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Table 12 Main meta-analyses for ex smoking of any product (or cigarettes, if any product not available) a

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

Characteristic Level Statisticb All lung cancerc Squamousd Adenoe
All All n 182 33 34
   F 5.80 (5.63-5.96) 10.25 (9.34-11.24) 4.38 (4.04-4.73)
   R 4.30 (3.93-4.71) 8.74 (6.94-11.01) 2.85 (2.20-3.70)
   H, PH 6.98, <0.001 3.54, <0.001 7.91, <0.001
   PE p < 0.001 NS p < 0.001
Sex Male n 100 17 17
   F 5.15 (4.93-5.37) 9.31 (8.27-10.47) 4.59 (4.10-5.15)
   R 4.48 (3.98-5.06) 8.41 (6.18-11.45) 3.45 (2.40-4.96)
  Female n 62 14 15
   F 5.81 (5.51-6.14) 11.66 (9.94-13.68) 4.48 (4.00-5.02)
   R 3.58 (3.00-4.29) 8.03 (5.18-12.45) 2.39 (1.55-3.69)
  Combined n 20 2 2
   F 6.98 (6.61-7.37) 15.23 (9.63-24.08) 1.97 (1.35-2.88)
   R 5.58 (4.23-7.36) 15.23 (9.63-24.08) 2.07 (0.67-6.38)
  Between levels PB <0.05 <0.1 NS
Location North America n 80 18 17
   F 6.79 (6.57-7.01) 10.83 (9.73-12.05) 5.69 (5.20-6.23)
   R 5.44 (4.91-6.03) 9.43 (6.84-13.01) 4.08 (3.08-5.39)
  United Kingdom n 21 0 0
   F 4.14 (3.48-4.92)   
   R 3.72 (2.51-5.50)   
  Scandinavia n 21 2 2
   F 2.67 (2.29-3.11) 4.06 (1.61-10.25) 1.48 (0.77-2.83)
   R 2.62 (2.01-3.42) 4.06 (1.61-10.25) 1.48 (0.77-2.83)
  Other Europe n 24 6 6
   F 3.57 (3.26-3.92) 9.10 (7.38-11.22) 2.27 (1.82-2.84)
   R 3.96 (3.07-5.12) 8.42 (5.03-14.10) 2.58 (1.47-4.52)
  China n 5 0 0
   F 3.46 (2.70-4.44)   
   R 3.09 (2.02-4.74)   
  Japan n 14 6 8
   F 2.35 (2.01-2.76) 9.32 (5.69-15.28) 1.60 (1.25-2.05)
   R 2.40 (1.99-2.89) 9.32 (5.69-15.28) 1.60 (1.25-2.05)
  Other Asia n 5 0 0
   F 2.13 (1.37-3.32)   
   R 2.12 (1.29-3.47)   
  Other or multiregion n 12 1 1
   F 5.77 (4.73-7.03) 3.60 (1.00-12.93) 4.80 (1.79-12.85)
   R 5.84 (4.60-7.41) 3.60 (1.00-12.93) 4.80 (1.79-12.85)
  Between levels PB <0.001 NS <0.001
Start year of study Before 1960 n 18 2 1
   F 3.55 (3.19-3.94) 1.34 (0.71-2.52) 1.42 (0.29-6.82)
   R 3.81 (2.84-5.11) 1.34 (0.71-2.52) 1.42 (0.29-6.82)
  1960-69 n 36 5 5
   F 4.06 (3.68-4.48) 11.29 (8.77-14.54) 3.56 (2.95-4.29)
   R 3.32 (2.71-4.08) 11.29 (8.77-14.54) 2.80 (1.86-4.21)
  1970-79 n 36 8 10
   F 3.81 (3.50-4.14) 9.85 (8.08-12.02) 2.38 (1.95-2.91)
   R 3.48 (2.85-4.25) 9.39 (6.00-14.68) 2.59 (1.75-3.84)
  1980-89 n 70 16 16
   F 6.91 (6.68-7.15) 10.97 (9.75-12.36) 5.67 (5.13-6.26)
   R 5.22 (4.65-5.86) 10.35 (7.57-14.15) 3.37 (2.35-4.85)
  1990 or later n 22 2 2
