A Cochrane review included 5 studies with a total of 2313 subjects without prior cerebral ischaemia (mean age 69 years). About half of participants were randomized to adjusted-dose warfarin with mean achieved INRs ranging between 2.0 to 2.6. During 1.5 years mean follow up, warfarin was associated with large, highly statistically significant reductions in all strokes (odds ratio (OR) 0.39, 95% confidence interval (CI) 0.26 to 0.59), ischemic stroke (OR 0.34, 95% CI 0.23 to 0.52), all disabling or fatal stroke (OR 0.47, 95% CI 0.28 to 0.80), death (OR 0.69, 95% CI 0.50 to 0.94) and the combined endpoint of all stroke, myocardial infarction or vascular death (OR 0.56, 95% CI 0.42 to 0.76). Intracranial or extracranial hemorrhage rates were not significantly increased but the confidence intervals were wide.
Comment: The low rates of serious bleeding observed in these trials may reflect patient selection, careful management of oral anticoagulation, and relatively low target INR ranges. Limitations include relatively short follow up and imprecise estimates of bleeding risks from the selected participants enrolled in the trials.
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