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1.  Meditation acutely improves psychomotor vigilance, and may decrease sleep need 
A number of benefits from meditation have been claimed by those who practice various traditions, but few have been well tested in scientifically controlled studies. Among these claims are improved performance and decreased sleep need. Therefore, in these studies we assess whether meditation leads to an immediate performance improvement on a well validated psychomotor vigilance task (PVT), and second, whether longer bouts of meditation may alter sleep need.
The primary study assessed PVT reaction times before and after 40 minute periods of mediation, nap, or a control activity using a within subject cross-over design.
This study utilized novice meditators who were current university students (n = 10). Novice meditators completed 40 minutes of meditation, nap, or control activities on six different days (two separate days for each condition), plus one night of total sleep deprivation on a different night, followed by 40 minutes of meditation.
A second study examined sleep times in long term experienced meditators (n = 7) vs. non-meditators (n = 23). Experienced meditators and controls were age and sex matched and living in the Delhi region of India at the time of the study. Both groups continued their normal activities while monitoring their sleep and meditation times.
Novice meditators were tested on the PVT before each activity, 10 minutes after each activity and one hour later. All ten novice meditators improved their PVT reaction times immediately following periods of meditation, and all but one got worse immediately following naps. Sleep deprivation produced a slower baseline reaction time (RT) on the PVT that still improved significantly following a period of meditation. In experiments with long-term experienced meditators, sleep duration was measured using both sleep journals and actigraphy. Sleep duration in these subjects was lower than control non-meditators and general population norms, with no apparent decrements in PVT scores.
These results suggest that meditation provides at least a short-term performance improvement even in novice meditators. In long term meditators, multiple hours spent in meditation are associated with a significant decrease in total sleep time when compared with age and sex matched controls who did not meditate. Whether meditation can actually replace a portion of sleep or pay-off sleep debt is under further investigation.
PMCID: PMC2919439  PMID: 20670413
2.  Melatonin for sleep problems in children with neurodevelopmental disorders: randomised double masked placebo controlled trial 
Objective To assess the effectiveness and safety of melatonin in treating severe sleep problems in children with neurodevelopmental disorders.
Design 12 week double masked randomised placebo controlled phase III trial.
Setting 19 hospitals across England and Wales.
Participants 146 children aged 3 years to 15 years 8 months were randomised. They had a range of neurological and developmental disorders and a severe sleep problem that had not responded to a standardised sleep behaviour advice booklet provided to parents four to six weeks before randomisation. A sleep problem was defined as the child not falling asleep within one hour of lights out or having less than six hours’ continuous sleep.
Interventions Immediate release melatonin or matching placebo capsules administered 45 minutes before the child’s bedtime for a period of 12 weeks. All children started with a 0.5 mg capsule, which was increased through 2 mg, 6 mg, and 12 mg depending on their response to treatment.
Main outcome measures Total sleep time at night after 12 weeks adjusted for baseline recorded in sleep diaries completed by the parent. Secondary outcomes included sleep onset latency, assessments of child behaviour, family functioning, and adverse events. Sleep was measured with diaries and actigraphy.
Results Melatonin increased total sleep time by 22.4 minutes (95% confidence interval 0.5 to 44.3 minutes) measured by sleep diaries (n=110) and 13.3 (−15.5 to 42.2) measured by actigraphy (n=59). Melatonin reduced sleep onset latency measured by sleep diaries (−37.5 minutes, −55.3 to −19.7 minutes) and actigraphy (−45.3 minutes, −68.8 to −21.9 minutes) and was most effective for children with the longest sleep latency (P=0.009). Melatonin was associated with earlier waking times than placebo (29.9 minutes, 13.6 to 46.3 minutes). Child behaviour and family functioning outcomes showed some improvement and favoured use of melatonin. Adverse events were mild and similar between the two groups.
Conclusions Children gained little additional sleep on melatonin; though they fell asleep significantly faster, waking times became earlier. Child behaviour and family functioning outcomes did not significantly improve. Melatonin was tolerable over this three month period. Comparisons with slow release melatonin preparations or melatonin analogues are required.
Trial registration ISRCT No 05534585.
PMCID: PMC3489506  PMID: 23129488
3.  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
4.  A Multicenter, Placebo-controlled Trial of Melatonin for Sleep Disturbance in Alzheimer’s Disease 
Sleep  2003;26(7):893-901.
To determine the safety and efficacy of 2 dose formulations of melatonin for the treatment of insomnia in patients with Alzheimer’s disease.
A multicenter, randomized, placebo-controlled clinical trial of 2 dose formulations of oral melatonin coordinated by the National Institute of Aging-funded Alzheimer’s Disease Cooperative Study. Subjects with Alzheimer’s disease and nighttime sleep disturbance were randomly assigned to 1 of 3 treatment groups: placebo, 2.5-mg slow-release melatonin, or 10-mg melatonin.
Private homes and long-term care facilities.
157 individuals were recruited by 36 Alzheimer’s disease research centers. Subjects with a diagnosis of Alzheimer’s disease were eligible if they averaged less than 7 hours of sleep per night (as documented by wrist actigraphy) and had 2 or more episodes per week of nighttime awakenings reported by the caregiver.
Nocturnal total sleep time, sleep efficiency, wake-time after sleep onset, and day-night sleep ratio during 2- to 3-week baseline and 2-month treatment periods. Sleep was defined by an automated algorithmic analysis of wrist actigraph data.
No statistically significant differences in objective sleep measures were seen between baseline and treatment periods for the any of the 3 groups. Nonsignificant trends for increased nocturnal total sleep time and decreased wake after sleep onset were observed in the melatonin groups relative to placebo. Trends for a greater percentage of subjects having more than a 30-minute increase in nocturnal total sleep time in the 10-mg melatonin group and for a decline in the day-night sleep ratio in the 2.5-mg sustained-release melatonin group, compared to placebo, were also seen. On subjective measures, caregiver ratings of sleep quality showed improvement in the 2.5-mg sustained-release melatonin group relative to placebo. There were no significant differences in the number or seriousness of adverse events between the placebo and melatonin groups.
Based on actigraphy as an objective measure of sleep time, melatonin is not an effective soporific agent in people with Alzheimer’s disease.