   F 4.73 (4.11-5.43) 8.38 (3.79-18.53) 1.58 (1.00-2.49)
   R 5.17 (3.66-7.31) 7.58 (1.98-29.00) 2.22 (0.56-8.79)
  Between levels PB <0.001 <0.001 NS
Study type Case–control n 123 28 30
   F 6.28 (6.09-6.48) 10.71 (9.74-11.76) 4.44 (4.10-4.81)
   R 4.88 (4.41-5.41) 9.94 (8.05-12.28) 2.96 (2.26-3.87)
  Prospectivef n 59 5 4
   F 3.84 (3.58-4.12) 2.34 (1.35-4.03) 1.87 (1.04-3.36)
   R 3.18 (2.70-3.74) 3.54 (1.38-9.09) 1.87 (1.04-3.36)
  Between levels PB <0.001 <0.05 NS
National cigarette tobacco type Virginia n 30 2 2
   F 3.95 (3.45-4.53) 9.22 (4.21-20.18) 2.03 (1.15-3.57)
   R 3.79 (2.85-5.04) 9.22 (4.21-20.18) 2.27 (0.92-5.59)
  Blended n 147 31 32
   F 5.94 (5.77-6.12) 10.26 (9.35-11.27) 4.44 (4.10-4.81)
   R 4.45 (4.04-4.91) 8.68 (6.83-11.04) 2.89 (2.22-3.77)
  Other n 5 0 0
   F 3.46 (2.70-4.44)   
   R 3.09 (2.02-4.74)   
  Between levels PB NS NS NS
Any proxy use Nog n 141 27 28
   F 6.02 (5.84-6.21) 10.17 (9.23-11.20) 4.46 (4.11-4.84)
   R 4.12 (3.70-4.59) 8.33 (6.38-10.89) 2.73 (2.04-3.65)
  Yes n 41 6 6
   F 4.60 (4.26-4.96) 11.24 (8.01-15.78) 3.30 (2.42-4.52)
   R 4.79 (4.20-5.47) 11.24 (8.01-15.78) 3.39 (2.25-5.11)
  Between levels PB <0.1 NS NS
Full histological confirmation No n 131 16 15
   F 5.73 (5.53-5.93) 8.91 (7.03-11.30) 3.50 (2.89-4.23)
   R 4.11 (3.68-4.60) 8.11 (5.05-13.01) 3.24 (2.13-4.94)
  Yes n 51 17 19
   F 5.93 (5.65-6.23) 10.51 (9.50-11.62) 4.59 (4.21-5.00)
   R 4.76 (4.02-5.63) 9.28 (7.08-12.15) 2.60 (1.85-3.65)
  Between levels PB NS NS NS
Number of casesg 100-249 n 51 7 9
   F 3.18 (2.79-3.64) 4.03 (2.17-7.49) 1.95 (1.40-2.70)
   R 3.36 (2.65-4.25) 4.03 (2.17-7.49) 1.95 (1.40-2.70)
  250-499 n 45 9 8
   F 4.21 (3.80-4.66) 4.59 (3.17-6.65) 1.86 (1.36-2.54)
   R 4.13 (3.42-4.99) 5.48 (2.84-10.58) 2.10 (1.21-3.64)
  500-999 n 37 4 4
   F 4.61 (4.21-5.04) 9.58 (5.65-16.25) 3.23 (2.13-4.90)
   R 4.86 (4.07-5.80) 9.58 (5.65-16.25) 3.58 (1.79-7.13)
  1000+ n 49 13 13
   F 6.39 (6.19-6.60) 11.13 (10.08-12.28) 5.00 (4.59-5.45)
   R 4.76 (4.13-5.48) 11.53 (8.87-14.99) 3.69 (2.60-5.22)
  Between levels PB <0.05 <0.01 <0.05
Smoking product Any n 81 9 9
   F 4.76 (4.51-5.02) 8.13 (5.16-12.79) 1.60 (1.21-2.12)
   R 4.09 (3.53-4.74) 8.13 (5.16-12.79) 1.68 (1.17-2.40)
  Cigarettes (ignoring n 90 23 25
  other products) F 6.38 (6.16-6.60) 10.75 (9.77-11.83) 4.77 (4.40-5.18)
   R 4.49 (3.98-5.06) 9.99 (7.93-12.58) 3.35 (2.54-4.41)
  Cigarettes only n 11 1 0
   F 4.96 (4.36-5.64) 1.23 (0.60-2.52)  
   R 4.18 (2.63-6.66) 1.23 (0.60-2.52)  
