RATIONALE

Daycare exposes young children to more infections early in life and may thereby prevent the development of asthma and allergy.

OBJECTIVES

To prospectively study the effect of daycare on the development of asthma and allergic sensitization during the first 8 years of life.

METHODS

In the Prevention and Incidence of Asthma and Mite Allergy birth cohort 3,963 newborn children were followed prospectively for 8 years. Daycare use and respiratory health were assessed yearly by questionnaires. At 8 years, sensitization to airborne allergens and airway responsiveness were measured. Daycare was defined as early (aged 0-2 yr), late (aged 2-4 yr), or none (no daycare before age 4 yr). Associations of daycare and/or older siblings with asthma symptoms (wheezing, shortness of breath, and inhaled steroids taken in the last year), airway responsiveness, and allergic sensitization were assessed in a longitudinal repeated-event analysis.

MEASUREMENTS AND MAIN RESULTS

Children with early daycare had more wheezing in the first years of life, but less wheezing and steroid use between 4 and 8 years of age. At the age of 8 years, early daycare was not protective for asthma symptoms (adjusted odds ratio [aOR], 0.99; 95% confidence interval [CI], 0.74-1.32), allergic sensitization (aOR 0.86; 95% CI, 0.63-1.18), or airway hyperresponsiveness (aOR, 0.80; 95% CI, 0.57-1.14). The transient reduction in airway symptoms between age 4 and 8 years was only observed in children without older siblings.

CONCLUSION

Early daycare is associated with an increase in airway symptoms until the age of 4 years, and fewer symptoms between the ages of 4 and 8 years. We found no protection against asthma symptoms, hyperresponsiveness, or allergic sensitization at the age of 8 years.