In addition to being good for the heart, high levels of so-called "good" cholesterol may protect against Alzheimer's disease, U.S. researchers said.
They found people over 65 who had the highest levels of high-density lipoprotein or HDL were 60 percent less likely to develop Alzheimer's disease over four years than people with the lowest HDL levels.
And it did not seem to matter if people had high HDL levels naturally or if they took widely used drugs called statins to increase "good" cholesterol levels, the researchers found.
The study points to a potential means of preventing Alzheimer's, an incurable brain-wasting disease that affects 26 million people globally and costs $604 billion to treat.
By raising HDL, "you can probably lower the frequency of Alzheimer's disease in the population," said Dr. Christiane Reitz of Columbia University's Taub Institute in New York, whose study appears in the Archives of Neurology.
Her team studied 1,130 people over 65 who were white, black or Hispanic and lived in New York City. Most were covered by Medicare, the federal insurance program for the elderly.
When they started the study, the volunteers had no history of memory or thinking problems. Over the course of the study, the team used medical and neurological data and did neuropsychological testing to diagnose Alzheimer's disease.
They divided people into four groups, or quartiles, based on cholesterol readings. Those in the highest group had HDL readings of 55 or higher. Those in the lowest quartile had HDL below 38.
"The highest quartile compared to the lowest had a 60 percent lower risk of developing Alzheimer's disease over four years," Reitz said in a telephone interview.
Reitz said the team looked specifically at people with probable or possible Alzheimer's disease, rather than vascular dementia or other forms of dementia.
They also looked at other cholesterol measures, such as total cholesterol, LDL and blood fats known as triglycerides.
"We looked at each of those measures independently. It seems to be an isolated effect for HDL," Reitz said.
An HDL reading of 60 or higher is considered protective against heart disease, according to the American Heart Association.
Reitz said an HDL reading of 55 or greater is achievable by changing diets and exercising. Some doctors also prescribe niacin, a B vitamin that can boost heart-protective HDL 25 percent, but this is not widely used because it causes uncomfortable facial flushing.
A new class of HDL-raising drugs called CETP inhibitors, such as Merck's experimental drug anacetrapib, are showing promise at significantly raising good HDL cholesterol.