Asthma, chronic bronchitis, chronic obstructive pulmonary disease (COPD) and respiratory symptoms among adults in Estonia : prevalence and risk factors : comparison with Sweden and Finland : the 'FinEsS' studies Estonia I

Abstract

The thesis is based on original research data of the Estonian part of the "FinEsS" studies, which are cross-sectional comparative studies between Finland, Estonia and Sweden aiming to estimate the prevalence of respiratory symptoms, asthma, chronic bronchitis, COPD and allergy and to assess risk factors for the diseases and conditions. In Estonia the study areas included Tallinn, the capital of the country, Saaremaa, an agricultural island in the Baltic Sea, and Narva, a heavily industrialised town located at the Russian border. The study consisted of two phases, first a postal questionnaire survey from the late autumn of 1995 to the spring of 1996. The postal survey was followed up from 1997 to 2000 by a structured interview, clinical examination, lung function test, skin prick test and bronchial provocation test in randomly selected sub-samples. A further aim included comparison of postal questionnaire results from Tallinn, Stockholm and Helsinki, all capitals located at the Baltic Sea.

Totally 24,307 subjects in Estonia aged 15 - 64 years were invited to the postal survey. After exclusion of subjects who had moved abroad, were living elsewhere, or were dead, 22,579 subjects remained. Of them, 17,525 subjects (77.6%) participated. From the questionnaire responders, 2,676 randomly selected subjects after stratification by age and gender were invited to take part in the follow-up studies, and 1,432 subjects (53.1 %) participated.

Of men, 57.2% were current smokers versus 28.1% of women. The most commonly reported respiratory symptom was sputum production, 29.5%, followed by longstanding cough, 24.0%. The prevalence of wheezing during the last 12 months was 21.7%, of recurrent wheeze 13.3%, and attacks of shortness of breath was reported by 12.5%. The prevalence of physician-diagnosed chronic bronchitis was 10.5%. Chronic bronchitis and all respiratory symptoms were most prevalent in Narva and the prevalence was lowest in Saaremaa. The prevalence of physiciandiagnosed asthma was 2% according to the postal questionnaire without no major difference between the areas, and a few years later it was according to interview 3.8%. The prevalence of COPD was 7.8% with no statistically significant differences between the three areas. After adjusting for the age and gender distribution and for smoking habits in the population of each area, the prevalence was slightly lower. Measuring prevalence of asthma in Estonia based on postal selfadministrated questionnaire and structured interview with results of functional and clinical data suggest that physiciandiagnosed asthma in Estonia reflects a considerable under-diagnosis. Disease criteria for asthma based on symptom combinations yielded a prevalence of 5-8%.

Smoking and a family history of obstructive airway diseases were risk factors for all respiratory symptoms, while increasing age was a risk factor for chronic bronchitis and bronchitic symptoms. Family history of asthma was the major risk factor for asthma. Increasing age, male sex and smoking (in men only) were dominating risk factors for COPD. In Estonia, physician-diagnosed chronic bronchitis and all respiratory symptoms were significantly more prevalent in nonEstonians than in native Estonians.

Living in Tallinn compared with the Nordic capitals Stockholm and Helsinki was associated with an increased risk for most respiratory symptoms. For Estonia, the prevalence of chronic bronchitis was found to be much higher, of physician-diagnosed asthma much lower, and of COPD nearly similar compared with Sweden and Finland. The considerable differences in prevalence rates of physician-diagnosed asthma between the Estonia, Finland, and Sweden could be explained by differences in diagnostic practices. Asthma in Estonia and chronic bronchitis in Sweden and Finland seemed to be underdiagnosed.