Allergen and Endotoxin Exposure, Infection, and Breastfeeding in Early Life, and Recurrent Wheezing in Infants: 18-month Follow-up of a Cohort Study

Abstract

RATIONALE: Factors in early life including infection, exposure to allergens and endotoxin, may play a role in development of sensitization and asthma. METHODS: One-hundred and four newborns were enrolled at birth in this cohort study. Children belonged to low-income families and were at high risk for asthma. Recurrent wheezing was defined as three or more wheezing episodes in the past year. Infection of the upper or lower respiratory tract requiring antibiotics was recorded. Dust samples were collected from bedding and floor of the infants' bedroom at enrollment. Endotoxin content was determined by Limulus Amebocyte Lysate assay, and major allergens from mites, cockroach, cat, dog, rat and mouse were quantitated by ELISA RESULTS: At age 18 months, 49/102 (48%) infants presented with recurrent wheezing. Multivariate analysis revealed that report of respiratory infection was significantly associated with recurrent wheezing, OR (95% CI)=3.72(1.36 - 10.22), p=0.008. Exposure to high levels of Mus m1 (greater than 1.6 μg/g of dust), and male gender correlated with significant reduction in frequency of recurrent wheezing, OR (95% CI)=0.11 (0.01 - 1.04); and OR 0.30 (0.12-0.76), respectively, p < 0.05. Exclusive breastfeeding for up to 6 months, and high level exposure to other indoor allergens showed no effect. Endotoxin in bedding ranged from 1.6 to 2,955 EU/mg of dust (GM 21.9EU/mg), with a tendency for high levels in bedding (>100EU/mg) being more frequently found among non-recurrent wheezers (p = 0.09). CONCLUSIONS: Respiratory infection was associated with recurrent wheezing, whereas male sex and exposure to high level of mouse allergens showed a protective effect early in life.