Statistical analysis
The percentage, mean (standard deviation, SD) and median (interquartile
range, IQR) were used to describe the severity of AD and its population
characteristic distribution. The Kruskal-Wallis rank test was conducted
to examine differences in severity distributions of AD with comorbid
diseases as well as seasonal factors, food-related factors,
environmental factors and psychological factors. Due to regional
differences in the severity of AD, data collected in this study had a
two-level structure: regional level and individual level. Therefore,
two-level mixed ordered logistic regression was used to evaluate each
factor associated with disease aggravation and calculate the 95%
confidence interval after adjusting for potential confounding factors.
Statistical tests were two-tailed with P < 0.05, and
data were analyzed by STATA 14.0 (StataCorp, College Station, Texas,
USA).