For decades, doctors have told their patients that high levels of HDL, otherwise known as “good cholesterol,” can protect them from heart disease. But a new study suggests that having lots of so-called good cholesterol doesn’t mean a lower risk of heart attack.
This does not mean that HDL levels have no impact.
An analysis of data from nearly 24,000 American adults found that having HDL cholesterol levels that were too low was associated with an increased risk of heart disease – in white adults, but not black adults, researchers reported on Monday. the Journal of the American College of Cardiology.
The new findings surprised the researchers, who originally designed their study to understand how cholesterol levels in middle-aged black and white adults without heart disease affected their future risks. Previous research on “good” cholesterol and heart disease has focused primarily on white adults.
“I didn’t expect that high HDL levels wouldn’t be protective,” said study lead author Nathalie Pamir, associate professor of cardiovascular medicine at Oregon Health School of Medicine. and Science University. “And I certainly didn’t expect low levels to have no predictive value for black adults.”
The new research, co-funded by the National Institutes of Health, is part of a growing body of evidence disputing that high HDL cholesterol levels protect against heart disease, experts say, though people don’t always get the message.
“Those of us with high HDL got a pat on the back from our doctors,” said Pamir, who is also a researcher at OHSU’s Knight Cardiovascular Institute Center for Preventive Cardiology. “We’ve been told your HDL is fine so don’t worry. You’re protected.
Low-density lipoproteins, or LDL, contribute to the buildup of fat in the arteries, increasing the risk of heart attack and stroke. High-density lipoproteins, or HDL, have long been thought to be protective because they transport cholesterol to the liver, where it is eliminated.
What is clearer now is that high HDL only adds to the total cholesterol count.
“It’s still cholesterol at the end of the day,” Pamir said. “More and more studies are coming out showing that HDL levels above 80 are detrimental when it comes to cardiovascular outcomes.”
The results suggest that the algorithms used to calculate an individual’s risk of coronary heart disease need to be adjusted because they currently show a lower risk if HDL is high, Pamir said.
Risk calculations must also take race into account, she said, adding that the differences seen in black adults may be due to socioeconomic factors rather than genetics.
What is a healthy cholesterol level?
Right now, the focus should be on the total cholesterol count, Pamir said.
Cholesterol levels are measured in milligrams per deciliter of blood (mg/dL). According to the American Heart Association, the optimal total cholesterol level for an adult is around 150 mg/dL, with LDL levels at or below 100 mg/dL.
To take a closer look at the impact of HDL on coronary heart disease risk, Pamir and his colleagues turned to data from the Reasons for Geographic and Racial Differences in Stroke (REGARDS) study. The researchers focused on 23,901 middle-aged black and white REGARDS participants who were enrolled from 2003 to 2007 and who did not have heart disease at baseline.
During an average follow-up of 10.7 years, there were 1,615 cardiovascular events, 41.1% among black participants and 45.5% among women. High LDL and the level of another fat known as triglyceride were associated with an increased risk of coronary heart disease in black and white participants.
Low HDL levels were associated with an increased risk of coronary heart disease in white participants, but not in black participants.
Dr. Howard Weintraub, clinical director of the Center for Cardiovascular Disease Prevention in NYU Langone Health’s Leon H. Cheney Division of Cardiology, hopes people will understand that high levels of HDL are not protective.
“Literally every day someone comes into my office with an HDL of 80 or 90,” said Weintraub, who was not involved in the new research. “When I tell them that doesn’t mean they’re bulletproof, they get discouraged because their doctor told them not to worry about their bad cholesterol because the good cholesterol was so good. .
The idea that HDL was protective was so accepted that drug companies developed drugs that increased “HDL levels by 100 percent, and people died,” Weintraub said.
High HDL levels are generally a marker of a healthy lifestyle, said cardiology specialist Dr. Robert Rosenson.
“People with high HDL levels are less likely to be overweight, more likely to be active, less likely to be smokers, and less likely to have prediabetes,” said Rosenson, director of lipids and metabolism at Mount Sinai Health System in New York, which was not involved in the new study.
Still, Rosenson called the new research important because patients with high HDL levels who should be taking cholesterol-lowering drugs might not receive them.
Another important finding is the difference in cardiovascular risk between black and white patients, said Dr. Leslie Cho, interventional cardiologist and section chief of preventive cardiology and cardiac rehabilitation at the Cleveland Clinic.
“Underrepresented minority groups should demand greater clinical (trial) representation,” said Cho, who was not involved in the new research. “It’s really important.”
Judy Silverman contributed.