O018 A 10 year follow-up of positive Multiple Sleep Latency Tests in a tertiary centre

BACKGROUND: There are limited robust population prevalence data and the natural history of central hypersomnolence disorders in Australia. We conducted a retrospective chart review of multiple sleep latency tests (MSLTs) conducted in an Australian Sleep unit and reviewed clinical outcomes over time, response to treatment and duration of follow-up. METHODS: 517 MSLTs were extracted from a metropolitan hospital’s database between 2011 and 2021; 215 were positive. Data were extracted from overnight polysomnography (PSG), MSLTs and electronic medical records. The results were analysed using t-test and linear regression models. RESULTS: The mean age was 36.7 years and 58% were female. 37 patients met the criteria for type 1 or 2 narcolepsy, 157 for idiopathic hypersomnolence and 21 for an alternative sleep disorder. Of those with narcolepsy, 84.6% were commenced on medication. Modafinil was the most commonly prescribed first line medication. At 1 year, 48% of patients in the narcolepsy group had complete or partial treatment success, compared with 24% in the idiopathic hypersomnolence group. At 3 years, 31% of narcolepsy patients and 12% of idiopathic hypersomnolence patients reported complete or partial treatment success. At 5 years, only 19% of narcolepsy patients and 6% of idiopathic hypersomnolence patients described ongoing treatment success. DISCUSSION: This study demonstrated a much higher prevalence of idiopathic hypersomnolence than expected. A significant number of patients were lost to follow-up, predominantly in the first 12 months, with progressive losses over the subsequent years. The reasons for these are unclear; however, would be important to explore in future studies.