Demographic and clinical characteristics
This study included a total of 16838 patients (mean age 30.94 years, SD ± 24.08 years) with AD enrolled from 205 hospitals across China from August, 2021 to September, 2022. The patients’ demographic characteristics are summarized in Table 1. Among all included patients with AD, the stratification criteria resulted in a high percentage of moderate (49.51%) AD patients with smaller proportions of mild (35.72%) and severe (14.77%) AD patients. In terms of gender distribution, 9156 patients were men (54.91%) and 3768 patients were women (45.09%). Females comprised a lower percentage of severe (12.14%) AD patients when compared to males (16.91%). The majority of patients included belong to the 18-60 years old age group. The age distribution of AD according to age was as follows: 0-2 years: 5.13%; 2-6 years: 12.74%; 6-12 years: 12.90%; 12-18 years: 7.91%; 18-60 years: 44.84%; and >60 years: 15.32%; In terms of severity, the proportion of patients with severe AD within each age group increased with age: from <10% in infants (0–2 years old) and preschoolers (2–5 years old) to 10–20% in children (6–11 years old), adolescents (12–17 years old), and adults (18–59 years old), to 26.56% in older adults (>60 years old). The proportion of patients with severe AD was the highest in patients with onset of AD at ≥60 years (26.73%). In terms of gender, the proportion of severe AD patients increased with the age of AD onset more drastically in males than females (Figure 1). There was a comparable proportion of moderate AD patients in males and females. There were less mild AD patients with older age of AD onset in males than females. In the entire study population, less AD patients included from rural areas of habitual residency. There was no significant difference in AD severity distribution between urban and rural areas of habitual residency. The proportion of AD severity group was similar across different levels of education. Overall, there was a higher proportion of patients with severe AD from northern China (north China 20.75%, northeast China 19.94%), while there was a lower proportion of patients with severe AD from western China (southwest China 10.72%, northwest China 10.93%) (Table 1). In the total population, the EASI score (mean 6.7, IQR 2.9–15) increased with AD severity; patients with severe AD had higher EASI scores than patients with mild and moderate AD (Table 1).