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

We summarize evidence for various indices

Peter N Lee

2012

Scholarcy highlights

  • Smoking is a known lung cancer cause, but no detailed quantitative systematic review exists
  • Results are selected for: sex – single sex results, combined sex results; adjustment for potential confounders – most available. b n = number of estimates combined, F = fixed-effect meta-analysis relative risk), R = random-effects meta-analysis RR, H = heterogeneity chisquared per degree of freedom, PH = probability value for heterogeneity expressed as p < 0.001, p < 0.01, p < 0.05, p < 0.1 or NS, PE = probability value for Egger’s test of publication bias expressed, PB = probability value for between levels expressed. c All or nearest available, must include at least squamous cell carcinoma and adenocarcinoma. d Squamous cell carcinoma or nearest available, but not including adenocarcinoma. e Adenocarcinoma or nearest available, but not including squamous cell carcinoma. f Or nested case–control or case-cohort in the case of 5 estimates for all lung cancer, 4 for squamous and 4 for adeno. g Or not known in the case of 10 estimates for all lung cancer, 2 for squamous, and 2 for adeno. h In the study as a whole
  • A Within each study, results for the relevant smoking product and smoking status are selected in the following preference order, within each sex, for: cigarette type – see notes f to i; unexposed group – see notes f to i; smoking product – any, cigarettes, cigarettes only; smoking status – ever, current; lung cancer type – see notes c to e; race – all or nearest available, otherwise by race; follow-up period – longest available; overlapping studies – principal, subsidiary; age – whole study, widest available age group; Results are selected for: sex – single sex results, combined sex results; adjustment for potential confounders – most available. b n = number of estimates combined, F = fixed-effect meta-analysis RR, R = random-effects meta-analysis RR, 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, PB = probability value for between levels expressed. c All or nearest available, must include at least squamous cell carcinoma and adenocarcinoma. d Squamous cell carcinoma or nearest available, but not including adenocarcinoma. e Adenocarcinoma or nearest available, but not including squamous cell carcinoma. f Or nearest available
  • Our analyses showed that for all lung cancer, risk increased with increasing tar level and with increasing fraction smoked, data here being more limited and non existent by histological type
  • After excluding studies involving less than 100 lung cancer cases, we identified 287 epidemiological studies of lung cancer which provided information on risk in relation to one or more of a defined list of smoking indices
  • Of the 267 independent principal studies, 262 provided RRs relating to all lung cancer, 84 provided RRs relating to squamous cell carcinoma, and 86 provided RRs relating to adenocarcinoma
  • One major conclusion is that for each outcome the relative risk for all major smoking indices were markedly heterogeneous

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