Study: Gender Makes Big Difference in Genetic Risk of Alzheimer's
Women have often been called the fairer sex, but do we have to be the only gender who is primarily at risk for Alzheimer’s disease if we have the gene variant ApoE4? A new study seems to support this news.
According to a new study out of Stanford University’s School of Medicine, researchers have found that women’s brains are more likely than men’s to be disrupted by this gene variant. (Stanford’s press release notes that 10-15 of the population carry one copy of this gene variant; however, 50 percent of people who develop Alzheimer’s are E4 carriers.) “The Stanford researchers demonstrated for the first time the existence of a gender distinction among outwardly healthy, older people who carry the ApoE4 variant,” Health News Digest reported. “In this group, women but not men exhibit two telltale characteristics that have been linked to Alzheimer’s disease: a signature change in their brain activity, and elevated levels of a protein called tau in their cerebrospinal fluid.”
In this study, Stanford researchers brain scans of 131 healthy people who, on average, were 70 years of age. All of these participants were screened to determine their cognitive status at the start of the study and were able to think and remember normally for their age. The scans were performed on “resting” participants who were awake in the scanner but who were not focused on a particular task. The researchers examined the connections in the brain’s memory network and found that the older women who had the E4 variant showed a loss of synchronized patterns of activity in the interconnected brain regions. This loss is typically seen in people who have Alzheimer’s disease.
The researchers then assessed records from a large public database coordinated by the Alzheimer’s Disease Neuroimaging Initiative to independently confirm their imaging-based observations. They studied 91 records of healthy 55- to 90-year-old volunteers whose cerebrospinal fluid had been collected. The records of these participants, who were an average of 75 years of age, were then divided into four groups – women with a copy of the E4 variant, women without the E4 variant, men with a copy of the E4 variant, and men without E4 variant. The researchers then checked the concentrations of tau in the cerebrospinal fluid. They found that the cerebrospinal fluid of women who carried at least one E4 variant was substantially enriched in tau; however, the cerebrospinal fluid of men who had at least one E4 variant was not substantially enriched. This finding confirmed the findings from the brain-imaging scans.
The Stanford researchers also took into account women’s longevity since they live longer on average than men. Old age has been shown to be the greatest risk factor for Alzheimer’s disease. “But the disparity in Alzheimer’s risk persists even if you correct for the different in longevity,” said Dr. Michael Greicius, assistant professor of neurology and neurological sciences and medical director of the Stanford Center for Memory Disorders and the study’s senior author. “This disparate impact of ApoE4 status on women versus men might account for a big part of the skewed gender ratio.”
The study’s findings, which were published in the June 13, 2012 issue of the Journal of Neuroscience, indicate that doctors shouldn’t assume that men with a single copy of ApoE4 have an elevated risk of Alzheimer’s disease. Furthermore, the study underscores that changes in the brain related to Alzheimer’s disease begin far earlier than when outwardly signs (such as memory loss) become apparent.
Primary Sources for This Sharepost:
Health News Digest. (2012). Common genetic risk factor for Alzheimer’s disrupts brain function in healthy, older women, but not men.
Goldman, B. (2012). Study shows common genetic risk factor for Alzheimer’s disrupts brain function in healthy, older women, but not men. Stanford School of Medicine.