In healthy adults aged 70 or older, taking 100 mg of aspirin daily for about 8 years is associated with a 24% higher risk of serious bleeding compared to not taking aspirin, and this increased...
Mechanism
Synthesis from 1 study
Aspirin weakens the stomach's natural defenses and makes blood less able to clot. In older people, this combination makes serious bleeding much more likely because their stomach lining is more fragile and their blood vessels are more prone to rupture. The bleeding risk stays high as long as aspirin...
Most probable mechanism
Taking aspirin daily blocks the body's ability to make protective chemicals in the stomach lining and reduces the stickiness of blood platelets. Without these protective chemicals, the stomach lining becomes more vulnerable to damage from stomach acid, leading to bleeding. At the same time, the reduced platelet stickiness makes it harder for blood to clot anywhere in the body, so even minor injuries or weak blood vessels can cause serious bleeding. In older adults, blood vessels are more fragile and the stomach lining is already thinner, so these effects combine to make major bleeding much more likely.
Aspirin irreversibly inhibits cyclooxygenase-1 in gastric epithelial cells, suppressing synthesis of cytoprotective prostaglandins PGE2 and PGI2
Reduced prostaglandin levels impair mucus secretion, bicarbonate neutralization, and mucosal blood flow, increasing susceptibility to acid-induced erosion and ulceration
Aspirin irreversibly acetylates cyclooxygenase-1 in platelets, inhibiting thromboxane A2 production and reducing platelet aggregation
Impaired platelet function and compromised gastric mucosal integrity together increase the likelihood of clinically significant bleeding events
Less supported by current evidence, but not ruled out
After stopping aspirin, the body produces more clot-promoting chemicals than before, which can cause sudden clot formation in arteries. These clots can damage blood vessel walls and increase pressure, potentially triggering bleeding elsewhere as a secondary effect.
After aspirin cessation, newly formed platelets with active cyclooxygenase-1 enter circulation, restoring and transiently exceeding baseline thromboxane A2 production
Elevated thromboxane A2 enhances platelet aggregation and vasoconstriction, promoting arterial thrombosis and endothelial injury
Thrombotic events cause vascular inflammation and mechanical stress on vessel walls, potentially contributing to rupture or secondary hemorrhage
Evidence from Studies
Supporting (1)
Community contributions welcome
Aspirin, cardiovascular events, and major bleeding in older adults: extended follow-up of the ASPREE trial
Contradicting (0)
Community contributions welcome
Gold Standard Evidence Needed
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