Aspirin: could it reduce your risk for cancer?

Nyedra W. Booker, PharmD, MPH and Margaret Dayhoff-Brannigan, PhD


Often called a “wonder drug,” aspirin reduces aches and pains, fever, and swelling, and lowers the risk of heart attack and stroke. Low dose aspirin is used as an inexpensive drug to prevent heart attacks and strokes in patients that have had previous attacks or have coronary artery disease. More recent research suggests it might also lower our chances of developing several types of cancer, and help keep cancer from spreading.

But, like all medications, aspirin has risks as well as benefits. Here’s what you need to know.

Preventing Heart Attacks and Stroke

Aspirin keeps blood cells from sticking together, which prevents blood clots. During a heart attack, blood clots can block the heart from pumping and getting oxygen into the blood. Taking low-dose (75-100 mg) aspirin daily can lower your risk of developing blood clots that cause cardiovascular disease, particularly in patients who have already had a heart attack. However, since aspirin prevents blood from clotting, it also prevents healing properly from normal injuries. Taking aspirin daily can prevent your stomach lining from being properly protected from stomach acids, making it more prone to ulcers and bleeding. It also increases your risk of excessive bleeding, especially after falling or other injuries.

Preventing and Fighting Cancer

Aspirin and many other pain killers reduce inflammation, and inflammation can contribute to the development of certain cancers.1  In addition, aspirin activates a protein called AMPK (adenosine monophosphate-activated protein kinase), which helps control how fast cells grow and change in the body.2

The first and best evidence that aspirin can prevent cancer emerged from studies showing that a daily dose of aspirin reduced the risk of colorectal cancer by 20%.3  The first studies suggested that people had to take aspirin for at least five years to reduce their risk of developing cancer, but some of the newer studies suggest that 2 years may also help prevent cancer.4,5

Five large studies of daily aspirin use in more than 17,000 patients for the prevention of heart attacks, strokes, and other vascular events, found that people taking aspirin every day were less likely to develop cancer or die from cancer.6  Compared to those who did not take aspirin, the almost 10,000 people who took a daily dose of aspirin reduced their risk of dying from colorectal and prostate cancers. The people taking aspirin who were diagnosed with colorectal, lung or brain cancer during the studies were also less likely to have their cancer spread (metastasize) to other parts of the body or organs. Daily aspirin use for about two years reduced the risk of cancer spreading to other organs, sometimes by as much as 40%. Most important, there were fewer total cancer-related deaths among the people taking aspirin every day. High dose aspirin (300+ mg/day) was used in the earliest trials (1978-1986) and also showed a reduction in the development or death from cancer. However, the larger dose did not provide any additional anti-cancer benefits, in fact patients taking a low dose aspirin had a higher overall survival rate.

In another analysis of more than 50 studies of daily aspirin use for the prevention of vascular events such as stroke, aspirin reduced the risk of both cancer and non-cancer related deaths.7  In the 34 studies (more than 69,000 participants) that included information about participants developing and dying from cancer, the people who took aspirin were less likely to develop colorectal cancer, uterine cancer, lymphoma and other types of cancer. Fewer deaths from cancer also occurred among the people taking a daily dose of aspirin than among those who took no aspirin. There were 562 deaths reported in the group taking aspirin, compared to 664 deaths in the group that didn’t take aspirin. The aspirin-takers were almost 40% less likely to die from cancer if they took aspirin for 5 years.

Does the Dose Matter?

A standard dose of aspirin (one pill) is typically 325 mgs, and a low-dose or “baby” aspirin is 81mg. Although called baby aspirin, children under 12 should not take aspirin due to the risk of Reye’s Syndrome.

Studies comparing the different doses of aspiring found that higher doses did not work any better to prevent heart disease or cancer, and should be avoided since they increase the risk of ulcers and internal bleeding. At doses as low as 75mg, daily aspirin not only lowered the risk of heart attack and stroke, but it appears to have prevented many types of cancer, including colon cancer and uterine cancer, as well as slowed the spread of cancer to distant organs.

