Infectious Disease

High mold growth in urban households associated with difficult-to-control asthma in adolescents

October 22, 2021

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The levels of mucus in urban homes where teenagers lived predicted hard-to-control asthma, and one study found these levels to be more likely in homes with windowed air conditioners.

Difficult-to-control asthma (DTC) – which indicates a lack of symptom control despite high-dose inhaled corticosteroids and maximum adjunct therapy – is according to Stephen J. Vesper, MS. More common among urban, non-white, and underserved populations, PhD, from the U.S. Environmental Protection Agency’s Center for Environmental Measurement and Modeling, and colleagues.

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DTC asthma can also result in more frequent exacerbations, poorer drug responses, and lower lung function than easy-to-control (ETC) asthma.

The Asthma Phenotypes in the Inner City (APIC) study showed that participants with DTC asthma – defined as a daily therapy of 500 g or more fluticasone with or without long-acting beta agonists – had a significantly higher frequency of sensitization to mold. but not on dust mites, cockroaches, rodents, pets, pollen, peanuts, or other foods as compared to participants with ETC asthma, defined as 100 g or less of fluticasone.

Researchers performed a post-hoc analysis of APIC dust samples from homes in Baltimore, Boston, Chicago, Cincinnati, Denver, Detroit, New York City, and Washington, DC, with the Environmental Relative Moldiness Index (ERMI) panel rating 36 Mold was used.

Group 1 in ERMI includes 26 molds that indicate water damage in the home, while group 2 includes 10 species that are primarily outdoors and often found indoors, including in homes that are not water damaged. Higher ERMI values ​​indicate a higher level of mold contamination in the household.

The APIC study initially collected 485 dust samples from the households of children aged 6 to 17 years with DTC and ETC asthma by wiping horizontally over floor surfaces with a cloth. The current study examined 265 of these samples that were frozen and stored at -20 ° C. The mean age of the children represented in these samples was 11 years and 57.73% were male.

The results, published in the Journal of Allergy and Clinical Immunology, showed no significant difference between the average summed logs of Group 1 and Group 2 molds found in the households of children with DTC and ETC asthma, nor were the average ERMI Values ​​significantly different between these homes, indicating that overall mold contamination was not a differentiator of difficulty in controlling asthma.

However, after comparing the average concentrations of each of the 36 molds in ERMI, the researchers found that Mucor – a microbial genus of about 40 species of mold in the Mucoraceae family – was the only mold with a significantly higher concentration in the homes of people with DTC. was asthma than those with ETC asthma (295 vs. 67 cell equivalents / mg dust; P <0.001).

The researchers found that Mucor grows in and around air conditioning (AC) and plumbing due to condensation, especially if the device is not cleaned or the filter is not changed regularly, which is good.

Mucor concentrations were a significant predictor of the likelihood of DTC asthma (P = 0.007) in homes with windowed AC units but not in homes that did not have windowed AC units. Indeed, Mucor concentration contributed to an increase of approximately 22% (OR = 1.6; 95% CI 1.2-2.2) in the ability to differentiate between cases of DTC and ETC asthma.

The researchers named their results in line with previous studies that identified exposure to mold as relevant to difficulty controlling asthma. However, they cautioned against quantifying other potential exposures, such as other molds and contaminants inside and outside the home, so only high levels of Mucor can be an indicator and not a cause of DTC.

In addition, the researchers wrote, new approaches are needed to help children with DTC asthma, including eliminating the conditions that contribute to high Mucor levels.

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