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1.  Efficacy and hypnotic effects of melatonin in shift-work nurses: double-blind, placebo-controlled crossover trial 
Night work is associated with disturbed sleep and wakefulness, particularly in relation to the night shift. Circadian rhythm sleep disorders are characterized by complaints of insomnia and excessive daytime sleepiness that are primarily due to alterations in the internal circadian timing system or a misalignment between the timing of sleep and the 24-h social and physical environment.
We evaluated the effect of oral intake of 5 mg melatonin taken 30 minutes before night time sleep on insomnia parameters as well as subjective sleep onset latency, number of awakenings, and duration of sleep. A double-blind, randomized, placebo-controlled crossover study with periods of 1 night and washouts of 4 days comparing melatonin with placebo tablets was conducted. We tried to improve night-time sleep during recovery from night work. Participants were 86 shift-worker nurses aged 24 to 46 years. Each participant completed a questionnaire immediately after awakening.
Sleep onset latency was significantly reduced while subjects were taking melatonin as compared with both placebo and baseline. There was no evidence that melatonin altered total sleep time (as compared with baseline total sleep time). No adverse effects of melatonin were noted during the treatment period.
Melatonin may be an effective treatment for shift workers with difficulty falling asleep.
PMCID: PMC2584099  PMID: 18957133
2.  Sleep Disturbances and Frailty Status in Older Community-Dwelling Men 
Test the hypothesis that sleep disturbances are independently associated with greater evidence of frailty in older men.
Cross-sectional analysis of prospective cohort study
Six U.S. centers
3133 men ≥67 years
Self reported sleep parameters (questionnaire); objective parameters of sleep wake patterns (actigraphy data collected for an average of 5.2 nights); and objective parameters of sleep disordered breathing, nocturnal hypoxemia, and periodic leg movements with arousals (PLMA) (in-home overnight polysomnography). Frailty status classified as robust, intermediate stage or frail using criteria similar to those used in the Cardiovascular Health Study frailty index.
The prevalence of sleep disturbances including poor sleep quality, excessive daytime sleepiness, short sleep duration, reduced sleep efficiency, prolonged sleep latency, sleep fragmentation (greater nighttime wakefulness and frequent long wake episodes), sleep disordered breathing, nocturnal hypoxemia and frequent PLMA was lowest among robust men, intermediate among men in the intermediate stage group, and highest among frail men (p-for-trend ≤0.002 for all sleep parameters). After adjusting for multiple potential confounders, self-reported poor sleep quality (Pittsburgh Sleep Quality Index <5, multivariable odds ratio (MOR) 1.28, 95%CI 1.09–1.50), sleep efficiency <70% (MOR 1.37, 95% CI 1.12–1.67), sleep latency ≥60 minutes (MOR 1.42, 95% CI 1.10–1.82), and sleep disordered breathing (respiratory disturbance index ≥15, MOR 1.38, 95% CI 1.15–1.65) were each independently associated with an increased odds of greater frailty status.
Sleep disturbances including poor self-reported sleep quality, reduced sleep efficiency, prolonged sleep latency and sleep disordered breathing are independently associated with greater evidence of frailty.
PMCID: PMC3024909  PMID: 19793160
sleep disturbances; frailty; aging
3.  A comparison of idiopathic hypersomnia and narcolepsy-cataplexy using self report measures and sleep diary data. 
Eighteen patients with idiopathic hypersomnia (IH) were compared with 50 patients with the narcoleptic syndrome of cataplexy and daytime sleepiness (NLS) using self report questionnaires and a diary of sleep/wake patterns. The IH group reported more consolidated nocturnal sleep, a lower propensity to nap, greater refreshment after naps, and a greater improvement in excessive daytime sleepiness since onset than the NLS group. In IH, the onset of excessive daytime sleepiness was predominantly associated with familial inheritance or a viral illness. Two variable--number of reported awakenings during nocturnal sleep and the reported change in sleepiness since onset--provided maximum discrimination between the IH and NLS groups. Confusional arousals, extended naps or nocturnal sleep, autonomic nervous system dysfunction, low ratings of medication effectiveness, or side effects of medication were not associated differentially with either IH or NLS.
