Calculation of ERS and genetic risk score
Environmental risk score was calculated using four environmental factors: antibiotic use during infancy, cesarean section delivery, breast milk feeding, and having older siblings. Weighted ERS was obtained using the following procedure: scores assigned to children according to the absence and presence of each environmental risk factor were multiplied by the crude odds ratio (OR) of each factor and then the sum of these scores was calculated and transformed in the natural log.
The PRS was calculated using four SNPs: IL-13 (rs20541, risk allele = A), CD14 (rs2569190, T), TLR4 (rs1927911, T), and GSTP1 (rs1695, G). The weighted PRS was calculated by the following procedure: the scores of each SNP were assigned to children according to the number of risk alleles carried by a child multiplied by the crude OR of each SNP for the risk of current AR, summed up, and transformed in a natural log.24