AD and Older Drivers

Sources: Johansson K, et al. Alzheimer’s disease (AD) and apolipoprotein e 4 allele in older drivers who died in automobile accidents. Lancet 1997;349:1143-1144; Rizzo M, et al. Simulated car crashes and crash predictors in drivers with Alzheimer disease. Arch Neurol 1997;54:545-551.

Johansson et al obtained the neuropathology of 98 randomly collected Swedish and Finnish drivers older than 64 years who died in automobile accidents. One-third of the killed drivers were diagnosed with Alzheimer’s disease (AD), and a further 20% had suggestive changes. Allele e4 was found in significantly more brains of Alzheimer drivers than in the remainder but did not affect the number of plaques. Increasing age by itself was associated with an increasing number of plaques.

The authors note that 47-53% of the killed drivers in this series may have had incipient AD, and this trend was accentuated in drivers older than 75 years. Other sources (Adler, et al. Am J Geriatr Psych 1996;4:110-120) have also reported a higher incidence of vehicular accidents in persons with early AD compared to controls. Physicians should strongly urge patients with AD not to drive and give a similar message to their families. State licensing rules would also be wise to include simple cognitive testing and annual licensing in persons older than age 75.

Bearing on the above, Rizzo et al used an Iowa Driving Simulator to compare the outcome of 21 persons with AD against 18 age linked, non AD controls. End points included dangerous errors, including possible death. The 18 controls had no simulated "crashes" and six "near misses." Six of the 21 AD cohort had a total of 21 crashes and 14 near misses. Several of the simulated crashes were judged as being potentially fatal if they occurred in real life. Abnormalities in several different neuropsychologic tests at the P < 0.002 level were associated with poor simulator outcomes; the major abnormalities dealt with spatial recognition, perceptual difficulty, disorientation for time, etc. The simulator findings are interesting but hardly practical for Motor Vehicle Services to screen driver capability. The high association of the neuropsychologic tests with dangerous performance in this study, however, suggests that simple cognitive tests could be sufficient to screen drivers older than 70 years as they re-apply for renewal of licenses. Neurologists may wish to take a public stand on this issue. —fp