Declining Comorbidity Burden Among Patients During First Hospitalization Associated with Thyroid Cancer in Poland: A Nationwide Study, 2012–2024

Background: Thyroid cancer (TC) is the most common endocrine malignancy worldwide. Although the burden of thyroid-related disorders accompanying TC has been extensively studied, less is known about the overall pattern of multimorbidity present at the time of diagnosis. The aim of this study was to characterize hospital-recorded comorbidities among patients during their first hospitalization associated with thyroid cancer in Poland and to evaluate temporal changes in these patterns between 2012 and 2024. Methods: This nationwide retrospective cohort study included 60,604 patients with a first thyroid-cancer-associated hospitalization recorded in Poland between 2012 and 2024 using data from the Nationwide General Hospital Morbidity Study. The study included all first hospitalizations with ICD-10 code C73 recorded in the database during the study period. Diagnoses accompanying thyroid cancer were classified according to ICD-10 chapters and analyzed descriptively. For the purposes of this study, incident cases were operationally defined as patients with a first hospitalization associated with ICD-10 code C73 recorded in the database during the study period. Temporal trends in age and major comorbidity groups were assessed using linear regression models. Results: A total of 60,604 patients with a first recorded hospitalization associated with TC were identified, including 49,794 women (82.2%) and 10,810 men (17.8%). The mean age at diagnosis was 51.1 ± 15.9 years. Endocrine, nutritional, and metabolic disorders constituted the most common comorbidity group, affecting 20,792 patients (34.3%), followed by cardiovascular diseases (13.6%) and neoplasms other than TC (5.0%). Hypothyroidism was the most frequent endocrine disorder, occurring in 11.5% of patients. During the study period, the mean age at diagnosis decreased from 53.7 years to 49.8 years (p < 0.001). A marked temporal decline in the prevalence of recorded comorbidities was observed during the study period, with endocrine/metabolic disorders decreasing from 52.0% to 25.3% and cardiovascular diseases from 19.9% to 7.7% (both p < 0.001). Additional malignancies most commonly involved the breast, lung, kidney and ovary. Conclusions: Patients with first thyroid-cancer-associated hospitalization recorded in the database frequently present with concomitant endocrine, cardiovascular, and oncological disorders. Over the study period, a substantial decline in the prevalence of recorded comorbidities was accompanied by a reduction in age at diagnosis, suggesting changes in the characteristics of patients recorded during thyroid-cancer-associated hospitalizations over time. These findings may have implications for healthcare planning and survivorship care by highlighting the evolving clinical profile of patients undergoing thyroid-cancer-associated hospitalization.