Hospital-Based Incidence Trends of Thyroid Cancer in Poland: Temporal Trends, Regional Disparities and Demographic Characteristics Based on a Nationwide Hospital Discharge Database (2012–2024)

Background: Thyroid cancer (TC) is the most common endocrine malignancy, with a steadily increasing incidence observed worldwide. However, temporal trends and demographic patterns may vary across populations. Objectives: To assess hospital-based incidence rates, demographic characteristics, and selected epidemiological patterns of TC in Poland between January 2012 and December 2024. Material and Methods: This population-based, retrospective study utilized hospitalization records of TC patients in Poland obtained from the Nationwide General Hospital Morbidity Study. Only first-time hospitalizations in the study period with reported primary or secondary diagnoses of TC were included in the study. Results: The study cohort included 60,604 patients, and the mean annual hospital-based incidence rate was 12.2 per 100,000 inhabitants (95% CI: 11.0–13.4). The hospital-based incidence rate decreased from 15.2 in 2012 to 9.8 per 100,000 in 2020, followed by a marked increase, peaking to 16.6 per 100,000 in 2024. Women constituted 82.2% of cases, indicating a strong sex-related disparity. The mean age at diagnosis was 51.1 years (SD: 15.9). The mean age at diagnosis was 51.1 years (SD: 15.9), and a greater proportion of hospitalized thyroid cancer patients were urban than rural residents (67.4% vs. 32.6%). Marked regional variation was observed, with the highest rates recorded in selected northern and central voivodeships. Conclusions: TC hospitalization hospital-based incidence rates in Poland showed significant temporal variability, with the lowest rate in 2020, which may reflect disruptions in healthcare access during the COVID-19 pandemic and a possible diagnostic catch-up effect in subsequent years. Regional disparities may suggest the potential influence of environmental, socioeconomic, or healthcare-related factors.