Risk of childhood asthma in relation to the timing of early child care exposures

Abstract

Objective: To examine whether early child care exposure influences the risk for development of asthma.

Study design: Longitudinal data from 939 children and their families from the National Institute of Child Health and Development Study of Early Child Care and Youth Development were analyzed. Exposure to other children in the primary child care setting as an infant (before 15 months) and as a toddler (16-36 months) were assessed as risk factors for persistent or late-onset asthma by age 15 via logistic regression.

Results: The number of children in the child-care environment when the child was a toddler was significantly associated with odds of asthma, even after adjusting for respiratory illnesses and other risk factors (P < .05). The fewer the children exposed to as toddlers, the higher the probability of persistent or late-onset asthma by age 15.

Conclusions: This study supports the theory of a protective effect of exposure to other children at an early age, especially as a toddler, on the risk of asthma. This effect appears to be independent of the number of reported respiratory tract illnesses, suggesting that other protective mechanisms related to the number of children in the child care environment may be involved.

Figure 1

Model-Predicted Probability of Asthma (Persistent or Late-Onset) by Number of Other Children in the Child-Care Environment as a Toddler* * Predicted probability as a function of mean number of other children in the child care setting as a toddler, using the final logistic model (Table IV), adjusting for all of the listed covariates. This figure presents specific probabilities for a Caucasian male whose mother did not report having asthma in a “clean” household who had 4 and 5 respiratory infections as an infant and toddler, respectively, who was not preterm, does not have eczema, and was breastfed, who was in primary care 32 hours per week in the first three years, who was around 2 other children in the primary care setting as an infant, with a mother with 14 years of education and is 29 years old and did not smoke during pregnancy, from an urban household with an income-to-needs ratio of 3 (all values are medians from the dataset). This overall relationship would remain no matter what values were chosen for the other covariates.