Forget Me Not

Investigators have long thought that highly educated people are
less likely to develop symptoms of Alzheimer's disease. This has spawned
the so-called "brain reserve" theory, the notion that the well educated
are protected from cognitive decline, either because they have more
neurons to lose or because they have a larger brain volume.

Neurologists now have to rethink this concept. New research
indicates that current tests may only detect cognitive decline among
people of average or little education, but are not designed to register
cognitive changes in highly educated patients. If this is the case, then
the "brain reserve" may be no more than a methodological
shortcoming.

In a study presented recently to the International
Neuropsychological Society, Holly Tuokko, Ph.D., a professor of
psychology at the University of Victoria in Canada, reviewed data from
the 1991 Canadian Study of Health and Aging, an epidemiological survey of
dementia in 1,879 subjects. In 1996, Tuokko retested 844 subjects who
exhibited no dementia in 1991. She classified the subjects' level of
education as low at 0 to 5 years, medium at 6 to 12 years, or high at
more than 13 years.

In 1996, less than 10 percent of the highly educated group were
considered cognitively impaired, compared with more than 20 percent of
the least educated subjects. But when Tuokko reviewed the 1991 data on
the highly educated subjects, she found that their cognitive performance
had been in the low-average range. "According to their level of
education, their scores should have been high-average," says Tuokko. "We
were calling their cognitive abilities normal, even though they probably
were not."

Tuokko says that future assessment of dementia in highly educated
people may involve comparing subjects' scores over time to their own
baselines.