Increasing prevalence of asthma and allergy in Beijing pre-school children： Is exclusive breastfeeding for more than 6 months protective

This study evaluated the prevalence and risk factors for asthma, allergy and related symptoms; and breastfeeding patterns and durations for 5479 Beijing children aged 3-6. Parents of children in randomly selected kindergartens wrote responses to a ques tionnaire used previously. The study aimed to evaluate trends in the prevalence of asthma and related illnesses, and to determine whether ＂more＂ breastfeeding, defined as exclusive, 〉 6 months, was associated with reduced prevalence. Asthma has increased in this age group between 1990 and 2011, with the steepest increase in the last 2-3 years. Of the total, 14.2% （779） children were breastfed exclusively for 〉 6 months. The efficacy of ＂more＂ breastfeeding was tested in a subset with two strong risk factors, positive family history （for asthma and/or allergy） and male gender. ＂More＂ breastfeeding was found to be significantly protective （aOR 0.42, P 〈 0.05） for this subset against Doctor-diagnosed asthma （D-asthma）. Protection that did not reach statistical significance was also found for this subset against Wheeze ever, Cough at night, Rhinitis ever, Doctor-diagnosed rhinitis （D-rhinitis） and Eczema. The greatest protective effects were found for girls with no family history of asthma or allergy, reaching statistical sig nificance for Wheeze ever （aOR 0.48, P 〈 0.01）, Cough at night （aOR 0.47, P 〈 0.01）, D-asthma （aOR 0.14, P 〈 0.01） and Rhini-tis ever （aOR 0.67, P 〈 0.05）. ＂More＂ breastfeeding was not consistently associated with either a protective or risk effect for Eczema.