Atopic Dermatitis Knowledge Centre
Understanding
Prevalence
Atopic dermatitis is a highly prevalent disease, affecting 10–30% of children and 1–3% of adults, in developed countries.1,4 Incidences have trebled over the past 30 years in industrialised societies but remain much lower in countries with predominantly rural or agricultural areas. The graph below demonstrates the prevalence of atopic dermatitis in Europe and shows the percentages of children aged 6–7 years and 13–14 years diagnosed with the disease.5
Prevalence estimates of atopic dermatitis in European countries (1999)5
It is estimated that 60% of atopic dermatitis patients develop symptoms in the first year of life and nearly 90% develop symptoms before the age of 5.6 It is less common for atopic dermatitis to first appear in adulthood but there is a tendency for the symptoms to be more severe in such patients. Once the condition has manifested itself, flares of varying severity and duration can occur at any age.
Several theories attempting to explain the dramatic increase in atopic dermatitis prevalence have been proposed. In 1989, Strachan suggested that allergic diseases were less common in children from larger families, due to an increased exposure to infectious agents from siblings, than in children from families with only one child.7 Increases in the use of antibiotics, antimicrobial cleaning agents and general improvements in living conditions have also been implicated as key factors responsible for the rise in the number of atopic dermatitis cases in developed nations. Reducing childhood exposure to pathogens was considered the principle reason for the increasing prevalence of atopic dermatitis. The underlying biological interpretation of this theory, known as the ‘hygiene hypothesis’, states that reduced exposure to microbial antigens affects the development of the immune response during early growth.8,9
Another mechanism thought to account for the growing prevalence of atopic dermatitis is an increase in gene-environment interactions . Individuals with specific variations in susceptibility genes are at higher risk of developing severe allergies and/or atopy when specific environmental factors are present.10 A more detailed description of the genetic factors and immune dysfunctions associated with atopic dermatitis predisposition are provided under the pathophysiology heading in this section.
References:
1. Leung DY, Boguniewicz M, Howell MD, et al. New insights into atopic dermatitis. J Clin Invest 2004; 113: 651-7.
4. Worldwide variation in prevalence of symptoms of asthma, allergic rhinoconjunctivitis, and atopic eczema: ISAAC. The International Study of Asthma and Allergies in Childhood (ISAAC) Steering Committee. Lancet 1998; 351: 1225-32.
5. Williams H, Robertson C, Stewart A, et al. Worldwide variations in the prevalence of symptoms of atopic eczema in the International Study of Asthma and Allergies in Childhood. J Allergy Clin Immunol 1999; 103: 125-38.
6. Akdis CA, Akdis M, Bieber T, et al. Diagnosis and treatment of atopic dermatitis in children and adults: European Academy of Allergology and Clinical Immunology/American Academy of Allergy, Asthma and Immunology/PRACTALL Consensus Report. J Allergy Clin Immunol 2006; 118: 152-69.
7. Strachan DP. Hay fever, hygiene, and household size. BMJ 1989; 299: 1259-60.
8. Martinez FD. The coming-of-age of the hygiene hypothesis. Respir Res 2001; 2: 129-32.
9. Strachan DP. Family size, infection and atopy: the first decade of the "hygiene hypothesis". Thorax 2000; 55 Suppl 1: S2-10.
10. Hoffjan S, Nicolae D, Ostrovnaya I, et al. Gene-environment interaction effects on the development of immune responses in the 1st year of life. Am J Hum Genet 2005; 76: 696-704.
© February 2010 Astellas Pharma Europe LTD.
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The Atopic Dermatitis Knowledge centre contained within www.epgonline.org and available at www.atopicdermatitisinfo.org is intended to be for educational use only and not designed to provide medical advice or professional services.