Atopic dermatitis epidemiological research methodology: a global scoping review

Atopic dermatitis (AD) has the highest burden of all skin diseases globally. While numerous systematic reviews and meta-analyses have attempted to estimate the burden of AD at country, regional and global levels, the variability in research methodology often leads to the exclusion of significant portions of data or the aggregation of data representing disparate factors. As a result, improving the understanding of the burden of AD requires a thorough review of the methodologies currently in use.

To identify and map the research methodology used in population-based epidemiological studies of AD in terms of the case definitions used, the severity assessment method, measures of frequency and key sociodemographic factors.

A systematic literature search was conducted, covering an 18-month period from 1 January 2023 to 31 July 2024. Original, population-based studies were included if they reported the prevalence and/or incidence of AD. Abstract screening and data extraction were done in duplicate and in a blinded manner. Descriptive analyses stratified by geographical region and age group are presented in tabular and graphical form.

A total of 111 studies from 48 countries were included. Data on AD prevalence used various diagnostic criteria, with studies defining cases by a physician diagnosis (n = 86/111; 77.5%), validated questionnaires (n = 15/111; 13.5%) and other methods (n = 10/111; 9.0%), with considerable heterogeneity between geographical regions. Nineteen studies (17.1%) reported the severity distribution. Geographical regions with the fewest studies on AD were the South-East Asian (n = 5/120; 4.2%) and African (n = 4/120; 3.0%) regions.

Recent population-based epidemiological studies on AD are highly heterogeneous, limiting meaningful comparisons across studies. Future research should aim to address this variability and fill key geographical gaps in the global burden data.