Asthma Diagnosis, Phenotypes and Severity, and Indoor Microbial Exposure among Urban and Rural Children in Saskatchewan, Canada
Date
2017-11-02
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
0000-0002-8650-0609
Type
Thesis
Degree Level
Doctoral
Abstract
Background: Childhood asthma is less common in rural compared to urban settings. This could be linked to possible asthma under-diagnosis in rural children. Furthermore, asthma presents with multiple phenotypes and degrees of severity; and may have varied associations with indoor microbial exposures.
Objectives: i) to investigate if rural children experience more asthma under-diagnosis compared to urban children; ii) to investigate the relationship between endotoxin and beta-(1→3)-D-glucan (BDG) with atopic asthma and exercise-induced bronchospasm (EIB); and iii) to examine the associations between endotoxin and BDG with asthma severity.
Methods: In 2015, following a 2013 cross-sectional study, we approached those who gave consent for further testing and repeated the survey and completed clinical assessments. The 2015 study included 335 schoolchildren (aged 7–17 years) in Saskatchewan, Canada. Play and mattress area settled dust sample collection was also completed. Asthma was identified based on survey responses and then based on a validated asthma algorithm. Children with confirmed asthma using the asthma algorithm (n = 116) formed the study population for the second (asthma phenotypes) and third (asthma severity) objectives. We evaluated asthma phenotypes based on skin prick testing and exercise challenge testing and asthma severity based on standard guidelines. Endotoxin and BDG were measured from dust samples using limulus amoebocyte lysate assay.
Results: The study population was comprised of 73.4% (large urban, LU), 13.7% (small urban, SU) and 12.8% (rural, R). The proportions of participants with survey-based vs. algorithm-based asthma classification were: 28.5% vs. 33.3% (LU), 34.8% vs. 41.3% (SU), and 20.9% vs. 34.9% (R). Among the algorithm-based asthma cases, 71.1% were atopic, 22.4% had EIB, 75.9% had mild asthma, and 24.1% had moderate/severe asthma. Play area endotoxin was inversely associated with atopic asthma while mattress endotoxin was positively associated with EIB. Furthermore, mattress endotoxin was positively associated with moderate/severe asthma and decreased lung function while play area BDG was inversely association with moderate/severe asthma.
Conclusion: The study revealed evidence of asthma under-diagnosis in rural children. Furthermore, the study provided evidence of varied associations between indoor microbial exposures and asthma phenotypes as well as asthma severity.
Description
Keywords
Asthma diagnosis, Atopic asthma, Exercise-induced bronchospasm, Asthma severity, Pulmonary function, House dust, Endotoxin, Beta-(1→3)-D-glucan, Schoolchildren, Urban-rural gradient, Saskatchewan
Citation
Degree
Doctor of Philosophy (Ph.D.)
Department
Community Health and Epidemiology
Program
Community and Population Health Science