Don't Skip Taking Aspirin After a Heart Attack, Scientists Suggest

New research suggests that for those who have experienced a heart attack, not taking aspirin as prescribed by a healthcare provider could raise the risk of a second heart attack, stroke, or death.

Most experts agree that aspirin for heart attack prevention could be risky for people without cardiovascular disease risk factors — primarily because the risks of bleeding associated with aspirin may outweigh the potential benefits.

However, it's a different story for those who have had a heart attack or myocardial infarction. For these individuals, healthcare providers often prescribe a daily low-dose (81 mg) aspirin to help prevent another heart attack by stopping blood clots from forming.

But some people may not adhere to their healthcare provider's advice and choose to stop taking the suggested pill. However, not much is known about whether discontinuing the drug could cause another heart attack, stroke, or death.

In new research to be presented on August 28 at the European Society of Cardiology Congress 2023, researchers used data from nationwide registries in Denmark to determine the outcomes of continuing and discontinuing aspirin therapy after a heart attack.

The researchers looked at 40,114 people aged 40 and older who had experienced a first-time heart attack. The participants had coronary stents placed and took aspirin as their healthcare provider prescribed during the first year after their cardiac event.

The researchers did not include people who took anticoagulants or had a stroke within that first year.

After evaluating adherence to daily aspirin therapy at years two, four, six, and eight after the participants' heart attack, the scientists found that adherence to aspirin progressively declined as time went on. For example, 90% of the participants continued aspirin therapy for two years following the heart attack, but that number fell to 84% at four years, 82% at six years, and 81% at eight years.

Then, the team assessed the participants' risks of recurrent heart attack, stroke, or death. They also considered factors that might influence these risks, such as age, high blood pressure, and high cholesterol.

The researchers discovered that non-adherent participants had a higher risk of having another heart attack, stroke, or death than those who continued taking daily aspirin.

Specifically, people with a previous heart attack who discontinued aspirin had a 29% increased risk of heart attack, stroke, or death at year two, a 40% increased risk at year four, a 31% increased risk at year six, and a 20% higher likelihood at year eight.

The researchers considered participants taking aspirin more than 80% of the time as adherent to aspirin therapy, and those who took it 80% or less were classified as non-adherent.

"Our results should be interpreted with caution because they show an association but do not establish causality. Since the study is registry-based, we do not have information about the specific reasons as to why patients did not take their aspirin," said study author Anna Meta Kristensen of Bispebjerg and Frederiksberg Hospital in Frederiksberg, Denmark, in a news release.

Kristensen also explained that the findings could not be generalized to all people who have experienced a heart attack because the participants in this study received stents and did not take other medications to prevent blood clots.

Still, Kristensen adds, "Our findings suggest that not taking aspirin as prescribed after a heart attack is linked to a higher risk of having another heart attack, a stroke, or dying. We recommend that all patients who have had a heart attack stay adherent to their aspirin in accordance with guidelines until randomized controlled trials have proven otherwise, and clinical guidelines have been changed."