Objective: To determine the prevalence and cessation of driving among older men with incident dementia in the Honolulu-Asia Aging Study.
Design: Retrospective cohort data from a community-based study of incident dementia.
Setting: The Honolulu Heart Program and the Honolulu-Asia Aging Study.
Participants: A total of 643 men who were evaluated for the incidence of Alzheimer's disease or other dementia between the fourth and the fifth examination of the Honolulu Heart Program.
Measurements: Driving history, diagnosis of dementia, grip strength, walking speed, standing balance test, interviewer's rating of vision status, and the neurologist's notes on mentions of driving behavior from informal interviews with a caregiver or family informant.
Results: The prevalence of driving declined dramatically with level of cognitive functioning. Among 162 men evaluated and found to have normal cognitive functioning, 78% still drove, compared with 62% of 287 men with poor cognitive functioning but no clinical dementia, 46% of 96 men with a new diagnosis of very mild dementia (Clinical Dementia Rating = 0.5), and 22% of 98 men with a new diagnosis of mild dementia (CDR = 1). Only one of 23 men diagnosed with moderate or more severe staged incident dementia (CDR > 1) was driving. About 10% of the 59 demented persons still driving relied on co-pilots, and only one driver was reported as involved in a crash according to a review of the neurologists' notes.
Conclusions: Incident dementia is a major cause of driving cessation. Based on these data, we estimate that approximately 4% of male drivers aged 75 years and older nationwide (about 175,000 men) have dementia. This number will increase with the projected growth of drivers aged 75 years and older.