Low-dose aspirin may not be effective in preventing cardiovascular events in people weighing 70 Kg (154 pounds) or more, a Lancet study suggests. Researchers analysed 10 trials that evaluated aspirin versus controls for primary prevention of cardiovascular events in 120,000 people.

Daily, low-dose aspirin (75–100 mg) was associated with reduced risk for cardiovascular events among those weighing less than 70 kg (odds ratio, 0.77), but there was no significant effect for heavier patients — roughly 80% of men in the study and nearly half of women weighed 70 kg or more. In the heavier group, low-dose aspirin may be even less effective in smokers and in those who take enteric-coated aspirin.

High-dose aspirin (300–325 or 500 mg), meanwhile, appeared to be effective in reducing primary cardiovascular events only patients weighing 70 kg or more (OR, 0.79).

The authors conclude: "A one-dose-fits-all approach to aspirin is unlikely to be optimal, and a more tailored strategy is required."