The limitation of our statistical methods is the small number of the reference for analysis of association between feeding pattern and asthma
(n = 4,116). Although the reference is prefer to large number, we used artificial milk users as the reference since we would like to know the effects of "any exposure to breast-milk" vs. none on the prevalence of asthma. When we recalculated adjusted odds ratio to see the effect of exclusive breast-feeding on prevalence of asthma comparing with the subjects with mixed- or artificial-milk-feeding, we obtained the similar result (Adjusted odds ratio: 1.126, 95 percent confidence interval: 1.031, 1.230; p < 0.01).