Robust evidence is in: a regular aspirin will reduce your risk of bowel cancer

Taking a quarter of an aspirin tablet a day could reduce bowel cancer risk by a fifth, according to a study carried out by researchers at Harvard University.

The study, published in the online journal JAMA Oncology, found that people who take aspirin every day for six years reduced their bowel cancer risk by 19 per cent.

They also found that taking 81mg of aspirin (a quarter of a standard dose) a day lowers the risk of all cancers by three per cent, and that middle-aged people who take the common painkiller are less likely to be diagnosed with cancer of any kind.

The researchers tracked almost 136,000 people over 32 years. The women (who were at least 30 when the study began) and men (who were at least 40) completed a questionnaire every two years over three decades. It included questions about diet, lifestyle and general health.

The researchers say the results of their study provide the strongest evidence yet that aspirin can prevent cancers developing. They suspect that the effect is caused by the reduction of an enzyme called cyclo-oxygenase, which is responsible for producing fatty acids essential for the central nervous system, but which also facilitates the development of tumours.

According to the researchers behind the study, aspirin use could save ‘thousands’ of lives, if combined with improved screening programmes.

The study’s lead author, Professor Andrew Chan, said: ‘It would be very reasonable for individuals to discuss with their physicians the advisability of taking aspirin to prevent gastrointestinal cancer, particularly if they have risk factors such as a family history.’

The researchers stop short of recommending aspirin for everyone, because in some patients it can cause stomach ulcers.

Instant analysis
This was a longitudinal observational study (also referred to as a prospective cohort study) seeking to link together information on individuals’ aspirin intake with any new cancer diagnoses. The particular strength of the study was the prospective nature of the data collection — over around 32 years — and the large sample size (136,000 healthcare professionals).

As in any large prospective study some of the questions varied slightly over time and this was also the case here in assessing aspirin use. But I would contend that by defining quite clearly that a regular aspirin user was a participant ‘who reported aspirin use at least twice a week’ the authors addressed this possible weakness. The other problem in any observational study is accounting for every conceivable variable that might also explain the findings. This issue was also well addressed by the researchers.

The most important result from this study was the significantly reduced risk of bowel cancer (19 per cent) among those consuming regular aspirin. Furthermore it is interesting to note that the authors also demonstrated dose-response effects — the magnitude of the bowel cancer risk reduction was proportional to both the duration of aspirin treatment and the amount of aspirin consumed.

For readers wishing to consider commencing on regular aspirin in order to reduce their risk of bowel cancer this study provides some sound evidence. However, there are also side effects associated with regular aspirin use — such as bleeding from the stomach — and, therefore, it is always recommended to speak with your own doctor first.

Finally, it is important to appreciate that, while regular aspirin use might indeed reduce an individual’s risk of bowel cancer, it will not eliminate the risk – so it is essential for all individuals over the age of 50 (and at younger ages if there is a strong family history) to also undergo regular bowel cancer screening. Research score: 4/5


  • John Smith

    This is quite a selective analysis of aspirin. The key point is regular baby aspirin use reduces overall mortality mainly through reducing the incidence of multiple cancers and the risk of dying from them. It also reduces the incidence of heart attacks and ischemic strokes. A good review covering all the benefits and harms of aspirin is Cuzick et al., 2014.

    http://annonc.oxfordjournals.org/content/26/1/47