Epidemiology of atopic dermatitis

Scroll down this page to learn more about the prevalence and incidence of atopic dermatitis as well as factors that contribute to its development.

Prevalence and incidence of atopic dermatitis

Atopic dermatitis, or atopic eczema, is the most common chronic skin condition and is characterised by acute episodes of eczematous, pruritic lesions over dry skin. It typically starts in early childhood and is widely reported to affect 15–20% of children and 1–3% of adults (Nutten, 2015). However, since the 1970s, the incidence of atopic dermatitis has increased 2- to 3-fold in industrialised nations (Avena-Woods, 2017). 

While atopic dermatitis affects a substantial number of infants and adults, the severity can differ significantly between patients. Studies have shown reasonable heterogeneity in the relative levels of severity observed in patients. Analysis of the 2007–2008 National Survey of Children’s Health found that 67% of US children reported mild disease, 26% reported moderate disease and 7% reported severe disease (Silverberg & Simpson, 2013; Silverberg & Simpson, 2014). However, a smaller study in the UK where disease severity was assessed by a dermatologist rather than patient self-report found that 84% of children had mild disease, 14% had moderate disease and just 2% had severe disease (Emerson et al., 1998).

Atopic dermatitis disease severity classification

Figure 1: Atopic dermatitis disease severity classification (National Institute for Health and Care Excellence, 2007).

In children, 60% develop the disease in the first year of life and 90% within the first 5 years of life (Eichenfield et al., 2014). It is also believed to represent the first step of the ‘atopic march’ towards other allergic conditions later in life such as asthma or allergic rhinitis (Nutten, 2015). In a 3-year, double-blind study of 1,091 infants (3–18 months of age) with recent onset atopic dermatitis (≤3 months), development of one or more atopic comorbidities was observed in 37.0% of infants at the end of observation (mean 2.8 years) (Schneider et al., 2016). 

Incidence of different atopic diseases in childhood and adolescence.

Figure 2: Incidence of different atopic diseases in childhood and adolescence (Barnetson & Rogers, 2002).

In 70% of patients with childhood atopic dermatitis a spontaneous remission before adolescence is achieved (Nutten et al. 2015). Interestingly, however, a prospective cohort study of children with mild to moderate atopic dermatitis reported that 80% of patients with >5 years of follow-up continued to have symptoms or use medication. Furthermore, as patients aged, they sought healthcare support less frequently potentially influencing the common perception of the frequency with which atopic dermatitis resolves over time (Margolis et al., 2014). However, conflicting data and ongoing debate continues on this topic indicating that more research is needed to fully understand the long-term impact of atopic dermatitis (Kim et al., 2016; Margolis & Mitra, 2017; Silverberg & Simpson, 2017).

Although prevalence figures of 15–20% in children and 1–3% in adults are commonly quoted (Nutten, 2015), the American Academy of Dermatology guidelines suggest a childhood prevalence of up to 25% (Eichenfield et al., 2014). Irrespective of the given prevalence, all these figures hide significant geographic and population variations. In the International Study of Asthma and Allergies in Childhood (ISAAC), a global study of 2 million children in 100 countries, prevalence in children aged 6–7 years was shown to be as low as 0.9% in parts of India and as high as 22.5% in Ecuador (Odhiambo et al., 2009).

Prevalence of atopic dermatitis in the last 12 months in phase 3 of the ISAAC study.

Figure 3: Prevalence of atopic dermatitis in the last 12 months in phase 3 of the ISAAC study. Figures in parentheses represent the range of prevalence observed in different regions of the country where available (Williams et al., 2008).

The different phases of the ISAAC study (phase 1 in early- to mid-1990s; phase 3 in early 2000s) have also enabled them to establish how the prevalence of atopic dermatitis is changing over time. In children aged 13 to 14 years old, the prevalence of atopic dermatitis in countries with very high levels has plateaued or decreased although the burden continued to rise in developing country settings. However, in children aged 6 to 7 years old, most countries showed an increase of two standard errors or more in atopic dermatitis over a 5- to 10-year period (Williams et al., 2008). Meanwhile, in the USA, the National Health Interview Survey revealed that the prevalence of atopic dermatitis among children increased from 8% in 1997 to 12% in 2010–2011. However, it appears to have subsequently plateaued in 2012–2013 (Silverberg, 2017).

While the ISAAC study provides valuable insight into the prevalence of childhood atopic dermatitis, are similar geographic disparities observed in the prevalence of adult disease? The European Community Respiratory Health Survey reported point prevalence rates that ranged from 0.3% (Switzerland) to 6.2% (Estonia) (Harrop et al., 2007). Furthermore, a series of US studies have identified point prevalence rates ranging from 3.2% to 10.7% depending on the population assessed and the definitions used (Hanifin & Reed, 2007; Silverberg & Hanifin, 2013; Silverberg, 2015) A recent international, cross-sectional, web-based survey sought to address these gaps in understanding and received over 90,000 responses from people in the USA, Canada, France, Germany, Italy, Spain, the UK and Japan. Among these respondents, the overall 12-month prevalence of adult atopic dermatitis was 4.9% (95% CI 4.6%, 5.2%). Regional variability was seen in many countries, but a higher point prevalence was observed in Southern European countries than elsewhere (p<0.05) (Barbarot et al., 2018).

Point prevalence of adult atopic dermatitis by country.

Figure 4: Point prevalence of adult atopic dermatitis by country (Barbarot et al., 2018).