Frequency and severity of lower respiratory infections associated with persistent asthma in children: A retrospective birth cohort population-based study

Background: The influences of frequency and severity of respiratory infections in early life on early and late asthma development have not yet been confirmed. Materials and Methods: Data from the National Health Insurance Research Database (NHIRD) for the period 1996-2012 were used to obtain a birth cohort of children. Persistent asthma (AS) was defined as AS diagnosis before the age of two years with persistence of AS to the age of twelve years. Late-onset AS referred to first AS diagnosis after the age of five years. Results: A total of 2,305 children were included in persistent AS group and a total of 2,834 children were included in late-onset AS group in our birth cohort study. There were significant differences in the frequencies of lower respiratory infections between the two groups , for those under 2 years of age and for those between 3 and 5 years of age (7.2± 6.1 vs 3.5±4.0 , 6.8±6.0 vs 4.9±5.0 respectively, p＜0.001). Rates of emergency department visits due to lower respiratory infection were 24.6% in persistent AS group and 9.0% in late-onset AS group with adjusted odds ratio (OR) of 3.2 (95% confidence interval (CI) : 2.7-3 .7) for under 2 years of age. At 2-5 years of age, frequencies were 20.4% and and 12.0% in persistent AS and late-onset AS groups, respectively, with adjusted OR of 1.8 (95% CI: 1.6-2.2). Hospitalization rates due to lower respiratory infection were 35.1% in persistent AS group and 9.6% in late-onset AS group with adjusted OR of 5.0 (95% CI:4.3-5 .8) for under 2 years of age. At 2-5 years of age, these rates were 25.6% and 11.9% in peristent AS and late-onset AS groups, respectively, with adjusted OR of 2.5 (95% CI:2.2-2.9). Conclusion: The frequency and severity of lower respiratory infections are associated with early and late asthma development.