BRONCHIOLITIS AND ASTHMA IN INFANCY AND EARLY-CHILDHOOD

Background. Many young children wheeze during respiratory infections, but the pathogenesis of these episodes and their relation to the devel opment of asthma later in life are not well understood. Methods. In a prospective study, we investigated the factors affecting wheezing befo re the age of three years and their relation to wheezing at six years of age. Of 1246 newborns in the Tucson, Arizona area enrolled between May 1980 and October 1984, follow-up data at both three and six years of age was available for 826. For these children, assessments in infan cy included measurement of cord-serum IgE levels (measured in 750 chil dren), pulmonary-function testing before any lower respiratory illness had occurred (125), measurement of serum IgE levels at nine months of age (672), and questionnaires completed by the children's parents whe n the children were one year old (800). Assessments at six years of ag e included measurement of serum IgE levels (in 460), pulmonary-functio n testing (526), and skin allergy testing (629). Results. At the age o f six years, 425 children (51.5 percent) had never wheezed, 164 (19.9 percent) had had at least one lower respiratory illness with wheezing during the first three years of life but had no wheezing at six years of age, 124 (15.0 percent) had no wheezing before the age of three yea rs but had wheezing at the age of six years, and 113 (13.7 percent) ha d wheezing both before three years of age and at six years of age. The children who had wheezing before three years of age but not at the ag e of six had diminished airway function (length-adjusted maximal expir atory flow at functional residual capacity [Vmax FRC]) both before the age of one year and at the age of six years, were more likely than th e other children to have mothers who smoked but not mothers with asthm a, and did not have elevated serum IgE levels or skin-test reactivity. Children who started wheezing in early life and continued to wheeze a t the age of six were more likely than the children who never wheezed to ha ve mothers with a history of asthma (P<0.01), to have elevated s erum IgE levels (P<0.001), to have normal lung function in the first y ear of life, and to have elevated serum IgE levels (P<0.001) and dimin ished values for VmaxFRC (P<0.01) at six years of age. Conclusions. Th e majority of infants with wheezing have transient conditions associat ed with diminished airway function at birth and do not have increased risks of asthma or allergies later in life. In a substantial minority of infants, however, wheezing episodes are probably related to a predi sposition to asthma.