Supplementary Material for: National trends and prevalence of atopic dermatitis and pandemic-related factors among Korean adults, 2007-2021

Purpose: Previous studies have variably reported inconclusive trends in the prevalence of atopic dermatitis (AD) among adults, and there is limited data on the impact of the COVID-19 pandemic. We aimed to investigate the national trends and age-stratified prevalence of AD among adults from 2007 to 2021 in South Korea, focusing mainly on the impact of the COVID-19 pandemic-related factors.
Methods: A nationwide cross-sectional study was conducted using the Korea National Health and Nutrition Examination Survey (KNHANES) data from 2007 to 2021. Overall and age-stratified prevalence for AD were assessed using weighted beta coefficients or odds ratios.
Results: A total of 83,566 adults over 20 years (male, 49.40%) were included. During the observation period, the prevalence of AD was stable in the overall population from 2.61% (95% CI, 2.29-2.93) in 2007-2009 to 2.15% (1.68-2.63) in 2020 and 2.38% (1.81-2.95) in 2021. However, the weighted prevalence of AD in adults aged 40 to 59 years old decreased during the pre-pandemic era, and the prevalence of AD in adults aged above 60 years significantly decreased during the pandemic, with a significant decline observed after the initial outbreak. From age-stratification analysis, the adults aged 40 to 59 years showed a significant increase after the pandemic outbreak was evident in specific variables: individuals with rural residence, lower education, and lower household income quartiles. Adults aged above 60 years old showed a significant decrease in the slope after the outbreak, evident in specific variables: individuals of female, rural residence, lower education, and lower household income quartiles.
Conclusion: We observed a stable overall prevalence of AD throughout the 15-year observation period. However, the age-stratified analysis suggested significantly different trends according to age-stratified groups and the impact of the COVID-19 pandemic on the prevalence of AD.

研究目的：既往研究对成人特应性皮炎（atopic dermatitis, AD）的患病率变化趋势报道不一、尚无定论，且针对新型冠状病毒肺炎（COVID-19）大流行影响的相关数据较为匮乏。本研究旨在探究2007至2021年韩国成人特应性皮炎的全国流行趋势及年龄分层患病率，重点分析新冠大流行相关因素的影响。
研究方法：本研究采用2007至2021年韩国国民健康与营养检查调查（Korea National Health and Nutrition Examination Survey, KNHANES）数据，开展一项全国性横断面研究。通过加权β系数或比值比（odds ratios, OR）评估成人特应性皮炎的总体患病率及年龄分层患病率。
研究结果：共纳入83566名20岁以上成人（男性占比49.40%）。研究观察期内，成人特应性皮炎总体患病率保持稳定：2007-2009年为2.61%（95%置信区间（95% confidence interval, 95%CI），2.29~2.93），2020年为2.15%（1.68~2.63），2021年为2.38%（1.81~2.95）。但40~59岁成人的加权患病率在大流行前阶段呈下降趋势，而60岁以上成人的患病率在大流行期间显著降低，疫情初始暴发后下降幅度尤为明显。经年龄分层分析显示，40~59岁成人在疫情暴发后，农村居住、低学历及家庭收入四分位数较低的亚组患病率显著升高；60岁以上成人在疫情暴发后，女性、农村居住、低学历及家庭收入四分位数较低的亚组患病率的变化斜率显著降低。
研究结论：本研究发现，15年观察期内成人特应性皮炎的总体患病率保持稳定。但年龄分层分析结果显示，不同年龄亚组的患病率变化趋势存在显著差异，且新冠大流行对特应性皮炎患病率存在明确影响。