PMCID: PMC4418658  PMID: 14655926
5.  Sleep Quality after Initial Chemotherapy for Breast Cancer 
Goals of Work
To characterize sleep quality and quantity prior to and in the first 3 nights after initial chemotherapy for breast cancer.
Patients and Methods
Secondary analysis of data from two separate randomized clinical trials (RCT) of behavioral interventions to improve fatigue and sleep. Patients came from two comprehensive cancer centers, three clinical cancer centers, and 10 community clinics in five states. Participants were women with stage I-IIIA breast cancer treated with anthracycline and/or cyclophosphamide based regimens.
Main Results
Baseline data from each RCT were used in the analysis. Sixty-five percent of women self-reported poor sleep in the month preceding chemotherapy using the Pittsburgh Sleep Quality Index (PSQI) score >5. Three nights of actigraphy data indicated a wide range of sleep experience with an average of 10 awakenings and time (minutes) awake after sleep onset (WASO-M) averaging 61 minutes per night. The first night’s sleep was the worst. There was no statistically significant relationship between self-reported poor sleep and sleep measures obtained by actigraphy. Women with poor sleep at baseline (global PSQI >5) had significantly lower (p<.001) physical (MOS PCS) and mental (MOS MCS) health status. However neither the PCS nor MCS was associated with any of the average actigraphy sleep parameters or Night 1 parameters in the aggregated sample. Increasing age was also associated with poorer sleep.
A high percent of women with breast cancer begin chemotherapy with disturbed sleep and the initial nights after chemotherapy are characterized by sleep fragmentation that disrupts sleep maintenance. Interventions should focus on strategies to decrease the number and duration of night awakenings. Further research is needed to identify predictors of poor sleep during this time.
PMCID: PMC2874643  PMID: 19521723
sleep; chemotherapy; breast cancer; actigraphy; neoplasm; function
6.  Perceived Control and Sleep in Hospitalized Older Adults: A Sound Hypothesis? 
To examine the associations between perceived control over sleep, noise levels, sleep duration and noise complaints in a cohort of hospitalized adults.
Prospective cohort study.
General medicine ward in an academic medical center.
118 hospitalized patients age 50 years and over (mean age 65 years, 57% female, 67% African American).
Sleep duration was measured via wrist actigraphy and noise levels in patient rooms were measured via sound monitors. Validated questionnaires used to assess sleep characteristics at baseline and sleep quality for each night. Perceived control over sleep was measured at baseline using the Sleep Self-Efficacy (SSE) scale (range 9–45).
Mean SSE score was 32.1 (SD = 9.4) and median score was 34 (IQR = 24–41). Average sleep duration for patients in the hospital was 333 minutes (5.5 hours). Forty-two percent of patients complained of noise disrupting their sleep. Linear regression clustered by subject showed that above median SSE was associated with longer sleep duration (+55 minutes 95%CI[14, 97], p=0.010). This association remained significant after controlling for objective noise levels and patient demographics (+50 minutes 95%CI [11, 90], p=0.014). In logistic regression controlling for noise level and patient demographics, those patients with high SSE were 51% less likely to complain of noise disruptions (OR=0.49 95%CI[0.25, 0.96], p=0.039).
Higher perceived control over sleep is associated with longer sleep duration, better sleep quality, and fewer reports of noise disruptions. In addition to noise control, interventions to boost perceived control may improve in-hospital sleep.
PMCID: PMC3764606  PMID: 23504939
Hospitalized Patients; Sleep Quality; Perceived Control
7.  A validation of wrist actigraphy against polysomnography in patients with schizophrenia or bipolar disorder 
Sleep disturbances are frequent in patients with schizophrenia or bipolar disorder. Actigraphy has been established as a generally reliable method to examine these disturbances across varying time spans, but the validity against polysomnography (PSG) is not well investigated for this population. We validated wrist-worn actigraphy against PSG in a population of chronic, medicated patients with schizophrenia or bipolar disorder.
Patients and methods
From a clinical trial, we derived data from 37 patients with schizophrenia and five patients with bipolar disorder who were examined with one-night PSG and concomitant actigraphy. The following sleep variables were compared between the two methods: total sleep time, sleep efficiency, sleep latency, number of awakenings, and time awake after sleep onset. The degree of consistency between the two methods was evaluated using the intra-class correlation coefficient and Bland–Altman plots. Subgroup analyses included splitting the analyses according to sex, diagnosis, and duration of wakefulness after sleep onset. PSG was considered the gold standard.
The intraclass correlation coefficient was high for total sleep time, moderate for the number of awakenings, and low or zero for the other examined sleep variables. These findings were reproduced in the subgroup analyses that compared men and women, as well as patients with bipolar versus schizophrenia spectrum disorders. When excluding patients with extensive periods of wakefulness after the initial sleep period (wake after sleep onset > 100 minutes), the reliability of the actigraphy-derived sleep variables markedly improved.
Actigraphy reliably measures the total sleep time in this specific patient population. For patients without extensive periods of wakefulness after sleep onset, actigraphy might provide a useful measure of sleep efficiency, sleep latency, and number of awakenings.
PMCID: PMC4559245  PMID: 26357475
actigraphy; polysomnography; validation; schizophrenia; bipolar disorder
8.  Strength Training and Walking Exercise and Social Activity Improve Sleep in Nursing Home and Assisted Living Residents: Randomized Controlled Trial 
To determine the effects of physical resistance strength training and walking (E), individualized social activity (SA), and both E and SA (ESA) compared to a usual care control group on total nocturnal sleep time in nursing home and assisted living residents.
Design, Setting and Participants
The study used a pretest-posttest experimental design with assignment to 1 of 4 groups for 7 weeks: 1) E (n = 55); 2) SA (n = 50); 3) ESA (n = 41); or 4) usual care control (n = 47). 193 residents in 10 nursing homes and 3 assisted living facilities were randomly assigned and 165 completed the study.
The E group participated in high intensity physical resistance strength training 3 days a week and on 2 days walked for up to 45 minutes. The SA group received social activity 1 hour daily 5 days a week. The ESA group received both E and SA, and the control group participated in usual activities provided in the homes.
Total nocturnal sleep time was measured by 2 nights of polysomnography at pre-and post-intervention. Sleep efficiency (SE), non-rapid eye movement (NREM) sleep, rapid eye movement sleep, and sleep onset latency were also analyzed.
