Impact of sleep debt on metabolic and endocrine function

Sleep duration, insomnia and behavioral problems among Chinese adolescents

This study examined the associations among sleep duration, insomnia, and behavioral problems in a sample of 1359 Chinese adolescents. Participants completed a self-administrated questionnaire that included questions on sleep duration and insomnia symptoms and the Youth Self-Report of Child Behavior Checklist. It was found that adolescents who complained of insomnia reported sleep duration only half an hour shorter than did those without insomnia. Sleep duration did not differ among adolescents reporting three different types of insomnia (difficulty initiating sleep, difficulty maintaining sleep, and early morning awakening). Adolescents with insomnia reported more behavioral problems than did those without complaints of insomnia. After adjustment for age and sex, sleep duration of less than 7 h a day was significantly associated with most behavioral problems in those without complaints of insomnia but with only a few behavioral problems in adolescents reporting insomnia. Results suggest that sleep duration in adolescents with insomnia is short, but not as short as reported in previous clinical studies. Insomnia and short sleep duration are associated with a wide range of behavioral and emotional problems in adolescents.

The genetics of sleep disorders

The contribution of genetic components to the pathology of sleep disorders is increasingly recognised as important. Genetic studies have identified genes that may be important in the regulation of circadian rhythms, which in turn determine the time of sleep onset and waking. Recent studies have shown that mutations in hPER2 are associated with autosomal-dominant familial advanced-sleep-phase syndrome. Genetic studies in a canine model of narcolepsy and in knock-out mice have led to the identification of the hypothalamic hypocretin (orexin) neurotransmitter system as a key target for human narcolepsy. The contribution of genetic factors to obstructive sleep apnoea syndrome (OSAS) has led to a better understanding of this complex disorder that may be part of a larger syndrome associated with respiratory, cardiovascular, and metabolic dysfunction. The aim of this review is to discuss the current knowledge on the role of genetic factors in sleep disorders, in particular circadian disorders, narcolepsy, restless-legs syndrome, and OSAS.

Do lonely days invade the nights? Potential social modulation of sleep efficiency

Loneliness predicts morbidity and mortality from broad-based causes, but the reasons for this effect remain unclear. Few differences in traditional health behaviors (e.g., smoking, exercise, nutrition) have been found to differentiate lonely and nonlonely individuals. We present evidence that a prototypic restorative behavior--sleep--does make such a differentiation, not through differences in time in bed or in sleep duration, but through differences in efficacy: In the study we report here, lonely individuals evinced poorer sleep efficiency and more time awake after sleep onset than nonlonely individuals. These results, which were observed in controlled laboratory conditions and were found to generalize to the home, suggest that lonely individuals may be less resilient than nonlonely individuals in part because they sleep more poorly. These results also raise the possibility that social factors such as loneliness not only may influence the selection of health behaviors but also may modulate the salubrity of restorative behaviors.

Effects of sleep pressure on endogenous cardiac autonomic activity and body temperature

This study investigated the effects of variations in sleep pressure on cardiac autonomic activity and body temperature. In a counterbalanced design, 12 healthy, young subjects (6 men and 6 women) remained recumbent during 30 h of wakefulness (high sleep pressure) and 6 h of wakefulness (low sleep pressure). Both periods of wakefulness were immediately followed by a sleep opportunity, and the first 2 h of sleep were analyzed. During extended hours of wakefulness, a reduction in heart rate was mediated by a decline in cardiac sympathetic activity (measured via preejection period) and the maintenance of cardiac parasympathetic activity (measured via respiratory sinus arrhythmia). In subsequent high-pressure sleep, parasympathetic activity was amplified and sympathetic activity was negatively associated with electroencephalographic slow-wave activity. Sleep deprivation had no impact on foot temperature, but it did alter the pattern of change in core body temperature. A downregulation of cardiac autonomic activity during both extended hours of wakefulness and subsequent sleep may respectively provide "protection" and "recovery" from the temporal extension of cardiac demand.

Morbidity of obstructive sleep apnea in children: facts and theory

Sleep-disordered breathing (SDB) is a frequent, albeit underdiagnosed, problem in children. If left untreated, SDB may lead to substantial morbidities affecting multiple target organs and systems. This review provides a detailed and current description of the current status of our understanding of SDB-associated morbidity in children, and provides recommendations of future research directions necessary for increasing our knowledge and awareness on the short- and long-term consequences of SDB during childhood.

