Allergen and Endotoxin Exposure, Infection, and Breastfeeding in Early Life, and Recurrent Wheezing in Children: 30-month Follow-up of a Cohort Study

Abstract

RationaleExposure to environmental factors early in life may play a role in development of sensitization and asthma.MethodsOne-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 within six months after birth. Endotoxin content was determined by Limulus Amebocyte Lysate assay, and major allergens from mites, cockroach, cat, dog, mouse and rat were quantitated by ELISA in dust extracts. Serum IgE antibodies were measured by ImmunoCAP.ResultsAt age 30 months, 51/99(51.5%) infants presented with recurrent wheezing. Multivariate analysis revealed that respiratory infection was strongly associated with recurrent wheezing, OR (95% CI) 8.65 (2.60-28.78), p = 0.001, whereas exposure to high levels of mouse allergen (Mus m 1 > 1.6 μg/g of dust) OR 0.11 (0.01-1.07), p = 0.058, and exclusive breast feeding for at least one month OR 0.08 (0.015-0.42), p = 0.003, showed a protective effect. Male gender and high level exposure to endotoxin had no effect. Sensitization to D. pteronyssinus (CAP score ≥ 2) was found in 25/90 (27%) children, with no association with recurrent wheezing. None of the children were sensitized to mouse or rat, including those exposed to high levels of mouse allergen.ConclusionsRespiratory infection was associated with recurrent wheezing, whereas high exposure to mouse allergen and exclusive breastfeeding showed a protective effect early in life. RationaleExposure to environmental factors early in life may play a role in development of sensitization and asthma. Exposure to environmental factors early in life may play a role in development of sensitization and asthma. MethodsOne-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 within six months after birth. Endotoxin content was determined by Limulus Amebocyte Lysate assay, and major allergens from mites, cockroach, cat, dog, mouse and rat were quantitated by ELISA in dust extracts. Serum IgE antibodies were measured by ImmunoCAP. 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 within six months after birth. Endotoxin content was determined by Limulus Amebocyte Lysate assay, and major allergens from mites, cockroach, cat, dog, mouse and rat were quantitated by ELISA in dust extracts. Serum IgE antibodies were measured by ImmunoCAP. ResultsAt age 30 months, 51/99(51.5%) infants presented with recurrent wheezing. Multivariate analysis revealed that respiratory infection was strongly associated with recurrent wheezing, OR (95% CI) 8.65 (2.60-28.78), p = 0.001, whereas exposure to high levels of mouse allergen (Mus m 1 > 1.6 μg/g of dust) OR 0.11 (0.01-1.07), p = 0.058, and exclusive breast feeding for at least one month OR 0.08 (0.015-0.42), p = 0.003, showed a protective effect. Male gender and high level exposure to endotoxin had no effect. Sensitization to D. pteronyssinus (CAP score ≥ 2) was found in 25/90 (27%) children, with no association with recurrent wheezing. None of the children were sensitized to mouse or rat, including those exposed to high levels of mouse allergen. At age 30 months, 51/99(51.5%) infants presented with recurrent wheezing. Multivariate analysis revealed that respiratory infection was strongly associated with recurrent wheezing, OR (95% CI) 8.65 (2.60-28.78), p = 0.001, whereas exposure to high levels of mouse allergen (Mus m 1 > 1.6 μg/g of dust) OR 0.11 (0.01-1.07), p = 0.058, and exclusive breast feeding for at least one month OR 0.08 (0.015-0.42), p = 0.003, showed a protective effect. Male gender and high level exposure to endotoxin had no effect. Sensitization to D. pteronyssinus (CAP score ≥ 2) was found in 25/90 (27%) children, with no association with recurrent wheezing. None of the children were sensitized to mouse or rat, including those exposed to high levels of mouse allergen. ConclusionsRespiratory infection was associated with recurrent wheezing, whereas high exposure to mouse allergen and exclusive breastfeeding showed a protective effect early in life. Respiratory infection was associated with recurrent wheezing, whereas high exposure to mouse allergen and exclusive breastfeeding showed a protective effect early in life.