From Columbia University College of Physicians and Surgeons
'Good' cholesterol reduces stroke risk
New York, NY- June 4, 2001-High levels of so-called "good" cholesterol in the blood sharply reduce the risk of stroke among elderly whites, blacks and Hispanics, Columbia researchers have found.
The finding adds to growing evidence that healthy behaviors such as exercise, weight loss, smoking cessation and moderate alcohol use may help prevent stroke. The study also underscores accumulating data showing that wider use of cholesterol-management drugs, called statins, could save lives.
Cholesterol is a waxy, organic substance that the body uses to transport fat through the blood. There are two types: "good" cholesterol, called high-density lipoprotein cholesterol (HDL-C), and its "bad" counterpart, low-density lipoprotein cholesterol (LDL-C).
LDL cholesterol is called bad because high levels of it promote blockage of the arteries, leading to heart attack or stroke. But HDL cholesterol is associated with the opposite effect, possibly because it helps clear "bad" cholesterol from the blood.
Past studies have found that high HDL cholesterol levels reduce the risk of heart disease, but few published studies show it also reduces stroke risk. In the Columbia study, to be published in the June 6 issue of the Journal of the American Medical Association, the researchers studied this effect among 1,444 northern Manhattan residents.
"It's a hefty risk reduction," said Ralph L. Sacco, M.D., the lead researcher. "Prior studies have not been as clear about the relationship between cholesterol and stroke." Dr. Sacco is associate professor of neurology and public health and associate chairman of neurology at Columbia University College of Physicians & Surgeons and associate director of the stroke division at Columbia Presbyterian Medical Center of New York-Presbyterian Hospital.
"Stroke is a huge public health problem" with few treatments for severe cases, he added. "More emphasis needs to be placed on prevention." Stroke is a death of brain tissue due to a lack of blood flow to the brain. The often disabling condition is responsible for 1 in 15 deaths in America yearly, according to the American Heart Association.
Stroke disproportionately affects the elderly, blacks and Hispanics, who are among the fastest-growing segments of the population. The risk of stroke more than doubles with each passing decade after age 55, and black males are 50 percent more likely to die from stroke than white males, according to American Heart Association figures.
The most common type of stroke is ischemic stroke, which occurs when a blood vessel is blocked. Ischemic stroke accounts for 4 in 5 cases of stroke, according to one study.
The Columbia researchers found that among the groups studied, people with high levels of HDL cholesterol had a lower risk of ischemic stroke by almost half, 47 percent.
It's not clear why HDL cholesterol has this effect, said the study's authors, but several explanations are possible. One is that HDL cholesterol helps to clear LDL cholesterol from the blood. LDL cholesterol is responsible for fatty buildups in arteries, a condition called atherosclerosis. Another possibility, the researchers said, is that HDL cholesterol prevents LDL cholesterol from reacting with oxygen, a chemical process that promotes atherosclerosis.
Consistent with both explanations is the observation that the steepest risk reduction found in the study was associated with a type of stroke that results from atherosclerosis. For this type of stroke, HDL-cholesterol was associated with an 80 percent risk reduction, the authors said.
The findings add to mounting evidence of the usefulness of cholesterol-management drugs called statins, the authors said. Statins have been shown to reduce the risk of heart disease and stroke, and experts say more Americans should take these drugs. Statins "mainly will reduce LDL, but also have some effect on HDL" cholesterol, said Dr. Sacco, which helps explain why statins lower the risk of stroke.
The research was supported by grants from the National Institute of Neurological Disorders and Stroke, the General Clinical Research Center, and the Columbia Center for the Active Life of Minority Elders.