A study from the University of California, Davis, found that low levels of "bad" (LDL) cholesterol and high levels of "good" (HDL) cholesterol are linked to lower levels of so-called amyloid plaque in the brain. A build-up of this plaque is an indication of Alzheimer's disease, the researchers said in a university news release.
The researchers suggested that maintaining healthy cholesterol levels is just as important for brain health as controlling blood pressure.
"Our study shows that both higher levels of HDL and lower levels of LDL cholesterol in the bloodstream are associated with lower levels of amyloid plaque deposits in the brain," the study's lead author, Bruce Reed, associate director of the UC Davis Alzheimer's Disease Center, said in the news release.
"Unhealthy patterns of cholesterol could be directly causing the higher levels of amyloid known to contribute to Alzheimer's, in the same way that such patterns promote heart disease," Reed said.
The study, which was published in the Dec. 30 online edition of the journal JAMA Neurology, involved 74 men and women recruited from California stroke clinics, support groups, senior-citizen facilities and the UC Davis Alzheimer's Disease Center. All of the participants were aged 70 or older. Of this group, three people had mild dementia, 33 had no problems with brain function and 38 had mild impairment of their brain function.
The investigators used brain scans to measure the participants' amyloid levels. The study revealed that higher fasting levels of LDL cholesterol and lower levels of HDL cholesterol both were associated with more accumulation of amyloid plaque in the brain.
Exactly how cholesterol affects amyloid deposits in the brain remains unclear, however, the researchers said.
In the United States, cholesterol is measured in milligrams of cholesterol per deciliter of blood, or mg/dL. HDL cholesterol should be 60 mg/dL or higher, the researchers said in the news release. LDL cholesterol should be 70 mg/dL or lower for those at very high risk for heart disease.
Reed and his colleagues said it's important to maintain healthy cholesterol levels in those who are showing signs of memory problems or dementia, regardless of their heart health.
"This study provides a reason to certainly continue cholesterol treatment in people who are developing memory loss regardless of concerns regarding their cardiovascular health," said Reed, who also is a professor in the UC Davis department of neurology.
"It also suggests a method of lowering amyloid levels in people who are middle-aged, when such build-up is just starting," Reed said in the news release.
"If modifying cholesterol levels in the brain early in life turns out to reduce amyloid deposits late in life, we could potentially make a significant difference in reducing the prevalence of Alzheimer's, a goal of an enormous amount of research and drug-development effort," he said.
The U.S. Centers for Disease Control and Prevention provides more information on the health effects of high cholesterol.