For example, a study comparing daily very low dose aspirin (30mg) to a daily dose of 283 mg for preventing vascular events, researchers found no significant difference in cancer deaths between the two groups. In six studies of daily low-dose aspirin use (75 to 100 mg), aspirin reduced the risk for cancer by almost 25% after at least 3 years of aspirin therapy. Daily aspirin use appeared to be particularly beneficial in reducing the risk for certain cancers of the female reproductive organs.7 For instance, there were significantly fewer cases of uterine cancer among the almost 16,000 women participating in six different aspirin trials. There were zero cases among women taking aspirin as compared to 9 cases in the non-aspirin groups in these studies.

Be Careful of the Risks

While these studies are exciting and reveal aspirin to be more of a wonder drug than we ever imagined, it’s important to remember that aspirin therapy is NOT for everyone. Aspirin belongs to a group of medications known as “blood thinners.”  As noted above, these drugs prevent the body from making potentially harmful clots that can block blood vessels and cause heart attacks and strokes. Patients already taking blood thinners (such as Coumadin,  heparin, Pradaxa, or Xeralto) who take aspirin may be at an increased risk for internal bleeding, ranging from mild to life-threatening.  People with severe liver and kidney disease are warned against using aspirin because aspirin can have toxic effects on these organs. In addition, asthma patients may be particularly sensitive to aspirin and can, as a result, experience asthma-related complications.8 Even some people who do not have asthma can have a bad reaction to aspirin that can lead to breathing problems.9

Research shows that for some patients, the risks of daily aspirin were high enough to counterbalance the benefits. For example, a study of almost 15,000 Japanese adults published in the December 2014 issue of the prestigious medical journal JAMA concluded that aspirin does not increase survival. The patients were randomly assigned into two groups: one group took 100mg of aspirin daily and a control group did not take aspirin. After 6.5 years, there was no difference in death rates between the two groups. While there were slight benefits of aspirin for heart disease there was also an increase in bleeding problems, particularly as a result of falls.10

A study in the Netherlands showed that the benefits of aspirin do not outweigh the risks for women under the age of 65. Similar to the Japanese study, they found that aspirin decreases risks of cardiovascular disease and colorectal cancer, but increases the risks of gastrointestinal bleeding. The risks gastrointestinal bleeding increases with age, but so does the risk of cardiovascular disease and colorectal cancer. It was determined that at ages greater than 65 the benefit of aspirin therapy is greater than the risk.1112

Patients in other countries may have different genetic make-up or health habits that can influence the risks and benefits of any drug, including aspirin. For that reason, a study of U.S. patients is likely to be the best predictor of the risks and benefits for U.S. patients. It is important to note that the studies showing the benefits to U.S. patients that were described earlier in this article did not look at general health or survival, but rather only looked at specific diseases. The other studies cited above clearly show that it is important to study overall survival to determine if the benefits of aspirin outweighs its risks.  More research is needed to find out if the benefits of aspirin outweigh the risks for men and women in the U.S.


What about taking aspirin every other day? Two of the largest studies of aspirin use for the prevention of cardiovascular disease, the Women’s Health Study (WHS) involving more than 39,000 women, and the Physician’s Health Study (PHS) of more than 22,000 men, had patients take aspirin every other day. The women took 100 mg every other day and the men took 325 mg every other day. Surprisingly, neither study showed a reduction in cancer risk or cancer-related deaths, even after more than 10 years of aspirin therapy. 13,14


Remember that aspirin is a drug, and it has risks even at low doses. You should discuss aspirin therapy first with your doctor and let him or her know:

  • Your medical history and the medicines you are currently using, whether they are prescription or over-the-counter
  • Any allergies or sensitivities you may have to aspirin
  • Any vitamins or dietary supplements you are currently taking

