Statins safely reduce the risk of cardiovascular illness even years after treatment is stopped, according to a probe into the popular cholesterol-busters.

Statins work by blocking a liver enzyme that makes fatty molecules which line arterial walls and boost the danger of heart disease and strokes. With worldwide annual sales of more than $20 billion, the drugs have been dubbed “the aspirin of the 21st century” because of their benefit and wide use.

But lingering questions persist about their long-term safety for the heart, liver and cancer risk.

Researchers at the Heart Protection Study Collaborative Group in Oxford looked at 20,536 patients at risk of cardiovascular disease who were randomly allocated 40mg daily of simvastatins or a dummy look-alike over more than five years.

During this period, those who took the statins saw a reduction in “bad” LDL cholesterol and a 23 per cent reduction in episodes of vascular ill-health compared to the placebo group.

The monitoring of the volunteers continued for a further six years after the trial ended. The benefits persisted throughout this monitoring period among those volunteers who stopped taking the statins, the investigators found.

In addition, there was no emergence of any health hazard among those who had taken, or were continuing to take, the drugs. A large number of cancers (nearly 3,500) developed during this follow-up period, but there was no difference in cancer incidence between the statin and placebo groups.

A previous investigation found that long-term use of statins was less risky than thought for people with non-alcoholic fatty liver disease, a common liver ailment.