PMCID: PMC486375  PMID: 8778267
4.  Self-reported Sleep Complaints With Long and Short Sleep: A Nationally Representative Sample 
Psychosomatic medicine  2004;66(2):239-241.
Although the problems associated with insufficient sleep have been thoroughly researched, there has been far less substantiation of problems associated with long sleep. Recent evidence shows that habitual sleep duration greater than 7 hours is associated with increased rates of mortality. This study compared the rates of sleep problems in both long and short sleepers.
Self-reported sleep complaints (eg, sleep onset latency, awakenings during the night, early morning awakenings, nonrestorative sleep, and daytime sleepiness) of nearly 1000 adults who participated in the National Sleep Foundation’s 2001 Sleep in America Poll, were compared with reported hours of weekday sleep.
There are U-shaped relationships of sleep complaints with reported weekday total sleep time. More specifically, 8-hour sleepers reported less frequent symptoms than long sleepers or 7-hour sleepers.
Thus, long sleepers, as well as short sleepers, report sleep problems, focusing attention to the often-overlooked problems of the long sleeper.
PMCID: PMC3687531  PMID: 15039509
sleep; sleep disorders; Long Sleeper Syndrome; Short Sleeper Syndrome; insomnia
5.  Sleep Deficiency and Sleep Health Problems in Chinese Adolescents 
A survey of sleep schedules, sleep health, and the impact on school performance was conducted in 585 adolescents in a high school in China. A high level of early and circadian-disadvantaged sleep/wake schedules during weekdays was observed. Significantly shorter sleep duration on weekdays was reported (P < 0.0001). Older teenagers slept significantly less than the younger teenagers (P < 0.0001). Complaints of inadequate sleep and sleepiness during weekdays were prevalent. Night awakenings were reported in 32.2% of students. Students with a sleep length of less than 7 hours, complaint of inadequate sleep, or excessive daytime sleepiness during weekdays were more likely to report an adverse effect of poor sleep on performance. The present observations are qualitatively similar to those reported in our study in American adolescents, particularly with respect to Chinese adolescents exhibiting a similar sleep deficiency on weekdays. We concluded that sleep deficiency and sleep health problems were prevalent in the participating adolescents in China, and were perceived to adversely affect school performance.
PMCID: PMC3620771  PMID: 23641162
sleep deprivation; sleep health problem; adolescents; school performance
Journal of biological rhythms  2009;24(4):313-321.
Delayed sleep phase syndrome (DSPS) is a circadian rhythm sleep disorder in which the timing of the sleep episode occurs later than desired and is associated with difficulty falling asleep, problems awakening on time (e.g., to meet work or school obligations), and daytime sleepiness. The phase relationship between the timing of sleep and endogenous circadian rhythms is critical to the initiation and maintenance of sleep, and significant alteration leads to impairment of sleep quality and duration. The aim of this retrospective study was to determine the phase relationship between sleep-wake times and physiological markers of circadian timing in clinic patients with DSPS. Objective and subjective measures of sleep timing and circadian phase markers (core body temperature and melatonin) were measured in patients with DSPS and compared with age-matched controls. As expected, significant delays in the timing of the major sleep episode and circadian phase of body temperature and melatonin rhythms were seen in the DSPS group when allowed to sleep at their own habitual schedules, but the phase relationship between sleep-wake times and circadian phase was similar between the two groups. These results suggest that the symptoms of insomnia and excessive daytime sleepiness in DSPS patients living under entrained real-life conditions cannot be explained by an alteration in the phase relationship between sleep-wake patterns and other physiological circadian rhythms.
PMCID: PMC3689431  PMID: 19625733
DSPS; circadian rhythm sleep disorder; circadian phase; circadian phase angle
7.  Actual and Perceived Sleep: Associations with Daytime Functioning among Postpartum Women 
Physiology & behavior  2010;102(2):234-238.
