Lung function in Lolland-Falster Health study (LOFUS)

Background: COPD prevalence in Denmark is estimated at 18% based on data from urban populations. However, studies suggest that using the clinical cut-off for airway obstruction in population studies may overestimate prevalence. The present study aims to compare estimated prevalence of airway obstruction using different cut-offs and to present lung function data from the Lolland-Falster Health Study, set in a rural-provincial area. Methods: Descriptive analysis of participant characteristics and self-reported respiratory disease and of spirometry results in the total population and in subgroups defined by these characteristics. Airway obstruction was assessed using previously published Danish reference values and defined according to either FEV ₁/FVC below lower limit of normal (LLN) 5% (as in clinical diagnosis) or 2.5% (suggested for population studies), or as FEV ₁/FVC < 70%. Results: Using either FEV ₁/FVC < 70% or LLN 5% cut-off, 19.0% of LOFUS participants aged 35 years or older had spirometry, suggesting airway obstruction. By the LLN 2.5% criterion, the proportion was considerably lower, 12.2%. The prevalence of airway obstruction was higher among current smokers, in participants with short education or reporting low leisure-time physical activity and in those with known respiratory disease. Approximately 40% of participants reporting known respiratory disease had normal spirometry, and 8.7% without known respiratory disease had airway obstruction. Conclusion: Prevalence of airway obstruction in this rural population was comparable to previous estimates from urban Danish population studies. The choice of cut-off impacts the estimated prevalence, and using the FEV ₁/FVC cut-off may overestimate prevalence. However, many participants with known respiratory disease had normal spirometry in this health study.