Total nocturnal sleep time significantly increased in the ESA group over that of control group (adjusted means 364.2 minutes versus 328.9 minutes), as did SE and NREM sleep.
High intensity physical resistance strength training and walking combined with social activity significantly improves sleep in nursing home and assisted living residents. The interventions by themselves did not have significant effects on sleep in this population.
PMCID: PMC3124380  PMID: 21314643
RCT; sleep; strength training; social activity; walking
9.  Sleep Patterns During Hospitalization Following Hematopoietic Stem Cell Transplantation 
Oncology nursing forum  2015;42(4):371-379.
To characterize patient-reported and objective sleep assessments and provide a preliminary examination of the relationships among sleep, quality of life, and demographic or treatment factors.
A secondary data analysis using a descriptive-correlational design.
University of Illinois Hospital and Health Sciences System.
40 patients undergoing a hematopoietic stem cell transplantation (HCT) hospitalized for the conditioning regimen, stem cell infusion, and immediate recovery period.
Each patient wore a wrist actigraph continuously from the fourth day following HCT to the eighth day to objectively assess sleep patterns (total sleep time, sleep onset latency, sleep efficiency, wake after sleep onset, and number of awakenings). At the end of the five-day period, patients completed measures of sleep disturbance and quality of life.
Main Research Variables
Objective sleep (total sleep time, sleep onset latency, sleep efficiency, wake after sleep onset, and number of awakenings), subjective sleep (sleep disturbance), and quality of life.
The mean total nighttime sleep (objectively obtained) was 232 minutes (SD = 71 minutes), with 14 patients (35%) sleeping less than three consecutive hours during one or more study days. Age was negatively correlated with patient-reported sleep disturbance. Patient-reported sleep disturbance was significantly associated with length of hospital stay. No correlations were found between patient-reported and objective sleep assessments.
This study objectively documents inadequate and irregular sleep in hospitalized patients undergoing HCT. Sole reliance on patient-reported sleep assessments may not represent the full extent of the problem.
Implications for Nursing
Attempts to streamline care during the night by not waking patients for routine care unless indicated by the patient’s condition (as advocated by the American Academy of Nursing) and providing supportive care for symptoms (such as diarrhea) during the night may reduce the number of awakenings and possibly improve overall sleep quality.
PMCID: PMC4547461  PMID: 26148316
hematopoietic stem cell transplantation; sleep; sleep disturbances; hospitalization
10.  Energy expenditure during sleep, sleep deprivation and sleep following sleep deprivation in adult humans 
The Journal of Physiology  2010;589(1):235-244.
Non-technical summary One of the proposed functions of sleep is to conserve energy. We determined the amount of energy conserved by sleep in humans, how much more energy is expended when missing a night of sleep, and how much energy is conserved during recovery sleep. Findings support the hypothesis that a function of sleep is to conserve energy in humans. Sleep deprivation increased energy expenditure indicating that maintaining wakefulness under bed-rest conditions is energetically costly. Recovery sleep after sleep deprivation reduced energy use compared to baseline sleep suggesting that human metabolic physiology has the capacity to make adjustments to respond to the energetic cost of sleep deprivation. The finding that sleep deprivation increases energy expenditure should not be interpreted that sleep deprivation is a safe or effective strategy for weight loss as other studies have shown that chronic sleep deprivation is associated with impaired cognition and weight gain.
Sleep has been proposed to be a physiological adaptation to conserve energy, but little research has examined this proposed function of sleep in humans. We quantified effects of sleep, sleep deprivation and recovery sleep on whole-body total daily energy expenditure (EE) and on EE during the habitual day and nighttime. We also determined effects of sleep stage during baseline and recovery sleep on EE. Seven healthy participants aged 22 ± 5 years (mean ±s.d.) maintained ∼8 h per night sleep schedules for 1 week before the study and consumed a weight-maintenance diet for 3 days prior to and during the laboratory protocol. Following a habituation night, subjects lived in a whole-room indirect calorimeter for 3 days. The first 24 h served as baseline – 16 h wakefulness, 8 h scheduled sleep – and this was followed by 40 h sleep deprivation and 8 h scheduled recovery sleep. Findings show that, compared to baseline, 24 h EE was significantly increased by ∼7% during the first 24 h of sleep deprivation and was significantly decreased by ∼5% during recovery, which included hours awake 25–40 and 8 h recovery sleep. During the night time, EE was significantly increased by ∼32% on the sleep deprivation night and significantly decreased by ∼4% during recovery sleep compared to baseline. Small differences in EE were observed among sleep stages, but wakefulness during the sleep episode was associated with increased energy expenditure. These findings provide support for the hypothesis that sleep conserves energy and that sleep deprivation increases total daily EE in humans.
PMCID: PMC3039272  PMID: 21059762
11.  Sleep estimates in children: parental versus actigraphic assessments 
Nature and Science of Sleep  2011;3:115-123.
In the context of increasing awareness about the need for assessment of sleep duration in community and clinical settings, the use of questionnaire-based tools may be fraught with reporter bias. Conversely, actigraphy provides objective assessments of sleep patterns. In this study, we aimed to determine the potential discrepancies between parentally-based sleep logs and concurrent actigraphic recordings in children over a one-week period.
We studied 327 children aged 3–10 years, and included otherwise healthy, nonsnoring children from the community who were reported by their parents to be nonsnorers and had normal polysomnography, habitually-snoring children from the community who completed the same protocol, and children with primary insomnia referred to the sleep clinic for evaluation in the absence of any known psychiatric illness. Actigraphy and parental sleep log were concomitantly recorded during one week.
Sleep logs displayed an average error in sleep onset after bedtime of about 30 minutes (P < 0.01) and of a few minutes before risetime in all groups. Furthermore, subjective parental reports were associated with an overestimated misperception of increased sleep duration of roughly one hour per night independent of group (P < 0.001).
The description of a child’s sleep by the parent appears appropriate as far as symptoms are concerned, but does not result in a correct estimate of sleep onset or duration. We advocate combined parental and actigraphic assessments in the evaluation of sleep complaints, particularly to rule out misperceptions and potentially to aid treatment. Actigraphy provides a more reliable tool than parental reports for assessing sleep in healthy children and in children with sleep problems.
