Meta-analysis: Healthy people don’t need to take aspirin to prevent heart disease
People with heart disease should continue to take the medicine, but for healthy individuals the side effects are so severe that they cancel out the good effect.
“The value of taking aspirin to prevent heart disease is very limited if you’re healthy to begin with. It has no effect on mortality – either overall mortality or cardiovascular mortality,” says Sigrun Halvorsen.
Halvorsen heads the department of cardiac medicine at Oslo University Hospital and is a professor at the University of Oslo. She is one of the researchers behind the new European meta-analysis where researchers have reviewed 13 large studies with data on over 160 000 patients.
Halvorsen says the new review confirms much of what other recent studies have shown. The meta-analysis has been published in BMC Medicine.
Less heart disease, more bleeding
Aspirin, also known as acetylsalicylic acid, reduces the risk of cardiovascular disease. The problem, however, is that the danger of bleeding increases. Blood coagulates poorly and wounds heal less well, both externally and inside the body.
The new meta-analysis shows that aspirin reduced the risk of severe heart failure by nine per cent. Heart attack risk was reduced by fourteen per cent and the risk of stroke was reduced by ten per cent. At the same time, the risk of bleeding increased by 46 per cent.
The researchers conclude that increased risk of bleeding more or less cancels out the gains.
“But it can be difficult to weigh the different events against each other and determine what the worst risk is,” says Halvorsen.
The researchers behind the new study believe that patients must be included in decision-making and participate in the assessment.
Aspirin as preventive measure not recommended
The use of aspirin as a primary preventive measure – that is, to prevent heart disease in people who were not ill to begin with – has been a common practice.
The reasons for this include family heart disease, high stress levels and high cholesterol in men in their 50s and 60s.
“In recent years though, this treatment has been increasingly debated, and there have been warnings against giving aspirin preventively . Over the past year several major studies have looked at the benefits of aspirin and who should be given aspirin preventively. We’ve now incorporated these studies into our meta-analysis,” says Halvorsen.
In this meta-analysis, the researchers wanted to look more closely at whether taking aspirin would benefit some population groups sufficiently to outweigh the bleeding risk.
“Our meta-analysis shows that the people who could benefit the most from aspirin are non-smokers, people who use statins, and men. But it’s still not clear whether the benefits would outweigh the disadvantages, so these findings are primarily hypothesis generating at this point,” Halvorsen says.
People with diabetes, who are at low risk of bleeding, have previously been shown to possibly benefit from taking aspirin preventively.
Works poorly for smokers
The researchers note in the study that, interestingly, aspirin appears to have less effect on smokers than on non-smokers. Similar findings have also been made in the past.
The study also shows that aspirin as a preventive treatment for heart disease is most effective for men and for patients using statins as treatment for high cholesterol.
The study also points out that patients with diabetes are at increased risk of cardiovascular disease, and therefore aspirin has a greater preventive effect in these patients.
In terms of whether this study could influence who should take aspirin preventively in the future, Halvorsen says the study shows that there is no convincing basis for people without heart disease to use aspirin.
“But at the same time, we can’t rule out that some patients might benefit from taking aspirin, and the group that might benefit the most are people with diabetes. New European guidelines state that diabetic patients with a high risk of heart attack, who don’t have a high bleeding risk, can take aspirin,” she says.
Effective for acute heart disease
A debate also arose earlier this fall about whether people should keep aspirin at home, in case of a heart attack. Steinar Madsen, medical director of the Norwegian Medicines Agency, told NRK (The Norwegian Broadcasting Corporation) that it was advisable to always have an aspirin on hand in case of a heart attack.
“If an acute myocardial infarction occurs, it’s good to take acetylsalicylic acid as soon as possible,” says Halvorsen.
She also emphasizes that all patients who have demonstrated heart disease should take aspirin as a preventive treatment against new heart attacks and strokes, and most heart patients should continue with aspirin indefinitely.
No need to change recommendations
Madsen is also a cardiologist and says the new meta-analysis confirms recent research on the use of aspirin for preventing cardiovascular disease.
"Taking low doses of acetylsalicylic acid shows a small positive effect on cardiovascular events, but also a clear increase in bleeding," says Madsen.
He points out that most guidelines have taken this into consideration and do not currently recommend acetylsalicylic acid as a preventive treatment.
“Although this study finds some groups that show a greater positive effect, it’s hardly enough reason to change the recommendations,” he says.
The Norwegian guidelines from 2017 (in Norwegian) provide a weak recommendation for the use of acetylsalicylic acid (ASA) in primary prevention of cardiovascular disease. They state that ASA should rarely be used preventively. However, in patients with particularly high risk and limited opportunities for other preventive measures, ASA can still be considered – after weighing the reduced risk against increased bleeding risk.
Reduction in aspirin use
Madsen emphasizes that the drug still has an important role to play for anyone with atherosclerosis.
He also points out that the use of acetylsalicylic acid in Norway has declined in recent years.
In 2012, there were around 380 000 users as compared to around 359 000 users in 2018.
“We’ve seen a steady increase from 2004 to 2012, followed by a steady decline. There are several explanations for the decline, including that we now have new blood thinners and new anti-platelet drugs. But overall, the decline also probably indicates that fewer patients are placed on ASA as a primary prevention of cardiovascular disease,” says Madsen.
Georg Gelbenegger et al: Aspirin for primary prevention of cardiovascular disease: a meta-analysis with a particular focus on subgroups, BMC Medicine, November 2019.