The use of low doses of aspirin is known to decrease the risk of both colorectal cancer (CRC) and cardiovascular disease (CVD). On the other hand, chronic aspirin use can also cause gastrointestinal (GI) bleeding which can be severe. So how should one make the decision as to whether or not to use aspirin?
In order to provide insights into this important question, Dr. Rob C M van Kruijsdijk of the University of Utrecht, the Netherlands and colleagues used data on nearly 29,000 healthy women who participated in the Women s Health Study (WHS). These women had been randomly assigned to receive either 100 mg aspirin on alternate days, or a placebo.
Using data from the WHS, the researchers developed models of risk reduction for primary prevention (that is, before these conditions developed) of CVD, cancer, and major gastrointestinal bleeding for women who had been followed for a median of 18 years. In particular, they wanted to ascertain whether the combined benefits for cancer and CVD outweighed the increase in bleeding events associated with chronic aspirin use, and which women would be most likely to benefit from its use.
Overall, the participants had a predicted 15-year risk of 11.4 percent for all adverse outcomes. Aspirin use, the investigators found, increased the risk of adverse outcomes by 0.42 percent an increase that was not statistically significant. However, when examining the risks in women 65 years old or older, they found a significant protective effect of aspirin on CVD of about 3 percent. There was also an increased risk of GI bleeding, but this increase was smaller than the benefit for CVD prevention.
The investigators summarized their results thusly: Although aspirin was associated with a modestly decreased 15-year risk of CVD and colorectal cancer, aspirin treatment resulted in small benefit or even harm in the majority of women if gastrointestinal bleeding were also taken into account. Age was the most important determinant for benefit of aspirin treatment; this was also reflected by the observation that treating only women ¥65 years of age resulted in a higher net benefit with regard to the combined outcomes compared to other treatment strategies, including prediction-based treatment.
ACSH s Dr. Gilbert Ross commented These results provide some insights into how to decide which women are most likely to benefit from the use of low-dose aspirin, while minimizing the possible negative effect of GI bleeding. Of course, he continued, other factors such as other CVD and bleeding risk factors, and family history, must also be taken into account when making such a decision.