Thursday, April 28, 2011
SCOTTSDALE, Ariz. — People who carry a gene associated with Alzheimer's disease and have cardiovascular risks experience age-related memory decline 20 to 25 years sooner than people who carry the gene without cardiovascular risk according to a 17-year Mayo Clinic-led study recently published in Neurology.
The gene most commonly associated with late-onset Alzheimer's is called apolipoprotein E (APOE), which has three common forms: APOE e2, which appears to reduce the risk of Alzheimer's; APOE e3, which doesn't seem to affect the risk of Alzheimer's either way; and APOE e4, which appears to increase the risk of Alzheimer's. About one in four people have one copy of the APOE e4 gene, which was inherited from one parent, and about two percent have two copies, which were inherited from both parents. If someone has two APOE e4 genes, the risk of Alzheimer's is even higher.
In 1994 Mayo Clinic physicians and researchers, led by Richard Caselli, M.D., a neurologist at Mayo Clinic in Arizona, began a longitudinal aging study to examine changes in cognitive skills with aging and the influence of increased risks for Alzheimer's disease.
Previous research derived from the same study shows that possession of even one copy of the APOE e4 gene accelerates age related memory decline beginning in the mid to late 50's and for that subset that has two copies of the gene the effect is more pronounced.
The latest research examined the influence of other common medical problems that cause cardiovascular disease such as hypertension, diabetes, smoking and high cholesterol in combination with APOE e4.
"We found that the small sub group, about two percent of the population, who has the double dose of the gene and have at least one of those factors, further accelerated the risk of memory decline," Dr. Caselli said. "If you looked at the performance of one of these people in their 40's with these cardiovascular risk factors they looked more like one of their gene mates in their 60's who didn't have those cardiovascular risk factors — so roughly a 20-25 year aging effect on their memory performance.
"We don't believe that everyone needs to go out and get genetic testing for Alzheimer's disease," Dr. Caselli added, "but we do want to emphasize what our cardiology colleagues have been telling us for years that treatment of hypertension, diabetes, smoking cessation and high cholesterol are all very important — this is one more reason to consider that."
The study was led by Mayo Clinic in Arizona and performed in collaboration with researchers from several other institutions in the Arizona Alzheimer's Consortium, including Arizona State University, Banner Alzheimer's Institute Barrow Neurological Institute, Banner Sun Health Research Institute, the University of Arizona and Mayo Clinic in Florida. Dr. Caselli and Eric Reiman, M.D., Director of the Arizona Alzheimer's Consortium, have been the principle investigators on the research since it began in 1994.
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