Underdiagnosis of COPD: The Japan COPD Real-World Data Epidemiological (CORE) Study.

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The prevalence of airflow obstruction in Japan is 3.8%-16.9%. This epidemiological study based on a large database aimed to reassess the prevalence of airflow obstruction in Japan and the diagnosis rate of chronic obstructive pulmonary disease (COPD). We used data regarding claims from the health insurance union and health checkups provided by JMDC. The present study included a subgroup of individuals aged ≥40 years who underwent health checkups involving spirometry between January and December 2019. The study endpoints were the prevalence of airflow obstruction, COPD diagnosis rate, disease stage, and respiratory function test results. Among 102,190 participants, 4113 (4.0%) had airflow obstruction. The prevalence of airflow obstruction was 5.3% in men and 2.1% in women. Among the study population, 6.8% were current smokers, while 3.4% were never or former smokers. Additionally, the prevalence of COPD increased with age. Approximately 8.4% of participants with airflow obstruction were diagnosed with COPD. Regarding the COPD diagnosis status, participants with airflow obstruction who were diagnosed with COPD were at a more advanced stage than those not diagnosed. Finally, patients diagnosed with COPD had significantly lower FEV1/FVC and FEV1 (p < 0.0001; Wilcoxon rank sum test). The epidemiological study based on a large database determined the COPD diagnosis rate related to airflow obstruction. The COPD diagnosis rate was extremely low among individuals who underwent health checkups, indicating the need for increased awareness about this medical condition. Moreover, primary care physicians should identify patients with suspected COPD and collaborate with pulmonologists to facilitate the early detection of COPD and enhance the COPD diagnosis rate.