Exposure to animals and the risk of allergic asthma: a population-based cross-sectional study in Finnish and Russian children

Timo T Hugg¹ , Maritta S Jaakkola²^,3 , Risto Ruotsalainen⁴ , Vadim Pushkarev⁵ and Jouni JK Jaakkola²^,6

¹South Karelia Allergy and Environment Institute, Joutseno, Finland and Institute of Health Sciences, University of Oulu, Oulu, Finland

²Institute of Occupational and Environmental Medicine, The University of Birmingham, Edgbaston, Birmingham B15 2TT, UK

³Department of Respiratory Medicine, Division of Medicine, University of Oulu, Oulu, Finland

⁴Director of the Indoor Air Quality Clinic, Allergy and Asthma Union, Paciuksenkatu 19, 00270 Helsinki, Finland

⁵Municipal Hospital of Svetogorsk, Pogranichnaya str. 13, Svetogorsk, Leningradskaya oblast, 188990, Russia

⁶Institute of Health Sciences, University of Oulu, Oulu, Finland

author email corresponding author email

Environmental Health 2008, 7:28doi:10.1186/1476-069X-7-28


Published:	6 June 2008

Abstract

Background

There is little information on potential differences in animal exposure between Finland and Russia and particularly on the effects of animal exposure on asthma among Russian children. The aim of the study was to compare the pet and farm animal exposures and to assess the relations of pre- and postnatal animal exposures to the occurrence of allergic asthma in Finnish and Russian school children.

Methods

We conducted a population-based cross-sectional study in neighbour towns on either side of the Finnish-Russian border; Imatra in Finland and Svetogorsk in Russia. The study population consisted of 512 Finnish and 581 Russian school children aged 7–16 years (response rate 79%). Multivariate logistic regression analysis was used to estimate adjusted odds ratios (OR) and 95% confidence intervals (CI) related to each exposure.

Results

Current indoor exposure to pets was more frequent among school children in Svetogorsk than in Imatra (67.5% vs. 56.0%, P < 0.001). Finnish children were exposed more frequently to dogs, whereas Russian children to cats during childhood and to farm animals during pregnancy and infancy. The risk of self-reported allergic asthma was inversely related to indoor dog keeping ever in Finland (adjusted OR 0.35, 95% CI 0.13, 0.95), whereas in Russia the risk of allergic asthma was increased in relation to combined indoor cat exposure during infancy and currently (4.56, 1.10, 18.91). The risk of asthma was elevated in relation to contact to farm animals during pregnancy (Finland: 1.95, 0.69, 5.50; Russia: 1.90, 0.70, 5.17) and early life (Finland: 2.05, 0.78, 5.40; Russia: 1.21, 0.39, 3.73).

Conclusion

Exposure to pets and farm animals during childhood differed significantly between Finland and Russia. Our study provides evidence that early-life exposure to cats increases the risk of asthma whereas exposure to dogs is protective. Our findings suggest that intermittent fetal and early-life exposure to farm animals increases the risk of allergic asthma in urban children visiting farms.