Some statins, drugs taken to protect the heart, may increase the risk of developing type-2 diabetes, according to researchers in Canada.
Their study of 1.5 million people, in the British Medical Journal, suggested powerful statins could increase the risk by 22% compared with weaker drugs.
Atorvastatin was linked to one extra case of diabetes for every 160 patients treated.
Experts said the benefits of statins still outweighed any risks.
Statins are a group of commonly prescribed drugs that lower the levels of bad cholesterol in the blood. This reduces the chances of a heart attack or stroke.
A team of researchers from hospitals in Toronto said there had been controversy around the risk of diabetes with different statins.
They looked at medical records of 1.5 million people over the age of 66 and compared the incidence of diabetes between people taking different statins.
Their report said: “We found that patients treated with atorvastatin, rosuvastatin, or simvastatin were at increased risk of new onset diabetes compared with those treated with pravastatin.
“Clinicians should consider this risk when they are contemplating statin treatment for individual patients.
“Preferential use of pravastatin… might be warranted.”
Commenting on the study, Prof. Risto Huupponen and Prof. Jorma Viikari, from the University of Turku, in Finland, said: “The overall benefit of statins still clearly outweighs the potential risk of diabetes.”
However, they said, the different statins should be targeted at the right patients.
They said: “The most potent statins, at least in higher doses, should preferably be reserved for patients who do not respond to low-potency treatment, but have a high total risk of cardiovascular disease.”
