Estimating national prevalence of type 1 diabetes mellitus in children in Ireland using a novel simple approach: an observational study.

Introduction: Diabetes mellitus type 1 or type 1 diabetes (T1D) is a common life-threatening autoimmune condition in children with accurate estimates of those affected required for appropriate healthcare planning. While the incidence of T1D is prospectively monitored by the Irish Childhood Diabetes National Register (ICDNR), to date there are limited data regarding its prevalence. This study aims to develop a simple, reusable method of estimating population disease prevalence, here applied to Irish childhood T1D. Methods: Using robust ICDNR national annual incidence data from 2008 to 2021, for T1D in children aged under 15 years, a simulation-based model was developed, assuming normal distributions for age-specific rates beyond the first year of life. Using this model, the number of children with T1D was calculated and accuracy was assessed through bootstrapping. This estimate was compared with the measured prevalence using incidence data reported to the ICDNR for those diagnosed and aged under 15 years from 1 January 2008 to 31 December 2022 and 1 January 2009 to 31 December 2023. Results: Applying this simulation model, the estimated number of children with T1D in Ireland in 2021 ranged between 1952 and 2050, yielding a national prevalence range of 0.20%-0.21%. The measured prevalence in 2022 and 2023, using cumulative incidence, was comparable and stable over the 2-year period at 2054 or 0.20%. Conclusions: This methodology serves as a practical tool to estimate the number affected by childhood T1D, critical for planning appropriate health services and allocating resources to meet their specific needs. This simple model can easily be applied to other populations or diseases with known incidence to estimate prevalence.