The association between perceived annoyances in the indoor environment at home and respiratory infections: A Danish cohort study with up to 19 years of follow-up

BACKGROUND AND AIM The relation between perceptions of environment and respiratory infections has been studied by few and with inconsistent findings. Exposure to environmental contaminants may trigger the onset of respiratory infections, either directly or indirectly via annoyance. Perceived annoyance at home caused by the indoor environment is reported by 28% of Danish adults. This study aims to investigate the rate of respiratory infections for individuals exposed to perceived annoyance from the indoor environment, stratified by chronic respiratory disease. METHODS A total of 16,688 individuals completed a questionnaire and were interviewed to the Danish Health and Morbidity Survey in 2000. We grouped all eligible individuals based on whether they perceived a low, medium or high annoyance from their home indoor environment by latent class analysis of 13 items. The items covered sensory annoyance and discomfort by the indoor air, lighting, acoustics, and thermal comfort. Participants were followed for respiratory infections in Danish registers, until they met the criteria for censoring or end of study (1/1/2019). Poisson regressions of incidence rates were applied to estimate incidence rate ratios (IRRs) with 95% confidence intervals (CIs) for respiratory infections for each group of perceived annoyance. RESULTS We observed a significantly increased incidence of respiratory infections with increasing perceived annoyance. The highest IRR of respiratory infections was in the group with high perceived annoyance (adjusted IRR: 1.13, 95% CI: 1.07-1.20) and progressive decreases among the medium annoyance group (adjusted IRR: 1.05, 95% CI: 1.00-1.10) compared with low annoyance (reference). CONCLUSIONS We observed a significant dose-response relationship between the level of perceived annoyance and respiratory infections. KEYWORDS: Home environment Indoor environment Respiratory infection Perceived annoyance Perceived environment Cohort study