Introduction The multiple sleep latency test (MSLT) was originally validated as a diagnostic test for narcolepsy.¹ Sleep disorders clinics use the MSLT to investigate a variety of presenting complaints. There is a paucity of data on normative values for the many hypersomnia diagnoses possible in the ICSD-3, which requires a mean sleep latency (MSL) of ≤8 mins on MSLT.² We aim to present MSLT values for typical presenting complaints to sleep disorders clinics.

Methods 200 consecutive patients who underwent an MSLT at our centre between 2021–2023 were included. MSLT, preceding polysomnography (PSG), and actigraphy data were collected. Patients were stratified by presenting complaint into 6 categories: narcolepsy with cataplexy, narcolepsy without cataplexy, idiopathic hypersomnia, long sleeper, hypersomnia due to a known precipitant, fatigue, rule out central hypersomnia. Preliminary analysis from the first 43 patients is shown in this abstract. Full analysis will be presented at the BSS conference. Data presented as mean ± standard deviation.

Results The narcolepsy with cataplexy group had the shortest MSL (5.13 ± 4.4 mins), whereas the idiopathic hypersomnia group had a longer MSL (10.00 ± 3.79 mins). Actigraphy data showed the long sleeper group had the greatest mean time in bed (619.33 ± 104.64 mins) but a normal mean estimated sleep time (478.67 ± 23.86 mins).

Discussion Our data suggest that a cut-off of ≤8 mins on MSLT for clinical hypersomnia is unsuitable. Alternative boundaries in the MSLT should be considered depending on presentation. PSG and actigraphy data, as well as the clinical interview, are all important tools to aid diagnosis.

References

1. Carskadon MA, Dement WC. The multiple sleep latency test: what does it measure. Sleep. 1982 Jan 1;5(Suppl 2):S67–72.

2. American Academy of Sleep Medicine. ICSD-3 – International classification of sleep disorders. 2014.