Doctors may have to weigh a serious potential risk before prescribing statins, the cholesterol-lowering drugs that are among most prescribed drugs in America. In a study published in Diabetologia, scientists from Finland found that men prescribed statins to lower their cholesterol had a 46% greater chance of developing diabetes after six years compared to those who weren’t taking the drug. What’s more, the statins seemed to make people more resistant to the effects of insulin—which breaks down sugar—and to secrete less insulin. The impact on insulin seemed to be greatest among those who started out with the lowest, and closest to normal, levels of blood glucose. And the higher the dose of the statin, and the longer the patients took them, the greater their risk of diabetes.
Previous studies have suggested that statins can raise blood sugar levels, and increase the risk of diabetes by anywhere from 10% to 20%, but none have documented an effect this large. Doctors often consider statins for patients who are at higher risk of heart disease, and one of the risk factors for future heart trouble is diabetes. So how do these results affect that decision?
“It’s a good news-bad news scenario,” says Dr. Robert Eckel, past president of the American Heart Association and professor of medicine at University of Colorado School of Medicine. “Although there is convincing evidence that patients on statins are at increased risk of new-onset diabetes, the benefit accrued [from statins] in reducing risks of heart attack, stroke and fatal heart disease trumps the effects of being new onset diabetics.”
In other words, the good that statins can do for people who are not yet diabetic but at higher risk of heart problems outweighs the increased risk of diabetes.
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And while the increased risk that the Finnish scientists found — 46% — is noteworthy, Eckel points out that the study involved only white men, and therefore may not be generalizable to a broader population. It’s not clear what the men’s family history or personal history of diabetes was; some may have had other risk factors for the disease that put them at higher risk of developing diabetes anyway, even if they didn’t take a statin.
Those who developed diabetes while taking statins were similar on many metabolic measures to those who developed diabetes but weren’t taking statins, suggesting that “that statin treatment increased the risk of diabetes independently of the risk profile of the background population,” the authors write. In a separate, U.S.-based study on statins, researchers found that those who went on to develop diabetes while taking statins also had risk factors for the disease before they started taking the medications.
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Which means that for confused patients, and their doctors, the current advice about who should take statins doesn’t change. The results, in fact, highlight the need for a discussion rather than just working through a checklist before prescribing statins. For patients who may not yet be diabetic, but are vulnerable to developing the disease and also may need a statin, Dr. Neil Stone, lead author of the 2013 American College of Cardiology and American Heart Association cholesterol guidelines, says he stresses the importance of lifestyle changes in diet and exercise.
“If you have a patient who is prone to developing diabetes, you’re getting into a higher risk group, because they also have risk factors associated with heart disease. So they have the potential to benefit from statins. If they are going to take a statin, I tell them we are going to help you get more fit, and work with your lifestyle. It’s even more important because if you don’t do that, and the patient decides to take the statin and go on with their unhealthy habits, then they are going to be even more prone to developing diabetes,” says Stone.
The patient’s family history of diabetes is another important part of the decision to start someone on a statin. It’s all about making sure that each patient’s risks and benefits are weighed carefully. And the potentially greater risk of diabetes created by statins should be part of that consideration. “Communication here is everything,” says Eckel.
Read next: New Hormone Discovered That Curbs Weight Gain, Diabetes Just Like Exercise
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