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PubMedDate not supplied

Emotional memory formation is enhanced across sleep intervals with high amounts of rapid eye movement sleep.

Recent studies indicated a selective activation during rapid eye movement (REM) sleep of the amygdala known to play a decisive role in the processing of emotional stimuli. This study compared memory retention of emotional versus neutral text material over intervals covering either early sleep known to be dominated by nonREM slow wave sleep (SWS) or late sleep, in which REM sleep is dominant. Two groups of men were tested across 3-h periods of early and late sleep (sleep group) or corresponding retention intervals filled with wakefulness (wake group). Sleep was recorded polysomnographically. Cortisol concentrations in saliva were monitored at acquisition and retrieval testing. As expected, the amount of REM sleep was about three times greater during late than during early retention sleep, whereas a reversed pattern was observed for SWS distribution (P < 0.001). Sleep improved retention, compared with the effects of wake intervals (P < 0.02). However, this effect was substantial only in the late night (P < 0.005), during which retention was generally worse than during the early night (P < 0.02). Late sleep particularly enhanced memory for emotional texts. This effect was highly significant in comparison with memory for neutral texts (P < 0.01) and in comparison with memory after late and early wake intervals (P < 0.001). Cortisol concentration differed between early and late retention intervals but not between sleep and wake conditions. Results are consonant with a supportive function of REM sleep predominating late sleep for the formation of emotional memory in humans.

Adult↗
PubMed2006

Comparison of sleep condition and sleep-related psychological activity after cognitive-behavior and pharmacological therapy for chronic insomnia.

BACKGROUND: Previous studies of insomnia focused mainly on the improvement of sleep condition and ignored the effects of sleep-related psychological activity and daytime function after pharmacological and behavioral treatments. We compared the clinical effects of both therapies on sleep condition, sleep-related psychological activity and daytime function in chronic insomnia. METHODS: Seventy-one patients with chronic insomnia were randomly divided into 4 groups and either received cognitive-behavior therapy (CBT, n = 19), pharmacological therapy (PCT, n = 17), CBT plus medication (Combined, n = 18) or placebo (n = 17). The treatments lasted for 8 weeks with follow-ups conducted at 3 and 8 months. On the day after treatment ended, all patients were assessed using a polysomnogram (PSG), a sleep diary and a psychological assessment. RESULTS: The three active treatments were more effective than placebo at the time the treatments were completed. Subjective sleep-onset latency, sleep efficacy and total sleep time were better in the PCT group than in the CBT group. At the 3-month follow-up, subjective and objective sleep-onset latency, sleep efficacy and total sleep time were better in the CBT group than in both the PCT and the Combined group. At the 8-month follow-up, the CBT group showed a steady comfortable sleep state, while the PCT and Combined groups were gradually returning to the pre-treatment condition. The Combined group showed a variable long-term effect. On the other hand, pre-sleep arousal at nighttime, dysfunctional beliefs about sleep as well as daytime functioning in the CBT group not only improved, but was better than in the other active treatment groups. CONCLUSION: Medication and Combined therapy produced a short-term effect on chronic insomnia while CBT had a long-term effect of improved sleep-related psychological activity and daytime functioning.

Adult↗
PubMed2002

Infant sleep placement after the back to sleep campaign.

OBJECTIVES: The Back to Sleep campaign has been credited with recent declines in the incidence of sudden infant death syndrome. Using survey data for the 1996-1998 birth cohorts, this epidemiologic study examines infant sleep position in a large, population-based sample. DATA AND METHODS: Data concerning infant sleep position are drawn from the 1996-1998 Pregnancy Risk Assessment Monitoring System for 15 states. Weighted multiple logistic regression analysis is used to examine correlates of infant sleep position. RESULTS: The prevalence of prone infant sleeping significantly declined between 1996 and 1998 (adjusted odds ratio [AOR] = 0.70; 95% confidence interval [CI] = [0.63, 0.78]). African Americans were more likely than non-Hispanic whites to sleep prone, (AOR = 1.45; 95% CI = 1.33,1.59), and were less likely to sleep supine (AOR = 0.52; 95% CI = 0.48, 0.57). Hispanic/Latinos were less likely overall than non-Hispanic whites to sleep prone (AOR = 0.81; 95% CI = 0.69, 0.95), but were also less likely to sleep supine (AOR = 0.78; 95% CI = 0.69, 0.87). Adherence to sleep position recommended by the American Academy of Pediatrics increased sharply among Hispanic/Latino infants. Very low birth weight infants and infants in larger families were less likely to sleep in the recommended supine position. Infants born between 1001 and 1500 g (AOR = 0.67; 95% CI = 0.57, 0.79), and extremely low birth weight infants between 500 and 1000 g (AOR = 0.57; 95% CI = 0.45, 0.72) were especially unlikely to sleep supine. Infants in households with more than 3 other children (AOR = 1.72; 95% CI = 1.08, 2.74) were more likely to sleep prone. CONCLUSIONS: The prevalence of supine infant sleep increased between 1996 and 1998. Low adherence to sleep position recommendations of the American Academy of Pediatrics among African Americans, very low birth weight infants, and infants in large families remain public health concerns.

