intervals (95% CIs), and causal mediation analysis (CMA) was used to assess the mediating effects of dementia.

Results: A total of 52,076 participants were included in the study. Compared to participants with no falls, participants with single and multiple falls had an increased risk of dementia (single fall, HRs = 1.18, 95% CIs 1.12-1.24; multiple falls, HRs = 1.66, 95% CIs 1.56-1.77) and all-cause mortality (single fall, HRs = 1.09, 95% CIs 1.04-1.15; multiple falls, HRs = 1.34, 95% CIs 1.26-1.43), and the risk increased with the number of falls (P for trend < 0.01). In addition, dementia significantly mediated the association between falls and risk of all-cause mortality (NIE: HRs = 1.02, 95% CIs 1.00-1.04, PM = 15.0%).

Conclusion: Falls are associated with the risk of dementia and all-cause mortality. Dementia has important mediating effects in the association between falls and the risk of all-cause mortality.