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. 2019 May;30(3):458-465.
doi: 10.1097/EDE.0000000000000964.

Modeling the Complex Exposure History of Smoking in Predicting Bladder Cancer: A Pooled Analysis of 15 Case-Control Studies

Frits H M van Osch  1   2 , Jelle Vlaanderen  3 , Sylvia H J Jochems  1   2 , Cristina Bosetti  4 , Jerry Polesel  5 , Stefano Porru  6   7 , Angela Carta  7   8 , Klaus Golka  9 , Xuejuan Jiang  10   11 , Mariana C Stern  10 , Wei-De Zhong  12 , Eliane Kellen  13 , Hermann Pohlabeln  14 , Li Tang  15 , James Marshall  15 , Gunnar Steineck  16 , Margaret R Karagas  17 , Kenneth C Johnson  18 , Zuo-Feng Zhang  19 , Jack A Taylor  20 , Carlo La Vecchia  21 , Richard T Bryan  2 , Frederik J van Schooten  22 , Anke Wesselius  1 , Maurice P Zeegers  1   2   23
Affiliations

Modeling the Complex Exposure History of Smoking in Predicting Bladder Cancer: A Pooled Analysis of 15 Case-Control Studies

Frits H M van Osch et al. Epidemiology. 2019 May.

Abstract

Background: Few studies have modeled smoking histories by combining smoking intensity and duration to show what profile of smoking behavior is associated with highest risk of bladder cancer. This study aims to provide insight into the association between smoking exposure history and bladder cancer risk by modeling both smoking intensity and duration in a pooled analysis.

Methods: We used data from 15 case-control studies included in the bladder cancer epidemiology and nutritional determinants study, including a total of 6,874 cases and 17,727 controls. To jointly interpret the effects of intensity and duration of smoking, we modeled excess odds ratios per pack-year by intensity continuously to estimate the risk difference between smokers with long duration/low intensity and short duration/high intensity.

Results: The pattern observed from the pooled excess odds ratios model indicated that for a fixed number of pack-years, smoking for a longer duration at lower intensity was more deleterious for bladder cancer risk than smoking more cigarettes/day for a shorter duration. We observed similar patterns within individual study samples.

Conclusions: This pooled analysis shows that long duration/low intensity smoking is associated with a greater increase in bladder cancer risk than short duration/high intensity smoking within equal pack-year categories, thus confirming studies in other smoking-related cancers and demonstrating that reducing exposure history to a single metric such as pack-years was too restrictive.

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Conflict of interest statement

The authors report no conflicts of interest.

Figures

FIGURE 1.
FIGURE 1.
Odds ratios (OR) for bladder cancer by cross-classified categories of pack–years and quintile categories of number of cigarettes smoked per day (CPD). Lines indicate fitted linear odds ratio models in pack–years, bars indicate 95% confidence intervals. Pooled data were limited to never and current smokers.
FIGURE 2.
FIGURE 2.
Estimated excess odds ratio (EOR) per pack–year for bladder cancer by cigarettes per day with bootstrapped 95% confidence intervals. The dotted line indicates a model including an extra spline for time since smoking cessation. Triangles depict locations of the knots of the restricted cubic splines (20th, 50th, and 80th percentile).
See this image and copyright information in PMC

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