Objective To estimate the impact of intensity of both smoking and occupational exposure to asbestos on the risk of lung cancer throughout the whole exposure history.
Methods Data on 2026 male cases and 2610 male controls came from the French ICARE (Investigation of occupational and environmental causes of respiratory cancers) population-based, case–control study. Lifetime smoking history and occupational history were collected from standardised questionnaires and face-to-face interviews. Occupational exposure to asbestos was assessed using a job exposure matrix. The effects of annual average daily intensity of smoking (reported average number of cigarettes smoked per day) and asbestos exposure (estimated average daily air concentration of asbestos fibres at work) were estimated using a flexible weighted cumulative index of exposure in logistic regression models.
Results Intensity of smoking in the 10 years preceding diagnosis had a much stronger association with the risk of lung cancer than more distant intensity. By contrast, intensity of asbestos exposure that occurred more than 40 years before diagnosis had a stronger association with the risk of lung cancer than more recent intensity, even if intensity in the 10 years preceding diagnosis also had a significant effect.
Conclusion Our results illustrate the dynamic of the effect of intensity of both smoking and occupational exposure to asbestos on the risk of lung cancer. They confirm that the timing of exposure plays an important role, and suggest that standard analytical methods assuming equal weights of intensity over the whole exposure history may be questionable.
- case-control study
- lung cancer
- dose-time-response relationship
- exposure intensity
- age-dependent susceptibility
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Contributors EL performed all statistical analyses and drafted the first version of the manuscript. AL contributed to the drafting of the manuscript and cosupervised all aspects of the manuscript. IS and DL supervised data collection within the ICARE study and contributed to the interpretation of the results. M-PS and PG contributed to the interpretation of the results in the final version. KL contributed to the drafting of the manuscript and supervised all aspects of the manuscript. All coauthors participated in the editing and correction of the final text.
Funding The French National Research Program for Environmental and Occupational Health of Anses with support of the Cancer TMOI of the French National Alliance for Life and Health Sciences (AVIESAN) – 2013/1/177.
Competing interests None declared.
Patient consent Obtained.
Ethics approval The Institutional Review Board of the French National Institute of Health and Medical Research (IRB-Inserm, n° 01-036) and by the French Data Protection Authority (CNIL n° 90120).
Provenance and peer review Not commissioned; externally peer reviewed.
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