Date: June 30, 2008  

Summary: Low levels of the so-called “good cholesterol” in middle age may increase the risk of memory loss and dementia later in life.  

Journal: Arteriosclerosis, Thrombosis and Vascular Biology

Journal citation: Arterioscler Thromb Vasc Biol. 2008;28:1557-1563

Read the original article: http://atvb.ahajournals.org/cgi/reprint/ATVBAHA.108.163998v1

Why it’s important: High cholesterol is associated with heart and blood vessel disease, but its relationship to brain function is less clear. Also, some drugs lower cholesterol levels in the blood but their effects on the brain are mixed. Understanding how high-density lipoprotein (HDL), or ”good” cholesterol, affects the risk of memory loss and other brain decline could give physicians a better clue about the effects of cholesterol-lowering drugs.

What’s already known: Good cholesterol or HDL is important in the maturation of nerve communication. It can also influence whether amyloids – fatty deposits – form in the brain. Many doctors agree that dementia could be affected by the levels of fats or lipids in the blood – either through changes in the diet or metabolism – leading to lowered levels of “bad” cholesterol called low-density lipoprotein. For that reason, studying the effects of cholesterol levels on the way the brain works in elderly people may result in spurious findings.

How this study was done: Researchers decided to study the relationship between blood fat levels in middle-aged people and dementia in old age.

Researchers relied on the Whitehall II study that began in 1985. It involved 3,673 civil servants ages 55 to 61. The information in this study is taken from phase 5 of the study (1995 to 1997) and phase 7 (2002 to 2004). During these periods, researchers took blood from patients who had not eaten for at least four hours. They then measured cholesterol levels in their blood, including “good’ cholesterol (HDL). The researchers then found out how well the people’s short-term memory worked in a test that involved remembering 20 words. Researchers adjusted the results for a variety of factors including education, occupation, heart disease, stroke, high blood pressure, diabetes, smoking, alcohol consumption and medicines taken.

What was found: Those with low levels of “good” cholesterol had a greater risk of memory loss than those with higher levels of “good” cholesterol. If HDL or good cholesterol decreased during the five-year period of the study, the patients had a higher risk of decline in short-term memory. Using drugs called statins to increase HDL and reduce low-density lipoprotein (LDL) had no effect on memory loss.

“Memory problems are key in the diagnosis of dementia,” said Archana Singh-Manoux, Ph.D., lead author of the study and senior research fellow with the French National Institute for Health and Medical Research (INSERM, France) and the University College London in England. “We found that a low level of HDL may be a risk factor for memory loss in late midlife. This suggests that low HDL cholesterol might also be a risk factor for dementia.” Why HDL affects dementia is unknown.

“Many previous investigations into the association between lipids and memory in the elderly have focused on total or LDL cholesterol because of their status as proven risk factors for cardiovascular disease,” Dr. Singh-Manoux said. “Our results show HDL cholesterol to be important for memory. Thus, physicians and patients should be encouraged to monitor levels of HDL cholesterol.”

The American Heart Association recommends regular exercise, avoiding trans fats in the diet, reducing all fats and consuming monosaturated fats such as olive, canola and peanut oils to raise HDL and lower LDL.

The bottom line: Increasing good cholesterol in middle age may reduce your risk of dementia later in life.



This content is reviewed regularly. Last updated 08/18/08.