Background: In the European Community Respiratory Health Survey (ECRHS) I, the lowest prevalence of asthma and atopy was found in Reykjavík (Iceland) and Tartu (Estonia). The aim of this study was to compare home environments in Reykjavík and Tartu to a town with a higher prevalence of asthma and atopy (Uppsala, Sweden) in an attempt to identify factors in the indoor environment that could explain these differences.
Method: A random sample of 129 ECRHS II participants was included in this analysis at each of the three study centres. The subjects answered a questionnaire, blood was analysed for specific immunoglobulin E, a methacholine test was performed and home indoor measurements were taken.
Results: The prevalence of atopy was 11.9% in Reykjavík, 35.5% in Uppsala and 28.2% in Tartu (P < 0.04). The level of indoor cat allergen was significantly lower in Reykjavík compared with Uppsala (P = 0.05). No mite allergens were identified in the 41 homes investigated in Reykjavík, while this was the case in 16% and 72% of the households in Uppsala and Tartu, respectively (P = 0.001). A positive association was found between asthma symptoms and cat allergen levels [odds ratio 1.53 (95% confidence interval 1.04-2.24)], while the levels of viable moulds were significantly associated with increased bronchial responsiveness.
Conclusions: Indoor exposure to allergens, moulds and bacteria was lower in Reykjavík than in the Swedish and Estonian centres. This finding indicates that the lower prevalence of allergic sensitization in Reykjavík may partly be related to lower indoor allergen exposure.