Table 2. Numbers of adequately powered studies (≥50% power) and median power within each meta-analysis (MA) with respect to a 30% relative risk reduction (RRR30), overall and by medical specialty, outcome type and intervention-comparison type.
| N | % of MA in whichall studies underpowered | % of MA in which ≥2 studies adequately powered | Median (IQR) of median power within meta-analyses | |
| All meta-analyses | 14886 | 70% | 17% | 0.13 (0.07 to 0.31) |
| Medical specialty | ||||
| Cancer | 689 | 53% | 35% | 0.24 (0.10 to 0.57) |
| Cardiovascular | 1192 | 68% | 19% | 0.11 (0.06 to 0.26) |
| Central nervous system/musculoskeletal | 1210 | 79% | 11% | 0.13 (0.06 to 0.26) |
| Digestive/endocr., nutritional and metabolic | 1464 | 75% | 16% | 0.11 (0.05 to 0.28) |
| Gynaecology, pregnancy and birth | 3905 | 72% | 15% | 0.11 (0.06 to 0.28) |
| Infectious diseases | 780 | 62% | 23% | 0.16 (0.08 to 0.42) |
| Mental health and behavioural conditions | 1977 | 73% | 17% | 0.14 (0.08 to 0.32) |
| Pathological conditions, symptoms and signs | 414 | 64% | 20% | 0.17 (0.08 to 0.39) |
| Respiratory diseases | 1310 | 75% | 15% | 0.12 (0.07 to 0.27) |
| Urogenital | 932 | 77% | 12% | 0.12 (0.06 to 0.25) |
| Other medical specialties1 | 1013 | 61% | 24% | 0.18 (0.08 to 0.41) |
| Outcome types | ||||
| Objective outcomes | ||||
| All-cause mortality | 1132 | 77% | 14% | 0.08 (0.05 to 0.18) |
| Semi-objective outcomes | ||||
| Obstetric outcomes | 1288 | 71% | 15% | 0.12 (0.07 to 0.25) |
| Cause-specific mortality/major morbidity event/composite (mortality or morbidity) | 907 | 76% | 14% | 0.08 (0.05 to 0.18) |
| Resource use/hospital stay/process | 680 | 59% | 22% | 0.20 (0.08 to 0.42) |
| Other semi-objective outcomes2 | 1711 | 79% | 12% | 0.10 (0.06 to 0.22) |
| Subjective outcomes | ||||
| Adverse events | 2330 | 81% | 11% | 0.11 (0.06 to 0.21) |
| Signs/symptoms reflecting continuation/end of condition | 2184 | 54% | 30% | 0.25 (0.12 to 0.52) |
| Infection/onset of new acute/chronic disease | 2038 | 75% | 13% | 0.11 (0.06 to 0.24) |
| Biological markers (dichotomised) | 947 | 66% | 21% | 0.16 (0.07 to 0.39) |
| General physical health | 276 | 75% | 11% | 0.13 (0.08 to 0.25) |
| Other subjective outcomes3 | 1331 | 59% | 24% | 0.22 (0.11 to 0.46) |
| Intervention-comparison types | ||||
| Pharmacological vs. Control/Placebo | 5599 | 68% | 18% | 0.13 (0.07 to 0.31) |
| Non-pharmacological4 vs. Control/Placebo | 2412 | 59% | 26% | 0.19 (0.08 to 0.47) |
| Active vs. Active | 6875 | 76% | 14% | 0.11 (0.06 to 0.26) |
1
Other medical specialties: Blood and immune system, Ear and nose, Eye, General health, Genetic disorders, Injuries, accidents and wounds, Mouth and dental, Skin.
2
Other semi-objective outcomes: External structure, Internal structure, Surgical/device related success/failure, Withdrawals/drop-outs.
3
Other subjective outcomes: Pain, Mental health outcomes, Quality of life/functioning, Consumption, Satisfaction with care, Composite (at least 1 non-mortality/morbidity).
4
Non-pharmacological interventions include interventions classified as medical devices, surgical, complex, resources and infrastructure, behavioural, psychological, physical, complementary, educational, radiotherapy, vaccines, cellular and gene, screening.