Pathways through which asthma risk factors contribute to asthma severity in inner-city children

Abstract

Background Pathway analyses can be used to determine how host and environmental factors contribute to asthma severity. Objective Investigate pathways explaining asthma severity in inner-city children. Methods Based on medical evidence in the published literature, we developed a conceptual model to describe how eight risk-factor domains (allergen sensitization, allergic inflammation, pulmonary physiology, stress, obesity, vitamin D, environmental tobacco smoke (ETS) exposure and rhinitis severity) are linked to asthma severity. To estimate the relative magnitude and significance of hypothesized relationships among these domains and asthma severity, we applied a causal network analysis to test our model in an Inner-City Asthma Consortium study. Participants comprised 6–17 year old children (n=561) with asthma and rhinitis from 9 U.S. inner-cities who were evaluated every two months for one year. Asthma severity was measured by a longitudinal composite assessment of day and night symptoms, exacerbations, and controller usage. Results Our conceptual model explained 53.4% of the variance in asthma severity. An allergy pathway (linking allergen sensitization, allergic inflammation, pulmonary physiology, and rhinitis severity domains to asthma severity) and ETS exposure pathway (linking ETS exposure and pulmonary physiology domains to asthma severity) exerted significant effects on asthma severity. Among the domains, pulmonary physiology and rhinitis severity had the largest significant standardized total effects on asthma severity (−0.51 and 0.48 respectively), followed by ETS exposure (0.30) and allergic inflammation (0.22). While vitamin D had modest but significant indirect effects on asthma severity, its total effect was insignificant (0.01). Conclusions The standardized effect sizes generated by a causal network analysis quantify the relative contributions of different domains and can be used to prioritize interventions to address asthma severity.

New Insights into Cockroach Allergens

“…The Inner-City Asthma Consortium - Asthma Phenotypes in the Inner City (APIC) study contributed to understanding the role of host and environmental factors influencing severity of asthma among inner-city children and adolescents in the US ●●[18,19]. Results of this study revealed that, in spite of good adherence to optimal treatment, inner-city children and adolescents with difficult-to-control asthma had little improvement in symptoms, exacerbations, and pulmonary physiology over a one-year follow-up.…”

“…Allergen sensitization, allergic inflammation, pulmonary physiology, environmental tobacco smoke (ETS) exposure, and rhinitis severity were significantly related to asthma severity, whereas stress, obesity, and vitamin D showed no significant effect on disease severity ●●[18]. Allergen sensitization was the strongest association detected (linked to allergic inflammation, and subsequently to pulmonary physiology and rhinitis severity) to contribute to asthma severity, suggesting that allergen sensitization could be the originating domain among the multiple pathways involved in severity of the disease ●●[18]. …”

Minimally important differences and risk levels for the Composite Asthma Severity Index

“…The APIC study 5-7 was an observational study designed to identify determinants of asthma severity. During the APIC study, children ages 6 to 17 years, with a wide range of asthma severity, received standardized guidelines-directed asthma treatment for one year.…”

Advances in environmental and occupational disorders in 2016

“…Thus, recognition of the amount of allergic inflammation in an inner-city child may not only assist in guiding allergen avoidance strategies, but may also predict children in need of closer monitoring due to difficult- to-control asthma. Finally, Lui et al(71) investigated pathways through which asthma risk factors contribute to asthma severity in these inner-city children. In this analysis, it was discovered that the allergy pathway and tobacco smoke exposure pathway exerted the predominant effects on asthma severity.…”

“…In the APIC study, environmental tobacco smoke was associated with worsening pulmonary physiology and increased asthma severity. (71) Horner et al(73) reported that increased child-reported stress during the day was associated with an increased likelihood of awakening that night from asthma, but not awakening for a reason other than asthma. Finally, a study of inner-city schools discovered that increased exposures to mouse allergen in the schools was associated with increased asthma symptom days and decreased lung function.…”