Research Links Heart Disease to Low Levels of ‘Good’ Cholesterol

WASHINGTON — A new study that calls into question year-old federal guidelines on heart disease risk has found that people with relatively low total cholesterol levels may nevertheless be developing coronary artery disease.

The research suggests that some people’s arteries become clogged more from a shortage of so-called “good” cholesterol than from an excess of “bad” cholesterol.

The study, released Wednesday by researchers at Johns Hopkins University, examined men and women with total cholesterol levels well below those recommended in federal guidelines. Of the 1,000 men and women in the study, 232 had coronary artery disease.

Two-thirds of the men with coronary artery disease and one-third of the women had unusually low levels of HDL cholesterol, the so-called “good” cholesterol, the researchers found. Recent studies suggest that a person’s risk of coronary disease rises as their HDL cholesterol levels fall.

The researchers, speaking at the American Heart Assn.’s annual scientific sessions, challenged the guidelines issued last year by the National Cholesterol Education Program. Those guidelines set the desirable level of total cholesterol for Americans at below 200 milligrams per deciliter of blood. People who fall within that guideline are not automatically tested for HDL cholesterol.

The researchers, headed by Dr. Michael Miller of the Johns Hopkins Department of atherosclerosis, recommended that the guidelines be reconsidered. They suggested that all people with coronary artery disease, no matter how low their total cholesterol, be tested specifically for HDL cholesterol and other fats.

“The bottom line is that for the past 15 years, the focus has been on high total cholesterol,” Miller said in an interview. “. . . But if you have too little of the good guys, the HDL, you’re also at risk.”

Artery Disease

Because his study focused on people with coronary artery disease, Miller said he could not comment on healthy people with low total cholesterol. He said he was not currently recommending that all healthy people automatically be tested for HDL too.

Elevated levels of cholesterol, a fat-like substance in the blood, have been linked to increased risk of heart disease. Along with fats and other substances, cholesterol can build up on artery walls, dangerously reducing blood flow to the heart.

More than half of all middle-aged Americans have total cholesterol levels above 200, a level at which heart disease risk is believed to rise sharply. Atherosclerosis, the narrowing of arteries, is a leading contributor to about 700,000 deaths a year by heart attack and stroke in the United States.

Scientists have known for some time that cholesterol falls broadly into several types: They include HDL, the so-called good type, and LDL, the bad. Cholesterol carried by low-density lipoproteins (LDL) is believed more likely to be deposited on artery walls. High-density lipoproteins (HDL) appear to transport cholesterol away from cells to the liver for excretion.

Commenting on Miller’s study Wednesday, Dr. Bernadine Healy, president of the American Heart Assn., warned against over-emphasizing HDL cholesterol. She said it is difficult to significantly raise a person’s HDL levels, while LDL levels can be more easily reduced.

Dietary changes or drug therapy can lower LDL levels dramatically--by as much as 40%, Healy said. Scientific studies have shown that lowering one’s LDL cholesterol levels can halt and even reverse buildup of plaque in the arteries, she said.

By contrast, Healy said she knows of no scientific proof that raising HDL levels will have the same effect.

Miller, however, countered that some recent studies suggest that exercise and even some drugs can raise HDL levels.