Atopy among schoolchildren in northern and southern Sweden in relation to pet ownership and early life events

Studies have suggested a higher prevalence of asthma and allergies in north ern, as compared to southern, Scandinavia. The aim of this study was to eva luate regional differences in atopy in relation to pet ownership and certai n early life events among schoolchildren (n=2108) aged 10-11 years from Lin koping in southern Sweden and Ostersund in northern Sweden. The parents com pleted a questionnaire, comprising questions on home environment, heredity, socio-economic conditions, and the core questions on symptoms from the Int ernational Study of Asthma and Allergies in Childhood. The children were sk in-prick tested to eight common inhalant allergens. Information on maternal smoking habits, gestational age, and anthropometric measures were obtained from the Swedish Medical Birth Registry. The prevalence of atopic symptoms and sensitization to pollen were similar in Ostersund and in Linkoping. A higher prevalence of sensitization to animal dander among children in Oster sund could be linked to a higher occurrence of pets in the community. Curre nt cat ownership was related to less sensitivity to cat allergen but only i n children with an atopic heredity. Ponderal index >30 kg/m(3) was related to an increased risk of atopic sensitization, both in Linkoping (adjusted o dds ratio 2.1; 95% confidence interval 1.1-4.0) and in Ostersund (adjusted odds ratio 2.0, 95% confidence interval 1.1-3.5). Maternal smoking during p regnancy was related to an increased risk of atopic sensitization among chi ldren in Linkoping, whereas current smoking was associated with a decreased risk of sensitization in Ostersund. In conclusion, we demonstrated that a high occurrence of pets in the community was associated with sensitization, whereas atopic symptoms were essentially unaffected. This study has also s uggested an association between body size at birth and atopic sensitization at 10-11 years of age.