Effects of slow-release caffeine and a nap on driving simulator performance after partial sleep deprivation

A driving simulator was used to evaluate the effectiveness of a 30-min. nap and 300-mg slow-release caffeine as countermeasures to drivers' sleepiness induced by partial sleep deprivation. 12 participants were allowed 45 hr. time in bed at the laboratory. Driving performance then was measured twice--at 9 a.m. and at 1 p.m.--by a 45-min. driving task on a simulator. Subjective sleepiness/alertness and mood were assessed four times on the Stanford Sleepiness Scale and the Profile of Mood States. Driving performance was assessed as Lane Drifting, Speed Deviation, and Accident Liability. A 30-min. nap opportunity and 300 mg of slow-release caffeine both were successful in counteracting drivers' sleepiness. The remedial effect of slow-release caffeine lasted longer than that of the nap, that is, it was also effective in the afternoon session. This suggests that slow-release caffeine represents a valuable countermeasure that, in the case of partial sleep deprivation, is preferred to a nap when sleepiness has to be counteracted for a longer time.     

Effects of noise on sleep inertia as a function of circadian placement of a one-hour nap.

The purpose of the present study was to analyse the arousing effects of noise on sleep inertia as a function of circadian placement of a one-hour nap. In a first experiment, we measured the effects of sleep inertia in a neutral acoustic environment after a one-hour nap placed either at 0100 or 0400 on response time during a spatial memory test. In a second experiment were analysed the effects of an intense continuous noise on sleep inertia. The results showed that noise produced a total abolition of sleep inertia after an early nap (0000 to 0100). This may be due to the arousing effect of noise; however, results are less clear after a late nap 0300 to 0400 as noise seems to be ineffective. This result is discussed in terms of either a function of time-of-day effect or of prior sleep intensity. Moreover, our data suggest a possible interaction of noise with partial sleep deprivation leading to a slight deleterious effect those subjects who did not sleep at all.     

Day-to-day variability in nap duration predicts medical morbidity in older adults

Objective: The objectives for the present study were to (a) examine within-person variability of nap duration and (b) assess how variability in nap duration is related to the number of health conditions in a sample of older adults. For highly variable behaviors such as sleep, it is important to consider fluctuations within the person instead of solely comparing averages of behaviors across persons. Method: Data were drawn from a previous study examining sleep in 103 community-dwelling older adults. Subjective estimates of napping behavior were obtained from sleep diaries and objective estimates of napping behavior were obtained using actigraphy. Both measures were collected for 14 consecutive days. The sampled data were aggregated in terms of (a) average daily time spent napping and (b) average within-person fluctuations in daily nap duration. The health measure consisted of the number of self-reported health conditions. Results: Both the objective and subjective measures revealed that there was considerable day-to-day fluctuation in nap duration and that variability in nap duration, not mean duration, uniquely predicted the number of health conditions, b = .03, b* = .26, t(100) = 2.71, p = .01. Conclusions: Duration of napping in older adults is a highly variable behavior, fluctuating as much within- as between-persons. Furthermore, variability in nap duration from day to day is predictive of greater medical morbidity, suggesting that clinicians should assess for inconsistencies in nap behavior in addition to duration, frequency, and timing. (PsycINFO Database Record (c) 2012 APA, all rights reserved).     

Retrieval from semantic memory during a night without sleep

It has been demonstrated that retrieval performance from semantic memory varies during the day. Specifically, the retrieval of low- relative to high-dominance category members is slower in the morning compared to later in the day. It has been suggested that the effect is related to a circadian arousal rhythm, which steadily rises during the day and rapidly declines at night. This study examines retrieval from semantic memory during the night. Sixteen subjects performed a semantic classification task once every hour throughout one night without sleep. Classification latencies became progressively slower, and the time taken to retrieve low- relative to high-dominance category members increased from midnight to 4 a.m. The trend reversed between 4 and 7 a.m. The pattern of results closely parallels the hypothesised circadian arousal rhythm. It is suggested that the variation in retrieval performance as a function of time of day may be related to fluctuations in a circadian arousal rhythm.     

