'Good' cholesterol: How much is too much?

New research challenges the popular belief that high-density lipoprotein cholesterol, also known as the "good" kind, is beneficial to one's health, regardless of its levels.

Physicians typically advise that people maintain high levels of high-density lipoprotein (HDL) cholesterol on the basis of the assumption that it prevents heart disease and stroke.

This protective effect is thought to be due to the HDL molecules, which "flush" cholesterol from the blood into the liver and out of the body.

However, little is known about people with very high levels of this type of cholesterol.

In fact, some recent research has suggested that high levels of it may actually raise the risk of premature mortality.

A new study reinforces this idea. It was presented by Dr. Marc Allard-Ratick, of the Emory University School of Medicine in Atlanta, GA, at the European Society of Cardiology Congress, held in Munich, Germany.

Time to change how we see HDL cholesterol

Dr. Allard-Ratick and colleagues examined the link between "good" cholesterol levels and the risk of heart attack and cardiovascular death in almost 6,000 individuals aged 63 years, on average.

Most had heart disease; the researchers followed them up over the course of 4 years, grouping them according to their levels of HDL cholesterol, measured in milligrams per deciliter (mg/dL).

During the follow-up period, 13 percent of the participants experienced a heart attack or died from cardiovascular disease.

Participants whose HDL cholesterol levels were 41–60 mg/dL were the least likely to experience a heart attack or die from a cardiovascular event.

However, for people with very low HDL cholesterol levels (less than 41 mg/dL) and those with very high levels (higher than 60 mg/dL), the risk of adverse cardiovascular events and death increased.

Specifically, people with cholesterol levels higher than 60 mg/dL were almost 50 percent more likely to have a heart attack or die from cardiovascular disease than those with levels at 41–60 mg/dL.

Dr. Allard-Ratick comments on these findings. "Our results," he explains, "are important because they contribute to a steadily growing body of evidence that very high HDL cholesterol levels may not be protective, and because unlike much of the other data available at this time, this study was conducted primarily in patients with established heart disease."

"It may be time to change the way we view HDL cholesterol. Traditionally, physicians have told their patients that the higher your 'good' cholesterol, the better. However, the results from this study and others suggest that this may no longer be the case."

Dr. Marc Allard-Ratick

He cautions that the reasons for the associations revealed remain unclear; but, he speculates, "one possible explanation is that extremely elevated HDL cholesterol may represent 'dysfunctional HDL' which may promote rather than protect against cardiovascular disease."

"One thing is certain," concludes Dr. Allard-Ratick: "the mantra of HDL cholesterol as the 'good' cholesterol may no longer be the case for everyone."