Nightly Sleep Duration in the 2-Week Period Preceding Multiple Sleep Latency Testing

Study Objective: To assess usual nightly sleep duration of patients referred for a Multiple Sleep Latency Test (MSLT). Design: Retrospective chart review. Setting: Military, hospital-based, sleep center. Patients: Fifty-four patients with excessive daytime sleepiness referred for an MSLT. Interventions: None. Measurements and Results: Self-reported average nightly sleep duration (6.13 +/- 1.23 hours), sleep log-recorded average nightly sleep duration (6.99 +/- 0.85 hours), and actigraphy-measured average nightly sleep duration (5.56 +/- 1.50 hours) were compared for the 2-week period immediately preceding an MSLT. One-way analysis of variance revealed a significant difference in the 3 estimates of nightly sleep duration (p < 0.0001), and only actigraphy-measured average nightly sleep duration correlated with mean sleep latency on the MSLT (r = 0.4258, p = 0.0016). Subgroup analysis showed that patients with a mean sleep latency shorter than 8 minutes slept an average of 1.57 hours less per night than did those patients with a mean sleep latency of 8 minutes or longer (4.53 +/- 1.37 vs 6.10 +/- 1.37 hours per night, p < 0.001) as measured by actigraphy. There was no difference in either self-reported average nightly sleep duration or sleep log-recorded average nightly sleep duration between the 2 subgroups. Conclusions: Prolonged actigraphy monitoring may provide useful clinical information about pre-MSLT sleep not always obtainable from patient self-reporting or sleep logs.