Table 1.
Design of trials of aspirin therapy included in meta-analysis
| Features | PHS 198917 | ETDRS 199221 | PPP 200322 | WHS 20058 | POPADAD 20089 | JPAD 200810 |
|---|---|---|---|---|---|---|
| Country | USA | USA | Italy | USA | Scotland | Japan |
| Type of trial | Primary | Mixed | Primary | Primary | Primary | Primary |
| Study design | Randomised double blind, placebo controlled trial | Randomised double blind, placebo controlled trial | Randomised open trial with 2×2 factorial design | Randomised double blind, 2×2 factorial, placebo controlled trial | Randomised double blind, 2×2 factorial, placebo controlled trial | Randomised open label, controlled trial with blinded end point assessment |
| Patient population | Healthy men | Men and women with type 1 and type 2 diabetes | Men and women aged >50 with ≥1 risk factors for cardiovascular disease | Healthy women | Patients aged ≥40 years with type 1 or type 2 diabetes and an ankle brachial pressure index ≤0.99 but no symptomatic cardiovascular disease | Patients with type 2 diabetes without history of atherosclerotic disease |
| Aspirin dose | 325 mg every other day | 650 mg/day | 100 mg/day | 100 mg every other day | 100 mg/day | 81 or 100 mg per day |
| Primary outcome measure | Cardiovascular mortality | All cause mortality | Composite end point of death from cardiovascular cause, myocardial infarction, stroke | Major cardiovascular events: non-fatal myocardial infarction, non-fatal stroke, death from cardiovascular causes | Death from coronary heart disease or stroke, non-fatal myocardial infarction or stroke, or amputation above ankle for critical limb ischaemia, death from coronary heart disease or stroke | Atherosclerotic events including fatal or non-fatal ischaemic heart disease, fatal or non-fatal stroke, and peripheral arterial disease |
| No of people with diabetes (% of sample where appropriate) | 533 (2.4) | 3711 | 1031 | 1027 (2.6) | 1276 | 2539 |
| Duration of therapy (years) | 5 | 5 | 3.6 | 10.1 | 6.7 | 4.37 |
| Completeness of follow-up (%) | 99.7* | 94.7 | 99.3* | 99.4* | 99.5 | 92.4 |
| Compliance with aspirin therapy (%) | NA | 91.8 | 71.8 | NA | 50 | 90 |
| Men (%) | 100 | 56.5 | 48.2 | — | 44.1 | 55 |
| Women (%) | — | 43.5 | 51.8 | 100 | 55.9 | 45 |
| Mean (SD) age (years) | NA | NA | 64.3 (7.5) | NA | NA | 65 (10) |
PHS=Physicians’ Health Study; ETDRS=Early Treatment Diabetic Retinopathy Study; PPP=Primary Prevention Project; WHS=Women’s Health Study; POPADAD=Prevention Of Progression of Arterial Disease And Diabetes; JPAD=Japanese Primary Prevention of Atherosclerosis with Aspirin for Diabetes; NA=not available.
*Data refer to whole sample.