The relation of breast feeding and other factors to the incidence of respiratory syncytial virus-associated lower respiratory tract illness (RSV-LRI) in the first year of life is examined. The study population is 1,179 healthy infants enrolled at birth between May 1980 and January 1984 into the Tucson Children's Respiratory Study, Tucson, Arizona. Each subject's data were assessed at each month of age during the first year of life, during those months when respiratory syncytial virus was isolated. A number of significant relations were observed, particularly between 1 and 3 months of age. At this age, the risk of having a RSV-LRI increased in association with less than 1-month or no breast feeding, with being male, and with increasing numbers of others sharing the child's bedroom. In multivariate analysis, only sex and the number of others sharing the room remained as significant direct effects. However, a significant interaction demonstrated that breast feeding has a protective role in relation to RSV-LRIs for those infants of mothers with a lower education level. The risk of having a RSV-LRI increases with combinations of risk factors. Being in day care was a significant risk factor in the 7- to 9-month age range. The RSV-LRI rate also varies by birth month. A separate case-control study assessed relations of RSV-LRIs with cord serum RSV antibody. Those with lower cord serum RSV antibody, who also have minimal breast feeding, were found to be especially at risk for RSV-LRIs in the first 5 months of life.
Peroxidase (myeloperoxidase or lactoperoxidase), hydrogen peroxide, and a halide such as iodide, bromide, or chloride form a potent virucidal system that is effective against polio and vaccinia viruis, particularly at a low pH. The peroxidase-halide-hydrogen peroxide system may contribute to the host defense against certain viral infections.
Cord serum IgE levels are predictive of subsequent atopic diseases early in life. Lower respiratory illnesses (LRI) have often been included with atopic diseases in infancy but have not been examined as a separate entity for a relation to cord IgE levels. Among 767 healthy newborns in Tucson, Arizona studied longitudinally, cord serum IgE levels were directly related to the subsequent incidence of eczema. In contrast, the incidence of LRI not only failed to show a direct relationship to IgE levels but actually decreased with increasing cord IgE levels from 34.8% in the lowest cord IgE group to 22.2% in the highest IgE group (greater than 1.0 IU/ml IgE; p for trend chi-square less than 0.03). Limiting LRI to those with wheeze did not alter the inverse relationship with IgE levels. The inverse LRI-IgE relationship was strong for non-RSV LRI, whereas RSV LRI had neither a direct nor an inverse relationship. These inverse LRI-IgE relationships were significant for LRI occurring in infants before but not after 6 months of age. Maternal (but not paternal) allergic history was associated with higher cord IgE levels and with an increased incidence of LRI, the latter effect being independent of IgE. This study suggests that most LRI in the first year of life are not early manifestations of an allergic predisposition.
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