Multiple sleep latency measures in narcolepsy and behaviourally induced insufficient sleep syndrome.
Level 4 - case-series / case-control
Case-control study comparing diagnostic sleep parameters across matched clinical and healthy cohorts
PubMed 19464232 · doi:10.1016/j.sleep.2009.03.008
What was done
Researchers evaluated multiple sleep latency test (MSLT) parameters, tracking sleep latencies to and transitions between sleep stages across 60 age-, gender-, and body mass index-matched subjects: 20 with hypocretin-deficient narcolepsy-cataplexy, 20 with actigraphy-confirmed behaviourally induced insufficient sleep syndrome, and 20 healthy controls.
What was found
Mean latency to NREM1 was significantly shorter in narcolepsy-cataplexy (1.8 +/- 1.5 minutes) than in behaviourally induced insufficient sleep syndrome (4.7 +/- 2.1 minutes, p < 0.001) and controls (11.4 +/- 3.3 minutes, p < 0.001). Mean latency to NREM2 was similar between narcolepsy-cataplexy (8.6 +/- 4.7 minutes) and insufficient sleep syndrome (8.1 +/- 2.7 minutes, p = 0.64). Latency to either NREM2 or REM was shorter in narcolepsy-cataplexy (4.4 +/- 2.9 minutes) than in insufficient sleep syndrome (7.9 +/- 3.5 minutes, p < 0.001). In naps with sleep onset REM periods, the sequence NREM1-REM-NREM2 occurred in 71% of narcolepsy-cataplexy naps versus 15% of insufficient sleep syndrome naps (p < 0.001), reflecting shorter latency from NREM1 to NREM2 in insufficient sleep syndrome (3.7 +/- 2.5 minutes) than in narcolepsy-cataplexy (6.1 +/- 5.9 minutes, p < 0.001).
Why it matters
Because both narcolepsy-cataplexy and severe sleep deprivation can produce multiple sleep onset REM periods on an MSLT, diagnostic overlap occurs. Identifying specific sleep architecture patterns, such as NREM1 latency of 2.5 minutes or less and REM sleep preceding NREM2, provides criteria to help differentiate the two conditions.
Limits
The sample size was small with 20 subjects per group. The narcolepsy cohort was limited to hypocretin-deficient narcolepsy-cataplexy, so findings may not generalize to narcolepsy without cataplexy. Diagnostic accuracy statistics such as sensitivity and specificity were not reported in the abstract.
Cited by
- supports Typical sleep onset latency is between 5 and 20 minutes, and falling asleep in under 2 minutes is an indicator of sleep deprivation.