Non-linear dose–response relationship between cigarette smoking and pancreatic cancer risk: Evidence from a meta-analysis of 42 observational studies

We reported all effect size produced by current meta-analysis as relative risk for simplicity

Li Zou

2013

Scholarcy highlights

  • Pancreatic cancer, as one of the most lethal human cancers, accounts for 266,000 deaths per year worldwide
  • Compared with non-smokers, the summary relative risk were 1.5 for 10 cigarettes/day, 1.9 for 20 cigarettes/day, 2.0 for 30 cigarettes/day and 2.1 for 40 cigarettes/day with marginal between-study heterogeneity
  • The summary RR for former smokers reduced with increasing time since quitting smoking compared with current smokers without heterogeneity
  • Non-linear dose–response associations were detected for all metrics of cigarette smoking in women, while linear relationships were observed for smoking duration and cumulative amount of cigarettes smoked in men except for smoking intensity
  • The following criteria were applied for literature selection: the study had a case-control, nested case-control, case-cohort or cohort design; the study evaluated the relationship between various dimensions of cigarette smoking, including intensity and duration of smoking, cumulative amount of cigarettes smoked and time since quitting smoking, and incidence or mortality of pancreatic cancer; investigators provided the following data: the number of cases, the total subjects or person-years and odds ratio, RRs or hazard ratios with 95% CIs for three or more quantitative categories of cigarette smoking
  • Our literature search identified 1256 publications, of which 1071 were excluded after review of title and abstract. 147 publications were further excluded after review of full-text because of the following reasons: no report of the association between cigarette smoking and pancreatic cancer risk, without a case-control, nested case-control or cohort design, data duplication and lack of sufficient information, such as only providing the data of pipe, cigar or snuff rather than cigarette, and the absence of individual data about the association between cigarette smoking and pancreatic cancer risk or essential data for dose–response meta-analysis
  • Previous pooled- and meta-analysis were performed by combining the same categories of cigarette exposure across individual studies or based on an assumption of linear trend, the shape of the dose–response remains poorly understood

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