Taking aspirin in your 40s could cut the risk of cancer developing later in life, according to research published in the Lancet Oncology.
In a detailed review of all the available evidence, Cancer Research UK scientists suggest that taking aspirin at an age before cancer begins to develop - and for at least 10 years - would maximise the drug's potential to prevent cancer.
Previous research suggests that people who take aspirin are less likely to develop colon cancer, breast cancer and possibly some other types of cancer. Aspirin blocks the effects of the COX enzymes, proteins involved in inflammation and found at unusually high levels in several types of cancer.
But regular use of the anti-inflammatory drug specifically for cancer prevention is not currently recommended as it has been linked to a number of side-effects including, gastrointestinal bleeding and stomach ulcers.
Common cancers, such as prostate, breast, lung and bowel, tend to develop after the age of 60. And the chances of aspirin causing bleeding in the abdomen are much higher in people over 60.
Study author, Professor Jack Cuzick, from the Cancer Research UK Centre for Epidemiology at Queen Mary, University of London , said: "Taking aspirin regularly in your mid 40s could maximise the effect this drug has on preventing cancer. Taking aspirin at this age, which is about the time pre-cancerous lesions usually begin to develop, may be the best time to stop the disease from progressing to actual cancer.
"And, as the risk of serious side effects of aspirin greatly increase after 60 years old, taking long-term treatment before this age will help to minimise these side effects."
"But many questions need to be answered before we would advise regular use of aspirin for cancer prevention. Future research and more clinical trials are needed to better identify those people who are at high risk of developing cancers and at low risk of side effects, who will benefit most from aspirin treatment."
"Some studies did not show a preventative effect, but the follow up was less than 10 years, so it may have been too early to see the effect."