Sleep and wake have a homeostatic relation that influences most aspects of physiology and waking behavior. Sleep disturbance has a detrimental effect on sleepiness and psychomotor vigilance. The purpose of this study was to identify which actual or perceived sleep characteristics accounted for the most variance in daytime functioning among postpartum mothers. Seventy first-time postpartum mothers' actual sleep (actigraphically estimated: total sleep time, number of wake bouts, length of nocturnal wake, and sleep efficiency) and perceived sleep (self-reported: number of awakenings, wake time, and sleep quality) was measured along with their daytime functioning (Stanford Sleepiness Scale [SSS], Epworth Sleepiness Scale [ESS], Visual Analogue of Fatigue Scale [VAFS], and morning Psychomotor Vigilance Test [PVT]). Data were repeatedly collected from the same sample during postpartum weeks 2, 7, and 13. Four stepwise linear regressions were calculated for each postpartum week to examine which objective and/or subjective variable(s) accounted for the most variance in daytime functioning. The SSS and VAFS were both most consistently associated with perceived sleep quality. The ESS was most consistently associated with actual total sleep time. PVT performance was most consistently associated with estimates of actual and perceived sleep efficiency. Actual and perceived sleep profiles were differentially associated with specific daytime functions. These results from postpartum mothers may indicate that populations who experience specific forms of sleep disturbance (e.g. fragmentation, deprivation) may also experience specific daytime conditions.
PMCID: PMC3010463  PMID: 21095200
Actual; actigraphy; subjective; objective; perceived; sleep; sleepiness; fatigue; performance; behavior; postpartum; maternal
8.  Sleep architecture and sleep-related mentation in securely and insecurely attached people 
Attachment & human development  2011;13(2):141-154.
Based on REM sleep’s brain activation patterns and its participation in consolidation of emotional memories, we tested the hypothesis that measures of REM sleep architecture and REM sleep-related mentation would be associated with attachment orientation. After a habituation night in a sleep lab, a convenience sample of 64 healthy volunteers were awakened 10 minutes into a REM sleep episode and 10 minutes into a control NREM sleep episode in counterbalanced order, then asked to report a dream and to rate themselves and a significant other on a list of trait adjectives. Relative to participants classified as having secure attachment orientations, participants classified as anxious took less time to enter REM sleep and had a higher frequency of REM dreams with aggression and self-denigrating themes. There were no significant differences across attachment groups in other measures of sleep architecture or in post REM-sleep awakening ratings on PANAS subscales reflecting mood and alertness. Selected aspects of REM sleep architecture and mentation appeared to be associated with attachment orientation. We suggest that REM sleep plays a role in processing experiences and emotions related to attachment, and that certain features of sleep and dreaming reflect attachment orientations.
PMCID: PMC3060050  PMID: 21390907
REM sleep; NREM sleep; REM latency; attachment status; dreams; mood
9.  DQB1*0602 predicts interindividual differences in physiologic sleep, sleepiness, and fatigue 
Neurology  2010;75(17):1509-1519.
The human leukocyte antigen (HLA) DQB1*0602 allele is closely associated with narcolepsy, a neurologic disorder characterized by excessive daytime sleepiness, fragmented sleep, and shortened REM sleep latency. We evaluated whether DQB1*0602 was a novel marker of interindividual differences by determining its relationship to sleep homeostatic, sleepiness, and cognitive responses to baseline and chronic partial sleep deprivation (PSD) conditions.
Ninety-two DQB1*0602-negative and 37 DQB1*0602-positive healthy adults participated in a protocol of 2 baseline 10 hours time in bed (TIB) nights followed by 5 consecutive 4 hours TIB nights. DQB1*0602 allelic frequencies did not differ significantly between Caucasians and African Americans.
During baseline, although DQB1*0602-positive subjects were subjectively sleepier and more fatigued, they showed greater sleep fragmentation, and decreased sleep homeostatic pressure and differentially sharper declines during the night (measured by non-REM EEG slow-wave energy [SWE]). During PSD, DQB1*0602-positive subjects were sleepier and showed more fragmented sleep, despite SWE elevation comparable to negative subjects. Moreover, they showed differentially greater REM sleep latency reductions and smaller stage 2 reductions, along with differentially greater increases in fatigue. Both groups demonstrated comparable cumulative decreases in cognitive performance.
DQB1*0602 positivity in a healthy population may represent a continuum of some sleep–wake features of narcolepsy. DQB1*0602 was associated with interindividual differences in sleep homeostasis, physiologic sleep, sleepiness, and fatigue—but not in cognitive measures—during baseline and chronic PSD. Thus, DQB1*0602 may represent a genetic biomarker for predicting such individual differences in basal and sleep loss conditions.
