The amount of "good cholesterol" in the blood remains an important marker for heart disease regardless of how much "bad cholesterol" is lowered, researchers said Wednesday.

Among patients taking cholesterol-lowering drugs called statins, the higher the HDL or good cholesterol, the less likely they were to have a heart attack or other "cardiovascular event," they found. Dr. Philip Barter of the Heart Research Institute in Sydney said the result is important because "it shows very, very clearly that the risk is real" when levels of good cholesterol, known as HDL, are too low.

"It means doctors can't ignore a low HDL even if they're treating people with statins. They need to attack the HDL as well, if the HDL remains low," Barter said.

Doctors have known for years that HDL, or high-density lipoprotein, protects against heart attacks and stroke, probably by cleaning up the bad low-density lipoprotein cholesterol, known as LDL.

"But it has not been clear whether a low HDL cholesterol level would remain a significant risk factor in people whose LDL cholesterol was reduced to very low levels," Barter and colleagues wrote in their report, published in the New England Journal of Medicine.

"Indeed, it had been argued hypothetically that if the LDL cholesterol level were reduced sufficiently, the level of HDL cholesterol might become irrelevant," they added.

No such luck.

Looking at a study of 9,700 patients taking the statin drug Lipitor in a study financed by maker Pfizer Inc., Barter and his international team of colleagues found that the higher a patient's HDL, the less likely he or she was to have a major cardiovascular event such as a stroke or heart attack.