Behavioral and physiological consequences of sleep restriction

Abstract

Adequate sleep is essential for general healthy functioning. This paper reviews recent research on the effects of chronic sleep restriction on neurobehavioral and physiological functioning and discusses implications for health and lifestyle. Restricting sleep below an individual's optimal time in bed (TIB) can cause a range of neurobehavioral deficits, including lapses of attention, slowed working memory, reduced cognitive throughput, depressed mood, and perseveration of thought. Neurobehavioral deficits accumulate across days of partial sleep loss to levels equivalent to those found after 1 to 3 nights of total sleep loss. Recent experiments reveal that following days of chronic restriction of sleep duration below 7 hours per night, significant daytime cognitive dysfunction accumulates to levels comparable to that found after severe acute total sleep deprivation. Additionally, individual variability in neurobehavioral responses to sleep restriction appears to be stable, suggesting a trait-like (possibly genetic) differential vulnerability or compensatory changes in the neurobiological systems involved in cognition. A causal role for reduced sleep duration in adverse health outcomes remains unclear, but laboratory studies of healthy adults subjected to sleep restriction have found adverse effects on endocrine functions, metabolic and inflammatory responses, suggesting that sleep restriction produces physiological consequences that may be unhealthy.

Figures

Figure 1

The effects of sleep restriction on NREM stage 2 sleep in Panel A; on NREM slow wave sleep (SWS) in Panel B; and on REM sleep in Panel C. Data are adapted from Van Dongen et al. Following 8 hours of time in bed on baseline nights (B1, B2, B3), sleep was restricted for 14 consecutive nights to either 4 hours of time in bed (•, n = 13 healthy adults), 6 hours of time in bed (▲, n = 13), or 8 hours of time in bed (■, n = 9). Restriction was implemented by delaying bed time and holding sleep offset time constant (07:30). Sleep restriction nights were followed by 3 nights of 10 hours of time in bed for recovery sleep (R1, R2, R3). Sleep stages were scored polysomnographically for 2 out of every 3 nights during the experiment. Panel A: During the 14 nights of restriction to 4 h of time in bed, NREM stage 2 sleep was decreased an average of more than 2 h per night relative to the 8-h control condition (p

Figure 2

The effects of varying doses of nocturnal sleep time on lapses of attention from the psychomotor vigilance test (PVT). Panel A from Van Dongen et al. involved experimental sleep restriction of n = 36 healthy adults for 14 consecutive nights. In this experiment sleep was restricted for 14 consecutive nights. Subjects were randomized to 4 h time in bed (n = 13), 6 h time in bed (n = 13), or 8 h time in bed (n = 9). PVT performance was assessed every 2 h (9 times each day) from 07:30 to 23:30. The graph shows systematic increases in lapses of sustained attention when sleep was restricted to either 4 h (p

Figure 3

Digit symbol substitution task (DSST) performance responses to varying doses of daily sleep across 14 days. Data from n = 35 subjects (8h condition n = 9, 6h condition n = 13 and 4h condition n = 13). Mean DSST per day (07:30–23:30), measured at 2-h intervals expressed relative to baseline (BL). The curves represent statistical nonlinear model-based best-fitting profiles of the DSST performance response to sleep loss. Adapted from Van Dongen et al.

Figure 4

Data from n = 35 subjects (8h condition n = 9, 6h condition n = 13 and 4h condition n = 13). Restriction of nocturnal sleep in healthy adults resulted in near-linear increases in Psychomotor Vigilance Test (PVT) lapses of attention across 14 days (coefficients of change near 1.0), but subjective ratings of sleepiness and fatigue (regardless of the psychometric scale used) showed a nonlinear coefficient below 0.5 for change over days. This meant that as objective performance continued to decline near-linearly, there were only minor further increases in the subjective ratings of sleepiness. By the end of the 14 days of sleep restriction, when performance was at its worst levels, subjects in the 4-h and 6-h sleep period conditions reported feeling only slightly sleepy. Therefore, unlike performance measures, sleepiness ratings appeared to show adaptation to chronic partial sleep deprivation. The lack of reports of intense feelings of sleepiness during chronic sleep restriction may explain why sleep restriction is widely practiced—people have the subjective impression they have adapted to it because they do not feel particularly sleepy. Adapted from Van Dongen et al.

Figure 5

Mean (SEM) plasma high-sensitivity C-reactive protein (CRP) in n = 4 subjects undergoing 10 consecutive nights of sleep restricted to 4.2 h time in bed, and in n = 5 control subjects who had 10 consecutive nights of sleep restricted to 8.2 h time in bed (closed squares). Significance of difference in change from baseline to day 10 between groups (p = 0.08 for interaction) by mixed-models analysis of variance on log-transformed data: the change from baseline to day 10 for the 4-h sleep restriction group was significant (p = 0.05), whereas the change from baseline to day 10 in the 8-h control group was not (p = 0.72). Figure adapted from Meier-Ewert et al.