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Additional file 1: Extended Methods

Introduction: Many paediatric cohort studies describe the risk of wheeze at an older age compared to wheeze at a younger age. Few studies have described the frequency of wheezing with age, which helps the interpretation of this risk data. Aim: To describe the incidence of wheeze presentations by age group to a tertiary paediatric hospital (PMH). Methods: 10 years (2004-2014) of retrospective data from the Emergency Department (ED) Database at PMH was analysed. This database system prospectively collects demographic data for every child & the attending physician must select from 3 diagnoses: bronchiolitis, wheeze, and asthma; for primary wheeze presentations. Results: There were a total of 36,872 ED wheeze presentations over 2004-2014; categorised as asthma (n=11,606), bronchiolitis (n=14,641), and wheeze (n=10,625). The distribution of these by age group is presented and an exponential line (y=22417.91*0.593 x , r 2 =0.9936) has good fit. Of total presentations, 43.2% were admitted, and of these no significant differences in proportions of bronchiolitis, wheeze and asthma were found. Those diagnosed as “wheeze” decreased with age, suggesting greater diagnostic certainty of asthma with age. Conclusion: These data show an exponential decrease in wheeze presentations with each year of life through childhood. This suggests that the propensity to wheeze declines exponentially with age and that the diagnoses used are somewhat arbitrary.