Effects of Experimentally-Induced Sleep Fragmentation on Sleep and Sleepiness

The effects of two levels of sleep fragmentation on sleep and daytime sleepiness were investigated in young adult males. Experimental subjects were informed while awake that tones would be presented periodically throughout the night and that their task was to terminate the tone by taking a deep breath. Eight subjects received tones after each minute of sleep and 8 received tones after each 4 min of sleep. Control subjects (N=8) HI did not receive (ones. The subjects were tested for daytime sleepiness using the Multiple Steep latency Test. It was found that: 1) subjects responded reliably lo tones presented during sleep; 2) behavioral control was accompanied by brief electro-physiological indices of arousal on almost all trials, and occasionally led to fall awakenings; 3) sleep was markedly altered in the 1-min condition; 4) a relatively small effect on sleep (reduced stage 4 sleep) was produced by the 4-min condition, and 5) daytime sleepiness was increased by the 1-min condition but not the 4-min condition. It was concluded that the most parsimonious explanation of these results is (he Continuity of Sleep hypothesis.     

Factors Related to Behavioral Control by Stimuli Presented During Sleep

Two experiments are presented concerning the control of learned behavior by stimuli presented during sleep. The rule of associative and nonassociative factors was assessed in Experiment 1. Group I was tested to demonstrate that, following instructions during wakefulness, subjects would terminate tones presented during sleep by taking a deep breath. To determine the likelihood of spontaneous responses during the tone, two groups were tested following the same instructions but with tones omitted on every trial (Group II) or every other trial (Group III). To determine whether breathing responses might be due to tone-elicited arousal. Group IV was tested without instructions to make the breathing response. Reliable responding was found only for Group I. Experiment 2 concerned within- and across-night patterns of responsiveness under the procedure investigated in Experiment 1. Subjects were tested for either 4 consecutive or 4 nonconsecutive nights. Response latencies increased within nights and also across nights with a greater rate of increase on consecutive nights. The data are discussed in relation to the importance of understanding the effects of behavioral demands during sleep.     

Sleep fragmentation in the elderly: Relationship to daytime sleep tendency

—Sleep in the elderly is known to be disturbed, and many elderly persons also complain of daytime sleepiness. The present study assessed sleep and waking behavior in 12 male (aged 63 to 86) and 12 female (ages 63 to 82) subjects. Sleep stages, respiration, and movement were recorded at night, and daytime sleep tendency was measured using the Multiple Sleep Latency Test during a single 24-hour period. Daytime sleepiness did not correlate with total sleep time or any sleep stage, but was significantly correlated with measures of sleep fragmentation. The latter included transient arousals, a measure of < 15-sec awakenings, and sleep-related respiration disturbance. These findings suggest that fragmented nocturnal sleep is a significant cause of reduced daytime w well-being in elderly individuals. The continuity of both sleep and wakefulness appears to be disrupted with age. Experimental strategies for achieving a rational sleep hygiene are discussed.     

Behavioral Control Over Sleeping Respiration in Normals for Ten Consecutive Nights

Behavioral control over sleeping respiration in 5 healthy college students was tested over 10 consecutive nights and 1 additional night 1–2 weeks later. Participants were polygraphically recorded each night and the records scored using standardized criteria. They were informed while awake that tones (.5 s on/off, 4000 Hz) would be presented to them (variable interval schedule, X?=7.5 min) during nighttime sleep and that their task was to terminate them by taking a deep breath. Behavioral control over respiration was maintained over the 10 nights. Latency to respond gradually increased over the first 5 nights and then leveled out for the remaining 5 nights. On the test night, 1–2 weeks following Night 10, latency to respond was similar to Nights 1 and 2. Percentage of time spent in each sleep stage and the pattern of arousals to tones and responses were similar to earlier reports (more stage 1, less stage 3–4; frequent arousals). It was concluded that behavioral control over sleeping respiration can be obtained and maintained in normal college students over at least 10 nights but a limiting factor may be the increase in response latency.     