= analysis of variance;
= Controlled Oral Word Association Test;
= Digit Span;
= Digit Symbol Substitution Task;
= human leukocyte antigen;
= Karolinska Sleepiness Scale;
= Maintenance of Wakefulness Test;
= Profile of Mood States;
= partial sleep deprivation;
= polysomnography;
= Psychomotor Vigilance Task;
= sleep onset latency;
= sleep deprivation/restriction;
= slow-wave activity;
= slow-wave energy;
= time in bed;
= Tower of London;
= total sleep deprivation;
= visual analog scale;
= wake after sleep onset.
PMCID: PMC2974463  PMID: 20975052
10.  Gender difference in the effect of daytime sleep on declarative memory for pictures*  
Objective: To investigate gender difference in the effects of daytime sleep on item and source memories, which are dissociable elements of declarative memory, and the effects of sleep on recollection and familiarity, which are two processes underlying recognition. Methods: Participants saw a series of pictures with either blue or red background, and were then given a pretest for item and source memories. Then males and females respectively were randomly assigned either to a wake or a sleep condition. In the wake condition, participants remained awake until the posttest; in the sleep condition, participants slept for 1 h until awakened and asked to remain awake until the posttest. Results: Daytime sleep contributed to retention of source memory rather than item memory in females, whereas males undergoing daytime sleep had a trend towards increased familiarity. For females, however, neither recollection nor familiarity appeared to be influenced by daytime sleep. Conclusion: The mechanism underlying gender difference may be linked with different memory traces resulting from different encoding strategies, as well as with different electrophysiological changes during daytime sleep.
PMCID: PMC2704972  PMID: 19585672
Gender difference; Declarative memory; Recollection; Familiarity; Daytime sleep
11.  A Longitudinal Study of Depression, Pain, and Stress as Predictors of Sleep Disturbance among Women with Metastatic Breast Cancer 
Biological psychology  2006;75(1):37-44.
Sleep disturbances are common among women with breast cancer and can have serious consequences. The present study examined depression, pain, life stress, and participation in group therapy in relation to sleep disturbances in a sample of women with metastatic breast cancer.
Ninety-three women with metastatic breast cancer participated in a large intervention trial examining the effect of the group therapy on their symptoms. They completed measures of depression, pain, life stress, and sleep disturbance at baseline, 4, 8 and 12 months.
The results showed that higher initial levels of depression at baseline predicted problems associated with getting up in the morning, waking up during the night, and daytime sleepiness. Increases in depression over the course of 12 months were associated with fewer hours of sleep, more problems with waking up during the night and more daytime sleepiness. Higher levels of pain at baseline predicted more problems getting to sleep. Increases in pain predicted more difficulty getting to sleep and more problems waking up during the night. Greater life stress at baseline predicted more problems getting to sleep and more daytime sleepiness.
Depression, pain, and life stress scores were each associated with different types of negative change in self-reported sleep disturbances. Depression, especially worsening depression, was associated with the greatest number of types of negative change. The relationships found between sleep disturbance and depression, pain, and life stress suggest specific ways to address the problem of sleep disturbance for women with metastatic breast cancer and show how different types of disturbed sleep may be clinical markers for depression, pain, or life stress in this population.
PMCID: PMC1894689  PMID: 17166646
sleep disturbance; metastatic breast cancer; pain; depression; stressful life events
12.  Disease and Degeneration of Aging Neural Systems that Integrate Sleep Drive and Circadian Oscillations 
Sleep/wake and circadian rest-activity rhythms become irregular with age. Typical outcomes include fragmented sleep during the night, advanced sleep phase syndrome and increased daytime sleepiness. These changes lead to a reduction in the quality of life due to cognitive impairments and emotional stress. More importantly, severely disrupted sleep and circadian rhythms have been associated with an increase in disease susceptibility. Additionally, many of the same brain areas affected by neurodegenerative diseases include the sleep and wake promoting systems. Any advances in our knowledge of these sleep/wake and circadian networks are necessary to target neural areas or connections for therapy. This review will discuss research that uses molecular, behavioral, genetic and anatomical methods to further our understanding of the interaction of these systems.
