Objective: To study occupational groups and occupational exposure in association with chronic obstructive respiratory diseases.

Methods: In early 2000s, structured interviews on chronic respiratory diseases and measurements of lung function as well as fractional expiratory nitric oxide (F_ENO) were performed in adult random population samples of Finland, Sweden and Estonia. Occupations were categorized according to three classification systems. Occupational exposure to vapours, gases, dusts and fumes (VGDF) was assessed by a Job-Exposure Matrix (JEM). The data from the countries were combined.

Results: COPD, smoking and occupational exposure were most common in Estonia, while asthma and occupations requiring higher educational levels in Sweden and Finland. In an adjusted regression model, non-manual workers had a three-fold risk for physician-diagnosed asthma (OR 3.18, 95%CI 1.07-9.47) compared to professionals and executives, and the risk was two-fold for healthcare & social workers (OR 2.28, 95%CI 1.14-4.59) compared to administration and sales. An increased risk for physician-diagnosed COPD was seen in manual workers, regardless of classification system, but in contrast to asthma, the risk was mostly explained by smoking and less by occupational exposure to VGDF. For F_ENO, no associations with occupation were observed.

Conclusions: In this multicenter study from Finland, Sweden and Estonia, COPD was consistently associated with manual occupations with high smoking prevalence, highlighting the need to control for tobacco smoking in studies on occupational associations. In contrast, asthma tended to associate with non-manual occupations requiring higher educational levels. The occupational associations with asthma were not driven by eosinophilic inflammation presented by increased F_ENO.