Incidence of GOLD-defined chronic obstructive pulmonary disease in a general adult population

SETTING: The incidence of chronic obstructive pulmonary disease (COPD) as defined by the Global Initiative for Chronic Obstructive Lung Disease (GOLD) has not previously been examined. OBJECTIVE: To estimate cumulative 9-year GOLD-defined COPD incidence in a general adult Norwegian population, to analyse sex, age, smoking habits and residential area as predictors, and to assess the level of underdiagnosis. DESIGN: Based on a random stratified population sample examined in 1987-1988, 908 adults (71%) participated in a follow-up examination in 1996-1997. Associations between risk factors and COPD incidence were examined with logistic regression analyses. RESULTS: The cumulative incidence of COPD among persons at risk in 1987-1988 was 6.1% (95% confidence interval [CI] 4.0-8.1). Adjusted odds ratios (OR) for current smokers and ex-smokers were 9.6 (95%CI 3.6-25.2) and 5.0 (95%CI 1.8-13.8), compared to never smokers. Risk for COPD incidence further increased with pack years. Subjects aged 45-74 had an OR of 9.8 (95%CI 4.3-22.5) relative to those aged 18-44. Sex and residential area were not significantly associated with COPD incidence. Only 43% of the incident cases had physician-diagnosed asthma, bronchitis, emphysema and/or COPD. CONCLUSION: Approximately 6% developed COPD over 9 years. Smoking and aging were important incidence predictors. Our study suggests a substantial underdiagnosis of COPD among adults in this community.