Work related asthma. A causal analysis controlling the healthy worker effect.

Orianne Dumas (1) , Nicole Le Moual (1) , Valérie Siroux (2) , Dick Heederik (3) , Judith Garcia-Aymerich (4, 5, 6, 7) , Raphaëlle Varraso (1) , Francine Kauffmann (1) , Xavier Basagaña (5, 6, 4)

1 CESP - Centre de recherche en épidémiologie et santé des populations
2 INSERM U823 - Institut d'oncologie/développement Albert Bonniot de Grenoble
3 IRAS - Division of Occupational and Environmental Health, Institute for Risk Assessment
4 CIBERESP - Centro de Investigación Biomédica en Red de Epidemiología y Salud Pública = Consortium for Biomedical Research of Epidemiology and Public Health
5 IMIM-Hospital del Mar
6 CREAL - Center for Research in Environmental Epidemiology
7 UPF - Universitat Pompeu Fabra [Barcelona]

The healthy worker effect usually leads to underestimation of the association between occupational exposure and asthma. The role of irritants in work-related asthma is disputed. We estimated the effect of occupational exposure on asthma expression in a longitudinal study, using marginal structural modelling to control for the healthy worker effect. Analyses included 1284 participants (17-79 years, 48% men) from the follow-up (2003-2007) of the French Epidemiological study on the Genetics and Environment of Asthma (case-control study). Age at asthma onset, periods with/without attacks over lifetime and occupational history were recorded retrospectively. Exposures to known asthmagens, irritants or low level of chemicals/allergens were evaluated through a job-exposure matrix. The job history was reconstructed into 5-year intervals. Thirty-one per cent of subjects had ever been exposed to occupational asthmagens. Among the 38% of subjects who had asthma (ever), presence of attacks was reported in 52% of all time periods. Using standard analyses, no association was observed between exposure to known asthmagens (OR (95% CI): 0.99 (0.72 to 1.36)) or to irritants/low level of chemicals/allergens (0.82 (0.56 to 1.20)) and asthma attacks. Using a marginal structural model, all associations increased with suggestive evidence for known asthmagens (1.26 (0.90 to 1.76)), and reaching statistical significance for irritants/low level of chemicals/allergens (1.56 (1.02 to 2.40)). The healthy worker effect has an important impact in risk assessment in work-related asthma studies. Marginal structural models are useful to eliminate imbalances in exposure due to disease-driven selection. Results support the role of irritants in work-related asthma.

Mots clés: Asthma; Healthy worker effect; Marginal structural models

Domaines: Santé publique et épidémiologie

Orianne Dumas, Nicole Le Moual, Valérie Siroux, Dick Heederik, Judith Garcia-Aymerich, et al.. Work related asthma. A causal analysis controlling the healthy worker effect.. Occupational and Environmental Medicine, 2013, 70 (9), pp.603-10. ⟨10.1136/oemed-2013-101362⟩. ⟨inserm-01324289⟩