Certain statins -- the widely used cholesterol-lowering drugs -- may increase your chances of developing type 2 diabetes, a new study suggests.
The risk was greatest for patients taking atorvastatin (brand name Lipitor), rosuvastatin (Crestor) and simvastatin (Zocor), the study said.
Focusing on almost 500,000 Ontario residents, researchers in Canada found that the overall odds of developing diabetes were low in patients prescribed statins. Still, people taking Lipitor had a 22 percent higher risk of new-onset diabetes, Crestor users had an 18 percent increased risk and people taking Zocor had a 10 percent increased risk, relative to those taking pravastatin (Pravachol), which appears to have a favorable effect on diabetes.
Physicians should weigh the risks and benefits when prescribing these medications, the researchers said in the study, which was published online May 23 in the journal BMJ.
This does not, however, mean that patients should stop taking their statins, the experts said. The study also showed only an association between statin use and higher risk of diabetes; it did not prove a cause-and-effect relationship.
"While this is an important study evaluating the relationship between statins and the risk of diabetes, the study has several flaws that make it difficult to generalize the results," said Dr. Dara Cohen, a professor of medicine in the department of endocrinology, diabetes and bone disease at the Icahn School of Medicine at Mount Sinai in New York City. "There was no data regarding weight, ethnicity and family history -- all important risk factors for the development of diabetes."
Cohen added that there was no information on the patients' cholesterol and blood sugar levels, and that higher-risk patients might automatically be prescribed stronger statins such as Lipitor, Crestor and Zocor.
Finnish doctors wrote in an accompanying editorial that this potential risk should not stop people from taking statins.
"The overall benefit of statins still clearly outweighs the potential risk of incident diabetes," researchers from the University of Turku said. Statins have been proven to reduce heart problems, they said, adding that the medications "play an important role in treatment."
Other statins did perform more favorably than Lipitor, Crestor and Zocor in terms of diabetes, the research found.
"Preferential use of pravastatin and potentially fluvastatin ... may be warranted," the study authors said in a journal news release, adding that Pravachol may even be beneficial to patients at high risk of diabetes. Fluvastatin (Lescol) was associated with a 5 percent decreased risk of diabetes and lovastatin (Mevacor) a 1 percent decreased risk.
In previous research, Crestor was associated with a 27 percent higher risk of diabetes, while Pravachol was linked to a 30 percent lower risk.
For this study, the researchers used patient information from three Canadian databases on 66-year-old men and women who were newly prescribed statins and followed for up to five years. Lipitor accounted for more than half of all new statin prescriptions, followed by Crestor, Zocor, Pravachol, Mevacor and Lescol.
The researchers said between 162 and 407 patients would have to be taking statins of various kinds for one extra patient to develop diabetes.
Results were similar for patients already diagnosed with heart disease and those taking statins to prevent it. Older patients using Lipitor and Zocor were at an increased risk regardless of dose, the researchers found.
People with type 2 diabetes have higher than normal blood sugar levels because their bodies don't make or properly use insulin. The researchers said it is possible that certain statins impair insulin secretion and inhibit insulin release, which could help explain the findings.