Abstract
BackgroundThe association between endotoxin exposure and asthma is complex and has been associated with rural living. We examined the relationship between domestic endotoxin and asthma or wheeze among rural school-aged children (6–18 years) and assessed the interaction between endotoxin and other characteristics with these outcomes.MethodsBetween 2005 and 2007 we conducted a case–control study of children 6–18 years in the rural region of Humboldt, Canada. Cases (n = 102) reported doctor-diagnosed asthma or wheeze in the past year. Controls (n = 208) were randomly selected from children without asthma or wheeze. Data were collected to ascertain symptoms, asthma history and indoor environmental exposures (questionnaire), endotoxin (dust collection from the play area floor and child’s mattress), and tobacco smoke exposure (saliva collection). Statistical testing was completed using multiple logistic regression to account for potential confounders and to assess interaction between risk factors. A stratified analysis was also completed to examine the effect of personal history of allergy.ResultsAmong children aged 6–12 years, mattress endotoxin concentration (EU/mg) and load (EU/m2) were inversely associated with being a case [odds ratio (OR) = 0.44, 95% confidence interval (CI) = 0.20-0.98; and OR = 0.38, 95% CI = 0.20-0.75, respectively]. These associations were not observed in older children or with play area endotoxin.ConclusionsOur results suggest that endotoxin exposure might be protective for asthma or wheeze. The protective effect is found in younger school-aged, non-allergic children. These results may help explain the inconsistencies in previous studies and suggest that the protective effects of endotoxin in the prevention of atopy and asthma or wheeze are most effective earlier in life.
Highlights
The association between endotoxin exposure and asthma is complex and has been associated with rural living
Higher mattress endotoxin was associated with a reduced risk of asthma/wheeze but the effect was greatest among children 12 years and younger and without a personal history of allergic disease
In conclusion, endotoxin appears to be associated with a decreased likelihood of having asthma or wheeze among children 12 years and younger and whose parents did not report a personal history of allergic disease
Summary
The association between endotoxin exposure and asthma is complex and has been associated with rural living. We examined the relationship between domestic endotoxin and asthma or wheeze among rural school-aged children (6–18 years) and assessed the interaction between endotoxin and other characteristics with these outcomes. Direct studies of household endotoxin exposure and the presence of asthma and wheeze among children have variably described reduced risk [7], increased risk [8] or no association [9,10]. One possible explanation for differences between studies could be interactions between endotoxin and other personal and environmental factors including rural living in associations with asthma. The purpose of this study was to examine associations between endotoxin exposure and asthma and wheeze in rural-residing children and to investigate the potential effect modification by personal and environmental characteristics on the association between endotoxin exposure and doctor diagnosed asthma or wheeze. We completed this study through the use of a case– control study design from a general population of children and adolescents
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