Immediate effects of an 8-h advance shift of the rest-activity cycle on 24-h profiles of cortisol

To investigate the adaptation of plasma cortisol profiles to an abrupt phase advance of the rest-activity cycle, eight normal young subjects were submitted in a sleep laboratory to an 8-h advance shift of their sleep-wake and dark-light cycles. The shift was achieved by advancing bedtimes from 2300-0700 to 1500-2300. Blood samples were obtained at 20-min intervals for 68 consecutive hours. The shift resulted within 6-9 h in a 3- to 4-h advance of timings of the nadir of the cortisol profile and of the end of the quiescent period but had no immediate effect on the timing of cortisol acrophase. The quiescent period of cortisol secretion was shortened and fragmented. Thus a major advance shift achieved without enforcing sleep deprivation results in a rapid partial adaptation of the temporal profiles of cortisol but also in a marked disruption of the cortisol quiescent period. Sleep onset was consistently followed by a decrease in cortisol concentrations. Conversely, both sleep-wake and dark-light transitions were consistently associated with cortisol secretory pulses.

Loneliness and health: potential mechanisms

OBJECTIVE

Two studies using cross-sectional designs explored four possible mechanisms by which loneliness may have deleterious effects on health: health behaviors, cardiovascular activation, cortisol levels, and sleep.

METHODS

In Study 1, we assessed autonomic activity, salivary cortisol levels, sleep quality, and health behaviors in 89 undergraduate students selected based on pretests to be among the top or bottom quintile in feelings of loneliness. In Study 2, we assessed blood pressure, heart rate, salivary cortisol levels, sleep quality, and health behaviors in 25 older adults whose loneliness was assessed at the time of testing at their residence.

RESULTS

Total peripheral resistance was higher in lonely than nonlonely participants, whereas cardiac contractility, heart rate, and cardiac output were higher in nonlonely than lonely participants. Lonely individuals also reported poorer sleep than nonlonely individuals. Study 2 indicated greater age-related increases in blood pressure and poorer sleep quality in lonely than nonlonely older adults. Mean salivary cortisol levels and health behaviors did not differ between groups in either study.

CONCLUSIONS

Results point to two potentially orthogonal predisease mechanisms that warrant special attention: cardiovascular activation and sleep dysfunction. Health behavior and cortisol regulation, however, may require more sensitive measures and large sample sizes to discern their roles in loneliness and health.

Diabetes and cardiovascular disease

This review focuses on several topics related to the epidemiology of diabetes and cardiovascular disease (CVD). These include the CVD risk factors common in the metabolic syndrome, behavioral risk factors and diabetes, gender differences in the association between diabetes and CVD risk, and how the clinical definition of diabetes influences the association of diabetes and CVD. Nontraditional risk factors potentially linking diabetes and CVD are also discussed, including chronic inflammation, advanced glycation endpoints, autonomic neuropathy, sleep-disordered breathing, and genetic susceptibility to diabetes-associated CVD risk.

Sleep and the hypothalamo-pituitary-adrenocortical system

The intention of this review is to summarize the current knowledge on the bidirectional interaction between sleep EEG and the secretion of corticotropin (ACTH) and cortisol. The administration of various hypothalamic-pituitary- adrenocortical (HPA) hormones and their antagonists exerts specific sleep-EEG changes in several species including humans. It is well documented that corticotropin releasing hormone (CRH) impairs sleep and enhances vigilance. In addition, it may promote REM sleep. Changes in the growth hormone-releasing hormone (GHRH):CRH ratio in favour of CRH appear to contribute to shallow sleep, elevated cortisol levels and blunted GH in depression and ageing. On the other hand, in women GHRH appears to exert CRH-like effects on sleep. Acute cortisol administration increases slow-wave sleep (SWS) and GH, probably due to feedback inhibition of CRH, and inhibits REM sleep. With the mixed glucocorticoid and progesterone receptor antagonist mifepriston sleep is disrupted. Subchronic administration of the glucocorticoid agonist methylprednisolone desinhibited REM sleep. A synergism of elevated CRH and cortisol activity may contribute to REM disinhibition during depression. Also ACTH and vasopressin modulate sleep specifically but their physiological role remains unclear. For example acute icv vasopressin enhances wakefulness in rats, whereas its long-term administration increases SWS in the elderly. In various studies the interaction of sleep EEG and HPA hormones has been investigated at the baseline, after manipulation of sleep-wake behaviour and after environmental changes. Most studies agree that the circadian pattern of cortisol is relatively independent from sleep and environmental influences. Some data suggest a major effect of light on cortisol secretion. Sleeping is widely associated with blunting and awakenings are linked with increases of HPA hormones.