PMCID: PMC3199684  PMID: 22028699
aging; neurodegenerative; sleep; wake; circadian; disease
13.  The impact of a week of simulated night work on sleep, circadian phase, and performance 
Methods: Fifteen healthy subjects participated in an adaptation and baseline night sleep, directly followed by seven simulated eight-hour night shifts (2300 to 0700 hours). At the end of each shift they were taken outside and exposed to natural light for 20 minutes. They then slept from approximately 0800 hours until they naturally awoke.
Results: There was a significant increase in mean performance on a visual psychomotor vigilance task across the week. Daytime sleep quality and quantity were not negatively affected. Total sleep time (TST) for each of the daytime sleeps was reduced, resulting in an average cumulative sleep debt of 3.53 hours prior to the final night shift. TST for each of the daytime sleep periods did not significantly differ from the baseline night, nor did TST significantly vary across the week. There was a significant decrease in wake time after sleep onset and sleep onset latency across the week; sleep efficiency showed a trend towards greater efficiency across the consecutive daytime sleeps. Hours of wakefulness prior to each simulated night shift significantly varied across the week. The melatonin profile significantly shifted across the week.
Conclusions: Results suggest that under optimal conditions, the sleep debt that accumulates during consecutive night shifts is relatively small and does not exacerbate decrements in night-time performance resulting from other factors. When sleep loss is minimised, adaptation of performance during consecutive night shifts can occur in conjunction with circadian adaptation.
PMCID: PMC1740426  PMID: 14573724
14.  The Impact of Moderate Sleep Loss on Neurophysiologic Signals during Working-Memory Task Performance 
Sleep  2002;25(7):784-794.
Study Objectives
This study examined how sleep loss affects neurophysiologic signals related to attention and working memory.
Subjective sleepiness, resting-state electroencephalogram, and behavior and electroencephalogram during performance of working-memory tasks were recorded in a within-subject, repeated-measures design.
Data collection occurred in a computerized laboratory setting.
Sixteen healthy adults (mean age, 26 years; 8 female)
Data from alert daytime baseline tests were compared with data from tests during a late-night, extended-wakefulness session that spanned up to 21 hours of sleep deprivation.
Measurements and Results
Alertness measured both subjectively and electrophysiologically decreased monotonically with increasing sleep deprivation. A lack of alertness-related changes in electroencephalographic measures of the overall mental effort exerted during task execution indicated that participants attempted to maintain high levels of performance throughout the late-night tests. Despite such continued effort, responses became slower, more variable, and more error prone within 1 hour after participants' normal time of sleep onset. This behavior failure was accompanied by significant degradation of event-related brain potentials related to the transient focusing of attention.
Moderate sleep loss compromises the function of neural circuits critical to subsecond attention allocation during working-memory tasks, even when an effort is made to maintain wakefulness and performance. Multivariate analyses indicate that combinations of working-memory-related behavior and neurophysiologic measures can be sensitive enough to permit reliable detection of such effects of sleep loss in individuals. Similar methods might prove useful for assessment of functional alertness in patients with sleep disorders.
PMCID: PMC1626388  PMID: 12405615
Fatigue; alertness; cognition; attention; working memory; electroencephalogram; event-related potentials
15.  Sleep-Dependent Consolidation of Value-Based Learning 
PLoS ONE  2013;8(10):e75326.
It has been suggested that sleep selectively enhances memories with future relevance. Given that sleep’s benefits can vary by item within a learning context, the present study investigated whether the amount of sleep-dependent consolidation may vary across items based on the value of the to-be-learned material. For this purpose, we used a value-based learning paradigm in which participants studied words paired with point values. There were two groups; participants either studied the words in the evening and were tested after a 12 hr interval containing a full night of sleep, or studied the words in the morning and were tested after 12 hr of continuous daytime wake. Free recall (F(1,36) = 19.35, p<.001) and recognition accuracy (F(1,36) = 7.59, p = .01) for words were better following sleep relative to wake. However there was no difference in the linear increase in the probability of delayed recall with increasing word value for sleep and wake groups (p = .74). Thus, while encoding may vary with the value of the to-be-learned item, sleep-dependent consolidation does not.
