Twenty eligible trials were found and 13 trials, with 80,594 patients (11,005 events), were analysed. No subgroup data were available for the seven trials, with 12,418 patients (1,618 events), which were not analysed. All trials included blinding of the outcome assessor. Individual patient data were available for 10 trials and three trials provided summary data by baseline systolic blood pressure.
There were statistically significant reductions in all outcomes, except death from any cause, which approached statistical significance. For example, the odds ratio for the composite outcome was 0.89 (95% CI 0.85 to 0.93; Ι²= 25%).
There were no statistically significant differences between subgroups on any outcome, except cardiovascular death. There was a greater risk of cardiovascular death in those with a systolic blood pressure less than 130mmHg (OR 0.83, 95% CI 0.75 to 0.91; Ι²=9%).
There was no statistically significant evidence of associations with the effectiveness of the intervention for age, baseline systolic blood pressure, degree of systolic blood pressure reduction during the trial, and duration of the trial. There was consistent benefit for those without diabetes and those without systolic heart failure.
Sensitivity analyses showed that the pooled results were similar for trials that were excluded due to a small sample size, or because no systolic blood pressure subgroup data were available. There was no evidence of publication bias.