Chronic cough and phlegm in relation to occupational exposures in a prospective cohort study (ECRHS III)

A causal relationship between occupational exposures and the development of chronic bronchitis and COPD has been recognized, but there is limited evidence from prospective population-based studies. The ECRHS is a multicentre cohort study that has recently completed a second follow-up after a mean of 19 years. We examined the relationship between occupational exposures and group-level changes in chronic bronchitis symptoms using 3 time points. We used repeated questionnaire data from 9175 ECRHS participants in 29 study centres, 6754 (74%) of whom completed the second follow-up. Occupational exposures were assessed from job histories up to the first follow-up using the ALOHA Job-Exposure Matrix. Absolute annual change in prevalence of chronic cough and/or chronic phlegm was assessed using Generalized Estimating Equation models, fitted separately for each study centre and pooled using multivariate meta-analysis. Any high exposure to dusts, gases or fumes (14% of participants) was associated with increasing prevalence of cough or phlegm in men (0.087%/year, p=0.002), and decreasing prevalence of cough with phlegm in women (-0.039%/ year, p