Ask the doctors: Recent studies call into question use of low-dose aspirin

Dear Doctor: Our dad had a mild stroke about a year ago and has been taking daily low-dose aspirin ever since. But I just heard about a new study that says this kind of therapy isn’t actually helpful and might even be dangerous. Is this true? Should he stop? I’m confused!

Dear Reader: We’ve been hearing from patients (and some friends and family) that they’re also confused by the new aspirin study you’re referring to. The truth is that while low-dose aspirin has indeed been associated with improved health outcomes for individuals like your father who have previously experienced a stroke or a heart attack, the idea of aspirin therapy as a hedge against cardiovascular disease in healthy adults has always been under debate. Now, a trio of studies published in September in the New England Journal of Medicine pave the way for a clearer understanding of the effects of low-dose aspirin therapy.

In the main study, which lasted about five years, researchers in Australia looked at the effects of low-dose aspirin therapy in 20,000 people with a median age of 74. Each person was in good health at the time that he or she entered the study, without a history of heart disease. Unlike the observational studies we’ve discussed lately, which draw conclusions from data in which variables are not under the researchers’ control, this was a randomized, double-blind, placebo-controlled trial. That means that half of the study participants took aspirin and half took a placebo. Study participants were randomly assigned to the two groups, and the double-blind part means that neither the participants nor the researchers knew which group was getting aspirin and which was getting the placebo.

Bottom line: This is the best type of study to figure out whether a specific exposure, in this case aspirin, is directly responsible for a particular outcome.

When the study was concluded, it turned out there was no observable difference in “disability-free survival” between the two groups. That is, low-dose aspirin therapy did not deliver additional health protections. What was different between the two groups was that over the course of the study, the participants taking low-dose aspirin had a measurably higher incidence of bleeding, some of it life-threatening. This finding was corroborated by two additional studies, which uncovered a higher risk of major hemorrhage among the aspirin group, as well as a higher incidence of “all-cause mortality.” The authors of the studies appear to be somewhat surprised by the results, which they called “unexpected.”

It’s important to keep in mind that the participants in these studies were all healthy adults without heart disease or stroke. However, for those individuals who have already had a heart attack or stroke, or who do have cardiac disease and other comorbidities, such as diabetes, there is significant data to support aspirin use. It is our opinion that those patients should not stop their aspirin regimens based on these findings.