A major clinical trial that added niacin to statin treatment for people with a history of heart disease was closed early due to lack of clinical benefit, according to a news release from the American Heart Association. These results are being interpreted as a disappointment in some early media reports.
The trial was based on a belief that simultaneously lowering bad LDL cholesterol (with a statin class medication) and increasing good HDL cholesterol (with niacin) would be superior to simply increasing LDL alone. This combination treatment has been associated with promising outcomes in previous studies, including one published just over a year ago in the New England Journal of Medicine.
I think the key to understanding why this new research study gave such an unexpected result is found in the biochemical roles of the two cholesterol types. LDL cholesterol is responsible for delivering cholesterol out to cells, and is the form of cholesterol that tends to deposit in arteries, contributing to atherosclerosis. HDL cholesterol acts sort of like a garbage truck, picking up cholesterol from the tissues and delivering it back to the liver for excretion. So the importance of HDL is magnified in the presence of more LDL.
But what is unique about the participants in this new research is that they were all people with advanced heart disease, and were being treated to the new LDL goal for very high-risk patients (LDL < 80 mg/dl), a level which you would only be likely to see in people eating extreme diets or being treated with aggressive statin therapy. It appears likely based on this trial that there is a level of LDL below which increases of HDL don’t provide any further benefit. Going back to the metaphor above, a garbage truck isn’t very useful if there isn’t any garbage to pick up.
Which is the long way of saying that I don’t believe this clinical trial is telling us that there is no role for niacin in the prevention of heart disease in people with low HDL cholesterol. While it is disappointing that a treatment effect was not seen in this specific population, the existing body of evidence suggests there are still many people who would still potentially benefit. Fortunately, we don’t have to rely on guesses for long – another major clinical trial of niacin in a less specific population should be published in the next year or two.
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