Wood stove heating, asthma and allergies.

In two German studies household wood or coal stove use was negatively associated with atopic sensitization and allergic rhinitis in childhood. Wood stove heating is strongly related to 'traditional lifestyle and therefore subjected to confounding factors possibly yet not known. The study was conducted to study these factors and the independent impact of early exposure to wood stove heating on subsequent asthma and atopic disease. In a questionnaire survey among 10667 Finnish university students aged 18-25 years, we investigated the association between wood stove heating at age 0-6 years and asthma and allergies up to young adulthood. Adjustment was made for factors related to the heating system and atopic disorders by using multivariate regression. Unadjusted lifetime prevalence rates for physician-diagnosed asthma, allergic rhinoconjunctivitis, atopic dermatitis and self-reported wheezing were lower among subjects with wood stove heating compared to other heating systems. There was a significant negative association between childhood wood stove heating and allergic rhinitis or conjunctivitis in the univariate model (OR 0.61, 95% CI 0.61-0.91), but not for the other diseases. The significant association disappeared in the multivariate analysis after adjusting for various family indoor and outdoor (adjusted OR 0.96, 95% CI 0.77-1.20) factors. The association between wood stove heating and allergic rhinoconjunctivitis was mainly confounded by childhood residential environment, especially the farm environment. Farm environment was found to be the main confounding factor related to association between wood stove heating and asthma, and atopic diseases.