Preceding night sleep time and multiple sleep latency test outcomes

Evidence supporting how much sleep the night before a multiple sleep latency test (MSLT) is required to generate valid results is lacking. We evaluated the association between preceding night total sleep time (TST) and next-day MSLT outcomes.

We retrospectively analyzed MSLT and preceding overnight diagnostic polysomnogram (PSG) data from January 1, 2008 until December 31, 2018 from St. Michael's Hospital (Toronto, Ontario, Canada). TST on the preceding overnight PSG was categorized as follows: ≥7.0 h vs. 6.00-6.99 h vs. 5.00-5.99 h vs. ≤5.00 h. Descriptive statistics at the univariate level were largely used.

A total of 141 persons underwent MSLT and they were distributed as follows by preceding overnight PSG TST category: ≥7.0 h: 24.8%; 6.00-6.99 h: 44.7%; 5.00-5.99 h: 20.6%; and, ≤ 5.00 h: 9.9%. In association with progressively longer TST on preceding overnight PSG, there were significant trends towards lower mean sleep onset latency (≥ 7.0 h: 8.22 min, 6.00-6.99 h: 8.93 min, 5.00-5.99 h: 11.12 min, ≤ 5.00 h: 9.82 min, p = 0.02) and greater frequency of severe sleepiness (≥ 7.0 h: 37.1%, 6.00-6.99 h: 20.6%, 5.00-5.99 h: 13.8%, ≤ 5.00 h: 7.1%, p = 0.008) on MSLT. No significant associations were observed between TST category and proportion fulfilling MSLT criteria for narcolepsy or idiopathic hypersomnia.

Our exploratory study did not demonstrate significantly increased markers of hypersomnia on MSLT among persons acquiring a TST < 6.00 h the night prior to testing, potentially supporting that MSLT results following a night with a TST < 6.00 h can be considered and not disregarded.