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 analysed 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.
Read: Scientists aim for prototype of cancer surgery device
Rates of oesophageal and stomach cancer were cut by 30 percent and deaths from these cancers by 35 to 50 percent.
Death rates reduced after five years
Professor Jack Cuzick, head of the centre 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.
Read: Top warning signs of cancer
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.
Easier to implement
"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," 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 fuelled debate over whether doctors should advise patients to take it as regularly as every day.
Read: Cancer: remission and the fear of recurrence
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.
Cuzick added that there was evidence that this side-effect could be more common in people who have the bacterium Helicobacter pylori in their stomach, which also causes peptic ulcers. He said people considering embarking on a regime of daily aspirin should talk to their GP and it might be possible to be tested first.
A second risk is stroke. Aspirin is already given to some people to reduce their risk of heart attacks or ischemic stroke, caused by blood clots, which it does by thinning the blood. But it is likely to worsen a haemorrhagic stroke, caused by bleeding in the brain.
The study also shows that 10 years of aspirin reduces heart attacks by 18% and deaths by 5%, but although it reduces stroke numbers by 5%, there is a 21% increase in deaths.
Read: Non-smokers can also get lung cancer
All the cancers in which aspirin has a beneficial effect have some lifestyle causes – from smoking in lung cancer to alcohol in oesophageal cancer and obesity in all of them. Taking aspirin, said Cuzick, "should not be seen as a reason for not improving your lifestyle". The drug, however, would reduce the cancer risk even in people who have a healthy lifestyle, he said.
Increasing numbers of people in middle age are already being prescribed cholesterol-lowering statins to reduce their risk of heart attacks and strokes. Recently there has been an outcry over the "medicalisation" of the population and concern about side-effects – which trial data suggest are less common and less serious than those in aspirin. Cuzick said there was no evidence of any interaction between the two drugs. "In many people, taking both of them is probably a good idea," he said.
You should talk to your GP first to see if you've got any of the major risk factors for bleeding, but if not I think the benefits substantially outweigh the risks," said the senior author, Prof Jack Cuzick.
Cat poo parasite could cure cancer
High-tech glasses may help surgeons see cancer
At-home test can spot most colon cancers
Image: Old dirty hand from Shutterstock
Additional source: the Guardian