Contribution of smoking change to 45-year trend in prevalence of chronic bronchitis in Finland

Aims: Tobacco smoking has been identified as the most important risk factor of chronic bronchitis. The aim of this study was to assess the contribution of smoking to the trends in prevalence of chronic bronchitis among men and women in Finland. Methods: For this purpose, we analysed questionnaires included in national FINRISK and FinHealth studies conducted between 1972 and 2017 in 5-year intervals. A total of 26,475 men and 28,684 women aged 30-59 years were included in the analysis. In addition to smoking, age and socioeconomic status were used as risk factors in the logistic regression model. Results: Smoking in Finland has declined from 51% to 23% in men between 1972 and 2017. In women, it increased from 11% in 1972 to 23% in 2002, with a following decrease to 16% in 2017. The prevalence of chronic bronchitis has generally followed the trend of smoking. The population attributable risk was 60% in men and 49% in women. A decrease in chronic bronchitis was observed in male never-smokers. Conclusions: Smoking is currently declining in Finland in both men and women. As result, the prevalence of chronic bronchitis is declining and it is approaching baseline independent of smoking. The decrease in never-smokers has yet to be explained.