It is generally assumed that older people make more mistakes and cause more crashes when driving, but there has been very little research to back up this assumption. In a recent study published in the Journal of the American Geriatrics Society, Japanese researchers have revealed that mandating cognitive screening for older drivers is indeed associated with lower crash rates in this population. Unfortunately, the flipside of this decrease in motor vehicle crashes is an increase in bike and pedestrian injuries among the same population, likely due to changes in the way in which they get around.
Previous research into the effects of cognitive testing on driving safety has been hampered by a lack of firm rules in the studied populations. In 2009, Japan began to require that everyone aged 75 and above complete cognitive testing during their license renewal process. Since 2017, anyone who tests positive has to be cleared of dementia by a doctor before they receive their new license. To investigate the effects of this policy change on the rates of motor vehicle crashes and resultant injuries, researchers from the University of Tsukuba decided to analyze Japan-wide collision and injury data.
We had nationwide police-reported data to analyze. And because we looked at collision and injury rates from as far back as 2012—when cognitive tests were required but did not affect license renewals—we were able to focus on changes that were specifically associated with the new policy."
Professor Masao Ichikawa, senior author of the study
By splitting the older population into age-and sex-based groups in the analysis, the research team revealed that after the policy change, men had a lower rate of motor vehicle crashes, while some age groups of both men and women had an increase in bike and pedestrian injuries.
"We think that this finding is probably related to the voluntary surrender of driving licenses and reduced driving rates among male drivers," says Professor Ichikawa. "Overall, however, our results suggest that preventing older people with cognitive impairments from driving is something of a two-edged sword, leading to both a decrease in collisions as drivers and an increase in injuries as vulnerable road users when people switch to other types of transport."
Given that no longer driving has many adverse health effects in older adults, screening for cognitive impairments should be used carefully, with the aim of removing only the drivers who are most likely to crash in the near future. Safe alternative transport options should also be considered so that pedestrian and bike injuries are avoided in older adults.
This study was supported by the Japan Society for the Promotion of Science KAKENHI (grant numbers 22 18K10081 and 21H03195).
Inada, H., et al. (2023) Association between mandatory cognitive testing for license renewal and motor vehicle collisions and road injuries. Journal of the American Geriatrics Society. doi.org/10.1111/jgs.18157.