Incidence and Demographic Characteristics of Type 1 Diabetes Mellitus in Children from Bihor County, Romania, 2014–2024: A Descriptive Single-Centre Study

Background/Objectives: Type 1 diabetes mellitus (T1DM) is a common chronic disease of childhood, with a rising incidence worldwide, across Europe, and in Romania. This retrospective, descriptive, single-centre study aimed to describe the demographic features, the temporal distribution and the approximate incidence of T1DM in children diagnosed in Bihor County, Romania. Methods: Of 174 children with newly diagnosed T1DM at Emergency Clinical County Hospital Bihor (2014–2024), 172 residing in Bihor County were analysed (two were excluded because they resided outside the county; none was excluded for missing data) for sex, age at onset, residence, and year and month of onset. The incidence was approximated using an assumed pediatric population (83,000–105,000 children aged 0–17 years), and the findings were set against official administrative registry data (INSP-CNSSP) for Bihor County and Romania. Results: The sex ratio was close to unity (47.1% girls; 95% confidence interval (CI) 39.8–54.5%). The rural share of cases (45.3%) did not differ significantly from the rural share of the county’s general all-ages population in the 2021 census (52.7%; p = 0.054), a non-age-matched comparison that should be interpreted cautiously. Mean age at onset was 9.2 ± 4.5 years (girls 9.7 ± 4.3, boys 8.7 ± 4.6 years; p = 0.135); the largest proportion of cases (37.8%) was observed at ages 10–14 years. The annual number of recorded new cases ranged from 11 to 23 without a statistically significant temporal trend (Poisson regression of case counts, without population offset, p = 0.185; rate ratio 1.27 for 2019–2024 versus 2014–2018, 95% CI 0.93–1.76, p = 0.126). The approximate crude incidence was 14.9–18.8 cases per 100,000 children/year (point estimate 16.6); this is an indicative estimate that is not directly comparable with national estimates for children aged 0–14 years. Administrative registry data (INSP-CNSSP), which cover all forms of diabetes and children in active follow-up, showed an increase in the number of children aged 0–14 years in follow-up from 32 (2012) to 187 (2021) and prevalence above the national average, but cannot confirm trends in pediatric T1DM incidence or prevalence. Conclusions: This descriptive single-centre series broadly followed national and European patterns in sex ratio, age distribution and seasonality, with a relatively stable number of recorded annual cases. Given the single-centre case ascertainment and approximate denominators, the findings should not be regarded as population-based incidence estimates or as evidence of a higher local incidence or burden of T1DM; confirmation through multi-source case ascertainment or registry linkage is needed.