PMCID: PMC3793990  PMID: 24130703
16.  Daytime and nighttime sleep patterns in adolescents with and without chronic pain 
The aims of the current study were to characterize daytime and nighttime sleep patterns of adolescents with chronic pain, and to compare their sleep patterns to a healthy age and sex-matched cohort.
Sixty-one adolescents from a pain clinic and 60 age and sex-matched youth from the community (mean age = 15.07; 69% female) participated. Participants underwent 10 days of actigraphic sleep monitoring to assess total sleep time (minutes of estimated sleep at night), wake minutes after initial sleep onset, sleep efficiency, and occurrence of sleep during the day.
Adolescents with chronic pain and healthy youth had similar nighttime sleep patterns (total sleep time, wake minutes after initial sleep onset, and sleep efficiency). However, adolescents with chronic pain spent more time sleeping during the day than their healthy peers. Longer daytime sleep was associated with more activity limitations in youth with chronic pain.
Although previous research using self-report methodology has indicated that adolescents with chronic pain commonly endorse poor sleep, findings from the current study suggest that these complaints may not be explained by differences in nighttime sleep patterns as measured by actigraphy. Use of multidimensional sleep assessment may help to understand the potential impact of sleep on chronic pain in adolescents.
PMCID: PMC3368097  PMID: 22149126
Chronic pain; sleep patterns; daytime sleep; actigraphy; adolescents
17.  Sleep and Daytime Functioning: A Short-term Longitudinal Study of Three Preschool-age Comparison Groups 
This study examined sleep, sleepiness, and daytime performance in 68 children with autism, 57 children with intellectual disability (ID), and 69 typically developing preschool children. Children in the autism and ID groups had poorer daytime performance and behaviors than the typically developing children. Children in the ID group also were significantly sleepier than children in both the autism and typically developing groups. These significant differences persisted over 6 months. Actigraph-defined sleep behaviors and problems did not relate to daytime sleepiness or daytime performance and behaviors for the children with autism or the typically developing group. For the ID group, longer night awakenings and lower sleep efficiency predicted more daytime sleepiness. For each group, parent-report sleep problems were associated with more daytime sleepiness and more behavior problems.
PMCID: PMC3500838  PMID: 22809074
autism; intellectual disability; behavior; sleep
18.  Sleep Disorders in Patients with Bronchial Asthma 
Materia Socio-Medica  2011;23(4):235-237.
Respiratory disturbances during sleep are recognized as extremely common disorders with important clinical consequences. Breathing disorders during sleep can result in broad range of clinical manifestations, the most prevalent of which are unrefreshing sleep, daytime sleepiness and fatigue, and cognitive impairmant. There is also evidence that respiratory-related sleep disturbances can contribute to several common cardiovascular and metabolic disorders, including systemic hypertension, cardiac dysfunction, and insulin-resistance. Correlations are found between asthma-related symptoms and sleep disturbances. Difficulties inducing sleep, sleep fragmentation on polysomnography, early morning awakenings and daytime sleepiness are more common in asthmatics compared with subjects without asthma. The “morning deep” in asthma is relevant for the characterization of asthma severity, and impact drugs’ choices. Sleep and night control of asthma could be relevant to evaluate disease’s control. Appropriate asthma control recovering is guarantor for better sleep quality in these patients and less clinical consequences of respiratory disturbances during sleep.
PMCID: PMC3633408  PMID: 23678304
bronchial asthma; sleep disorders.
19.  Prevalence, Patterns, and Persistence of Sleep Problems in the First 3 Years of Life 
Pediatrics  2012;129(2):e276-e284.
Examine the prevalence, patterns, and persistence of parent-reported sleep problems during the first 3 years of life.
Three hundred fifty-nine mother/child pairs participated in a prospective birth cohort study. Sleep questionnaires were administered to mothers when children were 6, 12, 24, and 36 months old. Sleep variables included parent response to a nonspecific query about the presence/absence of a sleep problem and 8 specific sleep outcome domains: sleep onset latency, sleep maintenance, 24-hour sleep duration, daytime sleep/naps, sleep location, restlessness/vocalization, nightmares/night terrors, and snoring.
