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. 2021 Nov 22;8:780438. doi: 10.3389/fmed.2021.780438

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Copyright © 2021 Jo, Hwang, Yoo, Lee, Jung, Shin, Yoon, Kim, Lee and Rhee.

This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

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Flow diagram of the subjects in two cohorts. AA, African American; ACO, asthma–chronic obstructive pulmonary disease (COPD) overlap; BDR, bronchodilator response; COPD, chronic obstructive pulmonary disease; FEV₁, forced expiratory volume in 1 s; FVC, forced vital capacity; KOCOSS, The Korean COPD Subgroup Study; NHW, non-Hispanic white; PY, pack-years.