Mismatch between subjective alertness and objective performance under sleep restriction is greatest during the biological night

Abstract

SUMMARYSubjective alertness may provide some insight into reduced performance capacity under conditions suboptimal to neurobehavioural functioning, yet the accuracy of this insight remains unclear. We therefore investigated whether subjective alertness reflects the full extent of neurobehavioural impairment during the biological night when sleep is restricted. Twenty-seven young healthy males were assigned to a standard forced desynchrony (FD) protocol (n = 13; 9.33 h in bed ⁄ 28 h day) or a sleeprestricted FD protocol (n = 14; 4.67 h in bed ⁄ 28 h day). For both protocols, subjective alertness and neurobehavioural performance were measured using a visual analogue scale (VAS) and the psychomotor vigilance task (PVT), respectively; both measures were given at various combinations of prior wake and circadian phase (biological night versus biological day). Scores on both measures were standardized within individuals against their respective baseline average and standard deviation. We found that PVT performance and VAS rating deviated from their respective baseline to a similar extent during the standard protocol, yet a greater deviation was observed for PVT performance than VAS rating during the sleep-restricted protocol. The discrepancy between the two measures during the sleep-restricted protocol was particularly prominent during the biological night compared with the biological day. Thus, subjective alertness did not reflect the full extent of performance impairment when sleep was restricted, particularly during the biological night. Given that subjective alertness is often the only available information upon which performance capacity is assessed, our results suggest that sleep-restricted individuals are likely to underestimate neurobehavioural impairment, particularly during the biological night. IN TROD UCTI ONShiftwork, in particular involving night work, disrupts the normal sleep ⁄ wake pattern in humans, causing temporary deficits in neurobehavioural performance and a heightened risk of errors and accidents (Akerstedt, 1998). Performance of safety-critical tasks could be maintained at an adequate level, and errors and accidents can be reduced, however, if necessary compensatory or preventative actions, such as mobilizing mental efforts and employing countermeasures, take place (Dinges et al., 1987;Fairclough and Graham, 1999;Purnell et al., 2002). Yet the application of such actions is guided by self-knowledge of performance capacity (Fairclough and Graham, 1999). Accurate knowledge of performance capacity, therefore, is critical for productivity and safety under conditions that are suboptimal for neurobehavioural functioning.Subjective alertness is arguably the most readily accessible information upon which performance capacity is

Circadian Adaptation to Night Shift Work Influences Sleep, Performance, Mood and the Autonomic Modulation of the Heart

“…Nevertheless, these changes were not observed in the objective measurement of performance levels (i.e., PVT). A partial mismatch between subjective and objective assessment of vigilance has been previously reported with sleep curtailment [70]–[72]. Subjective mood levels have been shown to follow a circadian variation, with lower levels in the early morning and to be reduced with the amount of time awake [73], consistent with our observations.…”

Residency Training: The King-Devick test and sleep deprivation

“…5 Although the ability to appropriately identify level of alertness has been debated, recent evidence suggests that subjective alertness and performance are modestly correlated, with most discrepancy during the biological night. 10 The association between subjective level of sleepiness and improvement in K-D test times in the current study provides further support for the concept that individuals are fairly effective in rating their level of alertness. However, self-report of sleepiness is a subjective measure not capable of capturing individual vulnerability to sleep deprivation effects.…”

Circadian and wakefulness-sleep modulation of cognition in humans

“…The individual contribution of sleep inertia, sleep homeostatic and circadian processes to the daily pattern of cognition can be modeled in forced desynchrony protocols that schedule sleep and wakefulness to occur across the circadian cycle. To date, forced desynchrony studies have modeled the independent contribution of sleep homeostatic and circadian processes for vigilance, working memory, sleepiness and mood (Czeisler et al, 1994; Boivin et al, 1997; Wyatt et al, 2004; Lee et al, 2009; Murray et al, 2009; Cohen et al, 2010; Grady et al, 2010; Silva et al, 2010; Zhou et al, 2011a, 2012; Matthews et al, 2012). General findings from these studies indicate that alertness, vigilance, cognitive speed, memory, mood, and driving performance, degrade with time awake and cycle with circadian phase.…”