This large-scale cohort covers individuals who underwent SARS-CoV-2 testing in South Korea from January 1, 2020 to May 1, 2020 supported by the Korean Centers for Disease Control and the National health insurance service (NHIS). For each patient who underwent SARS-CoV-2 testing, we combined medical data on COVID-19-related outcomes during the hospitalization with claim-based data from January 1, 2015 to May 1, 2020, including personal data (age, sex, region of residence, and socioeconomic status) and health care records of inpatients and outpatients throughout the past 5 years (including health care visits, prescriptions, diagnoses, and procedures), retrospectively. SARS-CoV-2 infection was defined by a positivity on a real-time RT–PCR assay of nasal or pharyngeal swabs (6). A history of COPD (J43-J44, apart from J430), diabetes mellitus (E10-14), ischemic heart disease (I20-25), cerebrovascular disease (I60-64, I69, and G45), hypertension (I10-13 and I15), or chronic kidney disease (N18-19) was defined by the physician diagnosis reporting of at least two claims within 1 year during this 5-year study period according to the appropriate International Classification of Disease, Tenth Revision (ICD-10) code (7). In this study, “exposure” comprised the development of COPD; the “primary outcome” was test positivity for SARS-CoV-2 among all patients who underwent SARS-CoV-2 testing, and the “secondary outcome” was severe disease or mortality of patients who tested positive for SARS-CoV-2. The definition of severe disease included: 1) requirement for oxygen supplementation, 2) intensive care units (ICU) admission, 3) intubation with mechanical ventilation, or 4) application of extracorporeal membrane oxygenation (ECMO).
We performed two rounds of propensity score matching to balance the baseline characteristics and to reduce potential confounders. We evaluated each propensity score matching in a 1:1 ratio using the ‘greedy nearest-neighbor’ algorithm and calculated the predicted probability of (a) individuals with a history of COPD versus individuals without a history of COPD among all patients who underwent SARS-CoV-2 testing (n = 129,120); (b) individuals with a history of COPD versus individuals without a history of COPD among patients with confirmed COVID-19 (n = 8,070). The adequacy of matching was evaluated by comparing the distributions of propensity score and standardized mean differences (SMDs). After utilizing a multivariate logistic regression model adjusted for history of angina, any type of cancer, hypertension (HTN), congestive heart failure (CHF), chronic kidney disease (CKD), cerebrovascular disease (CVD), diabetes mellitus (DM), hepatitis, and myocardial infarction (MI), estimation of the adjusted odds ratios (aORs) with 95% CIs was performed. Patient-related data were anonymized and the protocol was approved by the Institutional Review Board of Jeonbuk National University Hospital (2020-04-067).