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Table 6 Study sample size, overall and broken down by outcome type, intervention comparison type and medical area

From: Characteristics of meta-analyses and their component studies in the Cochrane Database of Systematic Reviews: a cross-sectional, descriptive analysis

   Studies 25% 50% 75% Max
All Total 112600 44 91 210 1242071
Data type Dichotomous 77237 50 102 243 1242071
  Continuous 29902 33 62 142 18851
  Mixed 5461 21 86 251 36511
Medical specialty Cancer 6441 72 154 326 266064
  Cardiovascular 10686 44 102 289 67800
  Central nervous system/musculoskeletal 8299 43 80 149 9440
  Digestive/endocr., nutritional and metabolic 15345 42 79 160 18819
  Gynaecology, pregnancy and birth 20098 60 118 293 23697
  Infectious diseases 4502 59 130 371 419748
  Mental health and behavioural conditions 15218 36 63 165 9020
  Pathological conditions, symptoms and signs 4448 40 61 115 2463
  Respiratory diseases 13153 36 87 227 82892
  Urogenital 5914 39 71 153 4912
  Other 8496 44 90 198 1242071
Interventions Pharm. vs. Control/Placebo 44156 41 90 222 58050
  Pharm. vs. Pharm. 28018 48 99 222 25180
  Pharm. vs. Non-Pharm. 2018 50 74 135 7711
  Non-Pharm. vs. Control/Placebo 20892 41 92 229 1242071
  Non-Pharm. vs. Non-Pharm. 17516 45 85 169 82892
Outcomes Signs/symptoms reflecting continuation/end of condition 17621 42 83 197 359600
  Adverse events 11898 49 100 242 82892
  Infection/onset of new acute/chronic disease 11284 56 110 258 1242071
  Biological markers 10578 35 64 147 266064
  General physical health 8959 30 66 177 131271
  Obstetric outcomes 7376 60 117 293 18453
  All-cause mortality 8302 52 110 281 259627
  Resource use/hospital stay/process 5454 50 98 200 419748
  Cause-specific mortality/major morbidity event/composite (mortality or morbidity) 5413 69 165 449 266064
  Other outcomes (semi-objective)1 10886 44 81 177 131271
  Other outcomes (subjective)2 14490 38 71 162 359600
  1. 1Other outcomes (semi-objective): External structure, Internal structure, Surgical/device related success/failure, Withdrawals/drop-outs
  2. 2Other outcomes (subjective): Pain, Mental health outcomes, Quality of life/functioning, Consumption, Satisfaction with care, Composite (at least 1 non-mortality/morbidity)