Statistical Analysis

The characteristics of subjects with or without asthma were examined by the chi-squared test or Student's t-test.

In order to control for confounding factors (such as age, gender, parental smoking, and parental history of asthma), multiple logistic regression analysis was employed. We used artificial milk users as the reference to investigate the effect of breast-feeding on the prevalence of asthma. We also conducted test of trend for dose response relationship.