PMCID: PMC3630966  PMID: 23616722
actigraphy; insomnia; sleep logs; snoring; sleep duration
12.  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
13.  Night-to-Night Sleep Variability in Older Adults with and Without Chronic Insomnia 
Sleep medicine  2009;11(1):56.
1) To quantify night-to-night variability in sleep behaviors and sleep measures among older chronic insomnia (CI) subjects and non-insomnia (NI) controls; 2) to investigate systematic temporal patterns of sleep behaviors and sleep measures across nights; and 3) to examine clinical correlates of sleep variability.
Sixty-one older adults with CI (71.4 years old, 67%F) and 31 older adults with NI (70.7 years old, 65%F) completed questionnaires and kept sleep diaries and wore wrist actigraphs for two weeks. Mixed models were used to estimate within-subject mean and standard deviation values; these were then compared across groups. Mixed models were also used to determine associations across nights of sleep measures.
CI and NI differed on mean values for clinical ratings and sleep diary measures, but not for actigraphy measures. CI also showed significantly greater variability than NI on most sleep diary measures and on actigraphically-measured wakefulness after sleep onset (WASO) and sleep efficiency. Among CI, neither diary nor actigraphy measures from one night correlated with values from the previous night. Diary WASO and sleep time and actigraphy sleep latency and sleep time, however, positively correlated with values from the previous two nights. Variability measures were not correlated with other global clinical measures among CI.
Compared to NI, older adults with CI report worse sleep and greater night-tonight variability, which was confirmed with actigraphy. There was little evidence for positive or negative correlation of sleep measures across nights. Variability of sleep may be an important target for insomnia treatments.
PMCID: PMC2818595  PMID: 19962939
insomnia; sleep diary; sleep; behavioral treatment; variability
14.  Effects of captopril and oxygen on sleep apnoea in patients with mild to moderate congestive cardiac failure. 
British Heart Journal  1995;73(3):237-241.
OBJECTIVES--To determine the effects of captopril and oxygen on sleep quality in patients with mild to moderate cardiac failure. DESIGN--An open observational study. PATIENTS--12 patients with New York Heart Association class II-III heart failure were studied at baseline. 9 of these patients were then examined at the end of 1 month of treatment with captopril; 9 of the patients were separately assessed during a single night of supplementary oxygen. MAIN OUTCOME MEASURES--Sleep patterns by polysomnography, overnight oximetry, and subjective sleep assessment using visual analogue scores. RESULTS--Abnormal sleep was present in all baseline studies. Complete polysomnograms after treatment with captopril were obtained in 8 patients. Light sleep (stages 1 and 2) was reduced (mean (SEM) 61%(8)% to 48%(6)% actual sleep time, P < 0.05) but slow wave (stages 3 and 4) and REM (rapid eye movement) sleep increased (25%(6)% to 31%(5)%, 14%(2)% to 21%(5)% actual sleep time, P < 0.05). Apnoeic episodes (242(59) to 118(30), P < 0.05), desaturation events (171(60) to 73(37), P < 0.05), and arousals (33(5) to 18(3) P < 0.01) were reduced. Visual analogue scores of sleep quality increased 49(5) to 69(5), P < 0.01). Complete polysomnograms were obtained in 7 patients treated with oxygen. Light sleep duration was reduced (55% (7)% to 42%(5)% actual sleep time, P < 0.05) and slow wave sleep increased (30%(5)% to 38%(6)% actual sleep time, P < 0.05). REM sleep duration was not significantly different. Total arousals (33(6)% to 20(2) P < 0.05), desaturation events (140(33) to 38(10), P < 0.01), and apnoeic episodes (212(53) to 157(33), P < 0.05) were reduced. Visual analogue scores of sleep quality were unchanged. CONCLUSIONS--Captopril and oxygen may improve sleep quality and reduce nocturnal desaturation in patients with mild to moderate cardiac failure. Improved sleep quality could explain the reduction in daytime symptoms seen after treatment in patients with chronic heart failure.
PMCID: PMC483805  PMID: 7727183
15.  Sleep-Disordered Breathing and Mortality: A Prospective Cohort Study 
PLoS Medicine  2009;6(8):e1000132.
In a cohort of 6,441 volunteers followed over an average of 8.2 years, Naresh Punjabi and colleagues find sleep-disordered breathing to be independently associated with mortality and identify predictive characteristics.
Sleep-disordered breathing is a common condition associated with adverse health outcomes including hypertension and cardiovascular disease. The overall objective of this study was to determine whether sleep-disordered breathing and its sequelae of intermittent hypoxemia and recurrent arousals are associated with mortality in a community sample of adults aged 40 years or older.
Methods and Findings
We prospectively examined whether sleep-disordered breathing was associated with an increased risk of death from any cause in 6,441 men and women participating in the Sleep Heart Health Study. Sleep-disordered breathing was assessed with the apnea–hypopnea index (AHI) based on an in-home polysomnogram. Survival analysis and proportional hazards regression models were used to calculate hazard ratios for mortality after adjusting for age, sex, race, smoking status, body mass index, and prevalent medical conditions. The average follow-up period for the cohort was 8.2 y during which 1,047 participants (587 men and 460 women) died. Compared to those without sleep-disordered breathing (AHI: <5 events/h), the fully adjusted hazard ratios for all-cause mortality in those with mild (AHI: 5.0–14.9 events/h), moderate (AHI: 15.0–29.9 events/h), and severe (AHI: ≥30.0 events/h) sleep-disordered breathing were 0.93 (95% CI: 0.80–1.08), 1.17 (95% CI: 0.97–1.42), and 1.46 (95% CI: 1.14–1.86), respectively. Stratified analyses by sex and age showed that the increased risk of death associated with severe sleep-disordered breathing was statistically significant in men aged 40–70 y (hazard ratio: 2.09; 95% CI: 1.31–3.33). Measures of sleep-related intermittent hypoxemia, but not sleep fragmentation, were independently associated with all-cause mortality. Coronary artery disease–related mortality associated with sleep-disordered breathing showed a pattern of association similar to all-cause mortality.
Sleep-disordered breathing is associated with all-cause mortality and specifically that due to coronary artery disease, particularly in men aged 40–70 y with severe sleep-disordered breathing.
