Dynamics of nap sleep during a 40 hour period.

Following 1 baseline night, the sleep of 8 adult males in equally space 1 h naps during a 40 h period was examined. Ten additional subjects were sleep-deprived for 40 h with 1 h periods of exercise given in place of naps. One recovery night followed the 40 h period for both groups. Total sleep time and the amount of stage REM during the naps were negatively related to the circadian-temperature cycle. Stage REM frequently appeared within 10 min of stage 1 onset and the normal sequence of stages REM and 4 were altered, demonstrating that the organization of sleep within a nap is quite different from that in monophasic nocturnal sleep. Auto-correlation and cross-correlation analyses showed that the relation of sleep stages from hour to hour in normal continuous baseline sleep was altered in nap-to-nap comparison. The timing of REM onset may be controlled by a sleep-dependent ultradian clock; the clock may stop upon awakening and resume at the next sleep onset. Naps had recuperative value in terms of maintaining the normal amounts of sleep stages on the recovery night; recovery sleep for the exercise group showed typical sleep-loss effects.     

Diurnal fluctuation of sleep propensity across the menstrual cycle

Most women experience sleep changes across the menstrual cycle. We applied the ultra-short sleep-wake schedule to healthy females to compare their 24-h sleep propensity rhythms in the follicular and luteal phases. The daytime (09.00-16.30 h) subjective sleepiness and the number of slow wave sleep-containing nap trials increased in the luteal phase compared to the follicular phase, but the mean sleep propensity did not change. During the periods of 17.00-00.30 h and 01.00-08.30 h there were no differences between the two phases. These results suggest that increased daytime sleepiness in the luteal phase may be related to brain mechanisms controlling slow wave sleep.     

Sleep studies on a 90-minute day.

After 2 adaptation and 2 baseline all-night sleep recordings, 5 normal young adult subjects (3 males) were placed on a schedule alternating 60 min of wakefulness and 30 min of sleep for 5 1/3 24-h periods. A 2-day recovery period followed. One male subject (MA15) was later placed on the identical protocol with the exception that he was allotted periods of 75 min of wakefulness and 15 min of sleep during the experimental period. One male narcolepsy-cataplexy patient was placed on the 60-30 schedule for 48 h. All subjects showed REM sleep during the schedule manipulation. REMM sleep occurred within 10 min of sleep onset (SOREMP) on 79 of 110 REM sleep occasions in the normals, on all 29 REM episodes in MA15, and on 16 of 17 REM periods in the narcoleptic. In the normals, REM sleep showed a tendency to recur on alternate 90-min cycles, while in the narcoleptic REM recurred on consecutive periods. Compared to baseline, REM sleep 24 h was decreased in the normals and increased in the narcoleptic. Time spent in slow wave sleep and stage 2 was also reduced in the normal subjects on the 90-min schedule, and stage 1 sleep time was increased. Peak sleep times for the 5 normals occurred between 09.00 and 12.30 and lowest sleep times from 21.00 to 02.00. During the first recovery night, sleep times ranged from 11.5 to 18.5 h, including significant increases of slow wave sleep and REM sleep. Except for SOREMPs, no signs of the narcolepsy-cataplexy syndrome were seen in any of the normal subjects.     

Ultrashort sleep-walking schedule. I. Evidence of ultradian rhythmicity in "sleepability'

After a 7-8 h sleep at home, 9 young adults were placed on an ultrashort 15 min waking-5 min sleeping schedule for 12 consecutive hours, followed by a monitored recovery night in the laboratory. Six of 4 of the 9 subjects were also investigated in the same way after one night of selective REM deprivation and after one night of total sleep deprivation, respectively. In the first experiment, the amount of stage 1 in each of the sleep attempts varied rhythmically with a frequency of about 14.4 c/day. The average variance at the peak spectral frequency significantly exceeded the mean variance at the rest of the spectral frequencies and the mean variance at the adjacent frequencies. Stage 2 occurred more often around 15-16 h, with no evidence of ultradian rhythmicity. Both REM deprivation and total sleep deprivation disrupted the 100 min periodicity in stage 1 and modified the distribution of stage 2 toward a bimodal rather than a unimodal distribution. The result of the first experiment were interpreted in the light of Kleitman's BRAC model. The ultradian rhythmicity in sleepiness is suggested to play a role in the adaptability and flexibility of the circadian sleep-waking cycle.     

