Fig. 2
Point prevalence of COPD among respondents ≥40 years old. The prevalence was calculated per 1000 persons and expressed with 95% confidence intervals, for three COPD definitions: previously diagnosed COPD (when self-reported by the respondent while completing the study questionnaire); COPD diagnosed by spirometry (confirmed by spirometry results based on the GOLD guideline (2011), i.e. FEV1/FVC < 0.70), and firstly diagnosed COPD by spirometry (when the respondent was diagnosed with COPD for the first time based on spirometry outcomes)