Prevalence of a parent-reported sleep problem was 10% at all assessment intervals. Night wakings and shorter sleep duration were associated with a parent-reported sleep problem during infancy and early toddlerhood (6–24 months), whereas nightmares and restless sleep emerged as associations with report of a sleep problem in later developmental periods (24–36 months). Prolonged sleep latency was associated with parent report of a sleep problem throughout the study period. In contrast, napping, sleep location, and snoring were not associated with parent-reported sleep problems. Twenty-one percent of children with sleep problems in infancy (compared with 6% of those without) had sleep problems in the third year of life.
Ten percent of children are reported to have a sleep problem at any given point during early childhood, and these problems persist in a significant minority of children throughout early development. Parent response to a single-item nonspecific sleep query may overlook relevant sleep behaviors and symptoms associated with clinical morbidity.
PMCID: PMC3357046  PMID: 22218837
sleep problems; infants; toddlers; prevalence; persistence
20.  How Aging Affects Sleep-Dependent Memory Consolidation? 
Memories are not stored as they were initially encoded but rather undergo a gradual reorganization process, termed memory consolidation. Numerous data indicate that sleep plays a major role in this process, notably due to the specific neurochemical environment and the electrophysiological activity observed during the night. Two putative, probably not exclusive, models (“hippocampo-neocortical dialogue” and “synaptic homeostasis hypothesis”) have been proposed to explain the beneficial effect of sleep on memory processes. However, all data gathered until now emerged from studies conducted in young subjects. The investigation of the relationships between sleep and memory in older adults has sparked off little interest until recently. Though, aging is characterized by memory impairment, changes in sleep architecture, as well as brain and neurochemical alterations. All these elements suggest that sleep-dependent memory consolidation may be impaired or occurs differently in older adults. This review outlines the mechanisms governing sleep-dependent memory consolidation, and the crucial points of this complex process that may dysfunction and result in impaired memory consolidation in aging.
PMCID: PMC3270392  PMID: 22347209
sleep; memory consolidation; aging; episodic memory; procedural memory; slow wave sleep, hippocampus
21.  Unfair Treatment is associated with Poor Sleep in African American and Caucasian Adults: Pittsburgh SleepSCORE Project 
To test the association between self-reported unfair treatment and objective and self-reported sleep characteristics in African American and Caucasian adults.
Cross-sectional study of 97 African American and 113 Caucasian middle-aged adults.
Main Outcome Measures
Participants completed: a) two night in-home, polysomnography (PSG) sleep study, b) sleep diaries and actigraph assessments across nine days and nights, and c) self-report measures of sleep quality in the past month, and daytime sleepiness in the past two weeks.
Greater unfair treatment was associated with reports of poorer self-reported sleep quality and greater daytime sleepiness, shorter sleep duration and lower sleep efficiency as measured by actigraphy and PSG, and a smaller proportion of rapid eye movement (REM) sleep. Racial/ethnic differences were few. Exploratory analyses showed that nightly worry partially mediated the associations of unfair treatment with sleep quality, daytime sleepiness, sleep efficiency (actigraphy), and proportion of REM sleep.
Perceptions of unfair treatment are associated with sleep disturbances in both African American and Caucasian adults. Future studies are needed to identify the pathways that account for the association between unfair treatment and sleep.
PMCID: PMC3131074  PMID: 21553979
unfair treatment; discrimination; sleep disturbance; worry; race/ethnicity
22.  Sleep Insufficiency, Sleep Health Problems and Performance in High School Students 
A survey on sleep schedule, sleep health, school performance and school start times was conducted in 1,941 adolescents. A high level of early and circadian-disadvantaged sleep/wake schedules during weekdays was observed. Shorter sleep duration on weekdays was reported, especially in upper classmen. Complaints of inadequate sleep and sleepiness during weekdays, alarm clock use, and napping were prevalent. Night awakening and prolonged sleep onset were common and associated with poor school performance. Students with a sleep length of less than 7 hours on both weekdays and weekends exhibited poorer performance, while those who made up this sleep loss on weekends did not. The total number of poor sleep factors in an individual also correlated with poor school performance. Earlier school start times were associated with a perception of poor sleep quality, shorter sleep duration and more sleep health problems. We conclude that sleep inadequacies and sleep health problems were prevalent in this population, especially in those who started school earlier in the morning, and that these poor sleep factors were associated with school performance.
