Confounding with familial determinants affects the association between mode of delivery and childhood asthma medication - a national cohort study

Abstract

Background: Mode of delivery may affect the risk of asthma but the findings have not been consistent and factors shared by siblings may confound the associations in previous studies.Methods: The association between mode of delivery and dispensed inhaled corticosteroid (ICS) (a marker of asthma) was examined in a register based national cohort (n=199 837). A cohort analysis of all first born children aged 2-5 and 6-9 years was performed. An age-matched sibling-pair analysis was also performed to account for shared genetic and environmental risk factors.Results: Analyses of first-borns demonstrated that elective caesarean section was associated with an increased risk of dispensed ICS in both 2..