Doubt Cast on the ‘Good’ in ‘Good Cholesterol’
Raising levels of “good” cholesterol may not be so good for you after all. A study published Wednesday by Boston-area scientists challenges the long-held idea that HDL cholesterol actively protects against heart disease, finding that people with genes that boosted their HDL did not have a lowered risk of heart attacks.
In the study appearing in the medical journal The Lancet, a team led by researchers from Massachusetts General Hospital and the Broad Institute examined the health of more than 100,000 people, some of them with genetic variations that elevated their levels of HDL, and found that those variations did not protect against heart attacks.
The results come shortly after a clinical trial of an HDL-raising drug being tested by the Swiss pharmaceutical giant Roche was halted, only the most recent high-profile problem to surface with a potential treatment aimed at lowering heart disease risk by boosting HDL.
“What this really suggests to us is we can’t simply assume just because something raises HDL cholesterol in the blood, that risk for heart attack will be lowered,” said Dr. Sekar Kathiresan, a cardiologist at Mass. General and associate member of the Broad Institute who led the work. “It’s very important, because if you ask the average person, the average doctor when they see someone with low HDL cholesterol, their impulse is to raise it with something.”
For several decades, the medical community has been drumming into patients the importance of knowing their cholesterol readings — many people can rattle off their levels of the “bad” LDL cholesterol and “good” HDL as easily as their Social Security number. Studies had found that higher levels of LDL were associated with increased risk for heart attacks, while the opposite was true for HDL. It’s also been clearly shown that statins, drugs that lower LDL cholesterol, decrease cardiovascular risk. But it has been unclear whether the association with HDL was analogous — whether raising HDL levels would be protective.
To test this notion in the new study, the scientists studied a gene variation that is present in about 2.6 percent of the population and raises HDL levels, with no effect on other cardiovascular risk factors. People with that gene should have a 13 percent decreased risk of heart attack, the researchers calculated. But when they compared them with people who did not have the gene, there was no difference in heart attack risk. In a second study, researchers examined a panel of 14 genetic variations that raised HDL levels and found inheriting those variations did not confer protection against heart attacks either.
For years, epidemiological studies have found that naturally high HDL levels are associated with heart disease protection, but it has not been clear whether those high levels are themselves protective. They could, for example, simply be a marker of a healthy lifestyle.