Perceived indoor environment and exacerbations of COPD and asthma - a cohort study between 2000-2018

Background. Ambient air pollution has been associated with exacerbations of chronic obstructive pulmonary disease (COPD) and asthma; however, little is known about indoor environmental factors. Our aim was to study the association between perceived indoor environment and the long-term risk of exacerbations of COPD or asthma. Methods. We followed 2,317 individuals aged >= 16 years with COPD or asthma from the Danish Health and Morbidity Survey from 2000 to 2018. Individuals developing COPD or asthma during the study period were included at the time of incident diagnosis. Individuals were grouped according to their patterns of perceived indoor environment and followed up for exacerbations defined based on information from the Danish National Health Registers. The association between perceived indoor environment and exacerbations was examined using a generalized mixed model with the Poisson distribution of the number of exacerbations and logarithmic transformation of follow-up time as offset. Analyses were adjusted for age, sex, education, household income, smoking, calendar year, construction year, urbanization, home ownership, and resident density. Results. A total of 5,352 exacerbations were recorded in 2,317 individuals during a median of 13.9 years (interquartile range, 7.9-18.2 years). The adjusted incidence rate ratio (IRR) of exacerbations were 1.40 (95% CI 0.85-2.29 and 0.82 (95% CI 0.49-1.38) among individuals with medium and high levels om annoyances, respectively. For annoyances related to temperature and traffic the IRR was 0.88 (95% CI 0.61-1.27) and 1.39 (95% CI 0.88-2.19), respectively. Conclusion. We found no association between indoor environment assessed as annoyances at a single time-point and exacerbations of COPD and asthma.