Indoor airborne bacterial communities and adult lung health: A cross-sectional study

Indoor microbial exposures influence respiratory health, yet how men and women respond differently to airborne bacterial communities remains unclear. This study aimed to assess sex-specific associations between indoor airborne bacteria, and lung function, and airway inflammation in adults.

Airborne dust was collected from the bedrooms of 1038 adults (463 men, 575 women) across five Nordic cities as part of the European Community Respiratory Health Survey (ECRHS) III. Bacterial communities were profiled using 16S rRNA amplicon sequencing. Bacterial and endotoxin loads were quantified via quantitative PCR (qPCR) and the Limulus amebocyte lysate (LAL) assay, respectively. Multivariable linear regression models stratified by sex were used to examine associations with lung function and airway inflammation.

Greater indoor bacterial diversity was associated with higher lung function in men (FEV₁ β = 0.17, 95% CI: 0.05 to 0.29, P = 0.003) and higher FeNO levels in women (β = 2.44, 95% CI: 0.73 to 4.15, P = 0.005). Endotoxin load was positively associated with FeNO in women (β = 0.37, 95% CI: 0.05 to 0.70, P = 0.02), but not in men. Genera from Actinobacteriota and Bacilli were associated with higher lung function, while Clostridia was linked to lower lung function and reduced FeNO. In contrast, several genera from Actinobacteriota and Gammaproteobacteria were positively associated with FeNO.

Indoor bacterial exposures were associated with respiratory health in a sex-specific pattern. These findings highlight the importance of microbial composition in shaping adult lung health and underscore the need for sex-specific approaches in future epidemiological research.