Objectives It is still not well established how
occupational air pollutants affect the prognosis of
asthma or
chronic obstructive pulmonary disease (
COPD). This study uses nationwide Danish registers and quantitative dust industry exposure matrices (IEM) for the farming and wood industries to estimate whether previous year dust exposure level impacts
hospital readmissions for workers diagnosed with
asthma or
COPD. Methods We identified all individuals with a first diagnosis of either
asthma (769 individuals) or
COPD (342 individuals) between 1997 and 2007 and followed them until the next hospital admission for
asthma or
COPD, emigration, death or 31 December 2007. We included only individuals who worked in either the wood or farming industries at least one year during follow-up. We used logistic regression analysis to investigate associations between dust exposure level in the previous year and
hospital readmission, adjusting for sex, age, time since first diagnosis, socioeconomic status, and labor force participation. Results
Asthma readmissions for individuals with low and high dust exposure were increased [adjusted rate ratio (RR adj) 2.52, 95% confidence interval (CI) 1.45-4.40] and RR adj2.64 (95% CI 1.52-4.60), respectively. For
COPD readmission, the risk estimates were RR adj1.36 (95% CI 0.57-3.23) for low and RR adj1.20 (95% CI 0.49-2.95) for high exposure level in the previous year. For
asthma readmission, stratified analyses by type of dust exposure during follow-up showed increased risks for both wood dust [RR adj2.67 (95% CI 1.35-5.26) high exposure level] and farming dust [RR adj3.59 (95% CI 1.11-11.59) high exposure level]. No clear associations were seen for
COPD readmissions. Conclusions This study indicates that exposure to wood or farm dust in the previous year increases the risk of
hospital readmission for individuals with
asthma but not for those with
COPD.