Study designs of evaluations included in the review
Randomised controlled trials (RCTs) were eligible for inclusion.
Specific interventions included in the review
Trials comparing a statin with a placebo, active control (except comparisons of high- and low-dose statins) or usual care control group were eligible for inclusion, provided that the only intervention difference between the groups was the use of statin. The included studies were of pravastatin (20 to 40 mg/day), lovastatin (20 to 40 mg/day), atorvastatin (10 mg/day) and simvastatin (40 mg/day). Apart from one study with a usual care control group, all of the studies compared statin with placebo.
Participants included in the review
Trials where at least 80% of participants were not known to have cardiovascular disease (defined as coronary artery disease, cerebrovascular disease and peripheral vascular disease) were eligible for inclusion. Studies targeted at patients with conditions that were not traditional risk factors for cardiovascular disease, such as dialysis patients, were excluded, as were studies that used ultrasound to pre-screen for atherosclerosis. In the included studies, 90% of patients had no evidence of cardiovascular disease. The mean low-density lipoprotein cholesterol (LDL-C) values ranged from 117 to 193 mg/dL. The mean age of the participants ranged from 55 to 75 years and in most studies the majority of participants were male. The participants were classified as being mainly at moderate or moderately high risk of a cardiovascular event.
Outcomes assessed in the review
Trials with a mean follow-up of at least one year and reporting at least 100 cardiovascular disease outcomes were eligible for inclusion. The primary outcomes of interest were major coronary events (nonfatal myocardial infarction and coronary heart disease death) and major cerebrovascular events (fatal and nonfatal strokes). The secondary outcomes were death from any cause, coronary heart disease death, nonfatal myocardial infarction, revascularisations and adverse outcomes. The mean length of follow-up in the included studies ranged from 3.2 to 5.2 years.
How were decisions on the relevance of primary studies made?
The authors did not state how the papers were selected for the review, or how many reviewers performed the selection.