Circadian Rhythms, Sleep Deprivation, and Human Performance - Progress in Molecular Biology and Translational Science - page 162

predicts that a single night of recovery sleep is inadequate to recover from a
prolonged period of sleep restriction, a finding we recently experimentally
confirmed. 33 It is recognized that further model development is needed to
integrate more comprehensive mathematical models of the circadian com-
ponent and to account for sleep inertia and trait-like individual differences in
vulnerability to sleep loss. 31
3. CIRCADIAN RHYTHMS OF PERFORMANCE
3.1. Subjective measures of sleepiness and alertness
A variety of subjective measures of sleepiness and alertness reflect circadian
variation, as long as the scale requests ratings about the near immediate state
of the subject. These include visual analogue scales, 34 Likert-type rating
scales such as the Stanford Sleepiness Scale 35 and the Karolinska Sleepiness
Scale, 36 and certain fatigue-related subscales of standard adjective checklists
such as the Activation-Deactivation Adjective Check List 37 and Profile of
Mood States. 38 Despite structural differences among these scales, all self-
reports of sleepiness are highly intercorrelated and because they are relative
psychometrics, they are subject to a number of sources of variance, including
different uses of the scale response range by different subjects. The effects of
cognitive performance testing on subsequent posttest subjective alertness
ratings are evident only when sleep loss has commenced and this effect is
modulated by circadian variation. 28
3.2. Objective measures of cognitive performance
Many studies rely on objective performance measures to track the temporal
dynamics of endogenous circadian rhythmicity. Circadian variation in
Figure 7.2 Psychomotor Vigilance Test (PVT) performance parameters of healthy adults
during an 88 h period of limited to no sleep in the laboratory. The open circles represent
13 subjects undergoing 88 h of total sleep deprivation, and the filled squares represent
15 control subjects given a 2-h time in bed nap opportunity once every 12 h
(0245-0445 h and 1445-1645 h) throughout the 88 h period (nap times are not
shown in the figure). Graph A: mean (SEM) PVT reaction times (RT), which as
RTs > 500 ms are frank errors of omission and referred to as lapses of attention
(i.e., responding too slowly). Graph B: mean (SEM) PVT errors of commission, which
result from premature responses and reflect impulsiveness (i.e., responding too fast).
Graph C: mean (SEM) of PVT RT standard deviations for each test bout, reflecting the
magnitude of interindividual differences in performance. The subjects who underwent
88 h without sleep showed clear circadian variation in both lapses of attention (A) and
premature responses (B), as well as interindividual differences in these effects (C).
Figure adapted and modified with permission from Ref. 24 .