Cholesterol-lowering statins may do more harm than good in people who have suffered a stroke, researchers warned.

People who have suffered a certain kind of stroke may be more likely to have a recurrence if they are taking statins to lower their risk of heart disease, a study has found.

A team at Harvard Medical School in Boston, America, found that patients who had had a haemorrhagic stroke, or a bleeding on the brain stroke, as opposed to a clot or blocking stroke, may increase their chances of having another if they were on statins.

The findings are published in the journal Archives of Neurology.

Millions of people take statins every day to reduce the risk of heart disease and of having a heart attack.

Doctors must weigh carefully the risks and benefits of using the drugs in stroke survivors, the researchers said, as the benefits of reducing the risk of heart disease in these patients may be outweighed by the increased risk of a second stroke.

Dr Michael Brandon Westover, of Massachusetts General Hospital and Harvard Medical School, Boston, and colleagues, wrote in the journal: "A particular subgroup of patients for whom the advisability of statin use is unclear are those at high risk for intracerebral haemorrhage.

"The reason for added concern is the increased incidence of intracerebral haemorrhage observed among subjects randomised to statin therapy in a clinical trial of secondary stroke prevention.

"Because intracerebral haemorrhage sufferers commonly have co-morbid [co-occurring] cardiovascular risk factors that would otherwise warrant cholesterol-lowering medication, it is important to weigh the risks and benefits of statin therapy in this population."

They said that for patients whose bleeding stroke occurred in the region of the brain known as the cerebrum the risk of a second stroke increased from 14 per cent to 22 per cent if they were on statins.

There was less effect if the original stroke had occurred in other parts of the brain, they said.

It is not known how statins increased the risk of certain kinds of bleeding stroke but the researchers suggested it may be because people with this kinds of stroke are more susceptible if their cholesterol levels are lowered or the drug itself may reduce the blood's ability to clot.

Dr Brandon Westover added: "In summary, mathematical decision analysis of the available data suggests that, because of the high risk of recurrent intracerebral haemorrhage in survivors of prior haemorrhagic stroke, even a small amplification of this risk by use of statins suffices to recommend that they should be avoided after intracerebral haemorrhage."

An accompanying editorial, written by Dr Larry Goldstein of Duke University in North Carolina, America, said: "Until and unless there are data to the contrary, or warranted by specific clinical circumstances, the use of statins in patients with haemorrhagic stroke should be guided by the maxim of nonmaleficence - Primum non nocere (first, do no harm)."