  Between levels PB NS <0.001 <0.01
Unexposed base Never any product n 121 17 18
   F 5.64 (5.44-5.85) 8.41 (7.12-9.94) 2.38 (2.06-2.76)
   R 4.35 (3.89-4.88) 6.63 (4.39-10.02) 2.17 (1.61-2.94)
  Never cigarettes n 61 16 16
   F 6.08 (5.80-6.37) 11.19 (10.00-12.51) 5.60 (5.10-6.15)
   R 4.18 (3.56-4.91) 11.13 (8.48-14.60) 3.83 (2.78-5.27)
  Between levels PB NS <0.05 <0.05
Number of adjustment factors 0 n 86 16 16
   F 6.10 (5.87-6.34) 9.81 (8.41-11.45) 2.82 (2.47-3.22)
   R 4.84 (4.26-5.50) 9.11 (6.95-11.94) 2.61 (1.91-3.58)
  1 n 48 10 9
   F 4.40 (4.11-4.71) 7.03 (5.21-9.47) 2.13 (1.66-2.73)
   R 3.96 (3.37-4.65) 6.43 (3.31-12.47) 2.17 (1.56-3.03)
  2+ n 48 7 9
   F 6.23 (5.91-6.58) 11.28 (9.94-12.80) 6.64 (5.97-7.39)
   R 3.81 (3.11-4.66) 11.09 (6.78-18.13) 4.42 (3.05-6.40)
  Between levels PB <0.1 NS <0.05
  1. a Within each study, results for ex smokers are selected in the following preference order, within each sex, for:
  2. smoking product – any, cigarettes (ignoring other products), cigarettes only;
  3. cigarette type – any, manufactured (with or without handrolled), manufactured only;
  4. unexposed group – never any product, never cigarettes, near equivalent (see Methods);
  5. follow-up period – longest available;
  6. lung cancer type – see notes c to e;
  7. race – all or nearest available, otherwise by race;
  8. overlapping studies – principal, subsidiary;
  9. age – whole study, widest available age group.
  10. Results are then selected for:
  11. sex – single sex results, combined sex results;
  12. adjustment for potential confounders – most available.
  13. b n = number of estimates combined, F = fixed-effect meta-analysis RR (95% CI), R = random-effects meta-analysis RR (95% CI), H = heterogeneity chisquared per degree of freedom, PH = probability value for heterogeneity expressed as p < 0.001, p < 0.05, p < 0.1 or NS (p ≥ 0.1), PE = probability value for Egger’s test of publication bias similarly expressed, PB = probability value for between levels (see Methods) similarly expressed.
  14. c All or nearest available, must include at least squamous cell carcinoma and adenocarcinoma.
  15. d Squamous cell carcinoma or nearest available, but not including adenocarcinoma.
  16. e Adenocarcinoma or nearest available, but not including squamous cell carcinoma.
  17. f Or nested case–control or case-cohort in the case of 5 estimates for all lung cancer, 3 for squamous and 3 for adenocarcinoma.
  18. g In the study as a whole.