The Potential Dangers of Preventative Aspirin Therapy

Do you regularly take aspirin in the hopes of preventing cardiovascular (heart and blood vessel) disease and cancer? You may want to rethink this: A recent study finds that for most people, the risks outweigh the benefits.

This study, published in the journal Heart, reports that "aspirin only moderately lowers cardiovascular risk, while increasing the risk of major gastrointestinal (GI) bleeding." The study evaluated the benefits of 100 mg (milligrams) of aspirin every other day in women 45 and older who did not have heart disease. The results indicated that once you consider the risk of GI bleeding, the most pronounced side effect of ongoing aspirin use, the risks outweighed the small benefits of cardiovascular and cancer prevention for women younger than 65.

Major GI bleeding is associated with anemia (low red blood cell count), dehydration, blood loss, shock and even death.

"The study did not support aspirin at 100mg every other day in all women," says Kirk Heyne, MD, a medical oncologist at Houston Methodist Hospital. "The study authors then dissected the data until they got a positive answer, which is restricting use only to women older than 65."

What the Numbers Mean

Physicians would have to treat 29 women before one would benefit from aspirin every other day, Heyne explains. And when 29 women are treated—and one person is saved from heart disease, stroke, and cancer—another will have major gastrointestinal bleeding.

Heyne also says most of the benefit is a reduction in cardiovascular disease, not colon cancer; 92 women would have to be treated with aspirin before one would benefit from the intervention, or not develop colon cancer.

This study is actually a continuation of a 2005 study, which found that aspirin was not helpful in women 45 and older who did not already have heart disease, explains Gregory S. Thomas, MD, MPH, FACC, FASNC, Medical Director of the MemorialCare Heart & Vascular Institute in Long Beach, CA.

"In the current study, the researchers followed the same patients for a longer time and tried to determine if there was a subgroup for whom aspirin was beneficial. They found a very mild potential benefit in women older than 65. However, when one looks 'backward' at the data and finds that a drug such as aspirin is helpful, it might just be chance," Thomas says. "However, this does not appear to be true, given the recent announcement of the results of a large trial in Japan."

The Japan study he refers to reported that cardiovascular disease is declining due to lifestyle changes (for example, more physical activity and less smoking) and medications (such as statins to lower cholesterol), Thomas explains. However, the risks of aspirin-related bleeding have not changed, so the net benefit of aspirin use is lower.

Furthermore, because the participants in the Heart study were wealthier, more educated women who likely have better lifestyle habits, the authors caution their results may not apply to the general population.

What The Data Mean for You

"The take home message for me, based on this study and other large well performed trials, is that aspirin is no longer of benefit in patients without evidence of disease," says Thomas. "Once vascular [blood vessel] disease has occurred, such as partial blockages of the arteries to the heart, brain, or legs, then I recommend aspirin unless a patient is at high risk of bleeding."

Gregory S. Thomas, MD, MPH, FACC, FASNC, Medical Director at MemorialCare Heart & Vascular Institute, reviewed this article.


Gregory S. Thomas, MD, MPH, FACC, FASNC. Medical Director, MemorialCare Heart & Vascular Institute, Long Beach Memorial Medical Center, Miller Children's Hospital of Long Beach, Clinical Professor & Director of Nuclear Cardiology Education, University of California, Irvine. Email message to author, January 30, 2015.

Kirk Heyne, MD. Medical oncologist at Houston Methodist Hospital. Email message to author. January 26, 2015.

Rob C.M. van Kruijsdijk, Frank L.J. Visseren, Paul M. Ridker, Johannes A.N. Dorresteijn, Julie E. Buring, Yolanda van der Graaf, Nancy R Cook. "Individualised Prediction of Alternate-Day Aspirin Treatment Effects on the Combined Risk of Cancer, Cardiovascular Disease and Gastrointestinal Bleeding in Healthy Women." Heart Online First, published on December 4, 2014 as 10.1136/heartjnl-2014-306342.