Black or African American↗
PubMed2004

Influence of sleep position experience on ability of prone-sleeping infants to escape from asphyxiating microenvironments by changing head position.

OBJECTIVE: Several studies have found that back- or side-sleeping infants who are inexperienced in prone sleeping are at much higher risk for sudden infant death syndrome (SIDS) when they turn to prone or are placed prone for sleep compared with infants who normally sleep prone. Moreover, such inexperienced infants are more likely to be found in the face-down position at death after being placed prone compared with SIDS infants who are experienced in prone sleeping. We hypothesized that lack of experience in prone sleeping is associated with increased difficulty in changing head position to avoid an asphyxiating sleep environment. METHODS: We studied 38 healthy infants while they slept prone. Half of these were experienced and half were inexperienced in prone sleeping. To create a mildly asphyxiating microenvironment, we placed infants to sleep prone with their faces covered by soft bedding. We recorded inspired CO2 (CO2I), electrocardiogram, and respiration, and we videotaped head movements. Also, we assessed gross motor development (Denver Development Scale). RESULTS: When sleeping prone, with their faces covered by bedding, all infants experienced mild asphyxia as a result of rebreathing. All aroused and attempted escape from this environment. Infants used 3 stereotyped head-repositioning strategies. The least effective was nuzzling into the bedding with occasional brief head lifts. More effective were head lifts combined with a head turn. Some infants, however, could turn only to 1 side, right or left. Infants who were inexperienced in prone sleeping had less effective protective behaviors than experienced infants. Infant age did not correlate with efficacy of protective behaviors. Infants who were experienced in prone sleep had advanced gross motor development compared with inexperienced infants. CONCLUSION: Infants who are inexperienced in prone sleeping have decreased ability to escape from asphyxiating sleep environments when placed prone. These observations potentially explain the increased risk associated with prone sleep in infants who are inexperienced. The increased occurrence of the face-down position in such infants is also potentially explained. These findings suggest that airway protective behaviors may be acquired through the mechanism of operant conditioning (learning).

Aging↗
PubMedDate not supplied

[Subjective sleep quality and spectral analysis of electroencephalography during nocturnal sleep].

INTRODUCTION: The relation between subjective sleep quality and the stages of polysomnography is unclear. Computerized sleep analysis provides a reliable tool for the study of sleep dynamics. OBJECTIVE: To study the relation between subjective sleep quality and spectral EEG parameters during nocturnal sleep. MATERIAL AND METHODS: Nocturnal sleep were recorded ambulatory in 26 subjects aged from 8 to 63. The following variables were extracted from EEG signal (Fz-Pz) quantified through the Fast Fourier Transformation (FFT): delta maximum, spectral peak, delta sleep time, efficiency and desynchronized sleep. A sleep diary was administered in the morning to assess the subjective sleep quality. Multiple regression and Anova were used for statistical analysis. RESULTS: Efficiency and delta maximum became significant predictors accounting for 54% of subjective sleep variance. The item 'how was your sleep?' was answered in a different way according to the delta maximum. CONCLUSIONS: Sleep depth, measured by spectral analysis, is an important predictor of the subjective sleep quality. The sleep classification in discrete stages ignores this feature.

Adolescent↗
PubMed2001

Gender and sleep in nightworkers: a quantitative analysis of sleep in days off.

