O079 Investigating Hypersomnolence Disorders in South Australia: A Retrospective Audit of Multiple Sleep Latency tests

INTRODUCTION: This study aims to evaluate the characteristics of patients with Narcolepsy Type 1 (NT1), Narcolepsy Type 2 (NT2), and Idiopathic Hypersomnolence (IH) along with diagnostic outcomes in patients referred for a multiple sleep latency test (MSLT) at an Australian hospital. METHODS: A retrospective audit was performed of all patients who completed an MSLT between January 2018 to January 2023. RESULTS: 431 participants (62.4% female; mean±SD age 40.2±16.4 years; BMI 28.6±7.4 kg/m²) who completed MSLTs were included. 95 participants (22%) had a positive MSLT of ≤ 8 minutes, of which 87% (n=83) had a prior night total sleep time on polysomnography of > 6 hours. Gender, age, and BMI did not vary significantly between participants with a mean sleep latency (MSL) ≤ 8 versus >8 minutes (p=0.9, p>0.9, p=0.1 0, respectively). Participants with an MSL ≤ 8 minutes had higher Epworth Sleepiness Scale scores 14.6 ± 5.1 vs 12.5 ± 5.0 (p < 0.001), with more sleep onset REM periods (SOMREPs) 0.82 ± 1.35 vs 0.14 ± 0.49 compared to those with MSL >8 minutes. Further data collection is in progress, but to date, diagnoses were available for 34 participants with MSL ≤ 8 minutes (6 NT1, 8 NT2, 8 IH, 12 Other [i.e., shiftwork disorder, sleep restriction, medication-induced]). DISCUSSION: This study seeks to estimate diagnostic frequency and characteristics of patients presenting for evaluation of hypersomnolence. The prevalence of MSL < 8 minutes (22.0%) is consistent with prior studies1,2. Analysis of diagnostic outcomes is pending further data collection in progress.