Alzheimer’s disease risk decreased by high levels of HDL cholesterol
MedWire News: High levels of high-density lipoprotein (HDL) cholesterol may be associated with a decreased risk for Alzheimer's disease in elderly individuals, research shows.
The team reports that high HDL cholesterol levels were associated with a 40% decreased risk for both probable and possible Alzheimer's disease.
"In addition, higher levels of total cholesterol, non-HDL cholesterol, and low-density lipoprotein (LDL) cholesterol were associated with a decreased risk of Alzheimer's disease in analyses adjusting for age, sex, education, ethnic group, and apolipoprotein (APO)Eε4 genotype," write Christiane Reitz (Columbia University, New York, USA) and colleagues in the Archives of Neurology.
In their prospective cohort study, the researchers examined baseline and follow-up data (collected between 1999 and 2001 and then at sequential intervals of 18 months) on 1130 elderly patients aged ≥65 years who were free from cognitive impairment.
The relationship between baseline lipid levels and incident probable (when the dementia cannot be explained by any other disorder) and possible (when the most likely cause of dementia is Alzheimer's disease, but there are other disorders that could contribute to the dementia such as stroke and Parkinson's disease) Alzheimer's disease was assessed.
Overall, there were 101 cases of incident Alzheimer's disease; 89 probable and 12 possible.
Higher plasma levels of HDL cholesterol (>55.0 mg/dl [1.4 mmol/l]) were associated with a 40% decreased risk for both probable and possible Alzheimer's disease, compared with lower HDL levels (≤55.0 mg/dl).
The team says that this association was driven by the highest HDL cholesterol level quartile, suggesting a threshold association.
Furthermore, higher plasma total cholesterol, non-HDL cholesterol, and LDL cholesterol levels were also associated with a 50%, 40%, and 20% decreased risk for probable and possible Alzheimer's disease, respectively, compared with lower levels, in models adjusting for age, gender, education, ethnic group, and APOEε4 genotypes.
However, when the models were further adjusted for vascular risk factors of lipid-lowering treatment, these associations were slightly attenuated and became nonsignificant.
"An interesting and seemingly paradoxical observation in our study is that both low non-HDL cholesterol and HDL cholesterol levels are associated with higher Alzheimer's disease risk," say Reitz and team.
But they suggest that HDL cholesterol levels are stronger predictors of Alzheimer's disease than other lipid measures in elderly individuals.
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By Nikki Withers