Methods Pooling the individual patient data from all randomised trials of aspirin versus control in secondary
prevention after TIA or ischaemic stroke, we studied the effects of aspirin on the risk and severity of recurrent stroke,
stratifi ed by the following time periods: less than 6 weeks, 6–12 weeks, and more than 12 weeks after randomisation.
We compared the severity of early recurrent strokes between treatment groups with shift analysis of modifi ed Rankin
Scale (mRS) score. To understand possible mechanisms of action, we also studied the time course of the interaction
between eff ects of aspirin and dipyridamole in secondary prevention of stroke. In a further analysis we pooled data
from trials of aspirin versus control in which patients were randomised less than 48 h after major acute stroke,
stratifi ed by severity of baseline neurological defi cit, to establish the very early time course of the eff ect of aspirin on
risk of recurrent ischaemic stroke and how this diff ers by severity at baseline.