Harvard Heart Letter

High HDL may not protect the heart

Concentrate on lowering LDL for now, experts advise.

HDL cholesterol is called "good" cholesterol, because higher levels of HDL are associated with lower risk of heart attack. But researchers are now questioning whether HDL protects the heart, and whether raising low levels is beneficial.

Harvard researchers studied individuals with genetically higher-than-normal HDL. In this study, published online May 12, 2012 in The Lancet, they expected a 13% lower risk of heart attack in individuals with the genetic variant. However, the risk was the same as in people who did not have the gene. "This suggests that just because an intervention raises HDL cholesterol, we cannot assume that risk for heart attack will drop," says principal study author Dr. Sekar Kathiresan, director of preventive cardiology at Harvard-affiliated Massachusetts General Hospital. "This highlights the difference between cause and association."

Many studies have found that people with naturally high levels of HDL have lower rates of cardiovascular disease. The assumption was that high levels of HDL explained the lower rates of disease, but that is not necessarily so. Some other factor may raise HDL and lead to lower rates of cardiovascular disease.

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