A new study suggests statin medications used to lower cholesterol may raise the risk of diabetes to a slight extent. Study authors advise patients not to stop taking their medications without talking to a doctor, because statins' proven power to prevent heart attacks and strokes outweighs any potential increase in type 2 diabetes risk.
But the results — a nearly 50% increase in diabetes among longtime statin users — should put brakes on the idea of prescribing these drugs to healthy people, which some have recommended as a way to prevent disease, says co-author JoAnn Manson, a professor of medicine at Harvard Medical School. In recent years, statins' success in preventing heart attacks — even among people without high cholesterol — has led some doctors to joke about “putting them in the water supply.”
In the study, 6.4% of women who didn't use statins developed diabetes during the eight to nine years of follow-up, Manson says. That rate rose to 9.9% among statin users. “I don't think there's any debate remaining, particularly in the higher doses, about whether statins slightly increase the risk of developing diabetes,” says cardiologist Steve Nissen of the Cleveland Clinic, who wasn't involved in the new study. Yet Nissen notes that statins, which sharply reduce the risk of heart attacks and death in people with heart disease, are “among the best drugs we've got.”
Patients taking statins should ask their doctors to monitor them for signs of diabetes, however, says Manson, a principal investigator in the long-running Women's Health Initiative, a study of 161,000 postmenopausal women launched in 1993, on which the new analysis is based. People taking statins also should be aware of some of the common early warning signs of diabetes, such as increased thirst and urination, as well as fatigue, says Carolyn Ecelbarger, an associate professor at Georgetown University Medical Center, who wasn't involved in the new study.
“These studies shouldn't be a cause for alarm,” says Manson, co-author of the study, in today's Archives of Internal Medicine. “But the findings do raise concerns.” Although statins have been used since 1987, this kind of side effect can take time to become apparent, says Robert Eckel, past president of the American Heart Association. Manson says the link to diabetes may appear more clearly in the Women's Health Initiative because the study was so large and the women were followed for such a long time. Doctors currently write 255 million prescriptions for cholesterol-lowering drugs each year, according to IMS Health, which monitors the pharmaceutical industry.
An increased risk of diabetes among statin users was first seen in 2008, in a randomized controlled trial of the drug Crestor, says Vivian Fonseca, the American Diabetes' Association's president for medicine and science. A 2011 analysis in the Journal of the American Medical Association and a 2010 analysis in The Lancet also found an increased risk of diabetes among statin users.
Fonseca says scientists still don't understand why statins appear to increase the risk of diabetes. But he says that other important drugs, such as the diuretics used to treat high blood pressure, also are known to increase the risk of diabetes. “Every medication has risks and benefits,” Fonseca says. “But you don't want people to have heart attacks because they are so worried about getting diabetes.”
About one in four Americans over age 45 take a statin, according to the National Center for Health Statistics. Use of statins among people older than 45 has increased tenfold in the past two decades, from 2% in the years 1988 to 1994 to 25% in the years 2005 to 2008, according to the National Center for Health Statistics. Americans spent nearly $19 billion on them, according to IMS Health, which researches the drug market. Nearly 26 million Americans — or 8.3% of the population — have diabetes, according to the American Diabetes Association. Experts say the obesity epidemic is the primary driver of the increase in diabetes.
“The conclusion still stands that overall, those people who've got existing heart disease or have had previous strokes, they still would get vast benefits from statins,” as would those at high risk for heart disease, said Naveed Sattar, a metabolism and diabetes researcher at the University of Glasgow, UK. Instead, the finding “may make us a bit more cautious about putting statins in the water, for example,” Sattar, who wasn't involved in the new study, told Reuters Health. Previous studies, mostly in men, have suggested a smaller, 10-to-12-percent increase in diabetes among statin users, according to Sattar. Those numbers may be more accurate because they come from trials in which participants were randomly assigned to take a statin or not, which can better account for possible differences in groups of patients, he added. What's more, this type of “observational” study can't prove cause-and-effect.
Still, “broadly speaking, this kind of confirms that stains may well increase diabetes risk,” Sattar said. Why that's the case isn't totally clear, he said, but statins' effects on the muscles and liver may lead the body to make slightly more sugar than it normally would, or cause users to exercise a bit less.
At the National Institutes of Health, diabetes specialist Dr. Judith Fradkin says statins’ benefits outweigh the potential side effect, and that newly developed diabetes won’t harm right away. “The danger here is alarming people and having them go off a medication that’s of proven benefit,” she says. But Dr. Beatrice Golomb of the University of California, San Diego, welcomed the new study as a needed note of caution for women, saying there’s less certainty about the drugs’ overall effects in them.
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