Occupational Exposures and Incidence of ASTHMA over Two Decades in the ECRHS

Introduction: Many occupational exposures have been associated with adult-onset asthma, but for very few agents is there evidence from longitudinal studies. Aims: We investigated associations between occupational exposures and the incidence of asthma over two decades in the ECRHS cohort. Methods: The general population-based, multicentre ECRHS cohort (13 countries) was followed up twice over 20 years. This analysis included data for 7027 (tier 1) from ECRHS I & III and 5901 (tier 2) from ECRHS II & III, for whom a complete occupational history could be reconstructed, and questionnaire. The incidence of adult-onset asthma among subjects without childhood asthma was defined by questions on asthma (ever) and medication by excluding asthma attack in last 12 months, asthma medication, and doctor’s diagnosed asthma at ECRHS I (for tier 1) or ECRHS II (for tier 2). Exposure was categorized into low, high and cumulative exposure using the updated occupational asthma-specific job-exposure matrix (OAsJEM). The outcome was investigated in adjusted Poisson regression models fitted with GEE and PAF calculated. Results: Low exposure to high molecular weight shellfish [tier 1 (RR2.10, 95%CI 1.08-4.12), PAF 24.7%; tier 2 (2.39,1.23-4.64), 16.3%] and flour [tier 1 (2.35,1.00-6.11), 17.2%; tier 2 (3.10,1.46-6.55), 14.2%] were associated with incident asthma. Low, high and cumulative exposures to bleach and indoor cleaning were also associated with incident asthma. Conclusion: These largest longitudinal findings strengthen and confirm the evidence that occupational exposures as a risk factor for adult-onset asthma. In future studies, exposure to these asthmagens should be controlled.