1. Absolute risk reductions of aspirin treatment in acute stroke.
| Outcome | Control event ratea |
No of events avoidedb (per 1000 people treated (95% CI)) |
NNTB or NNTHb |
| Death or dependence at end of follow‐up | 0.47 | 13 (3 to 23) | NNTB 79 (43 to 400) |
| Deaths from all causes during follow‐up | 0.13 | 9 (2 to 15) | NNTB 108 (66 to 436) |
| Pulmonary embolism during treatment period | 0.01 | 1 (0 to 2) | NNTB 693 (427 to 6700) |
| Recurrent ischaemic/unknown stroke during treatment period | 0.03 | 7 (4 to 10) | NNTB 140 (104 to 248) |
| Symptomatic intracranial haemorrhage during treatment period | 0.01 | −2 (i.e. 2 extra) (−4 to 0) | NNTH 574 (254 to 126,010) |
| Any recurrent stroke/intracranial haemorrhage during treatment | 0.04 | 5 (1 to 8) | NNTB 200 (123 to 868) |
| Major extracranial haemorrhage during treatment period | 0.01 | −4 (i.e. 4 extra) (−7 to −2) | NNTH 245 (153 to 481) |
| Complete recovery from stroke (post hoc) | 0.26 | 11 (2 to 21) | NNTB 89 (49 to 523) |
CI: confidence interval; NNTB: number needed to treat for an additional beneficial outcome; NNTH: number needed to treat for an additional harmful outcome.
aEstimated from the mean of the control event rate in the two largest trials (CAST 1997; IST 1997). bEstimated by applying the Peto odds ratio for the outcome for studies of aspirin. Calculator is available at: www.dcn.ed.ac.uk/csrg/entity/entity_NNT2.asp.