Characteristics of motor vehicle crashes of drivers with dementia of the Alzheimer type

Abstract

Objective: To determine whether there is a difference in crash rates and characteristics between drivers with dementia of the Alzheimer type (DAT) and nondemented older persons who were controls.

Design: A pilot study using a 5-year retrospective analysis of state-recorded crash data and crash characteristics followed by patient enrollment into a study on road test skills.

Setting: Alzheimer's Disease Research Center at Washington University in St. Louis, Missouri. Subjects were enrolled as volunteers in a longitudinal study of aging and DAT.

Participants: One hundred twenty-one subjects (58 nondemented, older drivers and 63 drivers with DAT) with a mean age of 77 years met the inclusion criteria for this study. DAT was diagnosed using validated clinical diagnostic criteria and was staged by the Clinical Dementia Rating (CDR) Scale. All subjects with DAT were in the very mild (CDR = 0.5) or mild (CDR = 1) stages.

Main outcome measure: State-recorded traffic crashes. Also, a daily driving diary was completed by each subject and used to estimate miles traveled per year.

Results: Subjects diagnosed with mild DAT (CDR = 1) reported less roadway exposure (average number of miles driven per year) than did drivers with very mild DAT (CDR = 0.5) or controls. Crashes in both groups were infrequent, with 0.07 state-recorded crashes per driver per year in the nondemented group (CDR = 0), 0.06 in the very mild DAT group (CDR = 0.5), and 0.04 in the mild DAT group (CDR = 1). There was no statistical difference in the crash frequency between groups, even when adjusting for exposure. Drivers with DAT had trends toward more at-fault crashes, crashes with injuries, and crashes in which the officer on the scene cited failure to yield.

Conclusions: In our sample, individuals with very mild or mild DAT who continued to drive seemed to have crash rates similar to those of the controls. There may be significant differences between the causes and the consequences of crashes involving drivers with DAT when compared with cognitively intact age-matched controls, but none were found in this pilot study. Further research on crash characteristics is needed in larger samples of community-based drivers with DAT across wider ranges of dementia severity to address issues such as driving competency and public safety.