One hundred and forty seven trials met the inclusion criteria (n=464,164): 92 were placebo controlled; 16 had no treatment controls; and 46 were active comparisons. Nearly a third of included trials were either single-blind or unblinded. Drop-out rates ranged from 0 to 20%.
Beta-blockers significantly reduced the risk of coronary events in patients with a history of coronary heart disease (RR 0.71, 95% CI: 0.66, 0.78, 37 trials) and after an acute myocardial infarction (RR 0.69, 95% CI: 0.62, 0.76, 27 trials), but not in patients with a long-term (11 trials) or no history (six trials) of coronary heart disease. All non-beta-blocker drugs combined showed a significant reduction in the risk of coronary events in patients with a history of coronary heart disease (RR 0.85, 95% CI: 0.81, 0.89, 64 trials).
With a reduction of 10mmHg in systolic, or 5mmHg in diastolic blood pressure, drugs significantly reduced the risk of coronary events (RR 0.78, 95% CI: 0.73, 0.83, 71 RCTs) and strokes (RR 0.59, 95% CI: 0.52, 0.67, 45 RCTs) compared to placebo. Results were reported separately for: patients with no history of vascular disease, or a history of coronary heart disease or stroke; different classes of drug; different baseline systolic and diastolic blood pressure.
Trials with active comparators showed no benefit of any one drug over another in the prevention of coronary events. For the prevention of stroke, calcium channel blockers had a greater preventative effect than other drugs (RR 0.91, 95% CI: 0.84, 0.98, 25 RCTs), and beta-blockers a less protective effect (RR 1.18, 95% CI: 1.03, 1.36, 13 RCTs).
Results of meta-analyses of cohort studies were presented alongside those from the current meta-analysis for comparison (see Other Publications of Related Interest).