People with heart problems who were started on cholesterol-lowering statins were more likely to develop diabetes if they were prescribed stronger versions of the drugs, a new study finds.
"This is not about stopping statins,"said lead author Colin R. Dormuth, from the University of British Columbia in Vancouver. "These patients should be on a statin, the question is, should they be on a higher or a lower dose?"
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Dormuth and his coauthors analyzed data on 137,000 patients from Canada, the U.S. and the UK. The patients were all prescribed statins after being hospitalized for a stroke, heart attack, or other major heart problem between 1997 and 2011. None of them had diabetes.
The researchers considered rosuvastatin (brand name Crestor) prescribed at 10 milligrams or more per day, atorvastatin (Lipitor) at 20 mg or more and simvastatin (Zocor) at 40 mg or more to be higher-potency statins. All other dosages were considered lower potency.
About 3,600 of the patients were diagnosed with diabetes within two years of starting the drugs, according to results published in BMJ.
Those prescribed a higher-potency statin were 15 percent more likely to be diagnosed with diabetes than those given lower dosages.
Previous studies have found that taking higher doses of statins reduces the risk of having another serious heart problem by the same amount - about 15 percent - compared to taking lower doses.
"Physicians need to weigh the small increase in benefit against the increase in diabetes risk," Dormuth said.
In other trials, rates of death among patients taking low-dose and high-dose statins have been the same. That means higher-dose statins do not extend life more than the low-dose versions, he said.
The higher dose may still be necessary for some patients, for example those with genetic conditions leading to very high cholesterol, he said.
The first major statin trial was published in 1994, but researchers did not suspect a link with diabetes until 2008, said David Preiss. He has studied statins and diabetes at the University of Glasgow in Scotland and was not part of the new study.
After that, two major trials were published which found that taking a statin puts people at slightly higher risk of developing diabetes and taking a stronger statin puts them at slightly higher risk than taking a weaker statin, he said.
"Commonly used statins, such as simvastatin, atorvastatin and rosuvastatin, taken at a lower dose probably puts one at 10 percent higher risk of developing diabetes," Preiss said. "Taking these same statins at high doses probably pushes this up to about 20 percent."
However, it's still not clear what explains the extra risk, researchers said.
The BMJ study is based on a review of the records of patients treated in day-to-day practice by doctors who individualized treatment for each patient, Preiss noted.
"In other words, there were inevitably differences between patients that were treated one way and those treated another way - and this limits the ability of such studies to be able to look at cause and effect," said Preiss in an email.
Statins have been linked to other health problems beyond diabetes, including kidney injury, and rhabdomyolysis, or rapid loss of muscle tissue, Dormuth noted.
"It's not as simple as comparing a small increase in diabetes to a small increase in heart protection," he said.
The new findings are important for doctors to consider when prescribing statins, but they shouldn't change anything patients are doing, he said.
"If patients are worried they should talk to their doctors," he said.
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