Sleep fragmentation in the elderly: Relationship to daytime sleep tendency

—Sleep in the elderly is known to be disturbed, and many elderly persons also complain of daytime sleepiness. The present study assessed sleep and waking behavior in 12 male (aged 63 to 86) and 12 female (ages 63 to 82) subjects. Sleep stages, respiration, and movement were recorded at night, and daytime sleep tendency was measured using the Multiple Sleep Latency Test during a single 24-hour period. Daytime sleepiness did not correlate with total sleep time or any sleep stage, but was significantly correlated with measures of sleep fragmentation. The latter included transient arousals, a measure of < 15-sec awakenings, and sleep-related respiration disturbance. These findings suggest that fragmented nocturnal sleep is a significant cause of reduced daytime w well-being in elderly individuals. The continuity of both sleep and wakefulness appears to be disrupted with age. Experimental strategies for achieving a rational sleep hygiene are discussed.     

Cumulative Effects of Sleep Restriction on Daytime Sleepiness

Sleep and daytime sleepiness were evaluated in 10 young adult subjects to determine whether restricting nocturnal step by a constant amount produces cumulative impairment. Subjects were studied for 12 consecutive days, including 3 baseline days with a 10-hr time in bed, 7 days with sleep restricted to 5 hrs, and 2 recovery days. In 5 subjects, recovery included a 10-hr time in bed; in the remaining subject, recovery induced a 5-hr time in bed with a 1-hr daytime nap. Sleepiness was measured using two self-rating scales and the multiple sleep latency test. During sleep restriction, nocturnal stage 2 and REM sleep were reduced and slow wave sleep was unaffected. Stanford Sleepiness Scales showed an immediate increase in daytime sleepiness that reached a plateau after 4 days. An analog sleepiness rating scale showed increased sleepiness after 2 restricted nights and leveled off after the fourth restricted night. The multiple sleep latency tests showed no effect of sleep restriction until the second day, followed by a progressive increase in sleepiness that persisted through the seventh sleep restriction day. During the recovery period, daytime sleepiness returned to basal values on all three measures following one full night of sleep; with a daytime nap, no further cumulative effects of sleep restriction were seen.     

Behavioral responsiveness in sleeping older adults

The control of behavior by stimuli presented during sleep, and related effects on sleep and daytime sleepiness, were investigated in 17 older (age = 60-74 years) adults. Experimental subjects (N = 8) were trained while awake to terminate tone presentations by taking a deep breath. Tones were then presented following sleep onset for four consecutive nights with a mean intertone interval of 4 min. Control subjects (N = 9) slept in the laboratory but did not receive tones. The daytime sleepiness of both groups was assessed by recording latency to sleep onset in a morning and afternoon nap test. It was found that the experimental subjects responded reliably to the tones. Responding, however, was almost invariably accompanied by disruption of sleep and overall sleep structure was markedly altered. Surprisingly, the daytime sleepiness of experimental subjects was not reliably greater than that of control subjects.     

Long-term extension to sleep -Are we really chronically sleep deprived?

During 26 consecutive nights, electroencephalographic recordings and/or actigraphs were used to monitor the nighttime sleep of 10 asymptomatic healthy sleepers (mean age = 23.6 years). The schedule comprised: 7 nights of base line sleep, 14 nights of extended sleep (up to 10 hr/night), and 5 nights of recovery sleep. During extended sleep, subject1, slept significantly longer (approximately 1 hr), but sleep latency and interim wakefulness deteriorated. Extended sleep produced no improvements to sell-rated mood or subjective sleepiness. Vigilance tests showed a small but significant reduction in reaction time following extended compared with both baseline and recovery nights. Ability to detect target tones did not change significantly. Multiple Sleep Latency Test scores during extended sleep showed small (about 1 min) reductions. These findings give little support to the view of chronic sleep deprivation in the average 7.5-hr sleeper.     

