Acute respiratory tract infections during the first 6 years of life : results from the German birth cohort study LoewenKIDS

Objectives: Acute respiratory tract infections (ARIs) often occur in early childhood and are mostly self- limited. However, they impose a high socioeconomic burden and can be associated with chronic diseases later in life. To date, data on self-reported ARIs beyond infancy are limited. This study aimed to describe the incidence and characteristics of self-reported ARIs in the first 6 years of life. Methods: Data were obtained from the LoewenKIDS birth cohort study, including 782 children born be- tween 2014 and 2018. Parents recorded daily ARI symptoms, which were classified into episodes for inci- dence and characteristics analysis. Regression analyses explored the influence of exposure factors on ARI incidence. Results: This longitudinal birth cohort study of a subsample of 258 children found a mean cumulative duration of 51.5 weeks (95% confidence interval: 47.5-55.6 weeks) of respiratory symptoms in the first 6 years of life, with large individual differences. Children with frequent infections in infancy had more infections in preschool age. Exposure factors explained only a small fraction of variation in incidence (5%). Conclusions: There is a substantial variation in susceptibility to ARIs in childhood, which is not explained by exposure factors.