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Table 7 Meta-regression results for ever 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 All lung cancer Squamous Adeno
   Estimateb(SEc) pd Estimateb(SEc) pd Estimateb(SEc) pd
Constant   +1.280 (0.052)   +1.281 (0.174)   +0.368 (0.178)  
Sex Male Base NS Base NS Base <0.05
  Female −0.040 (0.016)   −0.046 (0.072)   −0.275 (0.058)  
  Combined +0.018 (0.029)   −0.130 (0.141)   +0.102 (0.138)  
Location North America Base <0.001 Base <0.001 Base <0.001
  United Kingdom −0.108 (0.057)   −0.861 (0.266)   −0.535 (0.324)  
  Scandinavia −0.095 (0.051)   −0.484 (0.241)   −0.630 (0.190)  
  Other Europe −0.319 (0.039)   −0.609 (0.114)   −0.731 (0.107)  
  China −1.320 (0.024)   −1.028 (0.120)   −1.356 (0.094)  
  Japan −0.858 (0.053)   −0.562 (0.226)   −1.158 (0.119)  
  Other Asia −0.646 (0.060)   −0.390 (0.158)   −0.557 (0.127)  
  Other or multiregion −0.173 (0.076)   −0.031 (0.301)   −0.024 (0.213)  
Start year of study Before 1960 Base <0.001 Base <0.001 Base <0.05
  1960-69 +0.384 (0.047)   +0.819 (0.154)   +0.750 (0.166)  
  1970-79 +0.430 (0.045)   +0.802 (0.130)   +0.672 (0.150)  
  1980-89 +0.783 (0.042)   +0.990 (0.134)   +0.857 (0.155)  
  1990 or later +0.872 (0.063)   +1.788 (0.263)   +0.892 (0.200)  
Study type Case–control Base <0.01 Base NS Base NS
  Prospectivee +0.238 (0.036)   +0.395 (0.233)   +0.352 (0.140)  
Number of casesf 100-249 Base <0.001 Base <0.05 Base <0.05
  250-499 +0.101 (0.044)   +0.251 (0.152)   +0.265 (0.107)  
  500-999 +0.293 (0.043)   +0.729 (0.162)   +0.550 (0.121)  
  1000+ +0.290 (0.038)   +0.655 (0.145)   +0.594 (0.100)  
Number of adjustment factors 0 Base <0.05 Base <0.05 Base <0.1
  1 −0.171 (0.034)   +0.477 (0.147)   +0.391 (0.110)  
  2+ +0.017 (0.025)   −0.226 (0.097)   +0.272 (0.078)  
  1. a Based on the same data as for Table 5. See that table for further definition of RRs selected for analysis, and numbers of estimates of each characteristic level.
  2. b Estimates are of log RR. The predicted RR of a given estimate can be calculated by adding the constant to the values for the level of each characteristic applicable to the estimate (taking the value for a base level as zero) and taking the exponential of the result.
  3. c SE = standard error.
  4. d The p value is estimated from the drop in deviance from removing the characteristic from the fixed model using an F-test. It is expressed as p < 0.001, p < 0.01, p < 0.05, p < 0.1 or NS (p ≥ 0.1).
  5. e Or nested case–control or case-cohort in the case of 5 estimates for all lung cancer, 4 for squamous and 4 for adeno.
  6. f In the study as a whole.
  7. Note For the forward stepwise analyses, deviances, degrees of freedom and p values for inclusion in order of inclusion are as follows:
  8. All lung cancer: Constant 7470.075 on 327 d.f. (p < 0.001), location 2247.358 on 320 d.f. (p < 0.001), start year of study 1599.339 on 316 d.f. (p < 0.001), number of cases 1523.722 on 313 d.f. (p < 0.01), study type 1497.854 on 312 d.f. (p < 0.05) and number of adjustment variables 1463.482 on 310 d.f. (p < 0.05). Fixed model deviance 1454.810 on 308 d.f.
  9. Squamous: Constant 522.221 on 101 d.f. (p < 0.001), start year of study 419.586 on 97 d.f. (p < 0.001) and location 308.715 on 90 d.f. (p < 0.001). Fixed model deviance 260.432 on 82 d.f.
  10. Adeno: Constant 930.356 on 106 d.f. (p < 0.001), location 431.955 on 99 d.f. (p < 0.001), number of cases 369.648 on 96 d.f. (p <0.01), start year of study 328.896 on 92 d.f. (p < 0.05) and sex 307.336 on 90 d.f. (p < 0.05). Fixed model deviance 284.147 on 87 d.f.