Medicines commonly prescribed to reduce people's risk of heart attack may have limited use for treating other diseases, research suggests.
Previous studies had suggested the cholesterol-cutting drugs - called statins - might help people with non-heart related conditions too, including cancer, dementia and kidney disease.
Experts reviewed hundreds of studies and found positive signs the drugs could benefit people with certain conditions, in addition to their proven effects on heart disease, but the results are inconclusive.
The researchers say there is not enough evidence to support a change in current guidance for the way these drugs are prescribed.
Statins are a group of medicines that help to lower cholesterol levels in the blood. They are often prescribed to older people to help reduce their risk of heart disease and stroke, a benefit that is well established.
Researchers led by the University of Edinburgh analysed results from 256 studies that had investigated the benefits of taking statins for 278 non-heart disease conditions.
They found that statins can help to prevent deaths from kidney disease, which is already recognised in clinical guidelines. This may be because of the drugs' effects on lowering heart disease risk as there is no clear evidence that statins can help improve kidney function.
The team also found evidence that statins can help slow cancer progression, which they say warrants further investigation.
The researchers looked at the chronic lung condition COPD and found current data are insufficient to conclude whether statins help delay disease progression. More research will be needed to determine if the treatment has any benefit for these patients.
Previous studies had suggested that taking statins might reduce the risk of Alzheimer's and dementia, whereas other studies reported potential adverse effects on memory and thinking. The latest study did not identify any positive or negative links.
Muscle pain is a commonly reported side effect of taking statins. The team did not find strong evidence for an association but not all of the original studies had adequately reported side effects. Researchers say they cannot conclude that the drugs do not cause muscle pain.
There was a modest increase in diabetes among people treated with statins, but the researchers say the evidence is not enough to justify not taking the drugs.
The researchers say their findings underline the importance of lifestyle advice for patients taking statins who might be at risk of developing diabetes.
The research is published in the Annals of Internal Medicine.
Dr Evropi Theodoratou, who led the research at the University of Edinburgh's Usher Institute, said: "The role of statins in reducing the risk of heart disease is well established. Evidence that the drugs offer benefits for non-heart disease conditions is less clear cut, however. We found current evidence credibly supports a favourable link for just a few diseases.
"The absence of harmful side-effects associated with taking statins is reassuring. Yet, we cannot exclude the possibility that some reported harms - such as severe muscle pain - are too rare to rule out with certainty."
Annals of Internal Medicine