A systematic review 1 including 24 studies with a total of 65 987 subjects was abstracted in DARE.
All 24 trials were double-blind and placebo-controlled. Gastrointestinal haemorrhage occurred in 2.47% of patients taking aspirin compared with 1.42% taking placebo (OR 1.68, 95% CI1.51 to 1.88). The NNH was 106 (95% CI 82 to 140), based on an average of 28 months therapy.
At doses below 163 mg/day, gastrointestinal haemorrhage occurred in 2.30% of patients taking
aspirin, compared with 1.45% taking placebo (OR 1.59, 95% CI 1.40 to 1.81). Meta-regression showed no relation between gastrointestinal haemorrhage and dose. Omitting the two largest trials did not significantly change the results.
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