Cumulative occupational exposures and lung function decline in two large general population cohorts

RATIONALE: Few longitudinal studies have assessed the relationship between occupational exposures and lung function decline in the general population, with sufficiently long follow-up. OBJECTIVES: Our objective was to examine this potential association in two large cohorts (ECRHS and SAPALDIA). METHODS: General population samples aged 18 to 62 were randomly selected in 1991-1993, and followed up approximately 10 and 20 years later. Spirometry (without bronchodilation) was performed at each visit. Coded complete job histories during follow-up visits were linked to a Job-Exposure Matrix, generating cumulative exposure estimates for 12 occupational exposures. FEV1 and FVC were jointly modelled in linear mixed-effects models, fitted in a Bayesian framework, taking into account age and smoking. RESULTS: A total of 40,024 lung function measurements from 17,833 study participants were analyzed. We found accelerated declines in FEV1 and the FEV1/FVC ratio for exposure to biological dust, mineral dust and metals (FEV1 -15.1ml, -14.4ml and -18.7ml respectively, and FEV1/FVC -0.52%, -0.43% and -0.36% respectively, per 25 intensity-years of exposure). These declines were comparable in magnitude to those associated with long-term smoking. No effect modification by sex or smoking status was identified. Findings were similar between the ECRHS and SAPALDIA cohorts. CONCLUSIONS: Our results greatly strengthen the evidence base implicating occupation, independent of smoking, as a risk factor for lung function decline. This highlights the need to prevent or control these exposures in the workplace.