Environmental and lifestyle factors, including viral infections, in relation to development of allergy among children in Saint-Petersburg and Stockholm

Abstract: The increasing prevalence of allergic diseases in children, particularly noteworthy in developed countries, has become an object of international concern. A lack of exposure to a broad range of infectious agents in early life has been suggested as one of the contributing factors. An increase in allergy prevalence in Eastern Europe, including Russia, similar to that earlier noted in Western countries has recently been shown, suggesting that Westernization may contribute to the geographical differences. However, information based on validated, population-based studies on allergic diseases in Russian children is limited and the role of various environmental as well as lifestyle factors has not been clarified. In the first two studies the role of Epstein-Barr virus (EBV) and Cytomegalovirus (CMV) infections was investigated, including a potential interaction between the two viruses, for development of allergic conditions and sensitization in Swedish 4 year-old children. From a Swedish prospective birth cohort study on factors of importance for development of allergy, 2,581 children were enrolled. The classification of allergic diseases was based on questionnaire answers and determination of IgE-antibodies to common airborne and food allergens. Immunoglobulin G (IgG) to EBV was determined by indirect immunofluorescense and to CMV by an enzyme-linked immunosorbent assay. Total seropositivity to EBV and CMV was found in 53% and 46% of the children, respectively, while joint seropositivity was detected in 25%. There were no significant associations between seropositivity to either EBV or CMV and allergic manifestations. Seropositivity to CMV alone was related to IgE antibodies to airborne and food allergens. An antagonism between CMV and EBV in relation to sensitization to airborne and food allergens was suggested. Two other studies were aimed at providing internationally comparable data on the prevalence of allergic diseases and sensitization among Russian children as well as at elucidating the role of various environmental and lifestyle factors, including farm-related exposures. The study population comprised 1,702 children aged 2-7 years from Saint-Petersburg. A cross-sectional questionnaire-based survey was performed focusing on environmental and lifestyle factors as well as on occurrence of allergic diseases. Blood sampling was performed in a subgroup to determine allergen-specific IgE-antibodies to the most common airborne and food allergens. The response rate to the questionnaire survey was 85.1%. Allergic diseases were reported for 23% of the children and more than 30% exhibited IgE-antibodies to common allergens. Among environmental factors, physician-diagnosed asthma was associated with exposure to environmental tobacco smoke and wood smoke. Similar relations were indicated for current asthma and rhinitis symptoms as well as for diagnosed allergic rhinitis, but not for sensitization. Prenatal exposure to certain livestock, such as pigs, was associated with an increased prevalence of allergic diseases, but not with sensitization. Regular consumption of farm milk tended to decrease the risk of allergic conditions. In conclusion, the studies do not support the hypothesis that EBV or CMV infections in early childhood influence the pathogenesis of allergic diseases or allergen specific IgE-sensitization in children at 4 years of age. However, an EBV/CMV antagonism was suggested with respect to sensitization, underlining the importance of studying of viral interactions. The occurrence of allergic diseases and sensitization among children from Saint-Petersburg appears similar to the prevalence in Northern and Western Europe as well as the panorama of risk factors.