What you need to know about "good" cholesterol

“Bad” LDL cholesterol has long been associated with heart disease risk and doctors prescribe statins and other treatments to lower it when someone’s LDL levels are too high. 

Aiming for high levels of “good” HDL cholesterol looked like it might be another way to keep heart disease in check, but a new study suggests HDL is more complex than once thought. The findings, in the Journal of the American College of Cardiology, suggest that for most people, the HDL cholesterol number isn’t a good indicator of heart health.

Several recent randomized clinical trials tested whether raising people’s “good” cholesterol levels would cut the risk of heart disease, and found that it didn’t actually help. So researchers led by Dr. Dennis Ko, a senior scientist at the Institute for Clinical Evaluative Sciences in Ontario, Canada, decided to take advantage of “big data” to try to learn more about HDL’s role in heart disease. 

“We wanted to look at HDL because it’s been controversial. How come none of the drugs work?” said Ko, who is also an interventional cardiologist at Schulich Heart Centre at Sunnybrook Health Sciences Centre.

They looked at information pulled from a large population in Ontario — more than 630,000 patients without pre-existing cardiovascular disease, between the ages of 40 and 105. About half were women and half men. 

The researchers examined the relationship between HDL cholesterol levels and other cardiac risk factors, existing illnesses, medications that people were taking, and socioeconomic status, among others factors.

They also compared the HDL levels of healthier people to the HDL levels of people with poorer health habits, such as smoking.

Low levels of “good” HDL cholesterol were most common in people who were socioeconomically disadvantaged and who had less healthy behaviors, more cardiac risk factors and more medical problems. Ko said that even when they adjusted for unhealthy lifestyle factors, like smoking, lower HDL levels were still associated with a higher risk of cardiovascular-related death and other causes of death, including cancer.

High HDL levels were also associated with an increase in non-cardiovascular related deaths, though not heart-related deaths, Ko noted.

“We thought that the higher it [HDL levels] goes, the lower the outcomes, but in fact, it’s not a straight-line relationship. We saw high mortality in the very high [HDL] levels, too,” said Ko. “The conventional thinking to strive for as high an HDL level as possible is not as clear as we thought. It’s a marker associated with many things.”

Dr. Chip Lavie, medical director of cardiac rehabilitation and prevention and director of the stress testing laboratory at Ochsner Health System in New Orleans, told CBS News there were reasons why high HDL might be associated with more deaths.

“Extremely high HDL is probably related with alcoholism and liver diseases from alcohol and other disorders,” he said.

Dr. Suzanne Steinbaum, director of women’s heart health at Lenox Hill Hospital in New York City, said the new research raises questions about whether or not more HDL drug studies make sense at this point.

“We’ve been studying medications to specifically raise HDL and a lot of these trials really haven’t panned out, and what I think this study was trying to do was to say, is it worth it for us to keep trying to find a medication to increase HDL?” she said.

Steinbaum said HDL cholesterol levels need to be understood in the context of individual patients and within specific population groups — the way hormone replacement therapy has been studied in women.

“Every person needs to be looked at for their entire lifestyle and risk factors and other markers for heart disease. Perhaps at this stage, the least important focus should be on altering that HDL,” said Steinbaum.

She added, “I don’t think we fully understand enough about HDL. We need to figure out the role of HDL in certain populations to see who will benefit the most from it. Based on this study, the focus can’t just be on the HDL when we talk about altering the risks for heart disease.”

Study author Ko said we need to rethink what “good” cholesterol tells us about heart disease and health.

“The message is to think about HDL in the future as much less a direct cardiovascular marker,” he said. “If you have a very low level, that is a marker of poor general health. But I’d tell people to de-emphasize the numbers and emphasize doing things such as exercise and not smoking. Focusing on good lifestyle factors is probably more important.”