Nocturnal Asthma and Domestic Exposure to Fungi

Abstract

Fungal growth indoors is a common problem both in older and modern buildings. Numerous studies demonstrate a deterioration of asthma in environments with fungal growth but precise estimates of exposure levels have not been reported. This study was carried out to investigate whether levels of airborne fungi were higher in homes of subjects with nocturnal asthma as compared to controls. Subjects with nocturnal asthma (n = 42) and non-nocturnal asthma (n = 14) were recruited from an outpatient department. Subjects without disease or respiratory symptoms (n = 24) served as controls. Among the asthmatics, determinations were made of pulmonary function before and after treatment with bronchodilatators. The subjects were equipped with a pump and a filter and instructed to sample air in their bedroom. The filters were analysed for the content of N-acetylhexosaminidase (NAHA) as a marker of fungal cell biomass. In some houses the number of colony forming units was also determined. Patients with asthma had significantly higher activities of NAHA in their bedrooms as compared to controls (31.2 vs. 12.5 U m−3, p = 0.004). When the material was divided according to the 2nd quartile of NAHA (14.0 U m−3), 29 out of 42 subjects with nocturnal asthma had high values compared to 5 out of 24 for the controls (p<0.0001). The results support the hypothesis that patients with nocturnal asthma have high levels of fungi in their homes. This provides a basis for treatment and exposure diminution. Whether that exposure is causative for their disease; or if it aggravates already existing airway symptoms remains to be elucidated.