Elevated cholesterol levels in midlife – even levels considered only borderline elevated – significantly increase the risk of Alzheimer's disease and vascular dementia later in life, according to a new study by researchers at Kaiser Permanente's Division of Research and the University of Kuopio in Finland.
The study appears in the journal Dementia & Geriatric Cognitive Disorders.
The four-decade study of 9,844 men and women found that having high cholesterol in midlife (240 or higher milligrams per deciliter of blood) increases, by 66 percent, the risk for Alzheimer's disease later in life. Even borderline cholesterol levels (200 – 239 mg/dL) in midlife raised risk for late-life vascular dementia by nearly the same amount: 52 percent. Vascular dementia, the second most common form of dementia after Alzheimer's disease, is a group of dementia syndromes caused by conditions affecting the blood supply to the brain. Scientists are still trying to pinpoint the genetic factors and lifestyle causes for Alzheimer's disease.
By measuring cholesterol levels in 1964 to 1973 based on the 2002 Adult Treatment Panel III guidelines (the current practice standard) when the Kaiser Permanente Northern California members were 40 to 45 years old, then following the participants for 40 years, this study is the largest long-term study with the most diverse population to examine the midlife cholesterol levels and late-life dementia. It is also the first study to look at borderline high cholesterol levels and vascular dementia, rather than just Alzheimer's disease.
"Our study shows that even moderately high cholesterol levels in your 40s puts people at greater risk for Alzheimer's disease and vascular dementia decades later," said the study's senior author. Rachel Whitmer, Ph.D., a research scientist and epidemiologist at the Kaiser Permanente Division of Research in Oakland, Calif. "Considering that nearly 100 million Americans have either high or borderline cholesterol levels, this is a disturbing finding. The good news here is that what is good for the heart is also good for the mind, and this is an early risk factor for dementia that can be modified and managed by lowering cholesterol through healthy lifestyle changes."
This study, funded by the National Institutes of Health, adds to other research emphasizing the importance of addressing dementia risk factors in midlife, before an underlying disease or symptoms appear, the researchers said.
"Our findings add to the existing body of evidence on a degree of overlap between two dementia types in terms of risk factors, symptoms and neuropathology," said the study's lead author, Alina Solomon, MD, a researcher with the Department of Neurology at the University of Kuopio, Finland. "Dementia and cardiovascular disease are common major health problems, share several risk factors and often occur simultaneously, interacting with one another. A holistic approach that addresses multiple major health problems simultaneously is needed to effectively manage these disorders."
The study tracked members of Kaiser Permanente's Northern California Medical Group from 1967 to 2007 by using the multiphasic testing records pioneered by Kaiser Permanente founding physician Morris Collen, MD, who is widely regarded worldwide as a health care informatics pioneer. Of the original 9,844 participants, 598 were diagnosed with Alzheimer's disease or vascular dementia between 1994 and 2007, when the participants were between 61 and 88 years old.
This epidemiological study did not examine the mechanism of the link between cholesterol levels and dementia.
This study is part of an ongoing body of research at Kaiser Permanente to better understand the risk and protective factors for dementia. Dr. Whitmer recently authored two dementia-related studies: one that found a larger abdomen in midlife increases risk of late-life dementia, and one that showed that low blood sugar events in elderly patients with type 2 diabetes increase their risk for dementia. Another Kaiser Permanente study, led by Valerie Crooks of Kaiser Permanente in Southern California, found that having a strong social network of friends and family appears to decrease risk for dementia.
Other authors on this study include: Miia Kivipelto, MD, Ph.D., Department of Neurology, University of Kuopio, Finland, and the Aging Research Center, Karolinska Institutet, Stockholm, Sweden; Benjamin Wolozin, MD, Ph.D., Department of Pharmacology, Boston University School of Medicine; and Jufen Zhou, MS, Kaiser Permanente Division of Research. Additional funding for the study was provided by Kaiser Permanente Community Benefit, the Academy of Finland Marie-Curie EST Program, the Gamla Tjänarinnor Foundation, and Stiftelsen Dementia, Sweden.
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