TUESDAY, June 12, 2012 (HealthDay News) -- A common genetic risk factor for Alzheimer's disease disrupts brain function in healthy older women but has little effect in men, a new study has found.
People with two copies (one from each parent) of the ApoE4 gene variant are at extremely high risk for Alzheimer's. Only 2 percent of people have two copies of the variant, while about 15 percent of people carry a single copy.
In this study of 91 healthy older people, researchers looked at those with a single copy of the ApoE4 variant and found that women, but not men, exhibited two characteristics that have been linked to Alzheimer's disease.
The women had a signature change in their brain activity and elevated levels of a protein called tau in their cerebrospinal fluid.
The study, published June 13 in the Journal of Neuroscience, is the first to identify this gender difference in healthy older adults with one copy of the ApoE4 variants, according to a Stanford University news release.
The findings suggest that men who carry a single copy of the gene variant shouldn't be assumed to be at increased risk for Alzheimer's disease. The findings also may help explain why women are more likely than men to develop Alzheimer's disease, said Dr. Michael Greicius, assistant professor of neurology and neurological sciences and medical director at the Stanford Center for Memory Disorders, and colleagues.
Alzheimer's disease affects nearly 5 million people in the United States and nearly 30 million people worldwide, the news release noted. For every three women with Alzheimer's, about two men have the disease.
The U.S. National Institute of Neurological Disorders and Stroke has more about Alzheimer's disease.