Differences in sleep patterns between workdays and days off contribute to shiftwork effects on workers' health and well-being. But regardless of shift schedules, female workers face more difficulties in fulfilling their sleep need because of housework. This study analyzes gender differences concerning sleep in days off by comparing sleep patterns in male and female nightworkers, analyzing sleep as related to the presence of children and testing the association of sleep features between workdays and days off. Male (n = 16) and female (n = 30) workers at a plastic plant, working from 10 p.m. to 6 a.m., on weekdays, filled sleep logs for seven consecutive weeks. Male and female samples did not differ in length of night sleep or in total length of sleep. For both samples, sleep length/day in days off increased, but the difference was lager among females. Also important were the relations between sleep in workdays and days off, specially among women. Among female workers, the results indicated that workers with children tended to sleep less in Saturday mornings, suggesting a negative effect of motherhood on sleep not restricted to workdays. The general results indicate that sleep need on the one hand, and social factors on the other determine the actual amount of sleep.

Adult↗
PubMed1976

Effects of selective sleep deprivation on sleep-linked prolactin and growth hormone secretion.

1. The secretion of prolactin and growth-hormone (hGH) was investigated during sleep in 10 healthy volunteers (8 males and 2 females): The comparison of one baseline night, one night after daytime physical exercise, and one night with selective deprivation of sleep stages 3 and 4 and paradoxical sleep showed clear differences of prolactin and hGH secretion during sleep. 2. Prolactin secretion is entrained into the sleep cycle of Non-REM and REM periods. A maximum of plasma hormone elevations occurs during the first quarter of sleep cycles, i.e., during Non-REM periods and less frequent rises at the end of the cycles, mainly during REM periods. 3. In contrast to growth hormone, concentrations of prolactin remain high also during later cycles occurring toward morning. This shows that high prolactin, but not high concentrations of hGH, regularly occur during sleep cycles with small amounts of slow-wave sleep. 4. Maximal prolactin concentrations during sleep are affected neither by preceding daytime physical exercise nor by selective deprivation of slow sleep stages 3 and 4. This is further evidence that slow-wave sleep stages are not necessary for the development of high plasma prolactin concentrations. However, peak values of growth hormone in the first and second cycle are significantly diminished after selective deprivation of sleep stages 3 and 4. 5. In abnormally long sleep cycles with artificial delay of the first REM period, the cyclical rhythmicity of prolactin release seems disturbed. This is further evidence for the sleep-dependent rhythmicity in the secretion of this hormone.

Adult↗
PubMed1989

Administration of triazolam prior to recovery sleep: effects on sleep architecture, subsequent alertness and performance.

The effects of triazolam (0.125, 0.25, and 0.5 mg) versus placebo on recovery sleep staging, subsequent alertness and psychomotor performance were evaluated in humans. Forty-five healthy male subjects were deprived of sleep for 24 h, then administered a single dose of triazolam or placebo using a double-blind procedure. Subjects then attempted to obtain recovery sleep under non-sleep-conducive conditions (sitting upright in a well-lit, crowded chamber) for the next 6 h, followed by 18 more hours of sleep deprivation. During all sleep deprivation periods subjects were tested bihourly on a performance assessment battery which included symbol digit modalities tests (SDMT), four-letter search (FLS), logical reasoning (LR), time estimation (TE), visual vigilance (VV), and short term memory (STM) tasks. Sleepiness levels were measured objectively with multiple sleep latency tests (MSLT) and subjectively with the Stanford Sleepiness Scale (SSS). Compared to placebo, all doses of triazolam resulted in increased amounts of stage 3-4 sleep, and the 0.5 mg dose significantly reduced awakenings (Ps less than 0.05). Although subjects receiving triazolam averaged 21-42 min more total sleep time (TST) than subjects receiving placebo, differences in TST were not statistically significant. Apparent triazolam-mediated benefits to sleep quality resulted in no obvious improvements in performance or alertness levels during subsequent sleep deprivation. It was concluded that the increases in stage 3-4 sleep amounts were most likely due to triazolam-mediated increases arousal thresholds, and the triazolam mediated changes in sleep parameters obtained in the present study were not indicative of substantial changes in the recuperative value of sleep.

Adolescent↗
PubMed1986

Vasoactive intestinal polypeptide (VIP) and cerebrospinal fluid (CSF) of sleep-deprived cats restores REM sleep in insomniac recipients.