Acute dissociation after 1 night of sleep loss

Recent research has shown that dissociative symptoms are related to self-reports of deviant sleep experiences. The present study is the 1st to explore whether sleep loss can fuel dissociative symptoms. Twenty-five healthy volunteers were deprived of sleep for 1 night. Sleepiness and dissociative symptoms were assessed every 6 hr. The authors measured both spontaneous dissociative symptoms and dissociative symptoms induced by dot-staring during sensory deprivation. Sleepiness as well as spontaneous and induced dissociative symptoms were stable throughout the day but increased during the night. These findings provide further evidence for a robust relationship between disruptions in sleep patterns and dissociative symptoms.     

Slow wave sleep during a daytime nap is necessary for protection from subsequent interference and long-term retention

While it is now generally accepted that sleep facilitates the processing of newly acquired declarative information, questions still remain as to the type and length of sleep necessary to best benefit declarative memories. A better understanding could lend support in one direction or another as to the much-debated role of sleep, be it passive, permissive, or active, in memory processing. The present study employed a napping paradigm and compared performance on a bimodal paired-associates task of those who obtained a 10-min nap, containing only Stages 1 and 2 sleep, to those whose nap contained slow-wave sleep (SWS) and rapid eye movement (REM) sleep (60-min nap), as well as to subjects who remained awake. Measurements were obtained for baseline performance at training, after a sleep/no sleep interval for short-term retention, after a subsequent stimulus-related interference task, and again after a weeklong retention period. While all groups learned the information similarly, both nap groups performed better than the Wake group when examining short-term retention, approximately 1.5h after training (10-min p=.052, 60-min p=.002). However, performance benefits seen in the 10-min nap group proved to be temporary. Performance after a stimulus-related interference task revealed significantly better memory retention in the 60-min nap group, with interference disrupting the memory trace far less than both the Wake and 10-min nap groups (p<.001, p=.006, respectively). After a weeklong retention period, sleep's benefit to memory persisted in the 60-min nap group, with performance significantly greater than both the Wake and 10-min nap groups (p<.001, p=.004, respectively). It is our conclusion that SWS, obtained only by those in the 60-min nap group, served to actively facilitate the consolidation of learned bimodal paired-associates, supported by theories such as the Standard Theory of Consolidation as well as the Synaptic Homeostasis Hypothesis.     

Depression and sleep quality in older adults: a meta-analysis

The literature emphasizes depression and poor sleep quality as problems that affect many elderly individuals. However, these problems have been related in few studies and there is no meta-analysis performed so far on this relationship. The present research reviewed the studies performed on the subjective sleep quality in order to understand how it relates to depression in older adults. The review was conducted in January 2016 and comprised publications between 2005 and 2015. Based on the electronic databases Web of Science and EBSCO, we used the keywords ‘sleep quality’, ‘depression’, and ‘older’ to identify the empirical studies performed. After assessing the collected studies, we selected those that presented the elderly as participants, resulting in nine papers (N = 3069). A random-effects method was used to evaluate the relationship between depression and sleep. We found that an older person’s lack of good sleep quality is significantly related with depression. The main limitation of this study was the difficulty in collecting a greater number of studies. Future research should consider the importance of additional variables (e.g. moderators) in order to understand and investigate viable interventions for prevention and health promotion in the elderly.     

The effect of one night without sleep on problem-solving and immediate recall

Summary The aim of the study was to investigate the effect of spending one night without sleep on the performance of complex cognitive tasks, such as problem-solving, in comparison with a purely short-term memory task. One type of task investigated was immediate free recall, assumed to reflect the holding capacity of the working memory. The other type of task investigated was represented by syntactical reasoning and problem-solving tasks, assumed to reflect the processing (the mental transformation of input) and monitoring capacity of the working memory. Two experiments with a repeated-measures design were performed. Experiment 1 showed a significant decline in performance as a function of sleep loss on Raven's progressive matrices, a problem-solving task. No other main effect of sleep loss was found. Experiment 2 had a different order between tasks than Experiment 1 and the time without sleep was increased. A number-series induction task was also used in Experiment 2. A significant, negative effect of sleep loss in performance on Raven's progressive matrices was found in Experiment 2. The effects of sleep loss on the other tasks were nonsignificant. It is suggested that Raven's progressive-matrices task reflects the ability to monitor encoding operations (selective attention) and to monitor mental computations.     

