Incidence, prevalence, and ketoacidosis at onset of type 1 diabetes in Spain: a systematic review and critical assessment of the available evidence

The incidence, prevalence and onset of type 1 diabetes (T1D) with diabetic ketoacidosis (DKA) in Spain remain insufficiently characterized, despite multiple regional analyses. This study aims to summarize and critically assess epidemiologic data in Spain, incorporating insights from the clinician authors, considering clinically diagnosed T1D (stage 3). A systematic literature review of PubMed and Embase was conducted to identify available epidemiological evidence in Spain. Subsequently, nominal group techniques were applied to gather qualitative insights on methodological issues of the sources and estimates for the incidence, prevalence and onset of T1D with DKA. Of the 528 references identified and screened, 61 met eligibility criteria and were evaluated by clinician authors within the nominal group. Methodological insights suggested a meta-analysis to be the most robust source for pediatric incidence (incidence rate [IR]: 17.04 cases/100,000 inhabitants <15 years), complemented by an observational study using the capture-recapture method in Navarre (IRs per 100,000 inhabitants-years: 14.99 [<15 years], 15.8 [15-29 years], 7.6 [30-45 years], and 2.2 [≥45 years]). The most reliable prevalence estimates indicated rates of 1.01-1.44/1,000 inhabitants in pediatric populations, increasing to 9.0/1,000 inhabitants in adults. Onset of T1D with DKA showed highest frequency in individuals <15 years (36.0-48.0%), decreasing progressively with age: 26.1% (15-29 years), 19.2% (30-44 years), and 12.3% (≥45 years). A potential underestimation was highlighted for failing to account for their upward trend over time, the model-based estimates for people <15 years presented in the 11th Edition of the International Diabetes Federation Atlas being a potential alternative for both IR (24.1 cases/100,000 inhabitants <15 years) and prevalence (1.58 cases/1,000 inhabitants <15 years). This study synthesized and identified the most robust evidence available regarding the incidence, prevalence and onset of T1D with DKA in Spain. The findings highlight substantial heterogeneity across regions and emphasize the need for more comprehensive and standardized epidemiological research. Not applicable.