12/31/2013 10:20 am ET Updated Dec 06, 2017

Cholesterol Could Affect Plaque Buildup In The Brain, Study Finds

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By Don Rauf

While high “good” cholesterol and low “bad” cholesterol levels can stave off heart disease, cholesterol may also affect plaque buildup in the brain, which is linked to Alzheimer’s disease.

Scientists have long known that the head and heart are connected when it comes to health. For example, high blood pressure, increases the risk of stroke and plays a role in cognitive decline.

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New research has found that unhealthy levels of cholesterol in the bloodstream may increase deposits of amyloid plaques in the spaces between the brain's nerve cells, which may contribute to Alzheimer’s disease.

Bruce Reed, PhD, associate director of the University of California–Davis Alzheimer's Disease Center, led this study of 74 men and women from California stroke clinics, support groups, senior facilities, and the Alzheimer's Disease Center.

Participants were all 70 years and older and included three with mild dementia, 33 with normal cognitive function, and 38 with mild cognitive impairment.

Dr. Reed and his colleagues imaged patient brains using PET scans and a “tracer” that binds with amyloid plaques. This tracer was a radioactive element that attached to the plaque and could be viewed via positron emission tomography (PET), a nuclear medical imaging technique.

Protein pieces in the brain — called amyloid beta or Aβ — come from a larger protein found in the fatty membrane surrounding nerve cells, according to the Alzheimer’s Association. Amyloid can build up into plaque and block cell-to-cell signaling at synapses (the extremely small gaps where nerve impulses are transmitted and received).

Investigators also measured levels of HDL (high-density lipoprotein) and LDL (low-density lipoprotein). HDL travels through the bloodstream and removes harmful LDL. High levels of HDL and low levels of LDL have been shown to reduce the risk of heart disease.

The brain is rich in cholesterol, accounting for a quarter of all the body’s cholesterol, according to the authors.

Scientists discovered that elevated cerebral Aβ was linked to higher LDL levels and lower HDL levels in the blood in a pattern that mirrored the relationship between good and bad cholesterol in cardiovascular disease.

Cholesterol levels are measured in milligrams (mg) of cholesterol per deciliter (dL) of blood in the U.S. Recommended targets for those at high risk of heart disease are 60 mg/dl or higher for HDL and 70 mg/dL or lower for LDL.

Dr. Reed said that the results indicate a way for lowering amyloid levels in middle-aged people who may just be developing amyloid buildup.

"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,” said Dr. Reed in a press release.

Sarah Samaan, MD, cardiologist and physician partner at the Baylor Heart Hospital in Plano, Texas, told dailyRx News, “We still don't know enough about how and why [amyloid] plaques occur, but it's exciting to know that there may be ways to reduce our risk of the disease through lifestyle choices such as diet and exercise.”

Exercise is one of the best ways to raise HDL levels, and people who are physically active tend to have a lower likelihood for developing dementia, according to Dr. Samaan. She recommends a heart healthy Mediterranean diet and weight loss to lower LDL cholesterol.

The study was published online on December 30 in JAMA Neurology. The study was supported by grants from the National Institute on Aging.