Blind and non-blinded trials were included, as were studies of primary and secondary prevention. Because ischaemic and haemorrhagic strokes were not reliably distinguished in many of the trials, 'all strokes' was used as the main outcome. The number of intracranial and extracranial bleeds, and all-cause mortality data was also collected. There were six trials with 2900 patients and 186 strokes. This means that 18 patients have to be treated with adjusted-dose warfarin for 1.6 years to prevent one stroke that would have occurred without treatment.
Shaded area indicates harm from major extracranial bleeds.
Aspirin versus placebo There were six trials with 3225 patients and 349 strokes. This means that 48 patients have to be treated with aspirin for 1.5 years to prevent one stroke that would have occurred without treatment. All-cause mortality was not significantly reduced by aspirin. There were six trials with 2837 patients and 205 strokes. This means that 35 patients have to be treated with adjusted-dose warfarin for 2.2 years to prevent one stroke that would have occurred with aspirin.