PMCID: PMC3212860  PMID: 22084618
sleep deprivation; sleep health problem; adolescents; performance; school start time
23.  Selective REM-Sleep Deprivation Does Not Diminish Emotional Memory Consolidation in Young Healthy Subjects 
PLoS ONE  2014;9(2):e89849.
Sleep enhances memory consolidation and it has been hypothesized that rapid eye movement (REM) sleep in particular facilitates the consolidation of emotional memory. The aim of this study was to investigate this hypothesis using selective REM-sleep deprivation. We used a recognition memory task in which participants were shown negative and neutral pictures. Participants (N = 29 healthy medical students) were separated into two groups (undisturbed sleep and selective REM-sleep deprived). Both groups also worked on the memory task in a wake condition. Recognition accuracy was significantly better for negative than for neutral stimuli and better after the sleep than the wake condition. There was, however, no difference in the recognition accuracy (neutral and emotional) between the groups. In summary, our data suggest that REM-sleep deprivation was successful and that the resulting reduction of REM-sleep had no influence on memory consolidation whatsoever.
PMCID: PMC3937423  PMID: 24587073
24.  Nocturnal Awakening & Sleep Duration in Veterans with PTSD: An Actigraphic Study 
Objective: To assess whether awakenings from sleep and sleep duration in Post Traumatic Stress Disorder (PTSD) were related to demography, posttraumatic or depressive symptoms, subjective sleep quality, and daytime sleepiness.
Methods: Sample consisted of 23 veterans with lifetime PTSD and current sleep disturbance not due to apnea or other diagnosable conditions. Data collection included demography, two weeks of actigraphy, Beck Depression Inventory, Posttraumatic Checklist, Clinical Assessment of Posttraumatic Symptoms, Pittsburgh Sleep Quality Index, and Epworth Sleepiness Scale.
Results: The study revealed that awakenings increased with younger age. Variability in awakenings also increased with younger age (p = 0.002). More awakenings were associated with shorter sleep duration.
Conclusions: These paradoxical observations regarding younger age and more awakening may be related to increased sleep symptoms early in the course and then gradual waning of posttraumatic symptoms over time, since awakenings tend to increase with age in normals (rather than decrease, as we observed).
PMCID: PMC3817779  PMID: 24353674
PTSD; Insomnia; Actigraphy; Veteran
25.  The effects of Ramadan fasting on sleep patterns and daytime sleepiness: An objective assessment 
Ramadan fasting and its associated lifestyle changes have been linked to changes in sleep and daytime sleepiness. This study was designed to assess the effects of Ramadan fasting on patterns of sleep and daytime sleepiness.
The SenseWear Pro Armband™ was used to assess the duration and distribution of sleep in eight Muslim and eight non-Muslim volunteers during the last week of Shaaban [baseline (BL) and the first (R1) and second (R2) weeks of Ramadan (1430 H)]. OPTALERT™ was used to assess daytime drowsiness objectively using the John Drowsiness Scale (JDS) to assess sleepiness, and a visual reaction time test was used to assess mean reaction time (MRT).
The mean ages of Muslims and non-Muslims were 36.25 ± 4.46 and 34.75 ± 3.33 years, respectively. Although the start of work was delayed for Muslims from 0730 to 1000 hours, there was no change in working hours for non-Muslims. During Ramadan, bedtime and wake-up time were delayed, and there was a significant reduction in total sleep time for Muslims (5.91 ± 1.36 hours, 4.95 ± 1.46 hours, and 4.78 ± 1.36 hours during BL, R1, and R2, respectively, P < 0.001), but not for non-Muslims. JDS values in both Muslims and non-Muslims were normal at BL (1.70 ± 1.16 and 1.68 ± 1.07, respectively), and no changes occurred during Ramadan (R1 or R2), indicating no increase in daytime sleepiness. There were no significant changes in MRT during R1 and R2 from BL in either group.
Although the sleep cycle of the studied sample shifted during Ramadan among fast observers, there was no objective evidence for increased sleepiness during fasting.
PMCID: PMC3724373  PMID: 23914215
Ramadan; fasting; sleep; sleepiness; vigilance

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