NEW YORK (Reuters Health) - People who live to be well into their 90s appear to be at lower risk of developing the memory-robbing illness Alzheimer's disease than their younger counterparts, according to the results of a new study.

``If you have made it to your mid- to late-90s and don't have Alzheimer's disease, there is a pretty good chance you won't ever get it, even if you live a number of years longer,'' co-investigator Dr. John C. S. Breitner of Johns Hopkins University in Baltimore, Maryland, told Reuters Health in an interview.

This was true even for a few people who inherited two versions of the ApoE-e4 gene variant--one from each parent--who for some reason were spared the illness. People with one copy of ApoE-e4 and particularly those with two copies of this gene variant are known to be at higher risk of developing Alzheimer's disease, the researchers note in the January issue of the journal Neurology. The ApoE gene codes for a cholesterol-carrying molecule and comes in three versions: e2, e3 and e4.

``We studied an unusually large and long-lived population, so we were able to examine a person's chances of coming down with Alzheimer's disease at each year of age out to about 100 (years),'' Breitner said.

The researchers evaluated 3,308 men and women who reside in Cache County, Utah, who were aged 65 years or older. All of the participants underwent rigorous dementia screening and also had DNA analysis that determined their ApoE-e4 gene status.

Breitner said the investigation revealed that a person's chance of developing Alzheimer's doubled every 5 years until somewhere near age 90.

``After that, the annual increase slowed,'' he noted.

For men, the peak year--the highest chance of developing dementia--was at age 93, and it declined afterwards. For women, the peak occurred later, around 97 years, but there was still a noticeable decline afterwards, Breitner explained. In general, women over the age of 85 showed a higher risk of developing the disease compared with men, the report indicates.

``The most likely, but not the only explanation, is that there is a subgroup of the population who won't ever get Alzheimer's,'' Breitner told Reuters Health. ``These people are probably a distinct minority but they're still fairly numerous.''

In terms of genetics, the study findings indicate that men and women with two versions of the ApoE-e4 gene showed a stronger likelihood of developing Alzheimer's disease earlier in life as would be expected based on previous studies.

``We need to find out why some people seem to escape this dreaded disease, even in very late old age, while most others seem vulnerable to it,'' Breitner said.

``Genes may be the answer,'' he added, ``but it doesn't appear to be that the ApoE gene--otherwise an important predictor of risk for Alzheimer's--is involved.''

The most common form of dementia in the elderly, Alzheimer's now affects about 4 million Americans. The disease is marked by the formation of ``plaques'' and ``tangles'' in the brain, and researchers have identified a range of possible contributors to its onset.

SOURCE: Neurology 2002;58:209-218.

Reference Source 89

For more information on how to prevent other diseases, use
PreventDisease.com's "Quick Prevention Resources".