Differential effects of outdoor versus indoor fungal spores on asthma morbidity in inner-city children

Background

Although sensitization to fungal allergens is prevalent in inner-city children with asthma, the relationship between fungal exposure and morbidity is poorly understood.

Objective

We examined relationships between fungal sensitization, exposure, and asthma morbidity in inner-city children.

Methods

Participants were 5 to 11 years old and enrolled in the Inner-City Asthma Study. This report includes the subset of children with at least 1 positive skin test (PST) response to a fungal allergen extract; for these children, indoor and outdoor airborne culturable fungi levels were measured at baseline and throughout the 2-year study. Asthma morbidity measures were collected prospectively. The primary outcome was symptom days per 2 weeks.

Results

At baseline, children with a PST response to a fungal allergen extract had significantly more symptom days compared with those without a PST response to any fungal allergen extract (6.3 vs 5.7 days per 2 weeks, P = .04). During the study, increases in total fungal exposure and indoor Penicillium species exposure were associated with increases in symptom days and asthma-related unscheduled visits. Indoor exposures to total fungi and to Penicillium species were associated with significant increases in unscheduled visits, even after controlling for outdoor fungal levels. Adverse effects associated with exposure to a specific fungus were stronger among children with PST responses to that fungal allergen extract compared with those seen in children with negative skin test responses.

Conclusion

Outdoor fungal exposure is primarily associated with increased asthma symptoms and increased risk of exacerbations in this population.

Key words: Asthma, inner city, airborne fungi, indoor fungi, outdoor fungi, fungal allergens, children

Abbreviations used: DG18, Dichloran glycerol agar, ICAS, Inner-City Asthma Study, MSD, Maximum symptom day, NHLBI, National Heart, Lung, and Blood Institute, NST, Negative skin test, OR, Odds ratio, PST, Positive skin test, UV, Unscheduled visit