Published Online: October 2016
Children living in poor urban communities experience a high burden of severe asthma and exacerbations despite guidelines-directed care. While key factors underlying asthma severity have been identified, an integrated understanding of how these factors are linked and contribute to severe asthma is lacking.
In a study published in The Journal of Allergy & Clinical Immunology (JACI), Liu and colleagues used medical evidence in the published literature to develop a conceptual diagram of how 8 essential factors are linked to asthma severity: allergen sensitization, allergic inflammation, pulmonary physiology, stress, obesity, vitamin D, environmental tobacco smoke (ETS) exposure and rhinitis severity. They then used the NIH-sponsored Inner-City Asthma Consortium (ICAC) Asthma Phenotypes in the Inner City (APIC) study (published concurrently in the JACI – Pongracic et al) to test their concept using a causal network analysis. APIC participants comprised 6-17 year old children (n=561) with asthma and rhinitis from 9 U.S. urban centers who were evaluated and received guidelines-based asthma and rhinitis management every two months for one year. Asthma severity was characterized by a one-year composite assessment of day and night symptoms, exacerbations, and controller usage.
The researchers found their conceptual diagram explained a large part (53.4%) of the asthma severity observed in these children. Two pathways were the main contributors to asthma severity: an allergy pathway and an ETS exposure pathway. These pathways affected asthma mostly through their effects on lung function and the nose, such that pulmonary physiology and rhinitis severity had the largest effects on asthma severity, followed by ETS exposure and allergic inflammation. While vitamin D had a modest effect on allergic inflammation, its total effect on asthma severity was insignificant.
The authors conclude that, in inner-city children receiving guidelines-directed asthma and rhinitis care, the main factors affecting asthma severity are allergy and ETS exposure that exert their effects on lung function and the nose. This diagrammatic understanding of the key factors underlying severe asthma and their relative contributions can be used as a roadmap for prioritizing interventions to reduce disease severity and personalize asthma management, and for targeting interventional studies to improve guidelines-directed care.
The Journal of Allergy and Clinical Immunology (JACI) is an official scientific journal of the AAAAI, and is the most-cited journal in the field of allergy and clinical immunology.