Please see later in the article for the Editors' Summary
Editors' Summary
About 1 in 10 women and 1 in 4 men have a chronic condition called sleep-disordered breathing although most are unaware of their problem. Sleep-disordered breathing, which is commonest in middle-aged and elderly people, is characterized by numerous, brief (10 second or so) interruptions of breathing during sleep. These interruptions, which usually occur when relaxation of the upper airway muscles decreases airflow, lower the level of oxygen in the blood and, as a result, affected individuals are frequently aroused from deep sleep as they struggle to breathe. Symptoms of sleep-disordered breathing include loud snoring and daytime sleepiness. Treatments include lifestyle changes such as losing weight (excess fat around the neck increases airway collapse) and smoking cessation. Affected people can also use special devices to prevent them sleeping on their backs, but for severe sleep-disordered breathing, doctors often recommend continuous positive airway pressure (CPAP), a machine that pressurizes the upper airway through a face mask to keep it open.
Why Was This Study Done?
Sleep-disordered breathing is a serious condition. It is associated with several adverse health conditions including coronary artery disease (narrowing of the blood vessels that supply the heart, a condition that can cause a heart attack) and daytime sleepiness that can affect an individual's driving ability. In addition, several clinic- and community-based studies suggest that sleep-disordered sleeping may increase a person's risk of dying. However, because these studies have been small and have often failed to allow for other conditions and characteristics that affect an individual's risk of dying (“confounding factors”), they provide inconsistent or incomplete information about the potential association between sleep-disordered breathing and the risk of death. In this prospective cohort study (part of the Sleep Heart Health Study, which is researching the effects of sleep-disordered breathing on cardiovascular health), the researchers examine whether sleep-disordered breathing is associated with all-cause mortality (death from any cause) in a large community sample of adults. A prospective cohort study is one in which a group of participants is enrolled and then followed forward in time (in this case for several years) to see what happens to them.
What Did the Researchers Do and Find?
At enrollment, the study participants—more than 6,000 people aged 40 years or older, none of whom were being treated for sleep-disordered breathing—had a health examination. Their night-time breathing, sleep patterns, and blood oxygen levels were also assessed and these data used to calculate each participant's apnea-hypopnea index (AHI)—the number of apneas and hypopneas per hour. During the study follow-up period, 1,047 participants died. Compared to participants without sleep-disordered sleeping, participants with severe sleep-disordered breathing (an AHI of ≥30) were about one and a half times as likely to die from any cause after adjustment for potential confounding factors. People with milder sleep-disordered breathing did not have a statistically significant increased risk of dying. After dividing the participants into subgroups according to their age and sex, men aged 40–70 years with severe sleep-disordered breathing had a statistically increased risk of dying from any cause (twice the risk of men of a similar age without sleep-disordered breathing). Finally, death from coronary artery disease was also associated with sleep-disordered breathing in men but not in women.
What Do These Findings Mean?
These findings indicate that sleep-disordered breathing is associated with an increased risk of all-cause mortality, particularly in men aged 40–70 years, even after allowing for known confounding factors. They also suggest that the increased risk of death is specifically associated with coronary artery disease although further studies are needed to confirm this finding because it was based on the analysis of a small subgroup of study participants. Although this study is much larger than previous investigations into the association between sleep-disordered breathing and all-cause mortality, it has several limitations including its reliance on a single night's measurements for the diagnosis of sleep-disordered breathing. Nevertheless, these findings suggest that clinical trials should now be started to assess whether treatment can reduce the increased risk of death that seems to be associated with this common disorder.
Additional Information
Please access these Web sites via the online version of this summary at
The US National Heart Lung and Blood Institute has information (including a video) about sleep-disordered breathing (sleep apnea) (in English and Spanish)
The UK National Heath Service also provides information for patients about sleep apnea
MedlinePlus provides links to further information and advice about sleep-disordered breathing (in English and Spanish)
More information on the Sleep Heart Health Study is available
PMCID: PMC2722083  PMID: 19688045
16.  Effects of exercise with or without light exposure on sleep quality and hormone reponses 
The objectives of the present study were to determine the effect of sun exposure and aerobic exercise on quality of sleep and investigate sleep-related hormonal responses in college-aged males.
In this study, the cross-over design was utilized. The subjects (N = 10) without any physical problems or sleep disorders participated in the experimental performed 4 protocols in only sun exposure (for 30 minutes, EG1) protocol, only aerobic exercise (walking and jogging for 30 minutes, EG2) protocol, aerobic exercise with sun exposure (EG3) protocol, and control (no exercise and no sun exposure, EG4) protocol. Each protocol was 5 times per week with one-week break (wash-out period) between protocols to prevent the effects of the previous protocol. Total test period was should be 7 weeks (one week of protocol and one week of break). Before and after each aerobic exercise session, the subjects completed stretching to warm up for 5 to 10 minutes. Surveys consisting of (bedtime, wake-up time, sleep onset latency, and (Pittsburgh Sleep Quality Index (PSQI) were obtained before the test and after each protocol. After each protocol, the following sleep-related hormonal responses were measured: blood concentrations of melatonin, cortisol, epinephrine, and norepinephrine. One-way ANOVA was used to determine differences between protocols. Statistical significance was set at p < 0.05.
Bedtime of EG4 was significantly later than that of the EG1 or EG3. Wake-up time in the EG4 was significantly later than that of the EG1 or the EG3. Sleep onset latency in the EG4 was longer than that of the EG3. The quality of sleep in the EG4 was lower than that of the EG3. Sleep cycle in the EG4 was significantly shorter than that of the EG1. Blood melatonin concentrations of the EG3 was significantly higher than that of the EG4. There were no significant differences in blood concentrations of cortisol, epinephrine, or norepinephrine among protocols, with the order from the lowest to the highest values of EG1 < EG2 < EG3 < EG4.
The present data found that EG1 and EG3 showed positive sleep-related hormonal responses, sleep habits, and quality of sleep, indicating that sun exposure or exercise with sun exposure may improve the physical status and quality of life.
PMCID: PMC4241899  PMID: 25566466
exercise; sun exposure; sleep quality; sleep hormone
17.  Effects of L-serine ingestion on human sleep 
SpringerPlus  2014;3:456.
