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Table 8 Main meta-analyses for current 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 195 41 44
   F 9.29 (9.07-9.52) 13.77 (12.75-14.87) 4.77 (4.49-5.07)
   R 8.43 (7.63-9.31) 16.91 (13.14-21.76) 4.21 (3.32-5.34)
   H, PH 13.76, p < 0.001 7.22, p < 0.001 12.28, p < 0.001
   PE p < 0.05 NS NS
Sex Male n 108 22 22
   F 8.68 (8.36-9.02) 13.11 (11.85-14.51) 5.54 (5.04-6.09)
   R 9.16 (8.00-10.49) 17.73 (12.78-24.59) 5.56 (4.06-7.61)
  Female n 68 17 20
   F 8.06 (7.75-8.38) 13.44 (11.86-15.23) 4.40 (4.05-7.79)
   R 6.76 (5.65-8.08) 14.77 (9.42-23.17) 3.20 (2.18-4.71)
  Combined n 19 2 2
   F 13.19 (12.55-13.86) 34.23 (23.43-50.00) 3.11 (2.35-4.11)
   R 12.09 (9.38-15.60) 34.23 (23.43-50.00) 3.57 (1.06-12.07)
  Between levels PB <0.001 <0.01 <0.1
Location North America n 84 24 24
   F 12.45 (12.09-12.82) 17.99 (16.29-19.85) 7.63 (7.05-8.25)
   R 11.68 (10.61-12.85) 20.95 (15.41-28.48) 6.72 (5.50-8.21)
  United Kingdom n 25 0 0
   F 6.90 (6.10-7.81)   
   R 7.53 (5.40-10.50)   
  Scandinavia n 21 2 2
   F 8.16 (7.30-9.12) 15.51 (6.63-36.28) 4.66 (2.67-8.13)
   R 8.68 (7.14-10.54) 15.51 (6.63-36.28) 4.69 (2.62-8.40)
  Other Europe n 23 6 6
   F 5.88 (5.43-6.38) 12.22 (10.16-14.69) 2.65 (2.20-3.18)
   R 8.65 (5.98-12.51) 13.66 (7.38-25.30) 3.30 (1.93-5.65)
  China n 5 0 0
   F 3.07 (2.56-3.68)   
   R 2.94 (2.23-3.88)   
  Japan n 18 8 11
   F 3.68 (3.43-3.95) 6.85 (5.77-8.13) 2.11 (1.87-2.37)
   R 3.55 (3.05-4.14) 11.25 (6.89-18.35) 1.87 (1.42-2.47)
  Other Asia n 7 0 0
   F 2.91 (2.26-3.76)   
   R 2.90 (2.04-4.13)   
  Other or multiregion n 12 1 1
   F 7.09 (6.10-8.24) 10.40 (3.31-32.66) 7.90 (2.99-20.85)
   R 9.88 (6.89-14.17) 10.40 (3.31-32.66) 7.90 (2.99-20.85)
  Between levels PB <0.001 NS <0.001
Start year of study Before 1960 n 22 6 5
   F 6.13 (5.70-6.59) 6.87 (4.93-9.08) 3.35 (2.43-4.62)
   R 6.39 (4.70-8.69) 11.05 (4.07-30.00) 2.92 (1.17-7.28)
  1960-69 n 40 7 7
   F 5.43 (5.12-5.75) 10.55 (9.07-12.26) 4.22 (3.76-4.74)
   R 6.44 (5.21-7.95) 15.48 (7.08-33.83) 4.55 (2.50-8.30)
  1970-79 n 41 8 11
   F 7.27 (6.79-7.79) 14.53 (12.21-17.29) 2.99 (2.55-3.50)
   R 7.34 (5.94-9.06) 16.43 (8.67-31.14) 3.41 (2.10-5.53)
  1980-89 n 70 18 19
   F 12.35 (11.97-12.75) 16.70 (14.93-18.67) 6.38 (5.84-6.96)
   R 10.18 (9.02-11.49) 19.69 (15.08-25.71) 5.06 (3.65-7.02)
  1990 or later n 22 2 2
   F 10.32 (9.10-11.70) 20.79 (10.16-42.55) 2.28 (1.63-3.19)
   R 12.81 (8.70-18.85) 19.39 (6.38-58.88) 3.62 (0.92-14.29)
  Between levels PB <0.001 NS NS
Study type Case–control n 128 30 34
   F 9.69 (9.43-9.95) 13.59 (12.56-14.70) 4.71 (4.42-5.01)
   R 8.56 (7.58-9.68) 16.21 (12.23-21.50) 3.88 (2.96-5.07)
  Prospectivef n 67 11 10
   F 8.04 (7.65-8.46) 18.87 (12.90-27.59) 5.93 (4.59-7.66)
   R 8.15 (6.87-9.67) 19.63 (12.21-31.56) 5.95 (4.07-8.69)
  Between levels PB NS NS p < 0.1
National cigarette tobacco type Virginia n 34 2 2
   F 6.75 (6.12-7.44) 31.44 (15.03-65.78) 6.93 (4.35-11.07)
   R 8.01 (6.16-10.41) 31.44 (15.03-65.78) 6.93 (4.35-11.07)
