Methods: Data from 878 children of Cohort of Allergic Rhinitis in Korea (COAR-Korea) Study were analyzed. Children with rhinitis were recruited from 14 centers located in 6 provinces of South Korea between April 2008 and September 2010. All subjects were divided into allergic rhinitis (AR) group and nonallergic rhinitis (NAR) group according to skin prick test response. Data on environmental factors, including mode of delivery and breast-feeding duration, were collected using a questionnaire. Relationships were analyzed using logistic regression analyses.
Results: We found that 77% of the population with rhinitis had AR, whereas 23% had NAR. Compared with never breast-fed, breast-feeding for ≥ 12 month was significantly associated with a lower prevalence of AR (aOR, 0.64; 95% CI, 0.41-0.99). Children who were born by Cesarean section showed a higher prevalence of AR compared with those born by vaginal delivery (OR, 1.48; 95% CI, 1.05-2.09). However, after adjustment for confounders under study, this difference was lost (aOR, 1.40; 95% CI, 0.90-2.20). Children born by Cesarean section were shown significantly lower rates of breast-feeding initiation (70.5% vs. 78.9%, P = 0.005) and lower rates of longer (for ≥ 12 months) breast-feeding maintenance compared with those born by vaginal delivery (35.5% vs. 48.4%, P = 0.005).
Conclusions: Amongst environmental factors, longer duration (for >12 months) of breast-feeding seems to be the most powerful protective factor against the risk of developing AR in young children. However, breast-feeding behavior seemed to be affected by mode of delivery and must be considered as a strong confounding factor in evaluating the correlation between environmental risk factors and development of allergic diseases.