Figure 1.

Percentage of childhood asthma among preterm births versus term births, stratified by age group. (A) Childhood asthma measures assessed between ages 0 and 5 years. (B) Childhood asthma measures assessed between ages 6 and 9 years. The preterm group had a higher percentage of each asthma measure than the term group (P < 0.001). For asthma measures: ever asthma (≥1) = had at least one asthma diagnosis from the electronic medical record during the specified ages; recurrent asthma (≥2) = had two or more asthma diagnoses during the specified ages; recurrent asthma (≥4) = had four or more asthma diagnoses during follow-up time; ever wheezing (≥1) = had at least one wheezing diagnosis during the specified ages; recurrent wheezing (≥2) = had two or more wheezing diagnoses during the specified ages; recurrent wheezing (≥4) = had four or more wheezing diagnoses during the specified ages; ever asthma exacerbation = had an asthma exacerbation diagnosis during the specified ages. Please see Table E1 for more detailed description of asthma measures. SABAs = short-acting β-agonists.