Effect of flunitrazepam on sleep and memory

Flunitrazepam's (FNZ) effect on sleep and memory 1 mg and 2 mg was investigated in 6 healthy volunteers (mean age 21.5 ± 0.8 years) by polysomnography (PSG) and memory testing. A PSG was recorded on each study night. Memory testing was done before sleep (40 min after taking FNZ or placebo), and after waking (560 min after medication). Rapid eye movement (REM) latency was found to be prolonged on the FNZ 2 mg night (FNZ2N) compared to the baseline night (BN). Percentage of stage 2 sleep was increased in the FNZ2N as compared to BN, while REM percentage on both FNZ nights did not significantly differ from BN. The number of total REM and REM density were decreased in the FNZ2N compared to BN. Memory testing showed significant differences between before sleep and after waking on the FNZ2N. There was a significant correlation between the degree of impairment on memory testing and the rate of reduced REM density, but there was no significant correlation between degree of impairment on memory testing and the rate of increased non-REM sleep on the FNZ2N. The results of this study suggest that impairments in memory result from the dose of FNZ, and that there is a possibility of a relationship between memory disturbance and REM sleep suppression caused by this benzodiazepine.     

Sleep architecture, slow wave activity, and sleep spindles in adult patients with sleepwalking and sleep terrors.

OBJECTIVES: A very strong SWS intensity reflected by both an increased level of SWA and an abnormal sleep spindles distribution would be responsible for the major difficulty of parasomniac subjects in waking up from SWS, leading to episodes of parasomnia. METHODS: Eleven adult parasomniac subjects, 6 females and 5 males, with sleepwalking (SW) and/or sleep terrors (ST) and 11 age- and sex-matched control subjects underwent polysomnography (PSG) during 2 consecutive nights. After an habituation and selection night followed by a 16 h period of controlled wakefulness, the sleep EEGs of the parasomniac and control subjects were analyzed on the second night by computer-aided visual scoring (integrated digital filtering analysis, IDFA) and spectral analysis (fast Fourier transform, FFT). Throughout the night subject behaviour was controlled and recorded by means of a video infra-red camera and videotape recorder. RESULTS: Fifteen episodes of parasomnia were recorded during the second night in the 11 subjects. Sleep analysis showed significantly (P<0.05) decreased sleep efficiency and stage 2 sleep (absolute values and percentage of total sleep time) and increased (P<0.05) slow wave sleep (absolute values and percentage of total sleep time). Arousal index and wake-time after sleep onset were significantly higher in parasomniac subjects. Sleep fragmentation was mainly concentrated in stages 3 and 4. The slow wave activity (SWA) absolute values averaged during the 2 min immediately preceding an episode of parasomnia were significantly higher than the SWA averaged during 2 min in the same stage 10 min before an episode of parasomnia. Moreover, SWA was higher in the slow wave sleep (SWS) episodes preceding the episode of parasomnia than in the episodes preceding an awakening without an episode of parasomnia. The temporal course of SWA showed a slower exponential decay in both groups, but the time constant of the curve was larger in parasomniacs than in controls. Finally, in control subjects the sleep spindle index increased from the beginning to the end of the night while it was equally distributed in parasomniacs. CONCLUSIONS: An abnormal deep sleep associated with a high SWS fragmentation might be responsible for the occurrence of SW or ST episodes.     

Postural control after a night without sleep

The present study analysed the efficiency of postural control after 12 h of nocturnal forced wakefulness using Romberg's test comprising 1 min of recording with eyes-open and 1 min of recording with eyes-closed, with a 1 min break between the two sessions. Our aim was to see if the decreased postural control efficiency after a sleepless night was unspecific (in both eyes-closed and eyes-open conditions) or selective (in only one of the conditions). A total of 55 students spent a whole night awake at our laboratory and were tested at 22:00 and 08:00 h. In general, the results showed that postural sway increased, performing the recording from eyes-open to eyes-closed condition. The statokinesigram length (SL or efficiency of the postural system) increased after the sleepless night, while in eyes-open condition, the length in function of surface (LFS or accuracy of postural control) and Romberg's index (or contribution of vision to maintain posture) significantly decreased. This could indicate that after a night without sleep, there is a slower elaboration of visual inputs in the postural control process. On the basis of these results, the effects of sleep deprivation on cognitive performance were considered from a neuropsychological point of view.     

