Normal multiple sleep latency test values in adults: A systematic review and meta-analysis

Sleep latency is a measure of time it takes to enter sleep. Very short sleep latencies are indicative of excessive daytime sleepiness and pathological sleep conditions such as narcolepsy. The normal range of mean sleep latency calculated from the multiple sleep latency test in healthy adults is not well-established. We provide a review of normative mean sleep latency values on the multiple sleep latency test by synthesizing data from 110 healthy adult cohorts. We also examine the impact of demographic variables such as age, sex, body mass index, sleep architecture and sleep-disordered breathing as well as methodological variables such as sleep onset definitions and multiple sleep latency test protocols. The average mean sleep latency was 11.7 min (95% CI: 10.8-12.6; 95% PI: 5.2-18.2) for cohorts evaluated using the earlier definition of sleep onset and 11.8 min (95% CI: 10.7-12.8; 95% PI: 7.2-16.3) for those evaluated using the later definition. There were no significant associations between mean sleep latency and demographic or methodological variables. A negative association of -0.29 per one unit increase (95% CI: -0.55 to -0.04) was found between mean sleep latency and apnea-hypopnea index on prior night polysomnography. Establishing updated ranges for mean sleep latency among healthy adults may guide clinical decision-making surrounding sleep pathologies and inform future research into the associations between patient variables, daytime sleepiness, and sleep pathologies.