Finding opens door to prevention by showing older people with atherosclerosis or diabetes in combination with the ApoE4 gene are at much higher risk for memory loss, cognitive decline.
(Sacramento, Calif.) -- In a study that tracked changes in cardiovascular health and cognitive function in 5,888 community-dwelling senior citizens annually over a ten-year period, researchers at UC Davis School of Medicine and Medical Center say cognitive decline is not a normal part of aging for the majority of elderly people. In fact, only people with high levels of atherosclerosis or diabetes and also those with the apolipoprotein E4 gene associated with Alzheimer's disease are both at high risk for a decline in cognitive ability as they age. The results of the study are reported in the July 7 issue of the Journal of the American Medical Association.
"Seventy percent of individuals evaluated in this study showed no significant decline in cognitive function over the study period," says Mary N. Haan, director of the UC Davis Center for Aging and Health and lead author of the study. "We found that individuals whose cognitive ability remained constant during the study had two factors in common: they did not carry any of the apolipoprotein E4 genes, which is often associated with Alzheimer's disease, and they had little or no signs of diabetes or atherosclerosis."
In comparison, the researchers found that the greatest loss of cognitive ability occurred in people who had both high levels of atherosclerosis or diabetes and an Apo4E gene. These individuals were eight times more likely to show a decline in function compared to people with a low level of atherosclerosis and no genetic predisposition. Individuals with an E4 allele were three-to-four times more likely to show a decline in function than individuals without this genotype. And those with high levels of atherosclerosis were three times more likely to show a loss of function than those individuals without atherosclerosis.
"Other studies of the elderly have shown that people with the ApoE4 gene have a higher risk of Alzheimer's disease," says Haan. "But it was not clear what role atherosclerosis or diabetes might play. Our study is good news because it means that we may be able to reduce the risk of cognitive impairment, or even dementia, even in those who have a genetic predisposition for it by preventing atherosclerosis. We know a lot about preventing cardiovascular disease and not much about preventing cognitive impairment or dementia."
Each person in the study had a clinical assessment every year and answered questions about their health to track past history and incidence of diabetes and vascular diseases, including heart attack, congestive heart failure, atrial fibrillation, coronary artery bypass graft, the use of a pacemaker, stroke, or transient ischemic attack. Researchers identified early signs of vascular disease by measuring systolic blood pressure, carotid artery wall thickness with ultrasound, major ECG abnormalities and atrial fibrillation from ECG.
Cognitive function is defined as the intellectual process by which one becomes aware of, perceives, or comprehends ideas. It involves all aspects of perception, thinking, reasoning and remembering. The cognitive tests used in the study - the modified mini-mental state exam and the digit symbol substitution test - assessed short- and long-term memory, spatial abilities, mental processing speed and many other related cognitive abilities. These included recalling their date and country of birth, counting from 1 to 5 and then backwards again, naming specific body parts such as an arm or leg, identifying an animal that had four legs, recognizing associations between similar objects and activities, and following simple directions, such as folding a piece of paper in half.
Materials provided by University Of California, Davis - Medical Center. Note: Content may be edited for style and length.
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