The Rectal Motor Complex

To identify patterns of motility in the rectum of humans during the day while awake and at night during sleep, and to correlate the patterns with interdigestive duodenal motor complexes and sleep cycles, intraluminal rectal pressure was recorded in 12 healthy subjects (five female, seven male; mean age, 28 years) using a flexible, noncompliant, silastic catheter and an Arndorfer system with a single perfused rectal port 6 cm above the anorectal junction, duodenal motility was recorded via a perfused oroduodenal tube, and sleep stages were determined electroencephalographically. Discrete bursts of rectal motor waves, called rectal motor complexes (RMCs), were identified on 72 occasions in 11 of the 12 subjects during 157 hours of recording. The RMCs were found in daytime during fasting or after feeding (0.2 ± 0.1 RMCs/hour), but were more easily and frequently identified at night during sleep (0.8 RMCs/hour, p < .01). The complexes had a distinct onset, a mean duration ± SEM of 9.5 ± 1.0 minutes, and a distinct decline. Within each complex, the waves had a mean frequency of 3.8 ± 0.3 per minute and a mean amplitude of 19 ± 2.7 mm Hg. Complex-to-complex intervals at night averaged 74 ± 15 minutes. No clear-cut temporal association was present between the complexes and phase III of interdigestive duodenal motor complex or the REM stage of sleep.     

Ultrashort sleep-waking schedule. III. 'Gates' and 'forbidden zones' for sleep

Three experiments which utilized an ultrashort sleep-waking cycle were conducted to investigate the 24 h structure of sleepiness after 1 night of sleep deprivation under 2 experimental conditions: instructing subjects to attempt to fall asleep or instructing subjects to attempt to resist sleep. Six subjects participated in experiment 1. At 19.00 h they started a 13 min waking-7 min sleep attempt, or 13 min waking-7 min resisting sleep, until 19.00 h on the next day. Eight subjects were tested in a similar way in experiment 2, which started at 07.00 h after a night of sleep deprivation and lasted for 24 h. Eight subjects were similarly tested in experiment 3 which started at 11.00 h after a night of sleep deprivation and lasted for 36 h until 23.00 h on the next day. The results showed that in spite of the significant between-group differences in total sleep, the temporal structure of sleepiness was very similar in the 3 experiments. In each there was a bimodal distribution of sleepiness: a major nocturnal sleepiness crest and a secondary mid-afternoon sleepiness peak. These were separated by a 'forbidden zone' for sleep centred at around 20.00-22.00 h. The onset of the nocturnal sleep period (the sleep gate) was found to be a discrete event occurring as an 'all or none' phenomenon. Its timing was stable over a 2 week period, and independent of the specific experimental demands; there were no significant differences between the AS and RS conditions with respect to total sleep time or any of the sleep stages. These results, which demonstrate structured variations in sleepiness across the nycthemeron are discussed in the light of the recent modelling of sleep along homeostatic principles.     

Interactions between sleep normative data and sociocultural characteristics in the elderly

Objective

To present sleep patterns in elderly individuals and factors associated with short sleep and long daytime and nighttime sleep.

Methods

A total of 8091 subjects aged between 55 and 101 years representative of the noninstitutionalized general population of seven European countries (France, Finland, Italy, Germany, Portugal, Spain, and UK) were interviewed by telephone about their sleep habits and sleep disorders.

Results

The average sleep duration was 6 h and 57 min. Sleep duration was longer in men than in women. Five percent of the sample slept 5 h or less and 5% slept 9 h or more per night. Factors associated with short sleep (lower fifth percentile) were age, living in UK, no physical exercise, drinking six cups of coffee or more per day, taking a medication for sleep, difficulty initiating sleep, disrupted sleep, early morning awakening, and presence of an anxiety disorder. Factors associated with long sleep (≥95th percentile) were age, living in France, Portugal, or Spain, being underweight, no physical exercise, disrupted sleep, taking a medication for sleep, and presence of an anxiety disorder. Long daytime sleep (54 min or more) were age, being a man, being overweight or obese, physical disease, being dissatisfied with one's social life, smoking, drinking alcohol, and having a major depressive disorder.

