Chronic medical conditions and their association with crash risk and changes in driving habits: a prospective study of the GAZEL cohort

ObjectivesTo assess crash risk and driving habits associated with chronic medical conditions among drivers entering old age.DesignProspective cohort study.SettingFrench cohort GAZEL.Participants12 460 drivers in the analysis of road traffic crash, among whom 11 670 completed the follow-up period (2007–2014). We assessed driving cessation among 11 633 participants over the same period, and mileage and driving avoidance among the 4973 participants who returned a road safety questionnaire in 2015.Main outcome measuresYearly occurrence of at least one road crash as a driver; time to driving cessation; mileage; driving avoidance: at night, with bad weather, in heavy traffic, with glare conditions, over long distances.ResultsSeveral potentially risky conditions (angina, myocardial infarction, coronary disease; stroke; nephritic colic, urinary stones; glaucoma) were associated with lower mileage and/or driving avoidance and did not increase crash risk. Neither driving avoidance nor lower mileage was found for other conditions associated with an increased crash risk: hearing difficulties (adjusted OR 1.19, 95% CI 1.06 to 1.34); joint disorders (1.17, 95% CI 1.06 to 1.30). Depression, anxiety and stress was associated with an increased crash risk (1.23, 95% CI 1.01 to 1.49) despite increased driving avoidance. Parkinson’s disease was associated with driving cessation (adjusted HR 32.61, 95% CI 14.21 to 65.17).ConclusionsDepending on their condition, and probably on the associated risk perception, drivers entering old age report diverse driving habits. For example, hearing difficulties is a frequent condition, rarely considered a threat to road safety, and nonetheless associated with an increased crash risk.