PURPOSE OF THE STUDY.
The “biodiversity hypothesis” suggests that exposure to greater environmental biodiversity in the natural flora and fauna can contribute to immune tolerance. The aim of this study was to test this hypothesis by assessing the environments near children’s homes in relation to atopic sensitization.
Combined data from 3 studies that were completed in Finland and Estonia from 2003 to 2012, including a total of 1044 children aged 0.5 to 20 years.
Three data sets were used that included children from diverse environments in Finland and Estonia. The prevalence of atopic sensitization was determined by measuring serum specific immunoglobulin E to common inhalant allergens. Five land types around the homes of the children were calculated using a standardized classification: forest, agricultural land, built area, water bodies, and wetland areas.
The cover of forest and agricultural land within 2 to 5 km from the home was inversely and significantly associated with atopic sensitization. This was seen in patients older than 6 years, and the association was stronger in boys compared with girls and among children exposed to a dog at home. Skin microbiota showed a relative abundance of Proteobacteria that was significantly correlated with the land-use gradient in healthy but not atopic individuals, supporting the hypothesis of a strong environmental effect on the commensal microbiota.
Atopy is linked with low accessible green space (forest and agricultural land) within 2 to 5 km from the home. Early life exposure to green environments appeared to be most important. The loss of natural green areas and environmental biodiversity in developed countries leads to a decrease in beneficial environmental microbes and the development of atopy.
This fascinating study is 1 of a series that has emerged from Finland relating a variety of dietary and environmental factors to the development of allergic and other inflammatory diseases. Given the rising prevalence of allergic disease, it is extremely important that we understand the role that environmental factors, especially in early life, may play in the development of allergy so that preventive strategies might be developed. Although more studies in different environments are needed, specifically with more in-depth assessment of microbial exposures, data from these studies conducted in Finland clearly support the biodiversity hypothesis.
- Copyright © 2015 by the American Academy of Pediatrics