Increased traffic injuries among older unprotected road users following the introduction of an age-based cognitive test to the driver’s license renewal procedure in Japan

Abstract Background To deal with the increasing number of motor vehicle collisions (MVCs) among older drivers, a cognitive test has been introduced to a license renewal procedure for drivers aged ≥75 years since June 2009. This might have prompted the reduction or cessation of driving by older drivers. We therefore examined whether older drivers’ chance of experiencing MVCs as unprotected road users has increased after the test was introduced. Methods Using police-reported national data on MVCs from January 2005 through December 2016, we calculated the monthly injury rates (including deaths, severe injuries, and minor injuries) among unprotected road users (bicyclists and pedestrians) by sex and age group (70–74, 75–79, 80–84, and ≥85 years). The ratios of the injury rates of unprotected road users in the three oldest age groups (who were subjected to the test) to those aged 70–74 years (not subjected to the test) were also calculated. Then, we conducted an interrupted time-series analysis based on the injury rate ratios to control for extraneous factors affecting MVCs over the study period. Results There was a significant increase in traffic injuries of unprotected road users at the time the test was introduced among females aged 75–84 years, and at a later time among males aged ≥80 years and females aged ≥85 years. Conclusion Licensing policies for older drivers should be rigorously evaluated, taking into account the safety of older unprotected road users, and should be balanced against it.