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oai:figshare.com:article/33919945 2026-09-18T04:36:06Z category_427 portal_316 item_type_3 month_year_09_2026

Table 1_Same ICD-10 code, different estimands: four Polish National Health Fund obesity series, 2015–2025.docx Marcin Poboży (25069675) Anna Rulkiewicz (24659028) Wojciech Lisik (256418) Zoran Stojčev (25069678) Ewa Filipiak-Rokicka (25069681) Iwona Pilchowska (25069684) Justyna Domienik-Karłowicz (24659031) Public Health and Health Services not elsewhere classified administrative data ecological time series ICD-10 National Health Fund obesity Poland routinely collected health data Background<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.</p>Methods<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 2015–2025. 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.</p>Results<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 (−3.5%) but substantially larger for the three series requiring current-year activity (−39.4 to −44.3%).</p>Conclusions<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.</p> 2026-09-18T04:36:06Z Dataset Dataset 10.3389/fpubh.2026.1920632.s001 https://figshare.com/articles/dataset/Table_1_Same_ICD-10_code_different_estimands_four_Polish_National_Health_Fund_obesity_series_2015_2025_docx/33919945 CC BY 4.0