From Medscape Medical News
Janis Kelly
August 11, 2009 — Even moderately elevated cholesterol levels in midlife are strongly associated with later risk for Alzheimer's disease (AD) and vascular dementia (VaD), new research suggests.
Lead author Alina Solomon, MD, from the University of Kuopio, Finland, used data from the Kaiser Permanente Northern California Medical Group to investigate the relationship between midlife cholesterol and dementia and found that even cholesterol levels of 200 to 239 mg/dL increase risk.
"Both physicians and patients need to know that elevated cholesterol increases the risk not only for heart disease but also for dementia," Dr. Solomon told Medscape Psychiatry. "The most important finding was that even moderately elevated cholesterol at midlife can increase the risk of both AD and VaD later in life," she added. "This emphasizes the fact that AD and VaD may have more in common than was previously thought. Several studies have pointed out that there is a degree of overlap between the 2 dementia types in terms of risk factors, clinical symptoms, and neuropathology. Vascular factors can be associated with AD as well — not just with vascular forms of dementia."
The study is published in the August issue of Dementia and Geriatric Cognitive Disorders.
More than 9000 Subjects
Performed in collaboration with Rachel A. Whitmer, PhD, from Kaiser Permanente in Oakland, California, the study included 9844 subjects who had undergone detailed health evaluations during 1964 to 1973, when they were 40 to 45 years old.
Data from 1994 showed that 469 participants had AD, and 127 had VaD. The researchers adjusted for age, education, race/ethnic group, sex, midlife diabetes, hypertension, body mass index, and late-life stroke. They used cholesterol levels lower than 200 mg/dL as a reference point.
The analysis showed AD hazard ratios of 1.23 for midlife borderline cholesterol (200 – 239 mg/dL) and 1.57 for high cholesterol (≥240 mg/dL). Quartile analysis showed that hazard ratios were 1.31 for cholesterol levels of 221 to 238 mg/dL and 1.58 for levels of 249 to 500 mg/dL.
VaD hazard ratios were 1.50 for borderline cholesterol and 1.26 for high cholesterol.
Dr. Solomon said that the results were not entirely surprising, as previous studies have shown a link between high cholesterol and dementia risk. However, she added, this study is the largest to date, includes a heterogeneous population, and considers VaD as well as AD as an outcome.
Unanswered questions for future investigations include the roles of different cholesterol types, the significance of cholesterol changes after midlife in relation to dementia risk, and the effect of lipid-lowering treatment on dementia risk.
According to Dr. Solomon, the mechanisms behind the cholesterol-dementia association are not entirely clear.
"Our results remained significant even after taking into account several vascular-related factors and conditions, so other mechanisms may be involved as well. The brain is the most cholesterol-rich organ in the human body, but compared to serum cholesterol, far less is known about brain cholesterol and the interactions between the 2 cholesterol pools," she said.
What Is Bad for the Heart Is Bad for the Brain
Robert Stewart, MD, head of epidemiology at the Institute of Psychiatry, King's College London, United Kingdom, told Medscape Psychiatry that the Solomon study data are "convincing" and "consistent with those from other studies which have screened community populations for this disorder."
"In general, there is now a large body of evidence which indicates that what is bad for the heart is bad for the brain — that is, that that the well-known risk factors for coronary heart disease and stroke are also risk factors for dementia (whether this is classified as AD or VaD)," Dr. Stewart said.
"So the real message for clinicians is not to do anything differently, but to be aware that what they should be doing already — identifying and treating high cholesterol, high blood pressure, [and] diabetes and promoting healthy diet and active lifestyles — is likely to have more benefits than originally envisaged and should reduce risk of dementia as well as reducing risk of cardiovascular disease."
The authors have disclosed no relevant financial relationships.
Dement Geriatr Cogn Disord. 2009;28:75–80.
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