Sleep fragmentation and daytime sleepiness

It has been noted that clinical populations complaining of excessive daytime sleepiness (EDS) frequently have disrupted or fragmented nocturnal sleep. The relation between sleep fragmentation and daytime sleepiness has not been systematically studied. This study was designed to use correlational techniques evaluating the relation between these variables in patients complaining of EDS, patients complaining of insomnia, and asymptomatic controls. The four groups studied included patients complaining of EDS with sleep apnea (n = 15) or with periodic leg movements (n = 15), patients complaining of insomnia (n = 15), and healthy volunteers with no sleep complaint (n = 10). One night of polysomnography followed by a Multiple Sleep Latency Test was obtained for each subject. Each recording was evaluated using standard criteria and also by a four-level arousal scoring system. Across all subjects, the total number of arousals correlated significantly with sleepiness index (r = 0.48, p less than 0.001). Closer analysis of the data shows that, depending upon the sleep complaint, different types of arousals are predictive of degree of daytime sleepiness. It is concluded that the number and type of nocturnal arousals play an important role in subsequent daytime sleepiness.     

Sleep extension in sleepy and alert normals

Twenty-four healthy, young (21-35 years old) men with no complaints of daytime sleepiness, no habitual napping, and polysomnographically verified normal nocturnal sleep extended their time in bed (TIB) to 10 h for 6 consecutive nights to assess the effects of sleep extension on daytime sleepiness and performance. Twelve subjects had basal average daily sleep latencies of less than or equal to 6 min on the Multiple Sleep Latency Test and 12 had latencies of greater than or equal to 16 min before TIB was extended. The sleep extension improved daytime sleepiness differentially in the two groups. The degree of improvement was greater in the sleepy subjects than the alert subjects and the pattern of improvement differed between the groups. Sleepy subjects showed an immediate and uniform increase in alertness, while alert subjects did not show improvements until late in the extension. However, sleepy subjects never achieved the baseline level of sleepiness/alertness seen in the alert subjects.     

Performance and Sleepiness as a Function of Frequency and Placement of Sleep Disruption

Eight normal young adult sleepers spent 4 nonconsecutive weeks in the laboratory. Each week consisted of a baseline night followed by 2 consecutive nights of disrupted sleep, followed by 2 recovery nights. Disruption conditions included: a) brief awakening after each minute of accumulated sleep, b) brief awakening after each 10 min of accumulated sleep, c) 2.5 hrs of normal sleep followed by a brief awakening at each sleep onset, and d) total sleep deprivation. Morning testing revealed that all disruption conditions decreased sleep latency in a morning nap test. Performance after 1-min disruptions approximated that seen after total sleep loss. Performance decrements were less in the 10-min condition and least in the 2.5-hr sleep condition. Performance under baseline and total sleep loss conditions was used to predict performance during the sleep deprivation condition using four sleep stage rules. Total time asleep and total time asleep minus stage 1 predicted performance poorly. Total SWS plus REM predicted performance best but could not differentiate the 10-min and 2.5-hr conditions. Therefore, it was concluded that the data were most parsimoniously explained by the Sleep Continuity Theory—i.e., that periods of uninterrupted sleep in excess of 10 min are required for sleep to be restorative.     

Effects of Acute 3, 4-Methylenedioxymethamphetamine on Sleep and Daytime Sleepiness in MDMA Users: A Preliminary Study

Study Objective:

3, 4-Methylenedioxymethamphetamine (MDMA) affects monoamine neurotransmitters that play a critical role in sleep and daytime alertness. However, the acute effects of MDMA on sleep and daytime sleepiness have not been studied under placebo-controlled conditions. This study was designed to establish the effects of acute MDMA or placebo administration and sleep restriction on sleep and daytime sleepiness.

Design:

Participants with a history of MDMA use were studied on 3 sessions of 3 nights (baseline, treatment, and recovery) and 2 days (following night 2 and 3) per session. On treatment nights (night 2), participants received placebo or 2 mg/kg of MDMA or underwent a restricted bed schedule with placebo. Sleep restriction was a positive control to compare sleep loss and consequent sleepiness associated with MDMA use. The scheduled sleep period was 8 hours long on nonrestricted nights, and standard sleep recordings and daytime sleepiness tests were conducted. Age-matched controls received 1 night and day of standard sleep and daytime sleepiness testing.

Setting:

Sleep laboratory

Participants:

Seven recreational MDMA-users and 13 matched control subjects.

