Predicting Alzheimer's

Three sets of genes influence when the disease may crop up.

By Colin Allen, published on November 1, 2003 - last reviewed on January 23, 2015

The genetic story of Alzheimer's is becoming clearer--but not
simpler. Researchers from Duke University Medical Center have identified
three chromosomal regions that play a role in the onset of the disease.
Variants in each genetic segment increase the risk of dementia during
specific periods of life. By pinpointing these three regions, geneticists
are closer to understanding who is likely to develop the disease--and
when it may begin.

Two of the regions described in this study had not been found in
previous studies. One of the newly identified regions determines the risk
of very late-onset Alzheimer's, in which symptoms appear after the age of
80. The other increased susceptibility for early-onset disease--between
the ages of 50 and 60.

For the study, published in the November issue of
The American Journal of Human Genetics, Margaret
Pericak-Vance, the director of the Duke Center for Human Genetics, and
colleagues screened 437 families that included at least two members with
Alzheimer's disease.

Using a process known as ordered subsets linkage analysis,
researchers were able to identify which stretches of DNA were linked to
the disease and correlate age of onset with the genetic pattern. One area
of chromosome 15 was linked to families with very late-onset Alzheimer's;
variations on a stretch of chromosome 2 were correlated with early-onset
Alzheimer's. The genes that influence late-onset (between 60 and 75) lie
on chromosome 15, a region that had been identified in a previous Duke

Alzheimer's is the most common form of dementia for those over 65,
and the disease affects nearly 4 million Americans. It is characterized
by a loss of intellectual abilities such as judgment, memory and abstract