Aspirin should not be taken with certain other over-the-counter pain medications (NSAIDS), such as ibuprofen (Motrin and Advil) and naproxen (Aleve), because they can increase the risk of internal bleeding. But did you know that is also true for several herbs and nutritional supplements?  Vitamin E, fish oil (omega-3 fatty acids) and what’s known as the “four Gs” (garlic, ginger, gingko, and ginseng) can all increase your risk for bleeding when taken with aspirin and other blood thinners.15

Quitting smoking, eating a diet rich in fruits and vegetables, exercising, and avoiding sitting for hours at a time, are great ways to reduce your chance of developing heart disease and cancer without any side effects!   For people at highest risk who can’t make these behavior changes, however, aspirin could be a lifesaver.

If you are taking an anticoagulant such as Coumadin (Warfarin), heparin, Rivaroxaban, dabigatran or apixaban, you should not take aspirin daily because it can increase your risk of bleeding. Patients with mechanical valve replacements may benefit from treatment with both Coumadin and Aspirin, but only under specific instructions from a doctor.

For years, people at high risk for heart attack or stroke have been advised to take a low-dose (81 mg) of aspirin every day. The research on cancer could certainly add to the public’s enthusiasm about low-dose aspirin.  But as shown in the studies described in this article, more research is needed before we can conclude who is most likely to live longer or healthier lives from the daily use of aspirin, and how many years of taking aspirin will maximize the benefits.

  1. National Cancer Institute. NCI-Sponsored Trials of Cyclooxygenase (COX) Inhibitors for Cancer Prevention and Treatment. Accessed March 21, 2012. href=””>  
  2. Hawley SA, Fullerton MD, Ross FA, et al. The Ancient Drug Salicylate Directly Activates AMP-Activated Protein Kinase. Science. 2012; DOI:10.1126/science.1215327.  
  3. Rothwell PM, Wilson M, Elwin CE, et al. Long-term effect of aspirin on colorectal cancer incidence and mortality: 20-year follow-up of five randomised trials. Lancet. 2010;376:1741-50.  
  4. Flossmann E, Rothwell PM. Effect of aspirin on long-term risk of colorectal cancer: consistent evidence from randomized and observational studies. Lancet. 2007;369:1603-13.  
  5. Rothwell PM, Folkes FG, Belch JF, et al. Effect of daily aspirin on long-term risk of death due to cancer: analysis of individual patient data from randomised trials. Lancet. 2011;377:31-41.  
  6. Rothwell PM, Wilson M, Price JF, et al. Effect of daily aspirin on risk of cancer metastasis: a study of incident cancers during randomised controlled trials. Lancet. 2012;DOI:10.1016/S0140-6736(12)60209-8.  
  7. Rothwell PM, Price JF, Fowkes FG, et al. Short-term effects of daily aspirin on cancer incidence, mortality, and non-vascular death: analysis of the time course of risks and benefits in 51 randomised controlled trials. Lancet. 2012;DOI:10.1016/S0140-6736(11)61720-0.  
  8. FDA. Aspirin: Questions and Answers. Accessed March 27, 2012. href=””>  
  9. Angus Chen, class=”il”>Aspirin Both Triggers And Treats An Often-Missed Disease.” NPR, March 21, 2016.  
  10. href=”″>  
  11. href=””>  
  12. href=”″>  
  13. Cook NR, Lee IM, Gaziano JM, et al. Low-dose aspirin in the primary prevention of cancer: the Women’s Health Study: a randomized controlled trial. JAMA. 2005;294:47-55.  
  14. Sturmer T, Glynn RJ, Lee IM, et al. Aspirin use and colorectal cancer: post-trial follow-up data from the Physician’s Health Study. Ann Intern Med. 1998;128:713-20.  
  15. MedlinePlus: Drugs, Supplements, and Herbal Information. Accessed March 30, 2012. href=””>