Measurements and Results:

Acute MDMA shortened sleep primarily by increasing sleep latency, and it reduced stage 3/4 sleep and suppressed rapid eye movement (REM) sleep. The MDMA-reduced sleep time was not associated with increased daytime sleepiness the following day, as was seen in the sleep-restriction condition. Compared with control subjects, the MDMA users on the first night in the laboratory had shorter total sleep times and less stage 3/4 sleep. Average daily sleep latency on daytime sleepiness tests the day after nighttime placebo administration was increased in MDMA users compared with the control subjects, and MDMA users had an elevated number of sleep-onset REM periods on these tests, compared with control subjects.

Conclusions:

Acute MDMA administration disrupts sleep and REM sleep, specifically, without producing daytime sleepiness such as sleep restriction does. Compared with control subjects, recreational MDMA users showed evidence of hyperarousal and impaired REM function. The mechanism behind these effects is likely due to the deleterious effects of MDMA on catecholamines.^1–3

Citation:

Randall S; Johanson CE; Tancer M; Roehrs T. Effects of acute 3, 4-methylenedioxymethamphetamine on sleep and daytime sleepiness in MDMA users: a preliminary study. SLEEP 2009;32(11):1513-1519.     

Chronic Sleep Reduction: Daytime Vigilance Performance and EEG Measures of Sleepiness, With Particular Reference to "Practice" Effects

Six pairs of young adult 8-hr sleepers were divided equally into two groups, Reduction (R) and Control (C). They adhered to strict bed and arising times for six weeks. Additionally, R subjects reduced their sleep systematically to an average of 6 hrs per night. Following a baseline week, and on a weekly basis, “yoked” pairs of subjects, one from each group, were assessed for daytime sleepiness during prolonged vigilance performance, and by EEG measurement. All-night sleep EEGs were taken on R subjects before and at the end of the reduction. There were no significant differences between the groups for any of the daytime sleepiness measures, but both groups displayed significant “practice” effects over the weeks. R subjects experienced no major difficulties, except for some tiredness around awakening and lunchtime. Overall daytime sleepiness was not increased. Reduction was at the expense of REM and stage 2 sleep, and led to significant declines in sleep onset latency and in stages W + 1 at nighttime. SWS was not affected. This level of reduction in young adults seems to be achieved relatively easily.     

Waking quantitative electroencephalogram and auditory event-related potentials following experimentally induced sleep fragmentation

STUDY OBJECTIVES: Experimental sleep fragmentation involves inducing arousals by administering intrusive auditory stimuli throughout the night. It is intended to model the frequent and periodic disruption experienced in common sleep disorders. Sleep fragmentation leads to daytime sleepiness, although evidence of performance impairment has been inconsistent. The purpose of this study was to investigate brain physiology associated with this level of sleep disruption. Specifically, quantitative analysis of electroencephalography was carried out, and auditory event-related potentials were recorded during daytime performance assessment following sleep fragmentation in good sleepers. DESIGN: Participants spent 4 consecutive 24-hour periods in the laboratory. On nights 2 and 3, sleep was fragmented using auditory stimuli that were delivered with increasing intensity until an arousal was noted. This design aimed to investigate the cumulative effects of sleep fragmentation on daytime functioning. SETTING: Data were collected in a sleep research laboratory during a 96-hour protocol. PARTICIPANTS: Eight healthy adults (mean age = 33.25) with no sleep complaints. MEASUREMENTS AND RESULTS: During the day, participants performed a 40-minute computerized test battery at 2-hour intervals (9:00 am -7:00 pm). The battery was presented in a fixed order and included measures of mood, sleepiness, reaction time, and serial addition or subtraction. Results indicated that subjective sleepiness and mood were impaired following sleep-fragmentation nights, compared to both baseline and recovery conditions. No performance deficits were apparent. The alpha:theta ratio, reflecting relative slowing of the electroencephalogram, was dramatically reduced following the second night of sleep fragmentation. Reductions in N1 amplitude of the event-related potentials indicated that attention was impaired with respect to early encoding processes following sleep fragmentation. CONCLUSIONS: Electroencephalographic and event-related potentials data illustrate impairment in information-processing capabilities associated with reduced arousal elicited by experimental sleep fragmentation. This subtle degree of sleep disruption, where total sleep time is not reduced, leads to sustained impairment in alertness and attention.     

