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.