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. 2021 Feb 12;11:3735. doi: 10.1038/s41598-021-83226-9

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© The Author(s) 2021

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.

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Flowchart of the study cohort. Of 7590 COVID-19 patients, 4610 were aged 40 years or older. During the enrollment period, 4469 and 141 patients were categorized into the non-COPD and COPD groups, respectively. Among the COPD patients, 114 and 27 were classified into the non-severe and severe groups, respectively. COPD was defined by the ICD-10 codes and COPD medications prescribed during the enrollment period. The severity of COPD was classified based on the types of medications prescribed and the number of exacerbations during the measurement period. COVID-19 coronavirus disease 2019; COPD, chronic obstructive pulmonary disease; ICD-10, 10th revision of the International Statistical Classification of Diseases and Related Health Problems.