Nineteen RCTs (n=16,283, range 26 to 8,832) and eight cohort studies (n=212,171) were included in the review. Twelve RCTs were double-blinded, one single-blinded and six open label; dropout rates ranged from 4% to 41% across groups.
Using a non-informative prior distribution, risk of mortality in the RCTs was significantly lower in the intervention group compared to placebo (RR 0.73, 95% CrI 0.52 to 0.96); posterior probability of a mortality benefit from hormone therapy was 0.985.
When the cohort data were pooled and combined with the RCT data, resultant relative risk using an informative prior distribution was 0.72 (95% CrI 0.62, 0.82); posterior probability of a mortality benefit from hormone therapy was 1.00.
There was wide variation between studies (for example in trial size, medicines used, methods of administration and populations), but little inter-study heterogeneity was observed in the results. Funnel plots did not show evidence of publication bias.
Results for analyses based on different prior distributions were reported in the review.