HDL Lowers Stroke Death Risk

News about the so-called ìgoodî cholesterol -- HDL -- just keeps getting better.

Elevated high-density lipoprotein (HDL) cholesterol -- which has been shown to increase a personís resistance against heart attacks -- may also protect against ìischemicî stroke, Israeli scientists report today in the American Heart Association journal Stroke. Ischemic stroke, the most common form of stroke, occurs when blood flow to part of the brain is blocked. The other type, ìhemorrhagicî stroke, is caused by bleeding from a ruptured blood vessel.

Study co-author Uri Goldbourt, Ph.D., of the Neufeld Cardiac Research Institute at Sheba Medical Center in Tel-Hashomer, Israel, says, ìOur study indicates that high levels of HDL may be associated with protection against more than one vascular disease entity.î

HDL, a fat-carrying protein, is nicknamed the good cholesterol because it helps the body dispose of the fatty substance in the blood that can contribute to narrowing of the arteries, a process known as atherosclerosis. LDL (low-density lipoprotein) does just the opposite: excess LDL may deposit cholesterol in artery walls, promoting atherosclerosis. Blood vessels gradually become narrowed or blocked, raising the risk of heart attack or ischemic stroke.

In the Israeli study, researchers looked at rates of fatal stroke among 8,586 male civil servants and municipal employees included in the Israeli Ischemic Heart Disease Study, which was originally intended to identify risk factors for coronary heart disease in a multi-ethnic population. The major factors were blood pressure, HDL and LDL cholesterol levels, cigarette smoking, physical inactivity and diabetes.

However, the study also provided an opportunity for the research team led by David Tanne, M.D., to determine if these same factors are associated with risk of ischemic strokes that are caused by narrowing or clot formation in the carotid arteries, large vessels in the neck that supply the brain with blood.

During the studyís 21-year follow-up, 241 men died of stroke. Men who were in the lowest third for HDL levels -- HDL cholesterol below 35.5 milligrams per deciler (mg/dl) -- exhibited a risk of stroke that was 32 percent higher than those in the highest third -- HDL cholesterol above 42.5 mg/dl, reports Goldbourt, chief of epidemiology and biostatistics at the Neufeld Institute.

ìOur results provide additional evidence that low serum (blood) HDL cholesterol should be considered a risk factor for stroke,î he says. Goldbourt also notes, however, that low HDL cholesterol was weaker than other risk factors: older age, high blood pressure, cigarette smoking, and diabetes mellitus.

In accordance with American Heart Association guidelines and the National Cholesterol Education Program, blood cholesterol measurements are used to help assess a personís risk of heart attack. If total cholesterol is elevated, HDL and LDL are assessed in order to choose whether blood fat-lowering drugs or other interventions should be used to reduce this risk.

While Goldbourt says itís premature to change current recommendations to include routine testing for HDL to determine stroke risk, he stresses that it is well established that people can raise their HDL levels by smoking cessation, weight loss, and -- most importantly -- exercise.

ìOngoing studies will provide us within two years with information about the effects of actual intervention to raise HDL cholesterol in patients with heart disease. However, we know that these lifestyle changes can benefit each and every individual,î the investigator says.

Other studies that have linked low HDL cholesterol and increased risk of stroke include the Framingham (Mass.) Heart Study, a community-based epidemiological study into the causes of heart disease, and the Copenhagen (Denmark) City Heart Study. In these two studies, scientists looked at stroke rates within a six-year time span, whereas the Israeli study followed patients for 21 years, well into their 60s. And the conclusion of the two larger studies, the Danish and the Israeli groups, are almost numerically identical, Goldbourt notes.

Atherosclerosis is an antecedent of both heart attacks and strokes, but people get heart attacks earlier in life than strokes. Why? Because scientists say the coronary arteries serving the heart are more susceptible to the disease process than the blood vessels feeding the brain.

ìThe time lag for the development of atherosclerosis in the cerebral arteries compared with the coronary arteries is commensurate with the fact that ischemic stroke generally occurs later in life than coronary artery disease,î Goldbourt says ìA longer-term study of elderly persons may uncover a stronger association between HDL cholesterol and stroke.î

Senior author of the Stroke report David Tanne is now at Detroitís Henry Ford Hospital. His co-authors were Goldbourt and Shlomit Yaari, B.Sc.

Stroke is one of five scientific journals published by the American Heart Association, which has its national headquarters in Dallas.

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Media advisory:
Dr. Goldbourt may be reached in Israel;
972-3-534 4703 or fax 972-3-534 2392.
Dr. Tanne can be reached in Detroit;
(313) 876-7253.

Reporters may call (214) 706-1173
for a copy of the journal report.
(Please do not publish telephone or fax numbers.)