{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,18]],"date-time":"2026-09-18T05:08:05Z","timestamp":1789708085937,"version":"4.0.1"},"reference-count":34,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2026,9,18]],"date-time":"2026-09-18T00:00:00Z","timestamp":1789689600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Public Health"],"abstract":"<jats:sec>\n                    <jats:title>Background<\/jats:title>\n                    <jats:p>Poland's National Health Fund (NFZ) publishes four national series indexed by ICD-10 code E66. Although their labels suggest related measures of obesity, differences in analytical unit, entry rule, look-back period, and temporal structure may alter both the reported level and the apparent response to healthcare-system disruption. We examined whether selecting an official NFZ E66 series materially changes the level, trend, and permissible public-health interpretation of recorded obesity-related activity.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>This retrospective, descriptive ecological time-series study audited 44 annual resources covering registered morbidity, first-recorded patients, annual E66 patients, and E66-coded services in 2015\u20132025. We analyzed counts and population-scaled administrative rates, summarized long-term change using log-linear annual percentage change (APC), and used a one-year 2020 indicator as a descriptive pandemic-era stress test. An endpoint sensitivity analysis excluded 2025. Independent BMI sources provided cross-sectional contextual triangulation for 2025.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>In 2025, two official person-based series yielded 1,534,022 persons with a current or earlier principal E66 record and 325,769 persons with qualifying current-year E66 activity, a 4.7-fold difference arising from construction rather than alternative estimates of a single quantity. From 2015 to 2025, endpoint increases ranged from 178.1 to 332.5%, and population-scaled APCs from 10.5 to 14.5%. During 2020, the first year of the COVID-19 pandemic, deviations from the fitted trend were modest for registered morbidity (\u22123.5%) but substantially larger for the three series requiring current-year activity (\u221239.4 to \u221244.3%).<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>The same E66 code supports four distinct administrative trajectories. Their growth may reflect a genuine rise in clinical obesity together with changes in recognition, access, recording, and service delivery; the aggregates cannot separate these contributions. Explicit estimand definitions are therefore essential when NFZ indicators are used for surveillance or policy.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.3389\/fpubh.2026.1920632","type":"journal-article","created":{"date-parts":[[2026,9,18]],"date-time":"2026-09-18T04:37:01Z","timestamp":1789706221000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["Same ICD-10 code, different estimands: four Polish National Health Fund obesity series, 2015\u20132025"],"prefix":"10.3389","volume":"14","author":[{"given":"Marcin","family":"Pobo\u017cy","sequence":"first","affiliation":[{"name":"NZOZ Cichowski Pobozy Healthcare Facility","place":["Maciejowice, Poland"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Anna","family":"Rulkiewicz","sequence":"additional","affiliation":[{"name":"LUX MED Sp. z o.o.","place":["Warsaw, Poland"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Wojciech","family":"Lisik","sequence":"additional","affiliation":[{"name":"Department of General, Oncological, Metabolic and Thoracic Surgery, Military Institute of Medicine \u2013 National Research Institute","place":["Warsaw, Poland"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Zoran","family":"Stoj\u010dev","sequence":"additional","affiliation":[{"name":"2nd Department of General, Vascular and Oncological Surgery, Faculty of Medicine and Dentistry, Czerniakowski Hospital, Medical University of Warsaw","place":["Warsaw, Poland"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ewa","family":"Filipiak-Rokicka","sequence":"additional","affiliation":[{"name":"LUX MED Sp. z o.o.","place":["Warsaw, Poland"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Iwona","family":"Pilchowska","sequence":"additional","affiliation":[{"name":"LUX MED Sp. z o.o.","place":["Warsaw, Poland"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Justyna","family":"Domienik-Kar\u0142owicz","sequence":"additional","affiliation":[{"name":"University of Medical Sciences in Warsaw","place":["Warsaw, Poland"]},{"name":"Department of Internal Medicine and Cardiology with the Centre for Diagnosis and Treatment of Venous Thromboembolism, Infant Jesus Clinical Hospital, University Clinical Centre, Medical University of Warsaw","place":["Warsaw, Poland"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1965","published-online":{"date-parts":[[2026,9,18]]},"reference":[{"key":"B1","doi-asserted-by":"publisher","first-page":"221","DOI":"10.1016\/S2213-8587(25)00006-3","article-title":"Definition and diagnostic criteria of clinical obesity","volume":"13","author":"Rubino","year":"2025","journal-title":"Lancet Diabetes 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