High levels of high-density lipoprotein (HDL),
also known as “good” cholesterol, appear to be associated with a reduced risk
for Alzheimer’s disease in older adults.
”Dyslipidemia [high total cholesterol and
triglycerides] and late-onset Alzheimer’s disease are highly frequent in
western societies,” the authors write as background information in the article.
“More than 50 percent of the U.S. adult population has high cholesterol. About
1 percent of people age 65 to 69 years develop Alzheimer’s disease, and the
prevalence increases to more than 60 percent for people older than 95 years.”
Christiane Reitz and colleagues studied 1,130
older adults to examine the association of blood lipid (fat) levels with
Alzheimer’s disease. The study included a random sampling of Medicare
recipients 65 or older residing in northern Manhattan, with no history of
dementia or cognitive impairment. The researchers defined higher levels of HDL
cholesterol as 55 milligrams per deciliter or more.
To determine this association, data were
collected from medical, neurological and neuropsychological evaluations.
Additionally, the authors assigned a diagnosis of “probable” Alzheimer’s
disease when onset of dementia could not be explained by any other disorder. A
diagnosis of “possible” Alzheimer’s disease was made when the most likely cause
of dementia was Alzheimer’s disease but there were other disorders that could
contribute to the dementia, such as stroke or Parkinson disease.
During the course of follow-up, there were 101
new cases of Alzheimer’s disease, of which 89 were probable and 12 were
possible. The mean (average) age of individuals at the onset of probable and
possible Alzheimer’s disease was 83 years, and compared with people who were
not diagnosed with incident Alzheimer’s disease, those who did develop dementia
were more often Hispanic and had a higher prevalence of diabetes at the start
of the study. Higher plasma levels of HDL cholesterol were associated with a
decreased risk of both probable and possible Alzheimer’s disease, even after
adjusting for vascular risk factors and lipid-lowering treatments. Although
higher plasma total cholesterol, non-HDL cholesterol and LDL cholesterol levels
also were associated with decreased risks of probable and possible Alzheimer’s
disease, these associations became non-significant after adjusting for vascular
risk factors and lipid-lowering treatments.
“In this study, higher levels of HDL cholesterol
were associated with a decreased risk of both probable and possible Alzheimer’s
disease,” the authors conclude. “An important consideration in the
interpretation of the results is that it was conducted in an urban multiethnic
elderly community with a high prevalence of risk factors for mortality and
dementia. Thus, our results may not be generalizeable to cohorts with younger
individuals or to cohorts with participants with a lower morbidity [disease]
Arch Neurol. 2010;67(12):1491-1497.
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