Effects of total sleep loss on sleep tendency.

Effects of two nights of sleep loss were assessed in six young adult (18--21 yr.) volunteers (2 women, 4 men). Performance on the Wilkinson Addition Test fell significantly below baseline values during the sleep-loss procedure and recovered after one or two full nights of sleep. Performance on a Serial Alternation Task also declined during sleep loss. Mood and sleepiness, assessed by subjective self-rating scales, showed a significantly less positive mood and a greater degree of sleepiness during sleep loss, with a recovery to baseline levels after one full night of sleep. Sleep tendency, measured at 2-hr. intervals during all waking periods, was assessed using an objective measure of latency to sleep onset, the Sleep Latency Test. The scores fell to about 1 min. at 0600 on the first night of sleep loss and remained at similarly low values throughout the sleep loss period. After one night of recovery sleep the scores remained significantly below baseline levels, which were not achieved until after the second recovery night. The multiple sleep latency test appears to be a valuable operationally defined tool for measuring daytime sleepiness.     

The effects of sleep on episodic memory in older and younger adults

Evidence on sleep-dependent benefits for episodic memory remains elusive. Furthermore we know little about age-related changes on the effects of sleep on episodic memory. The study we report is the first to compare the effects of sleep on episodic memories in younger and older adults. Memories of stories and personal events were assessed following a retention interval that included sleep and following an equal duration of wakefulness. Both older and younger adults have superior memory following sleep compared to following wakefulness for both types of material. Amount of forgetting of personal events was less during wakefulness in older adults than in younger adults, possibly due to spontaneous rehearsal. Amount of time spent sleeping correlated highly with sleep benefit in older adults, suggesting that quantity of total sleep, and/or time spent in some stages of sleep, are important contributors to age-related differences in memory consolidation or protection from interference during sleep.     

One night of sleep deprivation affects reaction time, but not interference or facilitation in a Stroop task

The Stroop color-naming task is one of the most widely studied tasks involving the inhibition of a prepotent response, regarded as an executive function. Several studies have examined performance on versions of the Stroop task under conditions of acute sleep deprivation. Though these studies revealed effects on Stroop performance, the results often do not differentiate between general effects of sleep deprivation on performance and effects specifically on interference in the Stroop task. To examine the effect of prolonged wakefulness on performance on the Stroop task, we studied participants in a 40-h "constant routine" protocol during which they remained awake in constant conditions and performed a Stroop color-naming task every two hours. We found that reaction time was slowest when the color and word did not match (incongruent), fastest when the color and word did match (congruent), and intermediate when participants named the color of the non-word stimulus (neutral). Performance on all three trial types degraded significantly as a function of time awake. Extended wakefulness did not significantly change the additional time needed to respond when the color and word did not match (Stroop interference), nor did it change the amount of facilitation when color and word matched. These results indicate that one night of sleep deprivation influences performance on the Stroop task by an overall increase in response time, but does not appear to impact the underlying processes of interference or facilitation. The results suggest that the degree to which an "executive function" is affected by sleep deprivation may depend on the particular executive function studied and the degree to which it is subserved by the prefrontal cortex.     

One night of sleep is insufficient to achieve sleep-to-forget emotional decontextualisation processes

Neutral memories unbind from their emotional acquisition context when sleep is allowed the night after learning and testing takes place after two additional nights of sleep. However, mood-dependent memory (MDM) effects are not abolished after a restricted sleep episode mostly featuring non rapid-eye-movement (NREM) or rapid-eye-movement (REM) sleep. Here, we tested whether (1) one night of sleep featuring several NREM-REM sleep cycles is sufficient to suppress MDM effects and (2) a neutral mood is a sufficiently contrasting state to induce MDM effects, i.e. interfere with the recall of information learned in happy or sad states. Results disclosed MDM effects both in the post-learning sleep and wake conditions, with better recall in congruent than incongruent emotional contexts. Our findings suggest that the emotional unbinding needs several consecutive nights of sleep to be complete, and that even subtle mood changes are sufficient to produce MDM effects.     