In the past few years a steadily increasing number of substances have been suggested to qualify as sleep-inducing factors. Most 'sleep factors' appear to exert their effects on slow-wave sleep. Recently, however, it has been shown that the cerebrospinal fluid (CSF) of sleep-deprived cats may contain a rapid eye movement (REM) sleep factor, and that vasoactive intestinal peptide (VIP) may be a specific REM sleep inducer. The purpose of this study is to determine whether the CSF of sleep-deprived cats and VIP can reverse insomnia produced by parachlorophenylalanine (PCPA). Donor cats were sleep-deprived for 24 h and their CSF extracted. Some donor cats were additionally pre-treated with chloramphenicol, and some extracted CSF was heated. Recipient cats were injected with 400 mg/kg i.p. of PCPA on two consecutive days. Twenty-four h after the second injection, the recipient cats were intraventricularly injected with a 100-microliters of the various CSF types or 200 ng of VIP. The results showed that only CSF from sleep-deprived cats and VIP were capable of restoring REM sleep in the otherwise PCPA insomniac cats. Since the return of REM sleep was through an increase in its frequency, it is suggested that the CSF of sleep-deprived cats contains a VIP-like sleep factor possibly involved in triggering REM sleep.

Animals↗
PubMed2003

Sleep architecture in normal Caucasian and Hispanic children aged 6-11 years recorded during unattended home polysomnography: experience from the Tucson Children's Assessment of Sleep Apnea Study (TuCASA).

OBJECTIVE: To obtain normative sleep architecture data from unattended home polysomnography in Caucasian and Hispanic children aged 6-11 years. DESIGN AND SUBJECTS: Unattended home polysomnography was performed on a single night in Caucasian and Hispanic children aged 6-11 years as part of the Tucson Children's Assessment of Sleep Apnea Study (TuCASA), a cohort study designed to examine the prevalence and correlates of sleep disordered breathing. A subset of 42 children enrolled in TuCASA who had no symptoms of any sleep disorder and had polysomnograms without technical recording problems. RESULTS: Sleep architecture in preadolescent Caucasian and Hispanic children was not different between boys and girls. However, total sleep time (TST), sleep efficiency (SLE) and time spent in REM sleep declined with increasing age. In addition, the number of sleep to wake stage shifts was slightly higher in younger children. Hispanic children had less Stage 3/4 sleep (18+/-1 vs. 22+/-1%, P</=0.02) and correspondingly more Stage 2 sleep (55+/-2 vs. 50.0+/-1%, P</=0.02) than their Caucasian counterparts. CONCLUSIONS: Using unattended home polysomnography, indices of sleep duration and architecture are not different between preadolescent boys and girls. However, with increasing age, TST and SLE decreased. In addition, there are differences in sleep architecture between Caucasians and Hispanics, which may be an important consideration in the evaluation of children with sleep disorders.

Child↗
PubMed1996

Late-afternoon ethanol intake affects nocturnal sleep and the sleep EEG in middle-aged men.

The effect of a moderate dose of ethanol (0.55 g/kg of body weight), administered 6 hours before scheduled bedtime, on performance, nocturnal sleep, and the sleep electroencephalogram (EEG) was investigated in 10 healthy, middle-aged men (mean age: 61.6 +/- 0.9 years). By the beginning of the sleep episode, breath-ethanol concentrations had declined to zero in all subjects. Compared with the control condition (mineral water), sleep was perceived as more superficial. Sleep efficiency, total sleep time, stage 1, and rapid eye movement (REM) sleep were reduced. In the second half of the sleep episode, wakefulness exhibited a twofold increase. EEG power density in low delta frequencies was enhanced in non-REM sleep (1.25-2.5 Hz) and REM sleep (1.25-1.5 Hz). In slow wave sleep (i.e., stages 3 + 4), power density was increased not only in the low-frequency range (1.25-1.5, 2.25-4.0, 4.75-5.0 Hz) but also within the alpha (8.25-9.0 Hz) and sigma (12.25-13.0 Hz) band. The data demonstrate that late-afternoon ethanol intake in middle-aged men disrupts sleep consolidation, affects the sleep stage distribution, and alters the sleep EEG.

Caffeine↗
PubMed1996

The differences of self-ratings of sleep quality associated with epinephrine and wake time during 4 hour sleep.

