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Table 3 Distribution of the main characteristics of the 287 studies of lung cancer

From: Systematic review with meta-analysis of the epidemiological evidence in the 1900s relating smoking to lung cancer

Characteristic Level Principal studies Subsidiary studies All studies
   Outcomea Study typeb Total Total
   All Squamous Adeno CC prosp Total   
Study status Principal 262 84 86 209 58 267 - 267
  Subsidiary (19) (12) (12) (15) (5) (20) 20 20
Study type Case–control 204 73 75 209 - 209 15 224
  Prospective 52 9 9 - 52 52 4 56
  Other 6 2 2 - 6 6 1 7
Study sex Both 154 53 54 133 25 158 11 169
  Male 90 19 19 59 31 90 8 98
  Female 18 12 13 17 2 19 1 20
Lowest agec <20 or unlimited 177 56 57 165 16 181 13 194
  20-29 15 3 3 9 6 15 2 17
  30-39 39 15 16 26 14 40 5 45
  40+ 31 10 10 9 22 31 0 31
Highest age <60 16 2 2 10 6 16 3 19
  60-69 21 6 6 6 15 21 1 22
  70-79 29 11 12 23 7 30 3 33
  80+ or unlimited 196 65 66 170 30 200 13 213
Location North America 87 29 31 63 26 89 6 95
  United Kingdom 22 2 2 13 9 22 2 24
  Scandinavia 25 6 6 14 11 25 2 27
  Other Europe 42 13 12 39 4 43 7 50
  China 37 10 10 34 3 37 2 39
  Japan 17 8 9 15 3 18 1 19
  Other Asia 16 10 10 16 1 17 0 17
  Other 16 6 6 15 1 16 0 16
Start year of study <1960 47 12 12 33 14 47 1 48
  1960-69 40 13 13 21 19 40 6 46
  1970-79 59 17 19 45 16 61 7 68
  1980-89 83 33 33 78 8 86 5 91
  1990+ 33 9 9 32 1 33 1 34
Number of casesd 100-249 109 25 26 84 28 112 5 117
  250-499 70 25 26 57 15 72 3 75
  500-999 47 14 14 38 9 47 3 50
  1000+ 36 20 20 30 6 36 9 45
Risky occupational population No 244 83 85 203 46 249 18 267
  Mining 7 0 0 0 7 7 2 9
  Other risky 11 1 1 6 5 11 0 11
National cigarette tobacco type Virginia 42 6 6 30 12 42 2 44
  Blended 180 66 68 142 42 184 16 200
  Othere 40 12 12 37 4 41 2 43
Any proxy use None/unknown 189 66 67 137 56 193 17 210
  Yes 73 18 19 72 2 74 3 77
Full histological confirmation No 199 49 49 145 54 199 12 211
  Yes 63 35 37 64 4 68 8 76
Main outcome(s)a All 262 82 82 204 58 262 19 281
  Squamous 82 84 83 73 11 84 12 96
  Adeno 82 83 86 75 11 86 12 98
  All only 180 - - 133 47 180 8 188
  Squamous only - 1 - 1 0 1 0 1
  Adeno only - - 3 3 0 3 0 3
  more than one 82 83 83 72 11 83 12 95
  1. a Indicates whether the study provided data for all lung cancer, squamous cell carcinoma or adenocarcinoma, or their near equivalent definitions (see Methods). For squamous, the near equivalent definitions included are: Kreyberg I; squamous cell or small carcinoma; squamous cell or undifferentiated carcinoma; and not adenocarcinoma. For adeno, the near equivalent definitions included are: Kreyberg II; adenocarcinoma or large cell carcinoma; adenocarcinoma, alveolar or bronchioloalveolar carcinoma; not squamous cell or small cell carcinoma; and not squamous cell or undifferentiated carcinoma.
  2. b CC = case–control, prosp = prospective.
  3. c At start of study.
  4. d In study as a whole.
  5. e Indicates China and Taiwan.