To investigate the effects of L-serine intake on human sleep, we conducted two randomized double-blinded crossover studies. In Study 1, healthy subjects who were dissatisfied with their sleep were given L-serine or a placebo 30 min before going to bed. After waking the next morning, subjective sleep quality was rated using the Ogri-Shirakawa-Azumi subjective sleep rating scale. In Study 2, subjective sleep quality was rated using the St. Mary’s Hospital sleep questionnaire, and objective parameters, including sleep initiation time, number of nighttime awakenings, and hours of sleep, were evaluated using actigraphy. In Study 1, factors related to “sleep initiation” and “sleep maintenance” during the L-serine intake period were significantly improved compared to the placebo intake period (p = 0.02 and p = 0.008, respectively). In Study 2, scores for “How well did you sleep last night?” and “How satisfied were you with last night’s sleep?” were significantly better during L-serine intake compared to placebo (p = 0.04 and p = 0.03, respectively). Subjective evaluation of sleep quality on waking was thus improved. In addition, objective evaluation using actigraphy showed that the “number of nighttime awakenings” tended to be decreased (p = 0.08). These findings suggest that intake of L-serine before going to bed may improve human sleep.
PMCID: PMC4155056  PMID: 25197619
Human sleep; L-serine; Amino acid
18.  Apnea-Induced Rapid Eye Movement Sleep Disruption Impairs Human Spatial Navigational Memory 
The Journal of Neuroscience  2014;34(44):14571-14577.
Hippocampal electrophysiology and behavioral evidence support a role for sleep in spatial navigational memory, but the role of particular sleep stages is less clear. Although rodent models suggest the importance of rapid eye movement (REM) sleep in spatial navigational memory, a similar role for REM sleep has never been examined in humans. We recruited subjects with severe obstructive sleep apnea (OSA) who were well treated and adherent with continuous positive airway pressure (CPAP). Restricting CPAP withdrawal to REM through real-time monitoring of the polysomnogram provides a novel way of addressing the role of REM sleep in spatial navigational memory with a physiologically relevant stimulus. Individuals spent two different nights in the laboratory, during which subjects performed timed trials before and after sleep on one of two unique 3D spatial mazes. One night of sleep was normally consolidated with use of therapeutic CPAP throughout, whereas on the other night, CPAP was reduced only in REM sleep, allowing REM OSA to recur. REM disruption via this method caused REM sleep reduction and significantly fragmented any remaining REM sleep without affecting total sleep time, sleep efficiency, or slow-wave sleep. We observed improvements in maze performance after a night of normal sleep that were significantly attenuated after a night of REM disruption without changes in psychomotor vigilance. Furthermore, the improvement in maze completion time significantly positively correlated with the mean REM run duration across both sleep conditions. In conclusion, we demonstrate a novel role for REM sleep in human memory formation and highlight a significant cognitive consequence of OSA.
PMCID: PMC4212062  PMID: 25355211
continuous positive airway pressure (CPAP); obstructive sleep apnea; randomized controlled trial; REM sleep; sleep fragmentation; spatial navigational memory
19.  Obstructive Sleep Apnea and Risk of Cardiovascular Events and All-Cause Mortality: A Decade-Long Historical Cohort Study 
PLoS Medicine  2014;11(2):e1001599.
Tetyana Kendzerska and colleagues explore the association between physiological measures of obstructive sleep apnea other than the apnea-hypopnea index and the risk of cardiovascular events.
Please see later in the article for the Editors' Summary
Obstructive sleep apnea (OSA) has been reported to be a risk factor for cardiovascular (CV) disease. Although the apnea-hypopnea index (AHI) is the most commonly used measure of OSA, other less well studied OSA-related variables may be more pathophysiologically relevant and offer better prediction. The objective of this study was to evaluate the relationship between OSA-related variables and risk of CV events.
Methods and Findings
A historical cohort study was conducted using clinical database and health administrative data. Adults referred for suspected OSA who underwent diagnostic polysomnography at the sleep laboratory at St Michael's Hospital (Toronto, Canada) between 1994 and 2010 were followed through provincial health administrative data (Ontario, Canada) until May 2011 to examine the occurrence of a composite outcome (myocardial infarction, stroke, congestive heart failure, revascularization procedures, or death from any cause). Cox regression models were used to investigate the association between baseline OSA-related variables and composite outcome controlling for traditional risk factors. The results were expressed as hazard ratios (HRs) and 95% CIs; for continuous variables, HRs compare the 75th and 25th percentiles. Over a median follow-up of 68 months, 1,172 (11.5%) of 10,149 participants experienced our composite outcome. In a fully adjusted model, other than AHI OSA-related variables were significant independent predictors: time spent with oxygen saturation <90% (9 minutes versus 0; HR = 1.50, 95% CI 1.25–1.79), sleep time (4.9 versus 6.4 hours; HR = 1.20, 95% CI 1.12–1.27), awakenings (35 versus 18; HR = 1.06, 95% CI 1.02–1.10), periodic leg movements (13 versus 0/hour; HR = 1.05, 95% CI 1.03–1.07), heart rate (70 versus 56 beats per minute [bpm]; HR = 1.28, 95% CI 1.19–1.37), and daytime sleepiness (HR = 1.13, 95% CI 1.01–1.28).The main study limitation was lack of information about continuous positive airway pressure (CPAP) adherence.
OSA-related factors other than AHI were shown as important predictors of composite CV outcome and should be considered in future studies and clinical practice.
Please see later in the article for the Editors' Summary
Editors' Summary
Obstructive sleep apnea (OSA) is a common sleep-related breathing disorder, particularly among middle-aged and elderly people. It is characterized by apnea—a brief interruption in breathing that lasts at least 10 seconds—and hypopnea—a decrease of more than 50% in the amplitude of breathing that lasts at least 10 seconds or clear but smaller decrease in amplitude associated with either oxygen desaturation or an arousal. Patients with OSA experience numerous episodes of apnea and hypopnea during the night; severe OSA is defined as having 30 or more episodes per hour (an apnea-hypopnea index [AHI] of >30). These breathing interruptions occur when relaxation of the upper airway muscles decreases the airflow, which lowers the amount of oxygen in the blood. As a result, affected individuals frequently wake from deep sleep as they struggle to breathe. Symptoms of OSA include loud snoring and daytime sleepiness. Treatments include lifestyle changes such as losing weight (excess fat around the neck increases airway collapse) and smoking cessation. For severe OSA, doctors recommend continuous positive airway pressure (CPAP), in which a machine blows pressurized air through a face mask into the airway to keep it open.