Sleep and sleepiness in young individuals with high burnout scores

STUDY OBJECTIVES: Burnout is a growing health problem in Western society. This study aimed to investigate sleep in subjects scoring high on burnout but still at work. The purpose was also to study the diurnal pattern of sleepiness, as well as ratings of work stress and mood in groups with different burnout scores. DESIGN: Sleep was recorded in 2 groups (high vs low on burnout) during 2 nights; 1 before a workday and 1 before a day off, in a balanced order. Sleepiness ratings as well as daytime diary ratings were analyzed for the workday and the day off after the sleep recordings. SETTING: The polysomnographic recordings were made in the subjects' home. PARTICIPANTS: Twenty-four healthy individuals (14 women and 10 men) between the ages of 24 and 43 years participated. INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: A higher frequency of arousals during sleep (Workday: high burnout = 12+/-1 per hour, low burnout = 8+/-1 per hour; Day off: high burnout = 12+/-2 per hour, low burnout =8+/-1 per hour), and more subjective awakening problems were found in the high-burnout group. The diurnal pattern of sleepiness indicated that the high-burnout group did not recover in the same way as did the low-burnout group on the day off. Indicators of impaired recovery were also seen within the high-burnout group as a higher degree of bringing work home and working on weekends, as well as more complaints of work interfering with leisure time. CONCLUSIONS: Young subjects with high burnout scores, but who are still working, show more arousals during sleep and an absence of reduced sleepiness during days off.     

Sleepiness and REM Sleep Recurrence: The Effects of Stage 2 and REM Sleep Awakenings

Determinants of daytime sleepiness include sleep length, sleep continuity, and circadian factors. Sleep stage composition has not been seen as influencing subsequent daytime functioning; however, earlier studies did not focus explicitly on sleepiness. The present experiment studied the effects of selective sleep-stage restriction on an objective measure of sleep tendency, and explored the relationship between sleepiness and subsequent REM recurrence during REM deprivation. Daytime sleep latency was measured by a modified Multiple Sleep Latency Test prior to and following two nights of awakenings from either REM or Stage 2 sleep in 16 normal young adults. Sleep latency following these awakenings was also measured. REM sleep and Stage 2 awakenings produced comparable levels of sleepiness, both during the Awakening Nights and subsequent daytime Multiple Sleep Latency Testing. Pooling the groups, daytime and nocturnal sleepiness measures were correlated within individuals. In the REM-Awakening Group, Pre-Awakening daytime sleepiness was associated with the tendency for REM sleep to recur following experimental awakenings. Comparable levels of sleepiness may result from nonspecific processes such as sleep curtailment and fragmentation, or alternatively from separate REM and Stage 2 mechanisms. The relationship between REM sleep and sleepiness is discussed in the context of both state and trait models.     

Performance and sleepiness following moderate sleep disruption and slow wave sleep deprivation

Recent studies have shown that periodically disrupted sleep resulted in significant daytime sleepiness and performance loss in normal young adults. One study suggested that the periodicity of disturbance rather than the total number of sleep disturbances was the primary factor in causing degraded function. However, in that study, increased performance levels could have been associated with increased levels of slow wave sleep. The present study was designed to determine whether the amount of SWS rather than the periodic disruption of sleep accounts for decreased performance of Ss with disrupted sleep. Twelve normal young adults spent two 4-night periods in the laboratory. During one 4-night series, Ss were briefly aroused either following each 10 min of sleep or whenever they entered stage 3 sleep (No SWS condition). During the second series of nights, Ss were briefly aroused after each 10 min of sleep (SWS condition). In the second series, additional arousals were performed after 5-min periods (but not when Ss were in SWS) to equalize the total number of arousals in the SWS conditions with those in the No SWS condition. Total experimental arousals were equal in the disruption conditions, and the experimental manipulation was successful in reducing total SWS to infrequent epochs of stage 3 in the No SWS condition while allowing significantly more SWS in the SWS condition. In terms of sleep stages, this difference was balanced by increased stage 2 in the No SWS condition. Despite the differential occurrence of SWS, no performance, mood, or nap latency measure was different in the SWS vs.(ABSTRACT TRUNCATED AT 250 WORDS)     

