People who take cholesterol-lowering statins may be at twice the risk of developing type 2 diabetes, says a new study.

Statins are a class of drugs that can lower cholesterol and blood pressure, reducing the risk of heart attack and stroke. More than a quarter of middle-aged adults use a cholesterol-lowering drug, according to estimates. The study, published in the Diabetes Metabolism Research and Reviews journal, found that statin users had more than double the risk of a diabetes diagnosis compared to those who didn't take the drugs. Those who took the cholesterol-lowering drugs for more than two years had more than three times the risk of diabetes.

"The fact that increased duration of statin use was associated with an increased risk of diabetes - something we call a dose-dependent relationship - makes us think that this is likely a causal relationship," said the study's lead author Victoria Zigmont, a graduate student at the Ohio State University.

"Statins are very effective in preventing heart attacks and strokes. I would never recommend that people stop taking the statin they've been prescribed based on this study, but it should open up further discussions about diabetes prevention," Zigmont added.

For the study, the researchers included over 4,000 men and women who did not have diabetes, were candidates for statins based on heart disease risk and had not yet taken the drugs at the start of the study. About 16 per cent of the group - 755 patients - were eventually prescribed statins during the study period.

Researchers also found that statin users were 6.5 percent more likely to have a troublingly high HbA1c value - a routine blood test for diabetes that estimates average blood sugar over several months. "Although statins have clear benefits in appropriate patients, scientists and clinicians should further explore the impact of statins on human metabolism, in particular the interaction between lipid and carbohydrate metabolism," said co-author Steven Clinton, a Professor at the varsity.