Implications of reversibility testing on prevalence and risk factors for chronic obstructive pulmonary disease: a community study

Background: The Global Initiative for Obstructive Lung Disease (GOLD) has defined chronic obstructive pulmonary disease (COPD) as a post-bronchodilator ratio of forced expiratory volume in 1 second to forced vital capacity (FEV1/FVC) of <0.7. In the first general population based study to apply post-bronchodilator values, the prevalence and predictors of GOLD defined COPD were assessed and the implications of β2 agonist reversibility testing examined. Methods: Based on a random population sample, 2235 subjects (77%) aged 26–82 years performed spirometric tests before and 15 minutes after inhaling 0.3 mg salbutamol. Results: The prevalence of GOLD defined COPD was 7.0% (95% confidence interval (CI) 5.9 to 8.0). This estimate was 27% lower than COPD defined without bronchodilatation. One percent of the population had severe or very severe COPD. Compared with women, men had 3.1 (95% CI 2.1 to 4.8) times higher odds for COPD. Subjects with a smoking history of more than 20 pack years had an odds ratio (OR) of 6.2 (95% CI 3.4 to 11.0) for COPD relative to never-smokers, while subjects older than 75 years had an OR of 18.0 (95% CI 9.2 to 35.0) relative to those below 45 years. Subjects with primary education only had an OR of 2.8 (95% CI 1.4 to 5.3) compared with those with university education. Subjects with body mass index (BMI) <20 kg/m2 were more likely than subjects with BMI 25–29.9 kg/m2 to have COPD (OR 2.4, 95% CI 1.1 to 5.3). The adjusted proportion of COPD attributable to smoking was 68%. Conclusions: These results indicate that community programmes on prevention of COPD should focus on anti-smoking, nutritional aspects, and socioeconomic conditions. The effect of β2 reversibility testing on prevalence estimates of COPD was substantial.