Occupational exposure and chronic bronchitis in a sample of the general population in Telemark, Norway: a two-phased cross-sectional study.

Objectives: We aimed to estimate the prevalence of chronic bronchitis (CB), examine its association with occupational exposure to irritants assessed by self-reporting or the Nordic job exposure matrix (N-JEM) stratified by smoking status and estimate the population-attributable fraction (PAF) of CB from occupational exposure.

Methods: A two-phased, cross-sectional design was used to analyse a random sample collected in 2013 and 2018 of the population aged 16-55 years in Telemark County, Norway. CB was defined as cough and sputum production for ≥3 months over 2 consecutive years. The participants' occupational histories were categorised using the International Standard Classification of Occupations and linked to the N-JEM. Self-reported occupational exposure was also assessed. Logistic regression was performed with adjustments for age, sex and smoking status and yielded ORs, 95% CIs and associated PAFs.

Results: Of the 20 282 participants, 5.3% reported CB symptoms. CB was associated with the frequency of self-reported occupational exposure to vapours, gas, dust and fumes (VGDF), with increasing ORs ranging from 1.6 (95% CI 1.3 to 1.9) for seldom to 3.6 (95% CI 2.9 to 4.5) for daily exposure. Among ever-smokers, the N-JEM 'irritants' category was associated with CB (OR 1.4; 95% CI 1.1 to 1.8) to a similar degree as in the group that reported VGDF exposure (OR 2.1; 95% CI 1.7 to 2.5). The PAFs for CB from VGDF exposure were 41% overall, 49% among ever-smokers and 37% among never-smokers.

Conclusions: Occupational exposure to VGDF was associated with CB, when self-reported and for smokers when assessed by the N-JEM. Workplace exposure contributed to more than one third of the overall CB burden.