Microsleep assessment enhances interpretation of the Maintenance of Wakefulness Test

Abstract

Study objectives: The Maintenance of Wakefulness Test (MWT) is used to objectively evaluate an individual's ability to remain awake; however, microsleeps are not included in the assessment. We aimed to determine if microsleep data prior to sleep onset assisted in interpretation of ability to maintain wakefulness across a range of typical patient groups.

Methods: Forty-eight patients referred for overnight polysomnography and subsequent MWT were included. Patients were divided into 3 groups (treated obstructive sleep apnea [OSA], untreated OSA, or treated idiopathic hypersomnia or narcolepsy) based on prior medical diagnosis. Demographics, clinical characteristics, polysomnography, and MWT variables, including frequency, distribution, duration, and latency of microsleeps were compared between groups.

Results: Microsleeps were observed in MWT trials significantly more frequently in patients with treated idiopathic hypersomnia/narcolepsy over the course of the day (0.34 ± 0.06 vs 0.07 ± 0.02 microsleeps/min; P < .001) and in patients with untreated OSA toward the end of the day (0.31 ± 0.06 vs 0.05 ± 0.02 microsleeps/min; P < .001) compared to the group with treated OSA. Microsleeps were often observed in series and earlier in patients with treated idiopathic hypersomnia/narcolepsy (10.9 ± 1.6 minutes) and those with untreated OSA (16.2 ± 2.7 minutes) compared to the group with treated OSA (24.9 ± 3.0 minutes; P < .05), and, if taken into consideration, would increase the proportion of patients demonstrating inability to maintain wakefulness by 33% and 22%, respectively.

Conclusions: MWT performance varies significantly across patient groups. Microsleep analysis prior to sleep onset may be a more sensitive measure of patient daytime wakefulness than sleep latency alone and should be considered in MWT assessment.

Citation: Anniss AM, Young A, O'Driscoll DM. Microsleep assessment enhances interpretation of the Maintenance of Wakefulness Test. J Clin Sleep Med. 2021;17(8):1571-1578.

Keywords: excessive daytime sleepiness; hypersomnolence; narcolepsy; obstructive sleep apnea.

Figure 1. Comparison of sleep latency in separate MWT trials between groups.

*Patients in the treated OSA group showed significantly longer sleep latency times (P < .05) compared to the treated IH/Narc group in MWT trials 1, 3, and 4. #A significantly longer sleep latency (P < .01) was also found in the treated OSA group compared to the untreated OSA group in MWT trials 3 and 4. IH = idiopathic hypersomnia, MWT = Maintenance of Wakefulness Test, Narc = narcolepsy, OSA = obstructive sleep apnea.

Figure 2. Comparison of MWT mean sleep latency vs mean microsleep latency.

*Patients in all groups (treated OSA, untreated OSA, and treated IH/Narc) showed a significant reduction in mean time to first microsleep compared to mean sleep latency time (P = .001). #Mean sleep latency and mean first microsleep latency was also found to be significantly longer in the treated OSA group compared to the untreated OSA and treated IH/Narc group (P < .05). IH = idiopathic hypersomnia, MWT = Maintenance of Wakefulness Test, Narc = narcolepsy, OSA = obstructive sleep apnea.

Figure 3. Comparison of first microsleep latency in separate MWT trials between groups.

*Patients in the treated OSA group showed significantly longer latency to first microsleep (P < .05) compared to the treated IH/Narc group in MWT trials 1, 3 and 4. #A significantly longer first microsleep latency (P < .01) was also found in the treated OSA group compared to the untreated OSA group in MWT trial 4. ^A significant reduction in microsleep latency (P = .005) was also observed within the untreated OSA group in trials 3 and 4 compared to trial 1. IH = idiopathic hypersomnia, MWT = Maintenance of Wakefulness Test, Narc = narcolepsy, OSA = obstructive sleep apnea.

Figure 4. Number of microsleep series (2 or more adjoining epochs containing microsleeps) during MWT compared between groups.

The majority of patients in the treated OSA group (54%) had no microsleeps or microsleeps that were isolated and not observed in a series of adjoining epochs. In contrast, microsleeps in series or clusters were more frequently observed in the other population groups (P < .05) with 35% of untreated OSA and 59% of patients with treated IH/Narc having 4 or more instances of microsleep series during MWT compared to 0% in the treated OSA group. IH = idiopathic hypersomnia, MWT = Maintenance of Wakefulness Test, Narc = narcolepsy, OSA = obstructive sleep apnea.