Low-Dose Aspirin: Who Should Take It and Why

Primary vs Secondary Prevention

How to Take Aspirin Safely

• Take with food or milk to reduce stomach irritation
• Enteric-coated (EC) tablets are gentler on the stomach
• Never take aspirin with ibuprofen: ibuprofen blocks aspirin's antiplatelet effect
• Tell your dentist and all doctors you take daily aspirin

Why the advice on primary prevention changed

For decades low-dose aspirin was widely recommended to healthy adults to prevent a first heart attack. That advice has been substantially withdrawn. A 2019 meta-analysis of 20 randomised controlled trials involving 144,930 individuals without established cardiovascular disease found that aspirin reduced the risk of non-fatal heart attack by 21%, but had no statistically significant effect on cardiovascular death and increased the risk of major bleeding by 48%.² This includes the ARRIVE, ASCEND, and ASPREE trials. In people with diabetes specifically, the same analysis found aspirin had no benefit on heart attack or cardiovascular death, yet still increased bleeding by 49%. Several guidelines now advise against routine aspirin for primary prevention, particularly over the age of 70, and recommend an individual discussion where risk is high and bleeding risk is low.

The mechanism behind the bleeding risk is pharmacological. Aspirin irreversibly inhibits COX-1, the enzyme platelets use to make thromboxane A2, a clotting signal. Since platelets have no nucleus, they cannot regenerate COX-1, so the inhibition lasts the full 7–10 day platelet lifespan. The same COX-1 pathway in the stomach lining makes prostaglandins that protect against ulceration, and blocking it there raises the risk of gastric erosion and bleeding, independent of any antiplatelet effect.

The picture is quite different in secondary prevention. In people who have already had a heart attack, ischaemic stroke, or who have known coronary or peripheral arterial disease, the benefit clearly exceeds the bleeding risk and aspirin remains standard long-term therapy. If you are taking aspirin and are not sure which category applies to you, that is a worthwhile question to raise, because the answer determines whether continuing is appropriate.

Reducing the bleeding risk

• A proton pump inhibitor substantially reduces gastrointestinal bleeding and is recommended for those at higher risk, including older adults and anyone with previous ulcer disease.
• Avoiding concurrent NSAIDs, which multiply the ulcer risk; ibuprofen also interferes with aspirin's antiplatelet effect when taken shortly before it.
• Limiting alcohol, which independently raises gastrointestinal bleeding risk.
• Testing and treating Helicobacter pylori in those with ulcer history before long-term therapy.

Around surgery and dental work

Aspirin is frequently continued through minor procedures, including most dental extractions, cataract surgery and skin procedures, because the risk of stopping in someone with established cardiovascular disease can exceed the bleeding risk of continuing. Stopping is sometimes required for surgery with a high bleeding risk or where bleeding into a closed space would be serious. Because aspirin irreversibly inhibits platelets for their lifespan, an interruption of around seven days is needed for full recovery of platelet function. This decision belongs with the team performing the procedure together with your prescriber, and should not be taken unilaterally.

Warning signs while taking it

Black tarry stools, vomiting blood or material resembling coffee grounds, unexplained bruising, prolonged nosebleeds, or new severe headache all warrant prompt medical attention. Unexplained iron deficiency anaemia in someone taking long-term aspirin should prompt investigation for occult gastrointestinal bleeding rather than iron replacement alone.

References

The clinical information on this page is drawn from peer-reviewed sources indexed by the US National Library of Medicine. Links go to the source so you can read it yourself.

1. Salicylic Acid (Aspirin). In: StatPearls. Treasure Island (FL): StatPearls Publishing. NCBI Bookshelf NBK519032
2. Christiansen M, Grove EL, Hvas AM. Primary Prevention of Cardiovascular Events with Aspirin: Toward More Harm than Benefit – A Systematic Review and Meta-Analysis. Semin Thromb Hemost. 2019;45(5):478–489. PMID 31096304 · doi:10.1055/s-0039-1687905