Older automobile drivers : medical aspects

Abstract

Introduction: Older drivers (65+) are not a threat to traffic safety; the number of accidents involving older drivers is small compared to the number of younger drivers' accidents. However, a substantial number of studies have shown that when mileage is taken into consideration, older drivers have an increased risk for being involved in traffic accidents. Possible reasons for this increased accident risk among older drivers could be the effects of aging or the influence of disease. In many countries, there is a medical examination included in the license renewal procedure; its goals are to detect potential medical threats to traffic safety, and subsequently to take due precautions by treating and advising the driver, or by denying renewal. The aims of this study were to investigate the efficacy of medical screening of older drivers, and to identify risk factors for road traffic accidents among older drivers.

Methods: The efficacy of the medical examination included in the license renewal procedure was evaluated by comparing accident statistics in Sweden (where license renewal is a simple formality and where there is no compulsory medical check-up)and Finland (where the license expires at age 70 and can only be renewed after a medical check-up). With the aim of identifying risk factors for traffic accidents among older drivers, we investigated both drivers guilty of moving violations and drivers who died in traffic accidents. In one part of the study, a group of 37 older drivers found guilty of crashes (n = 23) or other moving violations (n = 14) was selected (cases where alcohol was involved were excluded). These were then compared to closely individually matched controls. An extensive battery of examinations, tests, and blood analyses was performed. Another part of the study included 98 older drivers who died in traffic accidents according to the definition used in official statistics. Neuropathological assessment was performed on Bielschowsky stained tissue from frontal and parietal brain areas, and diagnoses were made according to the commonly used CERAD criteria. We also retrieved data from drug analyses performed at the National Forensic Institute of Chemistry.

Results: The comparison of accident statistics between Sweden and Finland did not give evidence for any traffic safety effect of the license renewal procedure. Nor did the medical examination of drivers convicted for crashes uncover any differences compared to controls. However, tests of memory and visuospatial ability (copying a cube) indicated that cognitive impairment was more frequent in the crash group compared to controls. In the test of visual acuity with Snellen's 'E', which carries a greater cognitive load than letters, those drivers convicted of crashes scored lower than controls. The neuropathological assessment disclosed evidence of Alzheimer's disease in more than half of the deceased drivers. Blood samples from 23% of the male drivers 75+ revealed that, at the time of the fatal crash, they had in their blood drugs known to have an impact on cognitive functions.

Conclusion: Cognitive impairment seems to be a very important risk factor for older drivers' involvement in road traffic accidents. The cognitive impairment is often not great enough that it can be recognized or detected during the commonly performed doctor's examination. A detailed test of cognitive function should be included in the examination of older license applicants. The physician, and the older driver on medication, must also be made aware of the importance of drug influence on cognitive functions and the subsequent increase in accident risk when using such drugs.