0711 Association of Polysomnographic Characteristics and Mean Sleep Latency Test Across Central Disorders of Hypersomnolence

Abstract Introduction Associations between polysomnography (PSG) variables and next-day multiple sleep latency test (MSLT) outcomes across CNS disorders of hypersomnolence (CDH) are limited to observations in narcolepsy type 1 (NT1). We analyzed PSG–MSLT associations a U.S. cohort by diagnostic subgroups (NT1, narcolepsy type 2 (NT2) and idiopathic hypersomnia (IH)). Methods We analyzed valid paired PSG–MSLT studies from NT1, NT2, and IH patients diagnosed by clinical criteria. Analyses used Fisher’s exact tests, Kruskal–Wallis tests, ANOVA, and Spearman correlations. PSG variables were evaluated against MSLT mean sleep latency (MSL) and sleep onset REM period (SOREMP) number in the overall cohort and by subgroup. Results A total of 533 patients were included: mean age 33.9±13.4, 76.9% female. In NT1 (n=81), PSG–MSLT coupling was strongest. MSL showed the highest correlations with PSG sleep latency (ρ=0.59, p< 0.001), REM latency (REML) (ρ=0.34, p=0.002), and latencies to N1–N3. Individuals with a PSG SOREMP had shorter MSL (1.6[1.4, 3.5] vs 4.4[2.7, 7.1] min, p< 0.001), and more MSLT SOREMPs (5.0[5.0, 6.0] vs 2.0[2.0, 4.0], p< 0.001). PSG REML was negatively correlated with number of MSLT SOREMPs (ρ=-0.68, p< 0.001). In NT2 (n=149), observed associations persisted but were attenuated relative to NT1. MSL correlated with PSG sleep latency (ρ=0.26, p=0.001) and REML (ρ=0.20, p=0.017). Individuals with a PSG SOREMP had shorter MSL (3.3[2.2, 5.3] vs 5.1[3.7, 7.3] min, p=0.031) and more MSLT SOREMPs (5.0[4.0, 6.0] vs 2.0[1.0, 3.0], p< 0.001). Negative correlation between MSLT SOREMPs and PSG REML was observed (ρ=-0.41, p< 0.001). IH (n=303) displayed the weakest PSG–MSLT relationships, with patterns distinct from both NT1 and NT2. MSL correlated with PSG sleep latency (ρ=0.25, p< 0.001) and sleep stage latencies N1 and N2 (ρ=0.33 each, p< 0.001), but associations between PSG REML and MSL (ρ=0.10, p=0.098) and MSLT SOREMPS (ρ=-0.19, p>0.05) were weak. Conclusion Patients with clinical phenotypes of CDH demonstrate clear and distinct associations with next-day MSLT. NT1 shows the strongest PSG–MSLT coupling, NT2 moderate, and IH attenuated relationships. These findings underscore the potential value of PSG versus MSLT driven outcomes underscoring the absence of REM related relationships in IH that differentiate it from narcolepsy. Support (if any) None