Blood levels of HDL, the famously "good" kind of cholesterol, may not make a big difference to heart health after all -- particularly for Black people, a large new study suggests.
The study, of nearly 24,000 U.S. adults, found that low HDL levels were tied to a somewhat higher risk of heart attack among White people. That was not the case for Black adults, however.
Meanwhile, high HDL levels -- traditionally lauded as heart-healthy -- made no difference in heart risks for Black or White adults.
Experts said the findings call for a reevaluation of how HDL is used to predict people's risk of developing heart disease. More broadly, they said, researchers need to figure out whether various "traditional" heart disease risk factors have similar effects for all people.
"We need to expand our understanding of risk factors for all racial and ethnic groups," said senior researcher Nathalie Pamir, an associate professor of medicine at Oregon Health & Science University in Portland.
That understanding, she added, turns into treatment guidelines. "And our guidelines have to work for everyone," Pamir said.
HDL, or high-density lipoprotein, first gained its reputation as the "good" cholesterol with the Framingham Heart Study. Back in the 1970s, it found a correlation between higher HDL levels and a lower risk of heart attack.
The Framingham study is a major, still ongoing research project: Decades ago, it identified many of the factors now considered key in whether people develop heart problems or suffer a stroke: High blood pressure, high levels of "bad" LDL cholesterol, smoking and obesity raise those risks, while exercise and higher HDL lower the odds.
Today, HDL is considered too low if it's below 40 mg/dL for men or 50 mg/dL for women. Values between those numbers and 59 mg/dL are considered normal, but people are encouraged to shoot for a "desirable" 60 or higher.
The problem is, the Framingham participants were all White. And some recent studies with greater racial diversity have questioned whether low HDL is "bad" for everyone's heart.
The new findings, Pamir said, show that for Black Americans, that idea does not hold up.
The study, published Monday in the Journal of the American College of Cardiology, involved 23,901 U.S. adults age 45 and up who were free of coronary heart disease at the outset. That refers to heart disease caused by a buildup of artery-clogging "plaques."
About 42% of the participants were Black, and 58% were White.
Over the next decade, just over 1,600 people suffered a heart attack or died of coronary heart disease. It turned out that low HDL predicted a modestly higher risk of heart trouble, but in White people only: Those with low levels had a 22% higher risk than White participants with normal HDL.
Among Black adults, low HDL had no bearing on heart disease risk. What's more, high HDL offered no protection to anyone.
The findings on high HDL are not surprising, Pamir noted: Trials testing HDL-raising medication have found no heart protection, either.
"But the dogma is still 'high HDL is good,'" Pamir said. "You still get the pat on the back if your HDL is high."
The consequences, she added, could be greater than an undeserved pat on the back, though. Doctors use HDL, along with other risk factors like high blood pressure and high LDL, in estimating patients' risk of developing heart disease in the next 10 years. And that guides treatment decisions, such as whether to prescribe a statin.
For Black patients, though, neither low nor high HDL is a useful measurement.
If the findings lead to changes in how HDL is used, that would be a good thing, said Dr. Keith Ferdinand, a cardiologist and professor at Tulane University School of Medicine in New Orleans.
For Black patients, risk factors like high blood pressure, obesity and elevated LDL should be given more weight, according to Ferdinand, who wrote an editorial published with the study.
But ultimately, he said, social inequities are the main reason that Black Americans are about one-third more likely to die from heart disease or stroke than White Americans.
"It's not enough to just tweak HDL," Ferdinand stressed. "We need to address our structural inequities."
He said that when people cannot afford healthy food, have no safe places for exercise, face chronic stress, and cannot pay for medications, they are at greater risk of developing heart disease -- and have a harder time managing it when they do.
As for low HDL, Pamir said the steps recommended for raising it are good ones: They include exercise, quitting smoking, and avoiding "trans" fats in processed foods.
So Black adults with low HDL should keep doing those things, Pamir said. They do not, however, need to stress out about raising their numbers.
The study was funded by the U.S. National Institutes of Health.
The American Heart Association has advice on a heart-healthy lifestyle.
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