The present study examined the differences of self-ratings of 4 h sleep in three states: L-WE, where the percentage of waking time and urinary epinephrine are low (< 20% waking time); H-W, where the percentage of waking time and epinephrine levels increase along the basal regression line as determined by a previous study (20-100% waking time and < 7 ng/min); H-E, where epinephrine levels increase more than expected from the basal regression line for the two parameters (> 7 ng/min). Eight healthy male subjects participated twice in a 4 h polysomnograph experiment with four types of sleep onset (total of 64 observations). In group L-WE (52 observations for eight subjects), there were no excessively negative feelings on sleep latency, sleep depth, and feelings of sleep compared with usual sleep according to the questionnaire. Subjective sleep diagrams in group L-WE were similar to polysomnographic findings. Thus, group L-WE was thought objectively and subjectively to have a good sleep state. Groups H-W (eight observations for four subjects) and H-E (four observations for two subjects) had negative feelings regarding sleep depth and feelings of sleep compared with usual sleep. Approximately half the group H-W underrated their sleep compared with objective diagrams, while all cases in group H-E remarkably underrated their sleep in the subjective diagrams. The state of remarkable adrenal medullary secretory activity seen in group H-E and that of the slightly increased activity shown in group H-W were included in poor sleep states objectively and subjectively.

Adrenal Medulla↗
PubMed1990

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.

Adult↗
PubMed2006

Impaired performance in commercial drivers: role of sleep apnea and short sleep duration.

Sleepiness plays an important role in major crashes of commercial vehicles. Because determinants are likely to include inadequate sleep and sleep apnea, we evaluated the role of short sleep durations over 1 wk at home and sleep apnea in subjective sleepiness (Epworth Sleepiness Scale), objective sleepiness (reduced sleep latency as determined by the Multiple Sleep Latency Test), and neurobehavioral functioning (lapses in performance, tracking error in Divided Attention Driving Task) in commercial drivers. Studies were conducted in 247 of 551 drivers at higher risk for apnea and in 159 of 778 drivers at lower risk. A multivariate linear association between the sets of outcomes and risk factors was confirmed (p < 0.0001). Increases in subjective sleepiness were associated with shorter sleep durations but not with increases in severity of apnea. Increases in objective sleepiness and performance lapses, as well as poorer lane tracking, were associated with shorter sleep durations. Associations with sleep apnea severity were not as robust and not strictly monotonic. A significant linear association with sleep apnea was demonstrated only for reduced sleep latency. The effects of severe apnea (apnea-hypopnea index, at least 30 episodes/h), which occurred in 4.7%, and of sleep duration less than 5 h/night, which occurred in 13.5%, were similar in terms of their impact on objective sleepiness. Thus, addressing impairment in commercial drivers requires addressing both insufficient sleep and sleep apnea, the former being more common.

Automobile Driving↗
PubMed2004

Sleep of excessively crying infants: a 24-Hour Ambulatory Sleep Polygraphy study.

OBJECTIVE: Parents' reports suggest that excessively crying or colicky infants sleep less compared with control subjects. The aim of this study was to determine the sleep-wake structure of excessively crying infants throughout a 24-hour cycle. METHODS: A 24-hour sleep polygraphy study was conducted at home for 24 excessively crying infants and 23 control subjects at the age of 6 weeks. In addition, parental diaries were kept for 4 days. RESULTS: In sleep polygraphy recordings, no major differences between study groups were observed in either the duration or the structure of the 24-hour sleep. In the diaries, the parents overestimated the amount of sleep in both study groups. The parents of the control infants overestimated the amount of sleep more than the parents of excessively crying infants (69.8 minutes [standard deviation: 79.3] compared with 27.1 minutes [standard deviation: 65.4], respectively). In excessively crying infants, the proportion of rapid eye movement sleep was higher during the 3-hour period from the beginning of the first long sleep in the evening and lower during the preceding 3-hour period compared with the control group. CONCLUSIONS: The results of this study suggest that diary-based studies are prone to be biased as the parents of the control infants are more likely to overestimate the amount of infant's sleep and, therefore, report more sleep than the parents of the crying infants. Although no differences in the total amount of sleep or proportions of sleep stages were observed, excessively crying infants may be characterized by a disturbance that affects rapid eye movement and non-rapid eye movement sleep stage proportion during evening hours.

Case-Control Studies↗
PubMed1986

Endogenous sleep-substances and sleep regulation.

