Rationale: COPD is a major cause of mortality and morbidity in China. But, relatively little is known about the interregional variation of the disease prevalence and rate of under-diagnosis in the general population. We estimate the prevalence of air flow obstruction (AFO) using measured lung function in a large population-based study and compare it to self-reported physician diagnosed COPD. Methods: China Kadoorie Biobank involves 512,891 adults, aged 30-79, who were recruited during 2004-8 from 10 diverse regions of China. All the participants performed spirometry and gave information on self-reported history of doctor-diagnosed chronic bronchitis/emphysema, current medication and possible COPD risk factors. Results: The prevalence of AFO (ie, FEV 1 /FVC<0.7) was much higher in rural than in urban areas (men: 8.2% vs. 4.6%; women: 5.2% vs. 3.0%). In both sexes, the prevalence was also higher in those with poor education, lower income and older age. Similar trends were seen when using the lower limit of normal of FEV 1 /FVC for diagnosing AFO. Compared with self-reported COPD, 86.4% of the AFO cases were undetected prior to the survey; higher in women than in men (88.4% vs. 84.5%) but lower in rural than in urban areas (85.9% vs. 87.5%) with clear heterogeneity across regions for both men (75.4%-96.1%) and women (77.1%-98.0%). In both sexes, <40% of doctor diagnosed COPD were currently under medication. Conclusion: There was wide heterogeneity in prevalence of AFO across the ten different regions of China, with the large majority of them being undetected in both men and women.
Kurmi et al. (Sun,) studied this question.