Subjective memory concerns and car collisions: A cross-sectional cohort study among older Japanese drivers

Background: A previous study suggested older drivers with subjective memory concerns (SMC) had increased odds of experiencing car collisions, but whether SMC in different contexts and the number of SMC applicable items change this association is unknown. The aim of this study was to examine the association between SMC and car collisions among older drivers in Japan. Methods: This cross-sectional study was conducted using data from a Japanese community-based cohort study. Participants were community-dwelling older adults aged >= 60 years. SMC was assessed using five questions: 1) "Do you feel you have more problems with memory than most?" 2) "Do you have any difficulty with your memory?" 3) "Do you forget where you have left things more than you used to?" 4) "Do you forget the names of close friends or relatives?" and 5) "Do other people find you forgetful?" Participants were asked about their experiences with car collisions during the previous two years. Results: A total of 13,137 older drivers (72.1 +/- 5.5 years old, and 43.6 % female) were analyzed. Cochran-Armitage trend test showed that as the number of SMC applicable items increased, the percentage of the experiences of car collisions significantly increased (6.8 %-15.8 %, P < 0.001). Logistic regression models showed each SMC question was associated with an increased odds ratio (OR) of car collisions (OR 1.26 to 1.71, all P < 0.001) after adjusting for confounding factors. As the number of SMC applicable items increased, the OR of car collisions significantly increased (OR 1.19 to 2.28, all P < 0.05, P for trend <0.001). Conclusions: This cross-sectional study among community-dwelling older drivers in Japan suggested each SMC question and the number of applicable items were associated with car collisions. SMC may be a sign of increased risk of traffic incidents for older drivers.