Bronchitic symptoms and their relation to FEV1 in Italy, Sweden, and Norway.

Within the EU BioMed 1 concerted action on the epidemiology of chronic obstructive pulmonary disease (COPD), a comparison was made in a pooled database from Italy, Sweden and Norway, of smoking habits, symptoms common in COPD, their relation to forced expiratory volume in one second (FEV1), and risk factors for COPD. COPD in these analyses has been defined following the British Thoracic Society's guidelines (i.e. FEV1/vital capacity (VC) <70% and FEV1 <80% of predicted values (% pred)), and by using a more severe disease criterion defined as FEV1/VC <60%, and FEV1 <60% pred. The pooled data were from the Italian Po River Delta Study II performed in 1988-1991, the Obstructive Lung Disease in Northern Sweden Study I (1985-1987), and the study performed in the city of Bergen and its surroundings in Hordaland, Western Norway in 1985-1986. The proportion of male smokers was 42% in the Italian, 34% in the Swedish, and 33% in the Norwegian samples. The corresponding figures for females were 30% in Sweden, 25% in Italy, and 23% in Norway. The prevalence of any wheeze was 28% in the Norwegian versus 21% in both the Italian and the Swedish samples. The prevalence of sputum production was 20% both in Norway and Sweden, while it was 16% in Italy. All symptoms were strongly smoking dependent. The relation between lung function impairment and respiratory symptoms was also strongly dependent on age. Among young symptomatic subjects, the lung function was only slightly affected. In symptomatic subjects >60 yrs, the mean FEV1 was 76-81% pred among Norwegian males. The corresponding values were 83-84% in Sweden, and 79-88% in Italy. Among females, a similar lung function impairment was found, but the variation of the mean FEV1 values was large. Risk factors for chronic obstructive pulmonary disease were calculated by multiple logistic regression analysis. The dominating risk factor was age followed by smoking. Smoking yielded an odds ratio of 3.6 for chronic obstructive pulmonary disease, defined according to the British Thoracic Society's guidelines, while the odds ratio for smoking as a risk for the more severe chronic obstructive pulmonary disease was 5.3. Country and sex had no significant influence. However, for the more severe chronic obstructive pulmonary disease, living in Norway was associated with an odds ratio of 1.8, and living in Sweden with an odds ratio of 1.5 compared with living in Italy.