Journal of the American Academy of Dermatology
The Disease and Its EnvironmentAtopic dermatitis: The role of environmental and social factors, the European experience☆,☆☆,★
Section snippets
Genetic susceptibility
There is no doubt that the general propensity of atopy is genetically determined. However, the likelihood of developing allergic disease in a person is not constant over time and persons with no family history of atopy can develop AD. The genetic background of AD, however, could not explain the obviously rapidly increasing frequency of AD in the brief span of the past decades. Thus it seems that other and still unrecognized factors in the environment can affect the occurrence of AD in
Family associations
In addition, having more siblings has been shown to be associated with lower risk of atopic diseases. Having no siblings, compared with 3 or more siblings, was associated with a significantly higher risk of lifetime history of atopic eczema (odds ratio [OR], 1.28; 95% confidence interval [CI], 1.12-1.60) in a cross-sectional survey of 8387 Finnish schoolchildren aged 13 to 14 years.5 According to the results of the European Community Respiratory Health Service, atopy was negatively associated
Geographic differences
Several studies of persons belonging to the same ethnic group and having the same genetic background, but living under different conditions, have demonstrated that the incidence of atopic diseases is higher in industrialized countries than in former socialist countries of Eastern Europe.12 For example, in Northern and Eastern Europe the highest 1-year prevalence of flexural dermatitis was seen in Scandinavia, lower in the western part of the former socialist region, that is, Estonia, Latvia,
Migration studies
Studies of migrants also support the hypothesis that environmental factors associated with “urbanization” and “development” are important in the pathogenesis of AD. The risk of AD is greater for Asian children born in Australia when compared with recently immigrated Asian children.17 Polynesian immigrants in New Zealand have a higher prevalence of AD compared with similar genetic groups of their country of origin.18 London-born black Caribbean children have been shown to be at higher risk of AD
Social status
Other interesting observations showed a 1.5- to 2-fold higher prevalence of AD in higher compared with lower socioeconomic groups20, 21, 22 and in children living in privately owned rather than in rented houses. Modern, well-insulated houses have been associated with an increased risk for the development of sensitization and allergic manifestations.23
In addition, in the former East Germany, the lifetime prevalence rates of atopic disease were highest in the former social class in which parents
Western lifestyle
In Table I, epidemiologic observations are summarized that support the role of urbanization, development, and Western lifestyle for the increasing prevalence of atopic diseases within the past 30 years.
• Increasing prevalence over the past 30 years in industrialized Western countries • Prevalence higher in immigrants to
Conclusions
However, we can only speculate about the role of environmental factors and do not yet know whether these factors may enhance sensitization, trigger an allergic reaction in sensitized persons, or act because of their physical properties. Can the increase of AD be at least partly explained by the exposure to new or higher concentrations of airborne or dietary antigens and/or by environmental factors increasing the susceptibility to cutaneous irritation and sensitization? Epidemiologic studies on
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This article is part of a supplement sponsored by Novartis Pharma AG and Novartis Pharmaceuticals Corporation.
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Disclosure: The author attests that he has no conflicts of interest to disclose.
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Reprint requests: Professor Thomas L. Diepgen, University Hospital Heidelberg, Department of Social Medicine Center of Dermato-Epidemiology, Bergheimer Str 58, D-69115 Heidelberg, Germany. E-mail: [email protected].