The prevalence of chronic obstructive pulmonary disease in Uppsala, Sweden - the Burden of Obstructive Lung Disease (BOLD) study: Cross-sectional population-based study

Objectives: To estimate chronic obstructive pulmonary disease (COPD) prevalence in Uppsala and the impact of risk factors on disease prevalence using the standardised methods of the Burden of Obstructive Lung Disease (BOLD) study initiative. Methods: Randomly selected participants, aged 40years or more (n=548) responded to a questionnaire regarding smoking habits, respiratory symptoms, medical history, and exposure to airway irritants. Spirometry, with a post-bronchodilator test, was performed and COPD defined as post-bronchodilatory forced expiratory volume in 1s (FEV ₁)/forced vital capacity (FVC)<0.70 or FEV ₁/FVC<lower limit of normality (LLN). Circulatory inflammatory markers were measured. Results: COPD prevalence was 16.2%, which was the fourth lowest prevalence of COPD, compared with 12 other BOLD centres. Main risk factors for COPD were increasing age [odds ratio (OR)=2.08 per 10years] and smoking (OR=1.33 per 10 pack years). Higher education was protective (OR=0.70 per 5years). Previous tuberculosis was an almost significant risk factor for COPD (P=0.08). Subjects with COPD reported more respiratory symptoms but only 29% had previous doctor diagnosed COPD, asthma, chronic bronchitis or emphysema. Participants with COPD had higher levels of C-reactive protein (P=0.01), but no difference was observed in interleukin 6 (IL-6) levels. Using LLN instead of the fixed FEV ₁/FVC ratio reduced the prevalence of COPD to 10%. Conclusion: COPD prevalence in Uppsala was similar to other BOLD centres in high-income countries. Apart from known COPD risk factors (age, smoking, lower educational level), a history of tuberculosis may be associated with COPD even in high-income countries. COPD remains under-diagnosed, as only 29% of subjects with COPD had a previously diagnosed lung disorder.