Eighteen randomised controlled trials (141,235 participants; 40,275 women) were included in the review. There were 13,710 deaths (3,898 deaths in studies with sex-specific mortality data). All trials were randomised, reported allocation concealment, defined eligibility, had similar baseline characteristics, used intention-to-treat analyses and reported adherence details (between 63% and 98.8%). Three trials were not double blind. Seventeen trials were funded by the pharmaceutical industry. Follow-up ranged from 22.8 to 80.4 months.
On average, 85.5% (standard deviation 9.9%) of patients who were allocated to active treatment received it compared to 17.2% (standard deviation 9.9%) of patients in control groups.
Primary endpoints: Statin therapy statistically significantly reduced primary endpoints in women (OR 0.81, 95% CI 0.75 to 0.89) and men (OR 0.77, 95% CI 0.71 to 0.83). There was a non-significant trend towards greater benefit in men.
Sensitivity analysis did not significantly alter the findings. Analyses by type of prevention, level of baseline risk and type of endpoint did not significantly alter the findings. Meta-regression indicated factors that may influence the observed differences between women and men: percentage of men, percentage with cardiovascular disease, percentage of smokers, percentage taking aspirin and mean age.
All-cause mortality: Statin therapy reduced all-cause mortality in women (OR 0.90, 95% CI 0.82 to 0.99) and men (OR 0.84, 95% CI 0.77 to 0.92). Findings were similar in women when primary prevention trials were analysed separately but not for secondary prevention trials. The opposite was true for men.
The authors suggested there may be potential for publication bias.