Long-term use of the cholesterol-busting pills was linked with an increased risk of Type 2 diabetes of up to 30 per cent.
Statins, which cost just a few pence, are the most commonly prescribed drugs in Britain, with six million people taking them.
But they are controversial because they have been linked with causing muscle weakness. Other patients have complained of muscle aches, memory loss, kidney problems and sleep disturbance.
Doctors last night urged people prescribed statins to continue with their medication but warned that they should take extra steps to maintain a healthy lifestyle and reduce their diabetes risk.
In the first study of its kind, researchers focused on the development of diabetes among more than 3,200 statin users.
Over 10 years, statin use was linked to a 36 per cent increased risk of being diagnosed with type 2 diabetes, falling to 27 per cent after taking into account other risk factors.
More than four million Britons have type 2 diabetes and 12 million more are at risk of developing it.
The condition can lead to blindness, amputation of limbs, heart disease and stroke. Pav Kalsi, senior clinical adviser at Diabetes UK, said: “Statins can significantly reduce the risk of heart attacks and stroke, so it is important that people who have been prescribed statins continue to take them.
“If they have any concerns about the medication they are taking, then they should discuss this with their doctor. There are a number of different factors that can increase a person’s risk of type 2 diabetes.
“To reduce this risk, we recommend that people follow a balanced diet, do regular physical activity, maintain a healthy weight and have regular check-ups with their doctor.”
The new research by a team at Albert Einstein College of Medicine, New York, led by Dr Jill Crandall, is published in BMJ Open Diabetes Research & Care. Experts maintain the benefits of statins outweigh the risks.
Dr Crandall said: “For individual patients, a potential modest increase in diabetes risk clearly needs to be balanced against the consistent and highly significant reductions in myocardial infarction, stroke, and cardiovascular death associated with statin treatment. Nonetheless, glucose status should be monitored and healthy lifestyle behaviours reinforced in highrisk patients.”
Commenting on the research, GP Ian Campbell said: “This is a concern but people should not stop taking statins without speaking to their doctor first. Statins have a powerful effect on reducing the risk of heart disease and stroke and have been used safely for decades.
“The difficulty with this study is that the very people who would be on statins, who are already at risk of cardiovascular disease, are also, by its very nature, at risk of type 2 diabetes too. Does a statin make the risk worse, or is the risk already there? It may indeed be that the risk of type 2 diabetes is increased by taking statins, but how do we measure that against the risk of heart disease without statins? In other words, by stopping statins we might be swapping one risk for another.
“People who are concerned should reduce their total risk by keeping to a healthy weight, being physically active and making sure their blood pressure and cholesterol levels are well controlled.”
A separate study of more than 8,700 Finnish men aged 45 to 73 showed that taking statins over six years was linked to a 46 per cent increase in the risk of developing type 2 diabetes.