Asthma: Respiratory Symptoms, Atopy and Bronchial Hyperresponsiveness in Young Adults in Estonia and Sweden

Morbidity of asthma has increased over the world. The reasons for this increase have remained unclear. Studies in children have reported considerable East-West difference in the prevalence of atopy and respiratory allergies. The aim of this thesis was to compare the prevalence and risk factors of respi-ratory symptoms, atopic sensitisation and bronchial hyperresponsiveness (BHR) in young adults in Estonia and Sweden. Following the protocol of the European Community Respiratory Health Survey (ECRHS), two random population samples, 3000 from Tartu, Estonia, and 3600 from Uppsala, Sweden were investigated with postal questionnaires. Random sub samples and subjects with asthma-like complaints were subsequently interviewed, BHR was tested and serum samples analysed for total and specific IgE and eosinophil cationic protein (ECP). In a separate study two methacholine challenge methods, using either Spira Elektro2 or Mefar MB3 as dosimeters, were compared on 28 mild to moderate asthma patients. Symptoms of asthma and hay fever were less common in Esto-nia than in Sweden, while respiratory symptoms in general were more common in Estonia. The prevalence of BHR was high and the prevalence of atopy and the levels of serum ECP were low in Tartu. The differences between the two centres in the prevalence of atopy and allergic rhinitis diminished with age, indicating a probable cohort effect. Current smoking was a dominant risk factor for BHR and for all respiratory symptoms, except attacks of asthma, both in Tartu and Uppsala. There was some difference between risk factors for BHR and atopy between Tartu and Uppsala, mostly of social and environmental origin. The low prevalence of hay fever and asthma in Tartu seemed to be partly explained by a lack of awareness of atopy and allergic diseases in the Estonian society. The estimated cumulative dose causing a 20% fall in FEV1 was smaller and the decline of FEV1 /log(dose) curve steeper, using the Spira, compared to the Mefar protocol.