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Link found between cholesterol, memory: Low HDL levels associated with memory loss in study
(Milwaukee Journal Sentinel, The (KRT) Via Acquire Media NewsEdge) Jul. 5--For years, doctors have known that low levels of HDL cholesterol (the good kind) were a risk factor for heart disease, but now an intriguing new study has linked low HDL to memory loss in middle-aged men and women.
The research comes at a time when several pharmaceutical companies are trying to develop drugs that raise HDL as a way to prevent cardiovascular disease and when a variety of lifestyle measures have been shown to improve HDL levels.
A link between LDL cholesterol (the bad kind) and total cholesterol has been established over the last several years, but the new study provides an intriguing hint that HDL cholesterol may be a key player in the risk of developing dementia later in life, said Mark Sager, director of the Wisconsin Alzheimer's Institute.
"This study begins to say that HDL may be the most important cholesterol and may be protective in the brain," said Sager, a professor of medicine at the University of Wisconsin School of Medicine and Public Health.
Sager said he was impressed enough by the study's findings that he is considering looking at HDL cholesterol in the Wisconsin Registry for Alzheimer's Prevention, an ongoing study of 950 middle-aged men and women with at least one parent with Alzheimer's disease.
For instance, it would be interesting to find out if there was a connection between performance on cognitive testing and HDL cholesterol.
HDL cholesterol levels are a well-established risk factor for heart disease and stroke. Higher levels of HDL are associated with less risk and levels above 60 milligrams per deciliter are considered protective against cardiovascular disease.
Diet, exercise can help
Diet, exercise and other lifestyle measures can improve HDL levels as much as 20%, said Roger Blumenthal, a professor of medicine at Johns Hopkins University and spokesman for the American Heart Association.
Blumenthal, who was not a part of the study, said that while the study was not conclusive, it showed a strong association between HDL and memory.
The research is another piece of evidence that eventually diets will be designed specifically to improve brain health and to reduce the risk of dementia, said Piero Antuono, a professor of neurology at the Medical College of Wisconsin in Wauwatosa.
"A healthy cardiac lifestyle can have a widespread effect on brain function," said Antuono, who practices at Froedtert Hospital and the Zablocki VA Medical Center.
The study looked at 3,673 male and female civil servants ages 55 to 61 who were part of the ongoing Whitehall II Study in England and who were given memory tests over a five-year period.
At age 60, there was a 53% increased risk of memory loss in those with low HDL cholesterol, defined as less than 40 milligrams per deciliter, compared with those with high HDL, more than 60 mg/dl.
Also, over the five years, those with decreasing HDL levels had a 61% increased risk of decline in their ability to recall words from the memory test compared with those with high HDL.
"The results are important as HDL cholesterol levels can be raised by changes in diet and lifestyle," said lead author Archana Singh-Manoux, a senior research fellow with INSERM in France and University College in London.
Singh-Manoux noted that national guidelines stress the importance of lowering LDL cholesterol to reduce cardiovascular risk.
"Our results suggest that increasing HDL cholesterol might also be important for cognitive outcomes," Singh-Manoux said.
The study was published Tuesday in the American Heart Association journal Arteriosclerosis, Thrombosis and Vascular Biology.
Important for the brain
Cholesterol plays an important role in the brain, which contains about 23% of all cholesterol in the body.
It is believed that HDL cholesterol interferes with the formation of beta-amyloid, the protein clumps between brain cells that are associated with Alzheimer's disease. High levels of HDL cholesterol also might improve vascular health in the brain. HDL cholesterol might also have anti-inflammatory and anti-oxidant effects in the brain.
The study fits with other work showing that healthy arteries can go beyond improving heart disease risk, said William Thies, vice president for medical and scientific relations with the Alzheimer's Association.
"It looks like having good vascular risk factors in midlife is good for cognitive function later in life," said Thies, who was not a part of the study.
Thies said a limitation of the study is that it did not show precisely how HDL might protect against memory loss. The study also is preliminary and needs to be confirmed by other research.
"It (the study) is a hint that is not an area that you want to ignore . . . in maintaining a healthy brain," he said. "Whether this ends up as a clinically useful finding, we won't know for a while."
On the other hand, he said, there is no reason not to try to maintain healthy HDL levels.
"It has all kinds of benefits," he said.
How to raise HDL
There are several ways to raise HDL cholesterol, including aerobic exercise, moderate alcohol consumption, losing weight, avoiding trans fats and quitting smoking. Fish oil and other omega-3 fats, along with complex carbohydrates, also might improve HDL.
Taking niacin, also known as vitamin B3, also can significantly raise HDL cholesterol, but too much can cause side effects.
Several prescription drugs such as statins also can increase HDL.
To see more of the Milwaukee Journal Sentinel, or to subscribe to the newspaper, go to http://www.jsonline.com.
Copyright (c) 2008, Milwaukee Journal Sentinel
Distributed by McClatchy-Tribune Information Services.
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