Major study debunks cholesterol drug side-effect fears

Millions of Australians using drugs to combat bad cholesterol can rest easier after scientists dispelled common concerns over side effects.

Despite being highly effective at reducing low-density lipoprotein cholesterol, statins have long been blamed for dozens of medical conditions by those taking them.

Drug manufacturers even list possible side effects on their statin packaging and websites, causing some patients to stop taking the life-saving drugs.

But a University of Sydney and Oxford Population Health study has found statins don't cause most of the conditions often attributed to them, including memory loss, depression and erectile dysfunction.

"These are really important findings," cardiologist Anthony Keech told AAP on Friday.

"These very common symptoms are often blamed on the statin, and it turns out that almost all of them are not due to the statin."

The study of data from more than 30 million symptom reports from at least 150,000 people compared the results of those using statin therapies against a placebo (or dummy tablet) over about five years.

Researchers found statin therapy could not be linked to 62 of the 66 conditions often listed as a possible side effect by drug makers.

The incidence of symptoms was no different in patients taking the drug or the placebo.

The conditions included weight gain, nausea, fatigue or headache, excessive memory loss or dementia, depression, sleep disturbance, and erectile and sexual dysfunction.

"Whilst patients were commonly reporting symptoms when they came back to the clinic, it turns out they weren't actually caused by the statin itself," Professor Keech, director of cardiovascular research at the NHMRC Clinical Trials Centre in Sydney, said.

"It's really important that people don't get misled by things they read on the internet websites or in the product information."

There was a small increase in risk (about 0.1 per cent) for liver blood test abnormalities; however, there was no increase in liver disease, such as hepatitis or liver failure, according to the data.

The results will put patients prescribed statins at ease and allow those experiencing symptoms previously attributed to the drug to investigate other potential causes.

"Knowing that statins don't cause these symptoms will give the doctor and the patient an opportunity to find out other explanations ... that might be easily treatable if the correct diagnosis is made," Prof Keech said.

Previous work by the same researchers established that most muscle symptoms are not caused by statins and that statin therapy caused muscle symptoms in only one per cent of people during the first year of treatment with no excess thereafter.

The team has also shown that statins can cause a small increase in blood sugar levels, so people already at high risk might develop diabetes sooner.

Statins, which were discovered as a natural product produced by certain bacteria and fungi, lower cholesterol by reducing the liver's ability to produce new cholesterol.

This, in turn, lowers the bad cholesterol levels that get stuck in the arteries, reducing the risk of more arterial blockages.

Commercially developed versions are prescribed by doctors to reduce the risk of a heart attack or stroke in patients who have already had one, and in people who have never had one but are at high risk of doing so.