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Background: Multinational time-trend analyses of atopic disease have shown that the East–West gradients in prevalence are shrinking. We set out to clarify whether the disparities in the occurrence of atopy and atopic diseases in Finnish and Russian Karelia during the past 10 years have diminished and how the prevalence of atopy has evolved with successive years of birth. Methods: Two surveys with identical methodology were performed in 1997/1998 and 2007. The study population comprised randomly selected adults, aged 25–54 years, from Finnish and Russian Karelia. Serum samples were collected for total and specific IgE measurements. Clinical data were obtained by questionnaires. Results: Sensitization rates to birch pollen increased from 7.8% to 14.8% (P < 0.001) and to cat from 6.1% to 10.8% (P < 0.001) in Finland. In Russia, no significant increase was found. Contrary to this, total IgE remained stable in Finland but decreased significantly (P < 0.001) in Russia. Analyses based on years of birth revealed that the prevalence of sensitization to allergens increased with successive birth years in Finland, but remained stable in Russia. Over the 10 years, self-reported physician-diagnosed asthma increased from 5.5% to 8.1% (P = 0.05) and hay fever from 8.1% to 13.2% (P < 0.001) in Finland. Conclusions: Disparities in the prevalence of atopy and atopic disease between Finnish and Russian Karelia have further grown. The ‘allergy epidemic’ continues in Finland and is mainly attributable to the years of birth effect shown in atopy prevalence. In Russia, no signs of the epidemic are discernible, although the decrease in total IgE may indicate a change in environmental exposure. [ABSTRACT FROM AUTHOR]

Background and aim: The influence of microbial quality of drinking water from different sources on the occurrence of atopy has been poorly examined. This study was undertaken to clarify the association between the overall microbial content in drinking water and the occurrence of atopy among schoolchildren from two neighbouring areas with profound differences in living conditions and lifestyles. Methods: Drinking water samples were obtained from kitchens of nine schools in North Karelia, Finland and of nine schools from Pitkäranta, the Republic of Karelia, Russia. The pupils of these schools were participants of the Karelian Allergy Study. Occurrence of atopy, determined by skin prick test positivity (one or more) to 14 common airborne and food allergens, was measured in all 563 children, aged 7–16 years, from these 18 schools. Water samples were analysed using standard methods for drinking water analyses including viable counts for Escherichia coli, intestinal enterococci, coliform bacteria and heterotrophic bacteria. In addition, total cell counts including both viable and nonviable bacteria, algae and protozoans were assessed using epifluorescence microscope with 4′-6-diamidino-2-phenylindole (DAPI) staining. Results: In Finland, 29% of the children were sensitized to birch when compared with 2% of the Russian children ( P < 0.0001). Overall, sensitization rates for any of the pollens were 39% and 8% ( P < 0.0001), and for any of the allergens 48% and 16%, respectively ( P < 0.0001). Because of substantial differences in raw water sources and treatment practices, the total numbers of microbial cells in drinking water were many-fold higher in Russia than in Finland. A dose–response relationship was found for occurrence of atopy and the DAPI value indicative of microbial cell content in the water ( P < 0.0001). Further, multivariate logistic regression analysis revealed that high (>106 cells/ml) and intermediate (105–106 cells/ml) DAPI values were associated with reduced risk of atopy (odds ratio 0.34, 95% confidence interval 0.20–0.57 and 0.39, 0.23–0.69, respectively), independently from other factors. Conclusion: High overall content of micro-organisms in drinking water may be associated with reduced risk of atopy, independently from other determinants. [ABSTRACT FROM AUTHOR]