More than a third of heart attacks and strokes - the biggest causes of death and disability in the western world - could be prevented if all those thought to be at risk took cholesterol lowering drugs, a trial by British scientists reported yesterday.

"This is a stunning result, with massive public health implications," said Rory Collins, professor of medicine and epidemiology at Oxford University and lead investigator of the seven-year heart protection study.

"We've found that cholesterol lowering treatment can protect a far wider range of people than was previously thought, and that it can prevent strokes as well as heart attacks."

The study, funded by the Medical Research Council and the British Heart Foundation, involved 20,000 volunteers in Britain. It was set up to establish the benefits of statins - cholesterol lowering drugs - in people at risk of heart disease and strokes and whether taking them increased the risk of death from cancer or other diseases.

The answer, revealed yesterday at the American Heart Association meeting in California, was a resounding endorsement of the drugs.

"In this trial, 10,000 people were on a statin. If now, an extra 10m high risk people worldwide go on to statin treatment, this would save about 50,000 lives each year - that's a thousand a week," said Professor Collins.

"These results are at least as important as previous findings for aspirin's effects on heart attack and strokes. Those findings changed medical practice, and we expect these to have the same effect. In fact, statins are the new aspirin."

The study laid to rest the doubts over the benefit to women of taking statins. The drugs also reduced the death rate among those over 70 as well as younger people and among those who did not have high blood cholesterol levels as well as those who did.

"Irrespective of the blood cholesterol levels, a statin should now be considered for anybody with a history of heart disease, stroke, other occlusive vascular disease or diabetes," said Richard Peto, co-director with Prof Collins of the clinical trials service unit at Oxford and famous for his work on the health dangers of tobacco.

"I've been working on trials for more than 30 years in Oxford and this is far and away the most important set of results I've ever had anything to do with," said Professor Peto.

The study also found antioxidant vitamins did not reduce the death rates among those at risk of heart attacks and strokes, but there were no ill effects either.

"We found no excess risk of strokes due to bleeding or of cancers. This contradicts the apparent adverse trends in some previous smaller studies of vitamin E and of beta-carotene. We shall continue to follow the health of the study volunteers for years to come, so should know if some benefit emerges later," said Prof Collins.

The study was part funded by Merck, which manufactures simvastatin, the drug given to volunteers, and Roche, which supplied the vitamins, but the companies were not allowed any part in the design or conduct of the trial or analysis of the results, to ensure the trial's independence.

The 20,000 volunteers were divided into four groups and given different combinations of statins, vitamins and placebos. All will now be put on statins.

Statins reduce LDL or "bad cholesterol" while raising slightly levels of HDL or "good cholesterol" by inhibiting an enzyme in the liver called HMG-CoA reductase. Most statins are considered very safe, but in August the pharmaceutical giant Bayer was forced to withdraw its statin, called Lipobay or Baycol, after some patients suffered kidney failure.

Doctors around the world received the results of the trial with huge enthusiasm. "This is stunningly good news for people at high risk and especially those who are older who have had a stroke," said Peter Sandercock, professor of medical neurology at the University of Edinburgh and a stroke physician.

Sir Charles George, medical director of the British Heart Foundation, said the results "represent a major step forward in the fight against diseases of the heart and circulation - Britain's biggest killers".