Indoor fungi not linked to children´s asthma risk

Fungi such as moulds and yeasts in the indoor environment are not associated with an increased risk of asthma among children, according to a study conducted by the Finnish Institute for Health and Welfare (THL).

The study, which analysed the microbiota of about 380 Finnish homes, also found that the presence of farm-like microbiota in a home protected children from asthma even in urban homes.

Based on the new findings, it appears that bacteria in the living environment have a greater role in protecting against asthma than fungi do.  

From this same birth cohort, it was previously reported that higher levels of specific bacteria, most likely originated from outdoors, may reduce a child's risk of developing asthma.

There are moulds and yeasts everywhere in our living environment and they are a natural part of the microbiota of a normal home.

In the study, the number of fungal species, the diversity of fungal species or the amount of fungi in the samples were not linked to the risk of developing asthma.  

"Those 13 fungal genera that were related to asthma were inversely associated with asthma rather than being risk factors. Before starting this research, we believed we would find links to both types of fungi, those protecting against development of asthma and those increasing asthma risk. Our results provide a better understanding of fungi in the indoor environment," said Anne Karvonen, Chief Researcher of THL. 

"Moulds and yeasts in the indoor environment have often been linked to moisture damage buildings and the related health hazards. In the future, the aim will be to examine whether those fungi that are associated with moisture damage in the home can explain the connection between moisture damage and asthma. Based on the preliminary results of this study, it does not appear so. In future analyses, we will improve exposure assessment by studying the significance of living and dead microbial cells separately," said Martin Täubel, Chief Researcher at THL. 

The article ”Fungi in Early-Life House Dust Samples and the Development of Asthma” authored by THL researchers was published in The Annals of American Thoracic Society in August 2023.