Improved Neurobehavioral Performance during the Wake Maintenance Zone

Abstract

Study Objectives: Although impairment of daytime functioning is a symptom of many sleep disorders, there are limited data on their nature for some patient groups. The role of the circadian system on impaired functioning, specifi cally the wake maintenance zone (WMZ)-a ~3-h window of reduced sleep propensity that occurs shortly before the onset of melatonin synthesis-has received little attention. The study examined the infl uence of the WMZ on neurobehavioral performance under normal conditions and following sleep deprivation. Methods: Thirty-one adults (8 F; 18-29 y) completed an inpatient protocol including a baseline day (8-h sleep:16-h wake) and a ~50-h constant routine (CR), including regular assessment of plasma melatonin and neurobehavioral performance (i.e., auditory and visual psychomotor vigilance tests [aPVT, vPVT], Digit Symbol Substitution Test [DSST], and subjective sleepiness). Results: Performance in the 3 hours before the onset of melatonin secretion (i.e., the expected WMZ) was signifi cantly improved compared to performance during a 3-hour block earlier in the biological day, despite a longer time awake. The improvement during WMZ was most prominent after extended wakefulness (i.e., day 2 of the CR). Conclusions: These results suggest that alignment of circadian phase with respect to sleep-wake timing may affect cognitive performance, particularly when homeostatic sleep pressure is high, and especially when performance is assessed in the evening, near the predicted WMZ. The potential contribution of the WMZ to sleep-onset insomnia complaints should be assessed further, using objective neurobehavioral testing and simultaneous circadian phase measurement. Keywords: Cognition, sleep regulation, circadian, performance, melatonin, two-process model, PVT, DLMO Citation: Shekleton JA; Rajaratnam SMW; Gooley JJ; Van Reen E; Czeisler CA; Lockley SW. Improved neurobehavioral performance during the wake maintenance zone. J Clin Sleep Med 2013;9(4): 353-362. http://dx.doi.org/10.5664/jcsm.2588 S C I E N T I F I C I N V E S T I G A T I O N ST he assessment of daytime neurobehavioral impairments in sleep disordered patients has produced inconsistent results, particularly in patients with insomnia.1 In other sleep disorder populations, such as circadian rhythm sleep disorders (CRSDs), there is a paucity of investigations into the daytime impairments associated with the disorders.2 Yet, reports of daytime impairment are a core symptom in the diagnosis of many sleep disorders. The circadian system is known to modulate alertness and performance patterns, and is known to be dysregulated in CRSD. One mechanism by which the circadian system may manifest in the daytime impairments in these patients is via altered timing or amplitude of the wake maintenance zone (WMZ).The WMZ has previously been described as a 2-to 3-h window of reduced sleep propensity that occurs immediately prior to the evening onset of melatonin secretion and under normal conditions, occurs several hours prior to bedtime. 3,4 This window is c...

Synchronizing education to adolescent biology: ‘let teens sleep, start school later’

“…Most examinations are at 09:30 and both teaching and test start times impact on academic performance, with eveningness types achieving better outcomes in the later session and worse in examinations held early in the day (Beşoluk, Onder, and Deveci 2011). Surprisingly, Shekleton et al (2013) found general performance was better in the WMZ than earlier in the day. These data suggest that exploration of an upper time limit could be valuable in determining the appropriate end of the education day or educational provision for groups of adolescents.…”

“…Their interaction also generates a 'wake maintenance zone' (WMZ) which, paradoxically, occurs several hours before sleep is typically initiated (Dijk and Czeisler 1995;Shekleton et al 2013). This is a major factor in the sleep difficulties experienced by adolescents.…”

Circadian Phase and Phase Angle Disorders in Primary Insomnia

“…The circadian propensity for sleepiness is highest just before habitual wake time, at ~03:00-06:00 am and is lowest just before habitual sleep time, ~07:00-10:00 pm. 7,10 The latter time is often called the "wake maintenance zone" (WMZ), during which it is difficult to fall asleep. The WMZ ends with the onset of melatonin production.…”

“…The WMZ ends with the onset of melatonin production. 10,11 Sleep consolidation occurs when sleep is appropriately timed relative to the homeostatic and circadian drives. Circadian misalignment, that is, failing to hit this target and attempting sleep too early in the circadian cycle, during the WMZ, can result in difficulty falling asleep, whereas attempting to sleep too late in the cycle can cause difficulty maintaining sleep or early awakening.…”

A systematic review of the sleep, sleepiness, and performance implications of limited wake shift work schedules

“…Nevertheless, it is expected that the same trends will be evident. Specifically, it is hypothesized that LWSW schedules will be associated with shorter sleep, greater sleepiness and poorer performance where (i) more of the work time falls across the circadian nadir, (ii) more of the sleep opportunity falls during the WMZ, (iii) the work-to-rest ratio is high, and (iv) the consistency in the timing of work/rest bouts from one 24-hour cycle to the next is low (20,21). The aim of this review is to test these hypotheses and determine which LWSW schedules best promote sleep, alertness, and performance.…”