Subjective age and sleep in middle-aged and older adults

Objective: Chronological age is commonly used to explain change in sleep. The present study examines whether subjective age is associated with change in sleep difficulties across middle adulthood and old age.

Design: Participants were drawn from the second (2004–2005) and third (2013–2014) waves of the Midlife in the United States Survey (MIDUS, N = 2350; Mean Age: 55.54 years), the 2008 and 2014 waves of the Health and Retirement Study (HRS, N = 4066; Mean Age: 67.59 years) and the first (2011) and fourth (2014) waves of the National Health and Aging Trends Survey (NHATS, N = 3541; Mean Age: 76.46). In each sample, subjective age, sleep difficulties, depressive symptoms, anxiety and chronic conditions were assessed at baseline. Sleep difficulties was assessed again at follow-up.

Main outcome measures: Sleep difficulties.

Results: An older subjective age at baseline was related to an increase in sleep difficulties over time in the three samples, and was mediated, in part, through more depressive symptoms, anxiety and chronic conditions. Feeling older was associated with an increased likelihood of major sleeping difficulties at follow-up in the three samples.

Conclusion: Subjective age is a salient marker of individuals’ at risk for poor sleep quality, beyond chronological age.     

Recovery of performance during sleep following sleep deprivation in older normal and insomniac adult males

Groups of 12 normal and insomniac male subjects aged 55 to 71 yr. were sleep deprived for 64 hr. In both groups, the sleep loss was preceded by four baseline sleep nights and followed by four recovery nights. Reaction time, immediate recall, sleepiness, and body temperature were measured at approximately 2300, 0115, 0330, 0530, and 0800 during baseline, deprivation and recovery nights. Significant performance or mood differences were not found between the normal and insomniac males on any measure or at any testing period throughout the study. Performance of both groups declined characteristically during sleep loss while subjective sleepiness increased. As in young adults, degraded performance was restored by 8 hr. of recovery sleep. However, subjective sleepiness did not return to baseline levels until early in the second recovery night. It was concluded that chronic insomnia does not result in group performance deficits similar to those seen after chronic sleep loss; and the restorative function of sleep operates as efficiently in older insomniac subjects (who apparently have reduced need to sleep) as in older normal subjects.     

Lack of degradation in visuospatial perception of line orientation after one night of sleep loss

Sleep deprivation impairs a variety of cognitive abilities including vigilance, attention, and executive function. Although sleep loss has been shown to impair tasks requiring visual attention and spatial perception, it is not clear whether these deficits are exclusively a function of reduced attention and vigilance or if there are also alterations in visuospatial perception. Visuospatial perception and sustained vigilance performance were therefore examined in 54 healthy volunteers at rested baseline and again after one night of sleep deprivation using the Judgment of Line Orientation Test and a computerized test of psychomotor vigilance. Whereas psychomotor vigilance declined significantly from baseline to sleep-deprived testing, scores on the Judgment of Line Orientation did not change significantly. Results suggest that documented performance deficits associated with sleep loss are unlikely to be the result of dysfunction within systems of the brain responsible for simple visuospatial perception and processing of line angles.     

Experiments on extended performance: Repetition,age, and limited sleep periods

Four experiments on the effects on performance of extended time periods without sleep and on the effects of limited sleep, that is, naps, within such periods are reviewed. The performance measures included subjective measures and measures of performance on attention/persistence, continuous-production, precision, and cognitive tasks. Repeated periods of sleep deprivation did not result in decreased effects: Older subjects tended to be more vulnerable to sleep-loss decrements, and three different schedules of 4 h of sleep within a 60-h sleep-deprivation period had limited differential ameliorative effects.