The researchers, led by Professor Jack Cuzick, head of the centre for cancer prevention at Queen Mary University of London, say to reap the benefits of aspirin, the evidence shows that people need to take a daily dose of 75 to 100 milligrams for at least five years and probably up to 10 years between the ages of 50 and 65.
No benefit was seen while taking aspirin for the first three years and death rates were only reduced after five years, he and his team report in a review in the Annals of Oncologyjournal.
"Our study shows that if everyone aged between 50 and 65 started taking aspirin daily for at least 10 years, there would be a [relative] 9 per cent reduction in the number of cancers, strokes and heart attacks overall in men, and around 7 per cent in women," says Cuzick.
Side-effects
But the researchers also warned that taking aspirin long-term increases the risk of bleeding in the stomach.
Among 60-year-olds who take daily aspirin for 10 years, the risk of digestive tract bleeding increases from 2.2 per cent to 3.6 per cent, and this could be life-threatening in a small proportion of people, say the researchers.
The rate of gastrointestinal bleeding increases sharply over the age of 70.
Another side effect is peptic ulcer, the risk of which increased by 30 - 60 per cent.
"Whilst there are some serious side effects that can't be ignored, taking aspirin daily looks to be the most important thing we can do to reduce cancer after stopping smoking and reducing obesity, and will probably be much easier to implement," says Cuzick.
Aspirin is a cheap, over-the-counter drug generally used to combat pain or reduce fever.
The drug reduces the risk of clots forming in blood vessels and can protect against heart attacks and strokes, so it is often prescribed for people who already suffer with heart disease and have already had one or several attacks.
Aspirin also increases the risk of bleeding in the stomach to around one patient in every thousand per year, a factor which has fuelled debate over whether doctors should advise patients to take it as regularly as every day.
"The risk of bleeding depends on a number of known factors which people need to be aware of before starting regular aspirin and it would be advisable to consult a doctor before embarking on daily medication," says Cuzick.