{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,9]],"date-time":"2026-09-09T13:08:00Z","timestamp":1788959280215,"version":"build-2803163510"},"reference-count":17,"publisher":"BMJ","issue":"9","license":[{"start":{"date-parts":[[2026,9,9]],"date-time":"2026-09-09T00:00:00Z","timestamp":1788912000000},"content-version":"unspecified","delay-in-days":8,"URL":"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100003052","name":"Ministry of Trade, Industry and Energy","doi-asserted-by":"publisher","award":["RS-2025-02214034"],"award-info":[{"award-number":["RS-2025-02214034"]}],"id":[{"id":"10.13039\/501100003052","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100003725","name":"National Research Foundation of Korea","doi-asserted-by":"publisher","award":["2022R1F1A1073485"],"award-info":[{"award-number":["2022R1F1A1073485"]}],"id":[{"id":"10.13039\/501100003725","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["bmj.com"],"crossmark-restriction":true},"short-container-title":["BMJ Open"],"accepted":{"date-parts":[[2026,8,25]]},"published-print":{"date-parts":[[2026,9]]},"abstract":"<jats:sec>\n                    <jats:title>Objectives<\/jats:title>\n                    <jats:p>To compare baseline, cluster-based and trajectory-based classifications of continuity of primary care (COC) and to examine their associations with chronic obstructive pulmonary disease (COPD)-related hospitalisation and emergency department (ED) visits.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Design<\/jats:title>\n                    <jats:p>Population-based retrospective cohort study.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Setting<\/jats:title>\n                    <jats:p>National Health Insurance claims data from South Korea (Korean National Health Insurance Service), 2014\u20132021.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Participants<\/jats:title>\n                    <jats:p>92\u2009977 patients aged \u226540 years newly diagnosed with COPD between 2015 and 2016, with at least four ambulatory primary care visits during the exposure period.<\/jats:p>\n                    <jats:p>Primary and secondary outcome measures: The primary outcome was the incidence of COPD-related hospitalisation; the secondary outcome was the incidence of COPD-related ED visits. Continuity of primary care was quantified using the Continuity of Care Index (COCI) and classified using three approaches: (1) a baseline COCI-based method, (2) a cluster-based method using K-means clustering and (3) a trajectory-based method using group-based trajectory modelling. Fine-Gray subdistribution hazard models, accounting for death as a competing risk, were used to estimate adjusted HRs (aHRs).<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>Across all three classification approaches, low continuity of care was consistently associated with an increased risk of COPD-related hospitalisation (aHR 2.43, 95%\u2009CI 2.22 to 2.66 for baseline COCI; 2.26, 95%\u2009CI 2.06 to 2.47 for cluster-based; 2.73, 95%\u2009CI 2.49 to 2.99 for trajectory-based) and ED visits (aHR 2.32, 95%\u2009CI 2.04 to 2.63 for baseline COCI; 2.55, 95%\u2009CI 2.25 to 2.88 for cluster-based; 3.48, 95%\u2009CI 3.05 to 3.96 for trajectory-based). Effect estimates were consistently strongest for the trajectory-based approach and weakest for the baseline COCI approach. Agreement among the three classification methods was substantial (overall 87.2%; Fleiss\u2019 kappa 0.78).<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>Baseline COCI classification offers a pragmatic and robust measure of COC, producing effect estimates directionally consistent with those derived from more complex longitudinal approaches; however, observed transitions between continuity groups over time indicate that reliance on baseline classification alone may attenuate effect estimates when continuity patterns change. Trajectory-based methods may yield additional insight in populations with greater temporal variability in care patterns but entail substantially higher data and modelling requirements.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1136\/bmjopen-2026-117468","type":"journal-article","created":{"date-parts":[[2026,9,9]],"date-time":"2026-09-09T12:40:30Z","timestamp":1788957630000},"page":"e117468","update-policy":"https:\/\/doi.org\/10.1136\/crossmarkpolicy","source":"Crossref","is-referenced-by-count":0,"title":["Baseline and longitudinal measures of continuity of primary care and COPD-related service utilisation: a cohort study using Korean National Health Insurance Service claims data"],"prefix":"10.1136","volume":"16","author":[{"given":"Ae Jeong","family":"Jo","sequence":"first","affiliation":[{"name":"Department of Data Science, Gyeongkuk National University, Andong-si, Korea (the Republic of)"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sejung","family":"Kim","sequence":"additional","affiliation":[{"name":"Department of Data Science, Gyeongkuk National University, Andong-si, Korea (the Republic of)"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Eunjung","family":"Choo","sequence":"additional","affiliation":[{"name":"College of Pharmacy, Ajou University, Suwon-si, Korea (the Republic of)"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Nam Kyung","family":"Je","sequence":"additional","affiliation":[{"name":"College of Pharmacy, Pusan National University, Busan, Korea (the Republic of)"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Eun Jin","family":"Jang","sequence":"additional","affiliation":[{"name":"Department of Data Science, Gyeongkuk National University, Andong-si, Korea (the Republic of)"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6644-0808","authenticated-orcid":false,"given":"Iyn-Hyang","family":"Lee","sequence":"additional","affiliation":[{"name":"College of Pharmacy, Yeungnam University, Gyeongsan-si, Korea (the Republic of)"},{"name":"Department of Health Sciences, University of York, York, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"239","published-online":{"date-parts":[[2026,9,9]]},"reference":[{"key":"2026090905401406000_16.9.e117468.1","doi-asserted-by":"publisher","DOI":"10.1111\/j.1365-2753.2009.01235.x"},{"key":"2026090905401406000_16.9.e117468.2","doi-asserted-by":"crossref","first-page":"148","DOI":"10.1002\/pds.4372","article-title":"Methods for time-varying exposure related problems in pharmacoepidemiology: An overview","volume":"27","author":"Pazzagli","year":"2018","journal-title":"Pharmacoepidemiol Drug Saf"},{"key":"2026090905401406000_16.9.e117468.3","doi-asserted-by":"crossref","DOI":"10.1016\/j.eclinm.2022.101492","article-title":"Outcomes associated with higher relational continuity in the treatment of persons with asthma or chronic obstructive pulmonary disease: A systematic review","volume":"49","author":"Lytsy","year":"2022","journal-title":"EClinicalMedicine"},{"key":"2026090905401406000_16.9.e117468.4","doi-asserted-by":"crossref","DOI":"10.1136\/bmjopen-2021-053140","article-title":"Assessment of the effects of methodological choice in continuity of care research: a real-world example with dyslipidaemia cohort","volume":"11","author":"Choo","year":"2021","journal-title":"BMJ Open"},{"key":"2026090905401406000_16.9.e117468.5","doi-asserted-by":"crossref","DOI":"10.1136\/bmjresp-2024-002472","article-title":"Relationship between continuity of primary care and hospitalisation for patients with COPD: population-based cohort study from South Korea","volume":"11","author":"Lee","year":"2024","journal-title":"BMJ Open Respir Res"},{"key":"2026090905401406000_16.9.e117468.6","doi-asserted-by":"publisher","DOI":"10.1136\/bmj.39335.541782.AD"},{"key":"2026090905401406000_16.9.e117468.7","unstructured":"National Health Insurance Sharing Service . 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