Early Daycare Is Associated with an Increase in Airway Symptoms in Early Childhood but Is No Protection against Asthma or Atopy at 8 Years

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.