Why Was This Study Done?
OSA can be life-threatening. Most directly, daytime sleepiness can cause accidents, but OSA is also associated with an increased risk of developing cardiovascular disease (CVD, disease that affects the heart and the circulation). To date, studies that have investigated the association between OSA and the risk of myocardial infarction (heart attack), congestive heart failure, stroke, and other CVDs have used the AHI to diagnose and categorize the severity of OSA. However, by focussing on AHI, clinicians and researchers may be missing opportunities to improve their ability to predict which patients are at the highest risk of CVD. In this historical cohort study, the researchers investigate the association between other OSA-related variables (for example, blood oxygen saturation and sleep fragmentation) and the risk of cardiovascular events and all-cause mortality (death). A historical cohort study examines the medical records of groups of individuals who have different characteristics at baseline for the subsequent occurrence of specific outcomes.
What Did the Researchers Do and Find?
The researchers used administrative data (including hospitalization records and physicians' claims for services supplied to patients) to follow up adults referred for suspected OSA who underwent diagnostic polysomnography (a sleep study) at a single Canadian hospital between 1994 and 2010. A database of the polysomnography results provided information on OSA-related variables for all the study participants. Over an average follow-up of about 6 years, 11.5% of the 10,149 participants were hospitalized for a myocardial infarction, stroke, or congestive heart failure, underwent a revascularization procedure (an intervention that restores the blood supply to an organ or tissue after CVD has blocked a blood vessel), or had died from any cause. After adjusting for multiple established risk factors for CVD such as smoking and age in Cox regression models (a statistical approach that examines associations between patient variables and outcomes), several OSA-related variables (but not AHI) were significant predictors of CVD. The strongest OSA-related predictor of cardiovascular events or all-cause mortality was total sleep time spent with oxygen saturation below 90%, which increased the risk of a cardiovascular event or death by 50%. Other statistically significant OSA-related predictors (predictors that were unlikely to be associated with the outcome through chance) of cardiovascular events or death included total sleep time, number of awakenings, frequency of periodic leg movements, heart rate, and daytime sleepiness.
What Do These Findings Mean?
These findings indicate that OSA-related factors other than AHI are important predictors of the composite outcome of a cardiovascular event or all-cause mortality. Indeed, although AHI was significantly associated with the researchers' composite outcome in an analysis that did not consider other established risk factors for CVD (“confounders”), the association became non-significant after controlling for potential confounders. The accuracy of these findings, which need to be confirmed in other settings, is likely to be limited by the lack of information available about the use of CPAP by study participants and by the lack of adjustment for some important confounders. Importantly, however, these findings suggest that OSA-related factors other than AHI should be considered as predictors of CVD in future studies and in clinical practice.
Additional Information
Please access these websites via the online version of this summary at
The US National Heart Lung and Blood Institute has information (including several videos) about obstructive sleep apnea (in English and Spanish), sleep studies, heart disease, and other cardiovascular diseases (some information in English and Spanish)
The UK National Health Service Choices website provides information (including personal stories) about sleep apnea and about cardiovascular disease
The not-for-profit American Sleep Apnea Association provides detailed information about sleep apnea for patients and health-care professionals, including personal stories about the condition
The MedlinePlus encyclopedia has pages on obstructive sleep apnea and on polysomnography; MedlinePlus provides links to further information and advice about obstructive sleep apnea, heart diseases, and vascular diseases (in English and Spanish)
PMCID: PMC3913558  PMID: 24503600
Sleep medicine  2011;12(5):512-517.
The purpose of this study was to test the feasibility and acceptability of a gentle yoga intervention for sleep disturbance in older women with osteoarthritis (OA) and to collect initial efficacy data on the intervention.
All participants completed an 8-week yoga program that included 75-minute weekly classes and 20 minutes of nightly home practice. Participants were women with OA and symptoms consistent with insomnia. Symptom questionnaires and one week of wrist actigraphy and sleep diaries were completed for one week pre- and post-intervention.
Fourteen women were enrolled of whom 13 completed the study (mean age 65.2 ± 6.9 years). Participants attended a mean of 7.2 ± 1.0 classes and practiced at home 5.83 ± 1.66 nights/week. The Insomnia Severity Index and diary-reported sleep onset latency, sleep efficiency, and number of nights with insomnia were significantly improved at post-intervention versus pre-intervention (p < .05). Other sleep outcomes (Pittsburgh Sleep Quality Index, Epworth Sleepiness Scale, diary-reported total sleep time and wake after sleep onset) showed improvement on mean scores at post-intervention, but these were not statistically significant. Actigraphic sleep outcomes were not significantly changed.
This study supports the feasibility and acceptability of a standardized evening yoga practice for middle-aged to older women with OA. Preliminary efficacy findings support further research on this program as a potential treatment option for OA-related insomnia.
PMCID: PMC3120098  PMID: 21489869
Sleep; insomnia; osteoarthritis; aging; yoga; complementary therapies
21.  Effect of behavioural-educational intervention on sleep for primiparous women and their infants in early postpartum: multisite randomised controlled trial 
Objective To evaluate the effectiveness of a behavioural-educational sleep intervention delivered in the early postpartum in improving maternal and infant sleep.
Design Randomised controlled trial.
Setting Postpartum units of two university affiliated hospitals.
Participants 246 primiparous women and their infants randomised while in hospital with an internet based randomisation service to intervention (n=123) or usual care (n=123) groups.
Interventions The behavioural-educational sleep intervention included a 45-60 minute meeting with a nurse to discuss sleep information and strategies to promote maternal and infant sleep, a 20 page booklet with the content discussed, and phone contacts at one, two, and four weeks postpartum to reinforce information, provide support, and problem solve. The usual care group received calls at weeks one, two, and four to maintain contact without provision of advice.
Main outcome measures Primary outcome was maternal nocturnal (9 pm to 9 am) sleep (minutes) and secondary outcome was longest stretch of infant nocturnal sleep (minutes) measured at six and 12 weeks postpartum by actigraphy. Other outcomes measured at six and 12 weeks were number of maternal and infant night time awakenings by actigraphy, fatigue visual analogue scale, general sleep disturbance scale, and Edinburgh postnatal depression scale. Rates of exclusive breast feeding were measured at 12 weeks postpartum only.
