LONDON (Reuters) -- Taking a small daily dose of aspirin can significantly reduce the risk of developing - or dying from - bowel, stomach and oesophageal cancer, according to a large review of scientific studies.
Researchers who analyzed all available evidence from studies and clinical trials assessing benefits and harm found that taking aspirin for 10 years could cut bowel cancer cases by around 35 percent and deaths from the disease by 40 percent.
Rates of oesophageal and stomach cancer were cut by 30 percent and deaths from these cancers by 35 to 50 percent.
Professor Jack Cuzick, head of the center for cancer prevention at Queen Mary University of London, said the evidence showed that, to reap the benefits of aspirin, 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 reported in a review in the Annals of Oncology journal.
"Our study shows that if everyone aged between 50 and 65 started taking aspirin daily for at least 10 years, there would be a 9 percent reduction in the number of cancers, strokes and heart attacks overall in men, and around 7 percent in women,'' Cuzick said in a statement about the research.
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 percent to 3.6 percent, and this could be life-threatening in a small proportion of people, they said.
"While 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,'' Cuzick said.
Aspirin, originally developed by the German drugmaker Bayer, 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 therefore 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 fueled debate over whether doctors should advise patients to take it as regularly as every day.
Cuzick said the risk of bleeding "depends on a number of known factors which people need to be aware of before starting regular aspirin'' and advised people to consult a doctor before embarking on daily medication.