Conclusion

Sleep patterns considerably varied among the countries in the elderly population. Extreme values of sleep duration (short and long sleep) were associated with several sleep and mental health problems.     

Sleep habits in Nigerian undergraduates

Background –  Quantity of night sleep is shorter than 8 h in several developed countries, but similar data is not available for most African countries. The objective of this study was to describe the quantity of night sleep, factors that are associated with non-restorative sleep, and sleep habits in a population of undergraduates in Nigeria.
Methods –  Questionnaires were used to collect information about bedtimes, waketimes, intra-night awakenings, non-restorative sleep, and afternoon naps over a period of 14 days.
Results –  Mean duration of night sleep was 6.2 h (median 6.0, range 4.5–9.3), while mean duration of daytime naps was 70 min (median 75, range 10–315). Duration of night sleep was associated with day of the week and gender, but not with BMI. Non-restorative sleep, which occurred 25% of total sleep times, was associated with night sleep ≤5 h, hypnotic use, alarm to wake, heavy workload, and afternoon naps. Intra-night sleep awakening occurred 58.5% of total sleep times. Afternon naps were taken by 225 (82%) of subjects.
Conclusion –  Duration of night sleep in this African population is not longer than the duration in Western countries. Intra-night awakening and non-restorative sleep; however, occur more frequently, and afternoon nap is usually in excess of 1 h.     

Daytime vigilance in chronotypes: diurnal variations and effects of behavioral sleep fragmentation

Vigilance levels of 12 morning types (M-types) and 12 evening types (E-types) were investigated after a baseline night, 2 nights of sleep fragmentation (5 min of forced awakening every half-hour) and a recovery night. Sleep timing was adjusted to the preferred sleep schedule of each subject. Daytime vigilance levels were assessed with test series including a scale of subjective alertness, a psychomotor vigilance task (PVT), a waking EEG recording, and a sleep latency test. Test series were administered every 4h, beginning 1.5h after wake time. On the baseline day, significant diurnal variations were found for each vigilance measure, except for the PVT. Diurnal variations were similar in M-types and E-types. Sleep fragmentation decreased vigilance levels on each measure, except the PVT. Effects of sleep fragmentation and recovery were similar in the two chronotypes. These results highlight the similarities in diurnal variations of vigilance in the two chronotypes when studied at their preferred sleep schedule. Results were also compared between chronotypes with extremely early or late circadian phases ("Extreme" subgroup) and between those with similar, intermediate circadian phases ("Intermediate" subgroup). Diurnal variations of subjective alertness and sleep latencies differed between "Extreme" chronotypes but were identical between "Intermediate" chronotypes. There were no major differences in the response to sleep fragmentation in any subgroup. Since phase angles differed by the same amount between chronotypes within each subgroup, the results suggest that a difference in phase angle cannot be the only source of the differences observed in diurnal variations between "Extreme" chronotypes.     

Melatonin treatment in individuals with intellectual disability and chronic insomnia: a randomized placebo-controlled study

Background While several small‐number or open‐label studies suggest that melatonin improves sleep in individuals with intellectual disabilities (ID) with chronic sleep disturbance, a larger randomized control trial is necessary to validate these promising results. Methods The effectiveness of melatonin for the treatment of chronic sleep disturbance was assessed in a randomized double‐blind placebo‐controlled trial with 51 individuals with ID. All of these individuals presented with chronic ideopatic sleep disturbance for more than 1 year. The study consisted of a 1‐week baseline, followed by 4 weeks of treatment. Parents or other caregivers recorded lights off time, sleep onset time, night waking, wake up time and epileptic seizures. Endogenous melatonin cycle was measured in saliva before and after treatment. Results Compared with placebo, melatonin significantly advanced mean sleep onset time by 34 min, decreased mean sleep latency by 29 min, increased mean total sleep time by 48 min, reduced the mean number of times the person awoke during the night by 0.4, decreased the mean duration of these night waking periods by 17 min and advanced endogenous melatonin onset at night by an average of 2.01 h. Lights off time, sleep offset time and the number of nights per week with night waking did not change. Only few minor or temporary adverse reactions and no changes in seizure frequency were reported. Conclusions Melatonin treatment improves some aspects of chronic sleep disturbance in individuals with ID.     

