Case-control study of exclusive breast feeding and severe bronchiolitis in the United States.

BACKGROUND: Bronchiolitis is a major cause of infant illness, with few known modifiable risk factors. Breast feeding may reduce risk of severe bronchiolitis, but the association of exclusive vs. partial breast feeding with severe bronchiolitis is unclear. OBJECTIVE: To estimate the association of exclusive vs. partial breast feeding during ages 0-2.9 months with bronchiolitis hospitalisation during infancy. METHODS: We conducted a case-control study as a secondary analysis of two prospective US cohorts in the Multicenter Airway Research Collaboration. Cases were enrolled in a 17-centre study of infants hospitalised for bronchiolitis during 2011-2014 (n = 921). Controls were enrolled in a five-centre study of healthy infants during 2013-2014 and 2017 (n = 719). Breast feeding history during ages 0-2.9 months was collected by parent interview. Among breastfed infants, the association of exclusive vs. partial breast feeding with odds of bronchiolitis hospitalisation was estimated using a multivariable logistic regression model adjusted for demographic variables, parental asthma history, and early-life exposures. As a secondary analysis, we estimated the associations of exclusive, predominant, and occasional breast feeding vs. no breast feeding with the odds of bronchiolitis hospitalisation. RESULTS: Among 1640 infants, the prevalence of exclusive breast feeding was 187/921 (20.3%) among cases and 275/719 (38.3%) among controls. Exclusive vs. partial breast feeding was associated with 48% reduced odds of bronchiolitis hospitalisation (adjusted odds ratio [OR] 0.52, 95% confidence interval [CI] 0.39, 0.69). In the secondary analysis, exclusive vs. no breast feeding was associated with 58% reduced odds of bronchiolitis hospitalisation (OR 0.42, 95% CI 0.23, 0.77), whereas predominant breast feeding (OR 0.77, 95% CI 0.37, 1.57) and occasional breast feeding (OR 0.98, 95% CI 0.57, 1.69) were not associated with meaningfully reduced odds of bronchiolitis hospitalisation. CONCLUSION: Exclusive breast feeding had a strong protective association against bronchiolitis hospitalisation.

Blood eosinophils, specific immunoglobulin E, and bronchiolitis severity.

BACKGROUND: Bronchiolitis is the leading cause of hospitalization for United States infants. Blood eosinophil and serum specific IgE (sIgE) levels are separately linked to clinical severity but few studies have examined these biomarkers together. OBJECTIVE: Among infants hospitalized for bronchiolitis, we investigated the association between (1) blood eosinophilia and severity, (2) sIgE sensitization and severity, and (3) interaction between the two biomarkers on severity. METHODS: We enrolled 1016 infants hospitalized for bronchiolitis between 2011 and 2014 across 17 U.S. hospitals into a prospective cohort study. Of those, 873 (86%) had eosinophils measured and all had sIgE levels from blood collected at hospitalization. We investigated higher bronchiolitis severity using intensive care therapy as the outcome (i.e., intensive care unit admission, intubation, and/or receipt of continuous positive pressure ventilation). RESULTS: Among 873 infants in the analytic cohort, 18% had blood eosinophilia of ≥3%, and 20% were positive for sIgE. With regard to bronchiolitis severity, 15% received intensive care therapy. In unadjusted analyses, eosinophils ≥3% was not associated with intensive care therapy, while sIgE was associated with a significantly higher risk (odds ratio [OR]: 1.44, 95% confidence interval [CI]: 1.08-1.92; p = .01). In a multivariable model for intensive care therapy, eosinophilia remained unassociated with severity, and sIgE remained associated (OR: 1.60, 95% CI: 1.05-2.45; p = .03). Also, sIgE did not modify the association between eosinophil level and intensive care therapy (pinteraction = .14). CONCLUSION: Blood eosinophilia of ≥3% was not associated with bronchiolitis severity. By contrast, sIgE was independently associated with bronchiolitis severity and did not modify the association between eosinophil level and severity.

Socioeconomic Status and Bronchiolitis Severity Among Hospitalized Infants.

OBJECTIVE: To investigate the relationship between socioeconomic factors and bronchiolitis severity among hospitalized infants. METHODS: We performed a 17-center, prospective cohort study from 2011 to 2014. Children <1 year old hospitalized with bronchiolitis were enrolled. Socioeconomic factors included estimated median household income (MHI) per home ZIP code, parent-reported household income, number of adults and children in household, and insurance type. We defined higher bronchiolitis severity as receipt of intensive care treatment. Multivariable logistic regression was used to analyze the association between socioeconomic factors and bronchiolitis severity, with the final model adjusted for potential clustering by site. RESULTS: In multivariable models adjusted for demographic and clinical characteristics, estimated MHI was the socioeconomic factor most strongly associated with severity. Compared to infants with an intermediate MHI ($40,000-$79,999), odds of receiving intensive care treatment were significantly higher for those with MHI of ≥$80,000 (aOR 2.05, 95% CI 1.19-3.53). No significant associations were found for the other socioeconomic factors (all P > .30). While there were no significant differences in clinical presentation between income groups (all P > .25) or in receipt of mechanical ventilation alone (P = .98), infants with estimated MHI ≥$80,000 were significantly more likely to specifically have been admitted to the intensive care unit (P = .01). CONCLUSIONS: In this multicenter study of infants hospitalized with bronchiolitis, we identified higher median household income as a risk factor for intensive care treatment. This work may yield important biological or nonbiological insights for the future management of infants with bronchiolitis.