Sleep During and After Gradual Sleep Reduction

To determine: 1) the minimum amounts of sleep subjects would tolerate, 2) the changes in EEG sleep measures, and 3) whether subjects would revert to baseline sleep after study termination, 4 couples gradually reduced their sleep. Three couples reduced their TST in 30-min steps from a baseline of 8 hrs and one couple from a baseline of 6.5 hrs. Subjective estimates of sleep time, sleep quality, and mood were collected daily. Home EEG sleep recordings were obtained 3 nights a week. Two of the 8-hr sleepers reduced their sleep to 5.5 hrs, 2 to 5.0 hrs, and 2 reached 4.5 hrs. These 6 subjects continued sleeping 1 to 2.5 hrs below baseline amounts a year after reduction terminated. The 6.5-hr baseline couple reached 5.0 hrs and returned to 6.5 hrs TST during follow-up. Stages W, 2, and REM decreased significantly in absolute amounts. Percentage of stages W and 2 also decreased significantly. REM percent remained constant. Stage 3 was constant while stage 4 increased in both absolute and relative amounts. REM cycle length remained constant. Stage 4 rebound on 7-hr nights was not observed during times of greatest sleep reduction. Occurrences of stage REM within 10 min of stage 1 onset were observed in 2 subjects when their TST was below 6.5 hrs. Our results are consistent with other studies of shortened sleep, indicating that TST is the major determinant of sleep-stage characteristics.     

Sleep Stage Physiology, Mood, and Vigilance Responses to Total Sleep Deprivation in Healthy 80-Year-Olds and 20-Year-Olds

Little is known about sleep and the effects of total sleep loss in the 'old old' (i.e., 80-year-olds). We investigated sleep, mood, and performance responses to acute sleep deprivation in healthy 80-year-olds (n = 10) and 20-year-olds (n = 14). The protocol consisted of three nights of baseline sleep, one night of total sleep deprivation, and two nights of recovery sleep. Mood and vigilance were tested using visual analog scales and a Mackworth clock procedure in the morning and evening of each study day. Daytime sleepiness was measured by five naps on the days following the third and sixth nights. Old subjects had lower sleep efficiency and less delta sleep than young subjects. However, sleep continuity and delta sleep were enhanced in both groups on the first recovery night, indicating that sleep changes in old subjects are at least partially reversible by this procedure. Surprisingly, young subjects had shorter daytime sleep latencies than the old, suggesting a greater unmet sleep need in the former group. Mood and performance were disturbed by sleep loss in both groups, but to a greater extent among the young. This suggests that acute total sleep loss is a more disruptive procedure for the young than for the old.     

The effect of sleep fragmentation on daytime function

It is clear from this literature that fragmented sleep is less restorative than consolidated sleep, and leads to sleepiness-related daytime impairment. The optimal approach to the quantification of sleep fragmentation continues to be debated. Modest and erratic correlations between measures of sleepiness and traditional measures of EEG arousals have pushed investigators to try and find more sensitive measures of sleep fragmentation. Simply correlating various measures of sleep fragmentation with a measure of sleepiness has significant limitations. Since sleep fragmentation is not the only factor affecting daytime sleepiness, these correlations can be misleading. For example, a subject with severely fragmented sleep will show elevated sleepiness during the day. However, the overall correlation may be reduced because lack of fragmented sleep does not guarantee that the level of sleepiness will be low. Multivariate statistical modeling is needed to account for sources of variance simultaneously in the prediction of daytime sleepiness. In this way it may be possible to identify the optimal definition of sleep fragmentation. More studies are needed that evaluate "sub-cortical" arousals, EEG arousals, and daytime function simultaneously. Ideally, clarification of these measurement issues will lead to an improved understanding of sleep structure and the mechanism through which sleep fragmentation impacts daytime function.