Night diapers use and sleep in children with enuresis

Objective

We aimed to assess the association between night diapers use and sleep quality of school-aged children with enuresis.

Methods

The sleep patterns of 72 school-aged children (ages 6–9 y) with enuresis referred to a clinic specializing in bladder disorders and 63 healthy control children were assessed. Sleep measures were derived from four to five monitoring nights of actigraphy and daily logs.

Results

In comparison to controls, children with enuresis who did not wear night diapers had poorer sleep quality as reflected by both actigraphic measures (more activity during sleep and shorter periods of continuous sleep) and one reported measure (lower sleep quality). However, no differences were found on any of the sleep measures between children with enuresis wearing night diapers and controls. The reported sleep quality of all children with enuresis with and without night diapers was lower than controls.

Conclusions

Our results suggest that sleep patterns of school-aged children with enuresis who do not wear night diapers are impaired, and the sleep quality of children using night diapers is similar to those of healthy children. Thus, clinicians and healthcare providers should consider recommending sleeping with night diapers for untreated children with enuresis, based on its positive impact on sleep.     

Effects of acute morning and evening exercise on subjective and objective sleep quality in older individuals with insomnia

ObjectivesThe aims of this study were to compare the effects of acute morning or evening exercise on nocturnal sleep in individuals with two subjective insomnia symptoms: difficulty in initiating sleep (DIS), and early morning awakening (EMA), separately for the first vs the second halves of the night.MethodsOlder individuals (55–65 years old) with DIS (N = 15) or EMA (N = 15) and age- and sex-matched controls (N = 13) participated in this non-randomized crossover study. Participants were assigned to two exercise conditions (morning exercise and evening exercise) in counterbalanced order following the baseline condition with a two-week interval between conditions. A single session of aerobic step exercise was performed during each exercise condition. Nocturnal polysomnography was carried out to evaluate objective sleep quality. Patient global impression of change scale scores for nocturnal sleep were obtained to subjectively evaluate the different groups.ResultsAcute physical exercise did not improve subjective sleep quality. Morning exercise decreased the number of stage shifts over the whole night. The arousal index and the number of stage shifts were decreased especially during the second half of the night in all groups. Furthermore, morning exercise decreased the number of wake stages during the second half of the night in the DIS group, but not in the EMA group.ConclusionsAcute morning exercise can improve nocturnal sleep quality in individuals with difficulty initiating sleep, especially during the later part of the night.     

The U-shaped association between self-reported sleep duration and visual impairment in Korean adults: a population-based study

ObjectiveThis study aimed to investigate the association between self-reported sleep duration and visual impairment (VI) in Korean adults.MethodsThis population-based, cross-sectional study examined ophthalmologic data of 16,374 Koreans aged 19 years and older from the 2010–2012 Korea National Health and Nutrition Examination Survey (KNHNES V). VI data (best-corrected distance visual acuity worse than 0.5 logMAR in the better-seeing eye) were obtained from direct ophthalmologic examinations, and data on self-reported sleep duration (≤5, 6, 7, 8, or ≥9 h/night) were obtained using questionnaires. Multiple logistic regression analysis was conducted to examine the association between self-reported sleep duration and VI, and we also adjusted for possible covariates.ResultsThe weighted VI prevalences (95% CIs) were 1.23% (0.70–1.76), 0.40% (0.10–0.70), 0.18% (0.04–0.31), 0.42% (0.26–0.58), and 0.66% (0.25–1.07) for participants who slept ≤5, 6, 7, 8, and ≥9 h/night, respectively. Even after adjusting for demographic factors (age and sex), lifestyle factors (household income, occupation, smoking status, regular exercise, and suicidal thoughts), and medical factors (diabetes, hypertension, stroke, and history of ocular surgery), greater risk of VI was found in the ≤5 h/night (OR = 3.23, 95% CI: 1.43–7.31) and ≥9 h/night (OR = 2.56, 95% CI: 1.03–6.41) groups, compared to the 7 h/night group.ConclusionsIn Korean adults, self-reported sleep duration and VI exhibited a U-shaped association. Both very short (≤5 h/night) and very long (≥9 h/night) sleep durations were significantly associated with increased VI.     

