The Epidemiology and Global Burden of Atopic Dermatitis: A Narrative Review

Abstract

The global epidemiology of atopic dermatitis (AD) in the current decade (2009-2019) has not been extensively reported. Epidemiological studies play an important role in presenting the risk factors of AD, as detailed prevalence and incidence data could demonstrate the burden of disease in the population of adults, adolescents, and children in different geographical regions. Thus, the primary objective of this review was to assess and summarize the epidemiological studies of the prevalence and incidence of AD in different age groups, focusing on data from studies published for 2009 to 2019. After a thorough literature search, six countries were identified from African, Asian, and European regions respectively, who published studies on AD. In contrast, only two studies were identified from Australia and New Zealand, three countries from North America and two from South America published AD studies, respectively. The highest prevalence of AD from included studies was noted among Swedish children with 34%, while the lowest prevalence was in Tunisian children with 0.65%; studies reporting incidence data were far less numerous. A common trend in the prevalence of AD was that children would have a higher prevalence as compared to adolescents and adults. The severity and morbidity of the disease showed variance with age, sex, socioeconomic characteristics, geographical location, and ethnicity. Environmental factors played an important role as causative agents in AD. The risk factors that were proven to cause and induce AD were skin barrier impairments due to FLG mutation, changes in the environment, and diet. FLG mutation may impair the skin barrier function by disruption of pH and hydration maintenance of the skin. Lastly, there were only a few studies on the incidence of AD in the 21st century. Therefore, epidemiological studies on childhood and adulthood AD in different continents are still needed, especially on the incidence of AD during adulthood.

Keywords: atopic dermatitis; atopic eczema; epidemiology; filaggrin; immune dysregulation; incidence; prevalence; risk factors.

Figure 1

Chemical structures of the main components of the stratum corneum (SC) ceramides and their shorthand nomenclature.

Figure 2

Graphic summary of effects of skin barrier on the pathogenesis of atopic dermatitis (AD). Genetic and immunologic as well as mechanical factors such as scratching induce skin barrier damage, allowing contact of skin resident antigen-presenting cells to allergens, bacterial, and viral antigens as well as other environmental factors. Activated antigen-presenting cells migrate to lymph nodes and prime naive T cells into Th2 cells. Elevated Th2 cytokines, together with TNF-α and IFN-γ further damage skin barrier functions by inducing apoptosis of keratinocytes as well as impair the function of tight junctions and promote Th2 responses by enhancing TSLP expression of epithelial cells. Moreover, colonizing pathogens, such as Staphylococcus aureus, impair barrier function through the release of virulence factors to induce keratinocyte death and to boost Th2-type inflammation. Together, genetic and immunological factors contribute to the skin barrier dysfunction and play a major role in the pathogenesis of AD.

Figure 3

Prevalence of AD in Africa based on the reports published between 2009 and 2019.

Figure 4

Prevalence of AD in America based on the reports published between 2009 and 2019.

Figure 5

Prevalence of AD in Asia based on the reports published between 2009 and 2019.

Figure 6

Prevalence of AD in Europe based on the reports published between 2009 and 2019.

Figure 7

Prevalence of AD in Oceania based on the reports published between 2009 and 2019.