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Raising HDL Levels May Not Lower Heart Attack Risk

Gene Study Questions Impact of Increasing 'Good' Cholesterol Levels
By
WebMD Health News
Reviewed by Laura J. Martin, MD

May 16, 2012 -- It is widely believed that raising "good" cholesterol levels lowers heart attack risk, but surprising new research finds evidence that this may not be the case.

Genetic studies failed to show a link between higher concentrations of high-density lipoprotein (HDL) cholesterol and lower heart attack risk.

Millions of people take statin drugs like Crestor, Lipitor, Pravachol, and Zocor to lower their low-density lipoprotein (LDL), or "bad" cholesterol. Studies have shown that high LDL levels are linked to an increase in heart attack risk.

But the benefits of increasing HDL are less clear, and studies of HDL-raising drugs have been largely disappointing.

Higher HDL Not Protective

In the newly reported study, investigators from Harvard Medical School used a relatively new research technique that tests connections between genes and disease to examine whether HDL has a direct impact on heart attack risk.

In earlier studies, the researchers identified a gene variant found in about 2.6% of the population associated with elevated HDL levels.

People with the gene variant have levels that are, on average, about six points higher than people without it.

When the researchers looked for the variant in about 21,000 people who had experienced heart attacks and 95,000 people with no heart attack history, they found that carriers did, indeed, have higher HDL levels.

But they saw no evidence that these people also had a lower susceptibility to heart attacks.

"The expectation was that the people who carried this genetic variant would have a lower heart attack risk, but that is not what we found," says researcher Sekar Kathiresan, MD, of Harvard Medical School and Massachusetts General Hospital.

In a second study, which involved 14 more common gene variants also associated with HDL, the researchers once again found no evidence that the variants had a direct, protective role in heart attack risk.

Kathiresan tells WebMD that HDL remains an important tool for assessing heart disease risk, but he says the new research raises even more questions about the benefits of taking drugs to raise HDL levels.

HDL Drug Trials Disappointing

Many clinicians still prescribe the vitamin niacin to help raise HDL levels, even though a government-funded trial proved disappointing.

The trial was halted early a year ago when it was determined that people with heart disease who had low HDL levels did not benefit from the treatment.

There was even a suggestion that taking high doses of niacin raised stroke risk.

The drug company Pfizer abandoned its experimental HDL-boosting drug torcetrapib in 2006 when trials showed an increase in heart attack and stroke risk among users.

And earlier this month, Roche Pharmaceuticals abruptly stopped late-phase trials of its similar drug, dalcetrapib, finding no evidence of a lower heart attack risk in users.

American Heart Association past president Robert Eckel, MD, says the new research casts even more doubt on the strategy of raising HDL to lower heart and stroke risk.

Eckel is a professor of medicine at the University of Colorado School of Medicine in Aurora.

"HDL levels are related to risk, but that doesn't mean that raising HDL is beneficial," he says. "What we do know is that lowering LDL has a big impact on risk, so the take-home message remains, 'Get those LDL numbers down,'" he says.

Kathiresan says his research team will continue to search for genes that alter HDL and lower heart attack risk.

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Your total cholesterol level is in the Desirable range, but your level of "bad" LDL cholesterol is High. This may mean that your level of high-density lipoprotein (HDL), or "good" cholesterol, is too low. It is best to have a high level of "good" HDL and a low level of "bad" LDL. The HDL helps keep your LDL level in check. Ask your doctor for your HDL level. If your HDL is low, increasing your physical activity can increase it, which may help reduce your LDL level.

Your total cholesterol level is in the Desirable range, but your level of "bad" LDL cholesterol is Very High. This may mean that your level of high-density lipoprotein (HDL), or "good" cholesterol, is too low. It is best to have a high level of "good" HDL and a low level of "bad" LDL because the HDL helps keep your LDL level in check. Ask your doctor for your HDL level. If your HDL is low, increasing your physical activity can increase it, which may help reduce your LDL level.

Your total cholesterol level is Borderline High, but fortunately your level of "bad" LDL cholesterol is optimal. This could mean you have a high level of high-density lipoprotein, or "good" HDL cholesterol, which protects against heart disease. Or you could have other non-measured increases in LDL-like particles that can increase heart disease. Your LDL level also could be optimal if you are taking a statin medication. Please check with your doctor to get your complete lipid profile and see if you may need additional treatment. In the meantime, find more information on WebMD's Cholesterol Health Center.

Your total cholesterol level is Borderline High, but fortunately your level of "bad" LDL cholesterol is near optimal. This could mean you have a high level of high-density lipoprotein, or "good" HDL cholesterol, which protects against heart disease. Or you could have other non-measured increases in LDL-like particles that can increase heart disease. Your LDL level also could be optimal if you are taking a statin medication. Please check with your doctor to get your complete lipid profile and see if you may need additional treatment. In the meantime, find more information on WebMD's Cholesterol Health Center.

Your total cholesterol level is Borderline High. Your level of "bad" LDL cholesterol is Borderline High, too. Working to bring down your total cholesterol decreases your LDL cholesterol level. You can do this by exercising more and eating less food with saturated fats. Check food labels!

Your total cholesterol level is Borderline High. Your level of "bad" LDL cholesterol is High. Working to bring down your total cholesterol decreases your LDL cholesterol level. You can do this by exercising more and eating less food with saturated fats. Check food labels!

Your total cholesterol level is Borderline High. But your level of "bad" LDL cholesterol is Very High. Working to bring down your total cholesterol decreases your LDL cholesterol level. You can do this by exercising more and eating less food with saturated fats. Check food labels!

Your total cholesterol is High, but your level of "bad" LDL cholesterol is optimal. This could mean you have a high level of high-density lipoprotein, or "good" HDL cholesterol, which protects against heart disease. Or you could have elevated secondary lipids, such as non-HDL particles that increase the risk of heart disease. Your LDL level also could be optimal if you are taking a statin medication. Please check with your doctor to get your complete lipid profile and see if you may need additional treatment. In the meantime, find more information on WebMD's Cholesterol Health Center.

Your total cholesterol is High, but your level of "bad" LDL cholesterol is near optimal. This could mean you have a high level of high-density lipoprotein, or "good" HDL cholesterol, which protects against heart disease. Or you could have elevated secondary lipids, such as non-HDL particles that increase the risk of heart disease. Your LDL level also could be optimal if you are taking a statin medication. Please check with your doctor to get your complete lipid profile and see if you may need additional treatment. In the meantime, find more information on WebMD's Cholesterol Health Center.

Your total cholesterol level is High. Your level of "bad" LDL cholesterol is Borderline High. Working to bring down your total cholesterol decreases your LDL cholesterol level. You can do this by exercising more and eating less food with saturated fats. Check food labels!

Your total cholesterol level is High. Your level of "bad" LDL cholesterol is High, too. Working to bring down your total cholesterol decreases your LDL cholesterol level. You can do this by exercising more and eating less food with saturated fats. Check food labels! If you are struggling to bring down your total cholesterol and LDL cholesterol levels, your doctor may prescribe medication, such as statins. Following medication, dietary, and exercise instructions should result in improvements.

Your total cholesterol level is High, and your level of "bad" LDL cholesterol is Very High. Working to bring down your total cholesterol decreases your LDL cholesterol level. You can do this by exercising more and eating less food with saturated fats. Check food labels! If you are struggling to bring down your total cholesterol and LDL cholesterol levels, your doctor may prescribe statins or other cholesterol-lowering medications.

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