Sleep dysfunction in Rett syndrome: a trial of exogenous melatonin treatment

Nine girls with Rett syndrome (mean age, 10.1 years) were monitored 24 hours a day over a period of 10 weeks using wrist actigraphy. Baseline sleep-wake patterns were assessed for 1 week. Subsequently, patients underwent a 4-week melatonin treatment period in a double-blind, placebo-controlled, crossover protocol that employed a 1-week washout between treatment trials. Melatonin doses ranged from 2.5 to 7.5 mg, based upon individual body weight. Baseline sleep quality was poor compared with healthy children. At baseline the group demonstrated a low sleep efficiency (mean [±SE], 68.0±3.9%), long sleep-onset latency (42.1±12.0 minutes), and a short and fragmented total sleep time (7.5±0.3 hours; 15±2 awakenings per night). Melatonin significantly decreased sleep-onset latency to (mean ± SE) 19.1±5.3 minutes (P<0.05) during the first 3 weeks of treatment. While the variability of individual responsiveness was high, melatonin appeared to improve total sleep time and sleep efficiency in the patients with the worse baseline sleep quality. Finally, a 4-week administration of melatonin appears to be a safe treatment as no adverse side effects were detected, yet long-term effects of chronic melatonin use in pediatric patients are unknown at this time.     

The immediate effects of nasal continuous positive airway pressure treatment on sleep pattern in patients with obstructive sleep apnea syndrome

We studied the immediate effects of continuous positive airway pressure (CPAP) applied nasally on the pattern of sleep in 12 patients, aged 30-58 years, with obstructive sleep apnea syndrome. All patients demonstrated a moderate to severe syndrome on the control night; apnea index ranged 28-83 apneas/h sleep. Nasal CPAP completely abolished all obstructive apneas and allowed apnea-free breathing in all 12 patients. Nasal CPAP had a marked effect on the sleep pattern. It significantly reduced stage I/II non-rapid eye movement (NREM) sleep and markedly increased stage III/IV NREM and REM sleep on the first treatment night. Stage I/II NREM sleep decreased from a control of 62.7 +/- 2.3% to 29.1 +/- 2.3% on the first treatment night. Stage III/IV NREM sleep increased from a control of 6.7 +/- 1.6% to 31.5 +/- 1.6%. The rebound in this sleep stage was especially marked in 3 patients aged 55-58 years. REM sleep increased from a control of 18.4 +/- 2.0% to 30.6 +/- 2.0% on the first treatment night. There was an increase in REM density. All patients were treated for another 2 nights and their sleep pattern analyzed on the third night. All sleep stages were still significantly different to the control night. The possible mechanisms involved are discussed.     

Preliminary observations on the effects of sleep time in a sleep restriction paradigm

OBJECTIVE: To evaluate of the effect of 7 days of sleep restriction--with sleep placed at the beginning of night or early morning hours - on sleep variables, maintenance of wakefulness test, and serum leptin. METHODS: After screening young adults with questionnaires and actigraphy for 1 week, eight young adult males were recruited to participate in a sleep restriction study. The subjects were studied for baseline data for 2.5 days, with 8.5 h per night in bed, and then over 7 days of sleep restriction to 4 h per night with a 22:30 h bedtime for half the group and a 02:15 h bedtime for the other half. At the end of study, after one night of ad libitum sleep, subjects again had 2 days of 8.5 h in bed. Wakefulness was continuously verified and tests, including Maintenance of Wakefulness (MWT), were performed during the scheduled wake time. Blood was drawn six times throughout the 24 h of the 7th day of sleep restriction and after 2 days of the post-restriction schedule. RESULTS: There was individual variability in response to sleep restriction, but independent of group distribution, MWT was significantly affected by sleep restriction, with the early morning sleep group having less decrease in MWT score. Sleep efficiency was also better in this group, which also had shorter sleep latency. Independent of group distribution there was a greater increase in the percentage of slow wave sleep than rapid eye movement sleep, despite a clear internal variability and variability between subjects. Peak serum leptin was significantly decreased with 7 days of sleep restriction for all subjects. CONCLUSION: Sleep restriction to 4 h affected all subjects, but there were individual and group differences in MWT and sleep data. In this group of young adult males (mean age 19 years), there was a better overall adaptation to the early morning sleep, perhaps related to the general tendency in most adolescents to present some phase-delay during late teen-aged years.