Results All women who completed any outcome measures at six or 12 weeks were included in analysis. Sleep outcomes were completed at one or both of six and 12 weeks postpartum for 215 of 246 (87%) women (110/123 intervention and 105/123 usual care). Longitudinal mixed effects model analyses indicated no significant differences between the groups on any of the outcomes. The estimated mean difference in maternal nocturnal sleep between the intervention and usual care groups was 5.97 minutes (95% confidence interval −7.55 to 19.5 minutes, P=0.39). No differences in any outcomes were noted based on the specific nurse delivering the intervention or the number of phone contacts received.
Conclusion A behavioural-educational intervention delivered in the early postpartum, in hospital, and in the first weeks at home, was ineffective in improving maternal and infant sleep or other health outcomes in the first months postpartum.
Trial registration ISRCT No 13501166.
PMCID: PMC3603553  PMID: 23516146
22.  Sleep Patterns and Fatigue in New Mothers and Fathers 
Biological research for nursing  2004;5(4):311-318.
The purpose of this study was to describe the sleep patterns and fatigue of both mothers and fathers before and after childbirth. The authors used wrist actigraphy and questionnaires to estimate sleep and fatigue in 72 couples during their last month of pregnancy and 1st month postpartum. Both parents experienced more sleep disruption at night during the postpartum period as compared to the last month of pregnancy. Compared to fathers, with their stable 24-h sleep patterns over time, mothers had less sleep at night and more sleep during the day after the baby was born. Sleep patterns were also related to parents’work status and type of infant feeding. Both parents self-reported more sleep disturbance and fatigue during the 1st month postpartum than during pregnancy. Mothers reported more sleep disturbance than fathers, but there was no gender difference in ratings of fatigue. At both time points, fathers obtained less total sleep than mothers when sleep was objectively measured throughout the entire 24-h day. Further research is needed to determine the duration of sleep loss for both mothers and fathers, to evaluate the effect of disrupted sleep and sleep loss on psychosocial functioning and job performance, and to develop interventions for improving sleep patterns of new parents.
PMCID: PMC1307172  PMID: 15068660
sleep; fatigue; mothers; fathers; pregnancy; postpartum; naps
23.  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
24.  Postmenopausal hormones and sleep quality in the elderly: a population based study 
BMC Women's Health  2010;10:15.
Sleep disturbance and insomnia are commonly reported by postmenopausal women. However, the relationship between hormone therapy (HT) and sleep disturbances in postmenopausal community-dwelling adults is understudied. Using data from the multicenter Study of Osteoporotic Fractures (SOF), we tested the relationship between HT and sleep-wake estimated from actigraphy.
Sleep-wake was ascertained by wrist actigraphy in 3,123 women aged 84 ± 4 years (range 77-99) from the Study of Osteoporotic Fractures (SOF). This sample represents 30% of the original SOF study and 64% of participants seen at this visit. Data were collected for a mean of 4 consecutive 24-hour periods. Sleep parameters measured objectively included total sleep time, sleep efficiency (SE), sleep latency, wake after sleep onset (WASO), and nap time. All analyses were adjusted for potential confounders (age, clinic site, race, BMI, cognitive function, physical activity, depression, anxiety, education, marital status, age at menopause, alcohol use, prior hysterectomy, and medical conditions).
Actigraphy measurements were available for 424 current, 1,289 past, and 1,410 never users of HT. Women currently using HT had a shorter WASO time (76 vs. 82 minutes, P = 0.03) and fewer long-wake (≥ 5 minutes) episodes (6.5 vs. 7.1, P = 0.004) than never users. Past HT users had longer total sleep time than never users (413 vs. 403 minutes, P = 0.002). Women who never used HT had elevated odds of SE <70% (OR,1.37;95%CI,0.98-1.92) and significantly higher odds of WASO ≥ 90 minutes (OR,1.37;95%CI,1.02-1.83) and ≥ 8 long-wake episodes (OR,1.58;95%CI,1.18-2.12) when compared to current HT users.
Postmenopausal women currently using HT had improved sleep quality for two out of five objective measures: shorter WASO and fewer long-wake episodes. The mechanism behind these associations is not clear. For postmenopausal women, starting HT use should be considered carefully in balance with other risks since the vascular side-effects of hormone replacement may exceed its beneficial effects on sleep.
PMCID: PMC2876067  PMID: 20441593
25.  The effects of experimental sleep fragmentation on cognitive processing 
Sleep medicine  2010;11(4):378-385.
The primary objective of this study was to characterize the association between cyclic alternating pattern (CAP) and neurocognitive performance in a group of normal subjects before and after two nights of experimentally-induced sleep fragmentation.
Subjects and Methods
Fifteen healthy subjects underwent one night of uninterrupted and two sequential nights of experimental sleep fragmentation achieved by auditory and mechanical stimuli. Eight subjects were re-examined using a similar paradigm with three nights of uninterrupted sleep. Sleep was polygraphically recorded and CAP analysis was performed for all recordings. A battery of neurocognitive tests was performed for spatial attention, inhibition of return, mental rotation, and Stroop color word test in the afternoon following the first and third night of sleep under fragmented and non-fragmented conditions.
With sleep fragmentation, the percentage of slow-wave sleep was dramatically reduced and there was a two-fold increase in total CAP rate across all NREM sleep stages. Moreover, the number of all CAP A subtypes/hour of sleep (index) was significantly increased. Total CAP rate during the non-fragmented night correlated with reaction times. Similarly, the percentages of A1 and A3 subtypes were negatively and positively correlated with reaction times, respectively. Of the neurocognitive test battery, however, only values obtained from some subtests of the Mental Rotation test showed a significant improvement after sleep fragmentation.
The results of this study suggest that CAP A1 subtypes are associated with higher cognitive functioning, whereas CAP A3 subtypes are associated with lower cognitive functioning in young healthy subjects. The lack of cognitive functioning impairment after sleep fragmentation may be due to persistence and even enhancement of transient slow-wave activity contained in CAP A1 subtypes which also caused a significant enhancement of the EEG power spectrum in the lower frequencies.
PMCID: PMC2851141  PMID: 20226732
Cyclic Alternating Pattern; neurocognitive function; sleep fragmentation; slow-wave sleep; sleep instability; arousals

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