The Italian registry for narcolepsy and central disorders of hypersomnolence (ReN&IS): Baseline clinical and diagnostic findings

Objective: Central disorders of hypersomnolence, a wide and heterogeneous group of neurological disorders including narcolepsy type 1 (NT1), narcolepsy type 2 (NT2), and idiopathic hypersomnia (IH), are chronic, rare, under-recognized, and disabling conditions characterized by excessive daytime sleepiness (EDS) and other symptoms adversely impacting patients' lives. Large, harmonized real-world datasets are needed to improve phenotypic characterization, diagnostic accuracy, and translational research. Methods: The Italian Registry for Narcolepsy and Central Disorders of Hypersomnolence (ReN&IS) is a national, multicenter, observational registry established in 2022. This preliminary analysis presents and compares demographic features, disease presentation, diagnostic assessment, medical comorbidities, current treatment patterns, and symptoms' evolution across diagnostic NT1, NT2, and IH groups of patients enrolled across 20 Italian referral centers. Results: From March 2022 to September 2025, 480 cases were entered in the ReN&IS. NT1 accounted for 80.0% of cases, NT2 for 14.6%, and IH for 5.4%. NT1 showed younger age at onset and enrollment than NT2 and IH, as well as the highest burden of REM-sleep-related symptoms and clear biomarker profiles (HLA DQB1∗06:02 positivity and low cerebrospinal fluid orexin-A levels). Although most patients were treated with non-pharmacological (58-77%) and pharmacological (88-94%) interventions, residual EDS was common in the different groups (65-85%). Obesity and medical comorbidities, including cardiovascular, pulmonary, and connective tissue diseases did not significantly differ across groups. Conclusions: ReN&IS provides the first nationwide, real-world characterization of central disorders of hypersomnolence in Italy, highlighting diagnostic and therapeutic gaps, and offering a robust platform for future longitudinal and translational studies.