Table 3—

Overall raw and age-adjusted prevalence of chronic obstructive respiratory disease (COPD) by different criteria

Method of diagnosisSubjects with COPD/totalRaw prevalence (95% CI)Age-adjusted prevalence#(95% CI)
GOLD
 All ages116/74915.5 (13.0–18.3)9.3 (7.2–11.4)
 ≥40 yrs109/62417.5 (14.6–20.7)14.2 (11.0–17.0)
LLN FEV1/SVC+
 All ages73/7469.8 (7.8–12.2)7.0 (5.0–9.0)
 ≥40 yrs66/62110.6 (8.3–13.3)9.0 (6.7–11.3)
LLN FEV1/FVC
Post-bronchodilator
  All ages78/74910.4 (8.3–12.8)7.7 (5.5–9.9)
  ≥40 yrs69/62411.1 (8.7–13.8)9.5 (7.1–11.8)
 Pre-bronchodilator
  All ages120/74916.0 (13.5–18.9)14.5 (11.3–17.7)
  ≥40 yrs100/62416.0 (13.2–19.1)15.2 (12.0–18.5)
Doctor diagnosis§
 All ages79/74910.6 (8.4–13.0)9.8 (7.1–12.5)
 ≥40 yrs67/62410.7 (8.4–13.4)10.5 (7.8–13.2)
  • CI: confidence interval; GOLD: Global Initiative for Chronic Obstructive Lung Disease; LLN: lower limit of normal; FEV1: forced expiratory volume in one second; SVC: slow vital capacity; FVC: forced vital capacity. #: adjusted to the age distribution of the Wellington population at the 2001 census 12; : diagnostic criteria as per the GOLD guidelines; +: definition of an obstructive pulmonary defect based on FEV1/FVC ratio (the cut-off value of this ratio is set at the fifth percentile of the normal distribution rather than at a fixed value of 0.7). This ratio can be used with either pre- or post-bronchodilator values. Three subjects had missing data for SVC. §: based on the questions “Did your doctor ever tell you that you had chronic bronchitis?”, “Did a doctor ever tell you that you had emphysema?” and “Have you ever been told by a doctor that you had chronic obstructive respiratory disease?”