Recommendations for epidemiological studies on COPD.

The prevalence of chronic obstructive pulmonary disease (COPD) has been extensively studied, especially in Western Europe and North America. Few of these data are directly comparable because of differences between the surveys regarding composition of study populations, diagnostic criteria of the disease and definitions of the risk factors. Few community studies have examined phenotypes of COPD and included other ways of characterising the disease beyond that of spirometry. The objective of the present Task Force report is to present recommendations for the performance of general population studies in COPD in order to facilitate comparable and valid estimates on COPD prevalence by various risk factors. Diagnostic criteria in epidemiological settings, and standardised methods to examine the disease and its potential risk factors are discussed. The paper also offers practical advice for planning and performing an epidemiological study on COPD. The main message of the paper is that thorough planning is worth half the study. It is crucial to stick to standardised methods and good quality control during sampling. We recommend collecting biological markers, depending on the specific objectives of the study. Finally, studies of COPD in the population at large should assess various phenotypes of the disease.

Passive smoking and respiratory symptoms in the FinEsS Study.

The aim of the present study was to examine the relationship between reported environmental tobacco smoke (ETS) exposure and respiratory symptoms. In 1996, a postal questionnaire was randomly distributed in three areas of Estonia to a population-based sample, of which 4,995 females and 1,822 males had never smoked. The main outcome measures were current respiratory symptoms and the amount of reported ETS exposure outside the home. ETS exposure at home was more common in females (31% versus 19%), while exposure outside of the home was more common in males (53% versus 7%). Females reported more symptoms from tobacco smoke than males (37.7% versus 21.6%). If ETS exposure outside of the home exceeded 5 h daily, the risk for wheeze (odds ratio (OR) 2.67, 95% confidence interval (CI) 1.98-3.61) and physician-diagnosed asthma (OR 1.79, 1.02-3.16) were increased. ETS exposure outside of the home was shown to be strongly related to almost all respiratory symptoms in a dose/response manner. ETS exposure at home did not show significantly elevated ORs for any respiratory symptoms. This study shows that females seem to be more troubled by environmental smoke exposure than males and provides further evidence of the serious health hazards associated with environmental smoke exposure. Indeed, the findings of this study support a ban on smoking in the workplace and public areas.

Prevalence and risk factors for asthma and chronic bronchitis in the capitals Helsinki, Stockholm, and Tallinn.

The aim of this part of the FinEsS-studies was to assess whether differences existed in prevalence of asthma, chronic bronchitis, and respiratory symptoms between three Baltic capitals, and to examine risk factor profiles for respiratory conditions. In 1996, a postal survey was performed in these cities with a response rate of 72% in Stockholm, 76% in Helsinki, and 68% in Tallinn. The prevalence of physician-diagnosed asthma was 76% in Stockholm, 6.2% in Helsinki, and 2.3% in Tallinn, while respiratory symptoms were most common in Tallinn. The prevalence of physician-diagnosed chronic bronchitis was 10.6% in Tallinn, 3.4% in Helsinki, and 3.0% in Stockholm. Risk factor analyses revealed a significantly increased risk for those living in Tallinn compared to that of Stockholm for wheezing conditions, OR 1.56-1.69, longstanding cough, OR 1.92 (1.74-2.13), attacks of shortness of breath during the previous 12 months, OR 1.35 (1.20-1.52), and chronic productive cough, OR 1.49 (1.28-1.74). Subjects having symptoms common in asthma were more likely to have physician-diagnosed asthma in Stockholm and Helsinki than in Tallinn, while subjects having bronchitis symptoms had more often physician-diagnosed chronic bronchitis in Tallinn. Prevalence of respiratory symptoms was higher in Tallinn than in Stockholm and Helsinki, while physician-diagnosed asthma was more common in Stockholm and Helsinki. The prevalence of physician-diagnosed chronic bronchitis was three times as high in Tallinn as in Helsinki or Stockholm. Our results also suggest large differences in diagnostic practices between the three countries, while the differences between the capitals in true prevalence of disease may be small.

Asthma, chronic bronchitis and respiratory symptoms among adults in Estonia according to a postal questionnaire.

Epidemiological studies indicate a lower prevalence of asthma in Eastern than Western Europe. This study of the prevalence of asthma, chronic bronchitis, and respiratory symptoms was performed in three different regions of Estonia, a state incorporated in the Soviet Union until 1991. A postal questionnaire was sent to a random sample of 24,307 of the population aged 15-64 years. The response rate was 77.6%. The prevalence of physician-diagnosed asthma was 2.0% or considerably lower than in Northern and Western European countries. The prevalence of wheezing last 12 months, 21.7%, recurrent wheeze, 13.3%, and attacks of shortness of breath, 12.5%, were similar or even higher compared with prevalence rates found in the Nordic countries. The prevalence of physician-diagnosed chronic bronchitis was 10.7%, and was higher among women than in men, although the proportion of current smokers among men, 57%, was considerably greater than in women, 28%. A possible explanation to the high prevalence of respiratory symptoms also among non-smoking women may be exposure to environmental tobacco smoke in small, crowded Estonian homes. Diagnostic criteria based on the Soviet-time definitions is discussed as a possible explanation to the low prevalence of physician-diagnosed asthma and high prevalence of chronic bronchitis in Estonia compared with other Northern European countries.