In the search for endogenous sleep substances two approaches can be distinguished. The homeostatic approach assumes that the sleep substance accumulates during waking and dissipates during sleep. Sleep deprivation has been the principal tool for enhancing the level of a sleep substance in a donor animal before testing its hypnogenic effect in a recipient animal. Among the two sleep factors isolated by this approach, Factor S has been identified as a muramyl peptide, whereas the composition of Sleep Promoting Substance (SPS) has not yet been fully clarified. Recently, factors have been obtained from REM sleep deprived donors which are able to antagonize drug-induced REM sleep suppression in recipients. The homeostatic approach can be related to physiological processes underlying sleep homeostasis and circadian rhythms. The non-homeostatic approach to sleep substances is based on the serendipitous discovery of a hypnogenic action. While a number of such substances have been described, their relationship to physiological sleep regulation is unknown. Melatonin has been reported to induce or enhance sleep in animals and man. However, the doses used in human studies raise the plasma level far beyond the physiological range. Melatonin may influence circadian processes regulating sleep propensity.

Animals↗
PubMed2001

Comparison of actigraphic, polysomnographic, and subjective assessment of sleep parameters in sleep-disordered patients.

OBJECTIVE: Comparison of polysomnography (PSG)-derived sleep parameters (total sleep time, sleep efficiency, and number of awakenings) to those derived from actigraphy and subjective questionnaires. BACKGROUND: Actigraphy is commonly used to assist sleep specialists in the diagnosis of various sleep and circadian-rhythm disorders. However, few validation studies incorporate large sample sizes, typical sleep clinic patients, or comparisons with subjective reports of sleep parameters. METHODS: Clinical series with 100 consecutive sleep-disordered patients (69 men, 31 women, mean age of 49+/-14.7 years) at a tertiary sleep disorders center. Sensitivity, specificity, and accuracy measures were obtained from epoch-by-epoch comparison of PSG and actigraphic data. Subjective sleep parameter data were derived from questionnaires given to subjects in the morning following their recording night. RESULTS: We found that total sleep time and sleep efficiency did not significantly differ between PSG data and the combined data obtained from actigraphy and subjective reports. Using a high-threshold (low-wake-sensitivity) actigraphic algorithm, the number of awakenings was not significantly different from those detected by PSG. CONCLUSIONS: We recommend the use of subjective data as an adjunct to actigraphic data in estimating total sleep time and sleep efficiency in sleep-disordered patients, especially those with disorders of excessive somnolence.

Journal Article↗
PubMed2005

Can an inert sleeping pill affect sleep? Effects on polysomnographic, behavioral and subjective measures.

RATIONALE: Since two recent meta-analyses on sleep changes associated with placebo in clinical trials suggested a beneficial effect of placebo treatments, pointing to a dissociation between subjective and objective measures of sleep, the current experiment was directly aimed to assess the effects of an inert compound, administered with the suggestion that it was a hypnotic substance in subjects with mild sleep complaints. OBJECTIVES: The aim of this study was to compare subjective, behavioral, polysomnographic (PSG), and quantitative electroencephalographic (EEG) changes during a night preceded or not by the intake of two 50-mg lactose capsules. METHODS: Ten female students, selected by the Pittsburgh Sleep Quality Index, slept for three consecutive nights in a sleep laboratory, with the experimental (EXP) night defined by the administration of two 50-mg lactose pills. Self-ratings of sleep quality and performance were assessed upon morning awakening of baseline (BSL) and EXP nights. RESULTS: The EXP nights were self-rated as more restful and characterized by a decreased number of nocturnal awakenings than the BSL nights. PSG measures showed that wakefulness after sleep onset significantly decreased during the EXP night as compared to the BSL night. The EXP nights also showed an increase of 0.5-4.0 Hz power during nonrapid eye movement sleep and a decrease of EEG activity in the beta frequency range during rapid eye movement sleep only at central brain sites. A specific improvement of behavioral measures was also found upon morning awakening after the EXP night compared to the BSL night. CONCLUSIONS: The administration of an inert pill improves both the subjective and objective quality of sleep. The reduced sleep fragmentation and the effects on some quantitative EEG markers of sleep homeostasis suggest that the experimental manipulation induced coherent changes in the subsequent sleep, resembling an enhancement of sleep pressure. The regional differences of EEG activity suggest the involvement of a specific physiological mechanism distinct from that of effective treatments.

Adult↗