Eligible studies were randomised controlled trials that compared one or more antihypertensive drugs to each other or to no active treatment. Included drugs had to be in the classes: diuretics, beta-blockers, calcium-channel blockers, angiotensin converting enzyme inhibitors, angiotensin receptor blockers and alpha-blockers. Trials had to report cardiovascular morbidity or mortality as a primary outcome. Trials where at least half of the participants had a prior cardiovascular event were excluded. Trials in specific populations (such as those with diabetes or microalbuminuria) were excluded. High-dose diuretic trials were excluded.
Thirteen trials included diuretics, five included beta-blockers, 13 included calcium-channel blockers, eight included angiotensin converting enzyme inhibitors, three included angiotensin receptor blockers, one included alpha-blockers and 13 trials were placebo controlled. Most trials included only older participants (≥50 years). Four included only participants aged over 70. Five trials included adults aged under 50.
Study selection was performed independently by two reviewers.