Aspirin is most often used to relieve pain or reduce inflammation. Many cardiologists also recommend daily use of low-dose aspirin to prevent heart attacks and other heart-related problems. Only recently have studies begun to show that aspirin could have another very significant health benefit — protection against cancer.
In fact, the same low dose that doctors recommend for heart protection — 75 to 100 mg a day — happens to show promise in lowering overall cancer incidence and cancer mortality. Studies have shown that aspirin is associated with a 20 percent reduction in overall cancer cases between three and five years after the start of the aspirin regimen, and a 30 percent reduction during follow-up after five years.
In a recently published review of existing research, a team of researchers wanted to delve a little deeper into aspirin and its cancer-protective benefits, as well as complications that can arise with aspirin use, and whether the benefits outweigh the risks.
Aspirin Health Benefits
More than 50 clinical trials have been conducted to assess aspirin and its ability to protect against and treat cardiovascular problems, and nearly all have established that, even at very low doses (as low as 30 mg per day), aspirin has a substantial benefit in protecting people who are at high risk of heart attack and other heart complications.
Protection against cancer is a lesser-known benefit of aspirin use. Studies have pretty convincingly shown that aspirin use is especially helpful in preventing colorectal cancer (as well as its recurrence), and mortality from this form of cancer.
Recently published reports found taking “600 mg of daily aspirin for a mean of 25 months reduces the incidence of colorectal cancer by about 40 percent in patients with hereditary risk due to Lynch syndrome” (a genetic condition that increases risk).
Meta-analyses also suggest that daily aspirin use can protect against other forms of cancer, including cancers of the stomach and esophagus. In an analysis of 20 years of follow-up from three trials, death rates from esophageal cancer were reduced during the latter 10 years of follow-up.
While aspirin shows great promise for these cancers, for other forms, it is still too early to tell what, if any, effect it may have. For instance, studies have not been able to conclusively show a decrease in the incidence of lung cancer from aspirin use, but in an analysis of 20 years of follow-up, mortality was significantly decreased.
And some evidence exists that aspirin use might reduce breast cancer risk by up to 20 percent, but there’s no long-term follow-up at this point. Additionally, aspirin appears to have an effect on cancers of the prostate and ovaries, Hodgkin’s and non-Hodgkin’s lymphomas, and multiple myeloma, but more substantial research needs to be conducted before any definitive conclusions can be made.
Aspirin Side Effects
With so many health benefits, aspirin does, unfortunately, have a couple of side effects that can be potentially dangerous.
First, it can cause ulcers and bleeding, mainly in the upper gastrointestinal tract.
Second, aspirin interferes with the blood’s ability to clot. While clots can clog an artery, which can lead to a heart attack, these clots are also important to prevent loss of blood at the site of a wound.
Is Aspirin Therapy for You?
If you would like to consider aspirin use to reduce your risk of heart attack or cancer, it is very important to talk to your doctor. He or she can determine if the benefits of daily aspirin therapy outweigh the risks.
According to the researchers who conducted this review, if you delay any calculations of benefit until at least 10 years after the start of aspirin therapy treatment, the overall benefits would be small because “cancers of the colon, rectum, and esophagus together contribute to 10–12% of all cancer cases and deaths, and a 30-40% reduction in these will have a relatively minor impact on the overall benefit of treatment.”
If you are at a low risk for certain cancers and you consider that, then the risks of daily aspirin use probably outweigh the benefits.
On the flip side, if you have a strong family or personal risk of certain cancers, like colorectal, then it may make sense to start on aspirin therapy. It would make even more sense if you have a high risk of heart problems as well.
Of course, as with all medical decisions, these are things you and your doctor should figure out together.
 Rothwell PM et al. Short-term effects of daily aspirin on cancer incidence, mortality, and non-vascular death: an analysis of the time course of risks and benefits in 51 randomised controlled trials. Lancet. 2012 Mar 20. [Epub ahead of print.]
 Thun MJ, Jacobs EJ and Patrono C. The role of aspirin in cancer prevention. Nat Rev Clin Oncol. 2012 Apr 3. doi: 10.1038/nrclinonc.2011.199. [Epub ahead of print.]
 Rothwell PM et al. Effect of daily aspirin on long-term risk of death due to cancer: analysis of individual patient data from randomized trials. Lancet. 2011. 337, 31–41.