Objective: To determine whether medical conditions that can impair sensory, cognitive, or motor function increase the risk of injury due to motor vehicle collision in older drivers.
Design: Case-control study.
Setting: Group Health Cooperative of Puget Sound, a large prepaid health plan.
Participants: Group Health members age 65 or older who were licensed drivers in 5 counties. Cases were injured while driving during 1987 or 1988. Controls were matched to cases on age, gender, and county of residence but experienced no such injury during the study years.
Measurements: The outcome was injury requiring medical care due to a police-investigated motor vehicle collision. Risk factors evaluated included selected medical conditions active within the previous 3 years, as determined from the medical record.
Main results: Injury risk was 2.6-fold higher in older diabetic drivers (95% CI: 1.4-4.7), especially those treated with insulin (odds ratio [OR] = 5.8, 95% CI: 1.2-28.7) or oral hypoglycemic agents (OR = 3.1, 95% CI: 0.9-11.0), those with diabetes for over 5 years (OR = 3.9, 95% CI: 1.7-8.7), and those with both diabetes and coronary heart disease (OR = 8.0, 95% CI: 1.7-37.7). Increases were also found for older drivers with coronary artery disease (OR = 1.4), depression (OR = 1.7), alcohol abuse (OR = 2.1), or falls (OR = 1.4), but these associations could easily have arisen by chance.
Conclusions: Counseling about driving risks may be warranted for certain elderly diabetic drivers. Further research is needed to determine whether transient hypoglycemia or long-term complications explain these effects.