  Blended n 154 39 42
   F 9.70 (9.46-9.95) 13.65 (12.63-14.75) 4.74 (4.45-5.04)
   R 8.92 (8.01-9.94) 16.41 (12.68-21.24) 4.10 (3.21-5.23)
  Other n 7 0 0
   F 3.13 (2.64-3.72)   
   R 3.09 (2.50-3.83)   
  Between levels PB <0.001 NS p < 0.1
Any proxy use Nog n 156 35 38
   F 9.24 (9.00-9.48) 13.09 (12.09-14.18) 4.67 (4.39-4.98)
   R 8.04 (7.17-9.01) 15.78 (12.00-20.74) 3.88 (2.99-5.03)
  Yes n 39 6 6
   F 9.68 (9.05-10.36) 27.96 (20.74-37.69) 6.88 (5.27-8.97)
   R 10.03 (8.32-12.09) 27.96 (20.74-37.69) 6.88 (5.27-8.97)
  Between levels PB <0.05 <0.01 p < 0.01
Full histological confirmation No n 144 24 23
   F 8.87 (8.62-9.12) 11.53 (10.05-13.23) 3.99 (3.59-4.43)
   R 7.91 (7.00-8.93) 19.20 (12.62-29.22) 5.59 (3.98-7.84)
  Yes n 51 17 21
   F 10.45 (9.99-10.92) 14.94 (13.61-16.40) 5.25 (4.87-5.67)
   R 10.08 (8.46-12.01) 14.77 (10.61-20.57) 3.20 (2.28-4.49)
  Between levels PB <0.05 NS p < 0.05
Number of casesh 100-249 n 56 8 11
   F 5.50 (4.96-6.11) 5.62 (3.96-7.98) 2.54 (2.02-3.19)
   R 6.90 (5.46-8.72) 11.28 (5.08-25.04) 2.45 (1.54-3.90)
  250-499 n 48 9 9
   F 8.47 (7.79-9.22) 16.67 (11.49-24.18) 3.20 (2.59-3.95)
   R 8.60 (7.02-10.52) 17.09 (11.28-25.91) 3.83 (2.41-6.09)
  500-999 n 38 4 4
   F 7.56 (7.04-8.13) 22.44 (13.58-37.07) 7.35 (5.12-10.55)
   R 9.54 (7.65-11.89) 22.44 (13.58-37.07) 7.35 (5.12-10.55)
  1000+ n 53 20 20
   F 10.01 (9.74-10.29) 14.15 (13.03-15.35) 5.18 (4.84-5.54)
   R 9.03 (7.63-10.69) 17.87 (12.92-24.70) 4.97 (3.54-6.97)
  Between levels PB NS NS p <0.01
Smoking product Any n 85 9 11
   F 8.00 (7.64-8.37) 17.58 (11.99-25.77) 2.61 (2.16-3.14)
   R 7.57 (6.47-8.84) 17.76 (11.75-26.86) 2.40 (1.59-3.61)
  Cigarettes (ignoring n 95 26 28
  other products) F 9.84 (9.56-10.14) 13.51 (12.47-14.64) 5.11 (4.79-5.46)
   R 8.95 (7.76-10.33) 16.43 (12.08-22.33) 5.02 (3.76-6.70)
  Cigarettes only n 15 6 5
   F 9.77 (8.92-10.69) 17.80 (11.39-27.83) 5.69 (4.00-8.09)
   R 10.51 (7.70-14.34) 18.04 (9.79-33.27) 5.56 (2.61-11.85)
  Between levels PB NS NS p < 0.05
Unexposed base Never any product n 134 24 27
   F 8.80 (8.55-9.06) 9.80 (8.75-10.98) 3.01 (2.75-3.29)
   R 8.24 (7.28-9.34) 14.05 (9.75-20.23) 3.10 (2.37-4.07)
  Never cigarettes n 61 17 17
   F 10.43 (10.00-10.88) 18.44 (16.60-20.48) 7.17 (6.59-7.80)
   R 8.89 (7.52-10.51) 21.71 (16.38-28.76) 6.61 (4.89-8.95)
  Between levels PB NS <0.1 <0.001
Number of adjustment variables 0 n 86 16 17
   F 10.84 (10.46-11.23) 14.93 (13.02-17.12) 4.28 (3.83-4.79)
   R 9.40 (8.02-11.03) 17.15 (10.78-27.27) 3.90 (2.54-6.00)
  1 n 62 15 14
   F 7.80 (7.43-8.19) 19.11 (15.33-23.83) 3.25 (2.76-3.83)
   R 7.28 (6.14-8.63) 18.27 (12.55-26.60) 3.46 (2.27-5.29)
  2+ n 47 10 13
   F 8.49 (8.13-8.87) 12.24 (11.04-13.57) 5.58 (5.13-6.05)
   R 8.54 (7.02-10.39) 15.20 (9.40-24.58) 5.68 (3.80-8.49)
  Between levels PB p < 0.1 NS NS
  1. a Within each study, results for current 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 adeno.
  18. g Including not known.
  19. h In the study as a whole.