Association between vision impairment and driving exposure in older adults aged 70 years and over: a population-based examination.

PURPOSE To examine the relationship between vision impairment and driving exposure (amount of driving one does) in a population-based sample of older drivers and to examine to what extent cognitive status impacts this relationship. METHODS Enrollees consisted of a population-based sample of older adults from Alabama who were ≥70 years old, held a current driver's license, and had driven within the last 3 months. Three aspects of visual function were measured under binocular conditions - habitual distance visual acuity, contrast sensitivity and visual processing speed. General cognitive status was assessed with the mini-mental status examination. Driving exposure was estimated by the Driving Habits Questionnaire that asked about the number of miles, places, trips and days driven per week. RESULTS Drivers with impaired contrast sensitivity exhibited reduced annual mileage, and a decreased number of places and trips driven per week compared to those with normal contrast sensitivity, even after adjustment for other factors. Slowed visual processing speed was associated with reduced number of days driven per week after adjustment. Visual acuity deficit was not associated with changes in driving exposure. Cognitive status did not impact any of the associations between vision impairment and driving exposure. CONCLUSION Older drivers with contrast sensitivity impairment exhibit reduced driving exposure in terms of number of trips and places they drive per week, as well as decreased annual mileage. These apparent self-regulatory practices should be viewed as adaptive because contrast sensitivity impairment elevates motor vehicle collision (MVC) risk and reduction in driving exposure can reduce MVC risk.