RT Journal Article SR Electronic T1 Time-dependent effect of intensity of smoking and of occupational exposure to asbestos on the risk of lung cancer: results from the ICARE case–control study JF Occupational and Environmental Medicine JO Occup Environ Med FD BMJ Publishing Group Ltd SP oemed-2017-104953 DO 10.1136/oemed-2017-104953 A1 Emilie Lévêque A1 Aude Lacourt A1 Danièle Luce A1 Marie-Pierre Sylvestre A1 Pascal Guénel A1 Isabelle Stücker A1 Karen Leffondré YR 2018 UL http://oem.bmj.com/content/early/2018/05/17/oemed-2017-104953.abstract AB 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.