Ref (type)	Population	Outcome, Interventions	Results and statistical analysis	Effect size	Favours
Pain
Systematic review	Women with primary dysmenorrhoea 5 RCTs in this analysis	Proportion of women with at least moderate pain relief with aspirin with placebo Absolute results reported graphically	RR 1.60 95% CI 1.12 to 2.29 NNT 10 95% CI 5 to 50 The figure reported in the text (RR 1.60, 95% CI 1.12 to 2.29) differed slightly from the figure reported in the graph (RR 1.60, 95% CI 1.12 to 3.63)	Small effect size	aspirin
Systematic review	96 women Data from 1 RCT	Pain intensity, continuous data: mean difference final scores (4–5 point scales) with aspirin with placebo Absolute results not reported	Mean difference 0.0 95% CI –0.72 to +0.72 P = 1.0		Not significant
Systematic review	47 women Data from 1 RCT	Number of cycles where treatment gave moderate/good pain relief 13/89 (15%) with aspirin 9/90 (10%) with placebo	Reported as not significant P value not reported These data are per cycle rather than by participant		Not significant
Need for additional medication
Systematic review	205 women with primary dysmenorrhoea 3 RCTs in this analysis	Need for additional medication with aspirin with placebo Absolute results not reported	RR 0.79 95% CI 0.58 to 1.08		Not significant
Systematic review	96 women Data from 1 RCT	Additional analgesics required with aspirin with placebo Absolute results not reported	OR 0.72 95% CI 0.18 to 2.86 P = 0.64		Not significant