Mediating role of frailty/pre-frailty on the association between exercise participation and traffic crashes among Japanese community-dwelling older drivers

Background Driving is essential for maintaining independence. This study aimed to assess the mediating role of frailty status in the association between exercise participation and traffic crashes among Japanese community-dwelling older drivers. Methods This 2-year longitudinal study included data of 3,934 Japanese community-dwelling older drivers aged ≥ 65 years in Kasama City who did not require long-term care and participated in a postal survey in 2019 and 2021 at baseline and follow-up, respectively. The participants who exercised at least one–three times per month at baseline were classified as exercisers. Frailty status was assessed using the seven-domain Kihon Checklist. A self-reported history of traffic crashes was collected during the follow-up survey. The effect of exercise participation on traffic crash involvement was analyzed using logistic regression after adjusting for covariates. Mediation analyses were performed to determine the mediating effects of frailty status. Results A total of 357 (23.7%) and 1,147 (76.3%) older drivers were classified as exercisers and non-exercisers, respectively. Logistic regression analyses showed that exercise participation significantly reduced the risk of traffic crash involvement at follow-up (odds ratio [OR] = 0.586; 95% confidence interval [CI], 0.359–0.956) and was significantly associated with a lower risk of frailty/pre-frailty (OR = 0.479; 95% CI, 0.372–0.617). Although there was no significant association between exercise participation and traffic crash involvement at follow-up (OR = 0.631; 95% CI, 0.384–1.037), frailty/pre-frailty was associated with a significantly higher risk of traffic crash involvement compared with robustness (OR = 1.649; 95% CI, 1.061–2.563). The Sobel test revealed that frailty/pre-frailty mediated the association between exercise participation and traffic crash involvement at follow-up ( p  = .01). Additionally, among the seven domains of the Kihon Checklist, the physical domain mediated the association between exercise participation and traffic crash involvement at follow-up ( p  = .01). Conclusions Exercise participation could significantly lower the risk of traffic crashes, with frailty/pre-frailty acting as a mediating factor. Our findings indicated that managing frailty is crucial for both public health and crash prevention, emphasizing the need for promoting these measures among older drivers.