Second Opinion

MOTORISTS in their teens and 20s have a low opinion of elderly drivers, whom they regard as bumbling old fools who shouldn't be allowed on the roads. Elderly drivers have a low opinion of the young, pointing to statistics showing that the highest accident rates are among under- 25s (a point not lost on the insurance companies, which charge the highest rates to young, inexperienced drivers).

Some old drivers are indeed incompetent, and data from the US has shown that the accident rate rises substantially after the age of 70. More detailed American research has now shown that the dangerous elderly motorists are those with early symptoms of dementia, usually due to Alzheimer's disease. The study was done at the University of California in Los Angeles, where driving a car is seen as a God-given right for citizens of all ages. Eccentrics who try walking in the suburbs are likely to be questioned by the police.

The research team had little difficulty recruiting volunteers whose doctors had told them they had "mild cognitive impairment", but who thought they were still capable of driving. All were in their early 70s and had signs of early dementia due to Alzheimer's disease, or to narrowing of the arteries. Other volunteers of the same age had diabetes as their only medical condition, and a group of younger drivers was used for comparison.

All the drivers - the demented, the diabetics, and the young controls - were taken on a drive around a three-mile road network with intersections, speed bumps, traffic signs, signals, and parking lots. Each driver's performance was graded by an instructor in the car, which was fitted with an on-board computer which recorded braking speed, steering, crossing the centre line, and so on. The drivers also worked their way through a series of standard tests of mental ability, concentration and short-term memory.

The results showed that the 70-year-olds with diabetes did just as well on the test drives and mental tests as the younger drivers. The drivers with early dementia did worse. They drove slowly, and the mistakes they made were serious - for example, turning into a one-way street marked "no entry".

The conclusion was that drivers in their 70s in normal health (with normal vision) can perform at a level comparable with young, healthy adults - at least in a suburban, non-stressing environment. Statistics showing that drivers in this age group have high accident rates are, the report says, at least partly attributable to people continuing to drive after they have become mildly demented.

More people than ever before are reaching the age of 80, at which the risk of Alzheimer's disease is seven times higher than at 65. Should doctors instruct elderly patients with early dementia to stop driving? Doctors in Britain are reluctant to take on this task, since it may create bad feeling between them and their patients. The US research showed that tests of mental ability carried out in a clinic were reliable predictors of driving ability on the road. People who want to go on driving after 70 - and continue to be insured at a reasonable rate - may soon have to follow the example of California, and have regular tests of their abilities comparable to those conducted on their aged vehicles.