Design of the cohort study
The original cohort consisted of 100 children aged younger than 24 months who were hospitalized in 1992–1993 because of a first wheezing episode associated with LRTI.14 The study was performed in Kuopio University Children’s Hospital, Finland. After the index episode, the cohort was prospectively followed-up at four control visits: one year after the index episode14 and again at median ages of 4.0 years,15 7.2 years12 and 12.3 years.16 In 2010, 49 cohort subjects aged 17–20 years attended the last follow-up visit.17 Supplementary E-figure 1 provides information on the asthma status of the participants from 1992 to 2010. All the analyses in the current study include the data on the 49 participants who attended the clinical follow-up visit in 2010 at a mean age of 18.8 years.