Exclusive breast-feeding, the early-life microbiome and immune response, and common childhood respiratory illnesses

Background: The impact of breast-feeding on certain childhood respiratory illnesses remains controversial. Objective: We sought to examine the effect of exclusive breast-feeding on the early-life upper respiratory tract (URT) and gut microbiome, the URT immune response in infancy, and the risk of common pediatric respiratory diseases. Methods: We analyzed data from a birth cohort of healthy infants with prospective ascertainment of breast-feeding patterns and common pediatric pulmonary and atopic outcomes. In a subset of infants, we also characterized the URT and gut microbiome using 16S ribosomal RNA sequencing and measured 9 URT cytokines using magnetic bead-based assays. Results: Of the 1949 infants enrolled, 1495 (76.71%) had 4-year data. In adjusted analyses, exclusive breast-feeding (1) had an inverse dose-response on the a-diversity of the early-life URT and gut microbiome, (2) was positively associated with the URT levels of IFN-alpha, IFN-gamma, and IL-17A in infancy, and (3) had a protective dose-response on the development of a lower respiratory tract infection in infancy, 4-year current asthma, and 4-year ever allergic rhinitis (odds ratio [95% CI] for each 4 weeks of exclusive breast-feeding, 0.95 [0.91-0.99], 0.95 [0.90-0.99], and 0.95 [0.92-0.99], respectively). In exploratory analyses, we also found that the protective association of exclusive breast-feeding on 4-year current asthma was mediated through its impact on the gut microbiome (P = .03). Conclusions: Our results support a protective causal role of exclusive breast-feeding in the risk of developing a lower respiratory tract infection in infancy and asthma and allergic rhinitis in childhood. They also shed light on potential mechanisms of these associations, including the effect of exclusive breast-feeding on the gut microbiome.

Automated summary

Exclusive breast-feeding has a protective causal role in reducing the risk of lower respiratory tract infections, asthma, and allergic rhinitis in childhood. This association may be mediated through its impact on the early-life upper respiratory tract and gut microbiome, as well as the immune response in infancy.