Association between road vehicle collisions and recent medical contact in older drivers: a case-crossover study.

OBJECTIVE To estimate the association between past medical contacts and the risk of vehicle collision in a population of older drivers from the province of Quebec, Canada. DESIGN Case-crossover study. SETTING Quebec. PARTICIPANTS 111 699 older drivers involved in at least one vehicle collision between January 1988 and December 2000. MAIN OUTCOME MEASURES For each driver, the risk of having a vehicle collision while exposed and not exposed to a medical contact was compared. Separate conditional logistic regression analyses were conducted for all drivers and in four diagnostic-specific subgroups. RESULTS The study found a weak but statistically significant increased risk of all collisions being associated with a medical contact within 1 month before the collision, for all drivers (OR=1.10, 95% CI 1.08 to 1.11) and for drivers with diabetes (OR=1.07, 95% CI 1.03 to 1.11). CONCLUSION Older drivers who have a collision are more likely to have been in contact with a physician shortly before the collision. These findings suggest that there might be an opportunity to detect medical conditions that put older drivers at higher risk of collision; however, further research is needed to assess the potential effectiveness and practical modalities of screening.