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Drop in Cholesterol may be Early Indicator for Alzheimer Disease
Contradictions cloud our understanding of the role of cholesterol in the development of clinical dementia, including Alzheimer Disease (AD). Some studies suggest that high blood cholesterol levels in midlife increase the risk for AD, while others show that low levels late in life are associated with AD. Both weight loss and decreased blood pressure generally arises before the onset of AD. Thus, it has been predicted that a drop in cholesterol would also precede dementia.
The Honolulu-Asian Aging study, in which over 3700 Japanese-American men were followed for a total of 29 years, provided an opportunity to determine the effect of cholesterol on clinical dementia. Clinicians and scientists led by Lenore Launer, Ph.D. (NIH) published the results of their study in the January 6, 2007 issue of the Archives of Neurology. In this study, cholesterol levels of 1027 men born between 1900-1919 on the island of Oahu, HI were measured at five different times: between 1965-1968, twice during 1970-1974, 1980-1982, and 1991-1993. The men were initially evaluated between 1991-1993, and then followed annually through 1996, for the development of dementia.
Men who developed dementia had lower cholesterol levels at all evaluations in this study. While these differences were small, ranging from a two- to14-point difference in total cholesterol, they were consistent over time and statistically significant. The largest difference in cholesterol levels between men with or without dementia was documented between 1980-1982: an average of 15 years prior to the diagnosis of dementia (Stewart et al., 2007 Arch Neurol 64). The correlation between lower cholesterol and dementia was not associated with any potentially compounding factors, such as poor general health, a relevant genetic mutation, and lipid-lowering treatment.
It is not clear from any study to date why a spontaneous drop in cholesterol would predate the onset of dementia such as AD. Or whether the drop in cholesterol is the cause of dementia or the effect of some other disease process in the body. Nonetheless, because any significant weight loss or decline in blood pressure occurs only 3-6 years before diagnosis, a drop in cholesterol appears to be the earliest known predictor of dementia--detectable almost 10 years earlier.
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