Potentially harmful sleep habits of 3-year-old children in Japan

To examine the sleep habits of 3-year-old children, we questioned guardians during a routine health examination for 3-year-old children at a public health center. According to the 1105 questionnaires analyzed, the proportion of children who fell asleep at 10 p.m. or later was 49.6%. The nocturnal sleep onset time was significantly correlated with the wake-up time in the morning and was significantly negatively correlated with the nocturnal sleep duration. The average daily total sleep duration (nocturnal sleep duration + nap duration) of regular nap-takers showed a significant negative correlation with the nocturnal sleep onset time. The average values for height, weight, and body mass index (BMI) were not correlated with the nocturnal sleep onset time. Children who went to sleep later got less sleep than those who went to sleep earlier. Because sleep debt has a harmful impact on older children and adults, late sleep onset may have adverse health consequences in young children.

Sleep-disordered breathing and insulin resistance in middle-aged and overweight men

Sleep-disordered breathing is a prevalent condition associated with impairment of daytime function and may predispose individuals to metabolic abnormalities independent of obesity. The primary objective of this study was to determine the metabolic consequences and community prevalence of sleep-disordered breathing in mildly obese, but otherwise healthy, individuals. One hundred and fifty healthy men, without diabetes or cardiopulmonary disease, were recruited from the community. Measurements included polysomnography, a multiple sleep latency test, an oral glucose tolerance test, determination of body fat by hydrodensitometry, and fasting insulin and lipids. The prevalence of sleep-disordered breathing, depending on the apnea-hypopnea index (AHI) cutoff, ranged from 40 to 60%. After adjusting for body mass index (BMI) and percent body fat, an AHI gt-or-equal, slanted 5 events/h was associated with an increased risk of having impaired or diabetic glucose tolerance (odds ratio, 2.15; 95% CI, 1.05-4.38). The impairment in glucose tolerance was related to the severity of oxygen desaturation (DeltaSa(O(2))) associated with sleep-disordered breathing. For a 4% decrease in oxygen saturation, the associated odds ratio for worsening glucose tolerance was 1.99 (95% CI, 1.11 to 3.56) after adjusting for percent body fat, BMI, and AHI. Multivariable linear regression analyses revealed that increasing AHI was associated with worsening insulin resistance independent of obesity. Thus, sleep-disordered breathing is a prevalent condition in mildly obese men and is independently associated with glucose intolerance and insulin resistance.

An epidemiological study on relationship between the hours of sleep and life style factors in Japanese factory workers

To prevent "life style-related diseases", it is necessary to evaluate not only the factors directly related to sleep but also the relationship between sleep and other life style-related factors (such as smoking, alcohol drinking, food habits, and exercise routines). There have been no extensive studies conducted on these relationships. A survey was conducted on 2,000 employees of a large plant over a 6-year period to provide data that would allow one to analyze correlation between hours of sleep and other life style factors, such as smoking, alcohol drinking, dietary habit, and exercise. It focused on a serial evaluation, with special reference to the correlation between sleep and smoking and drinking habits, exercise, and food habits. In relation to smoking or an alcohol drinking habit, no significant correlation was found between those who did not get enough sleep and those who got adequate sleep. For the dietary habits, the group with insufficient hours of sleep was related to a less than satisfactory frequency of meal taking, irregularity of eating, snacking habits, excessive seasoning of food, and consumption of insufficient quantities of vegetables. Conversely, it was recognized that those who have satisfactory food habits are more likely to enjoy an appropriate amount of sleep. Those who fail to get sufficient sleep engage in food habits that are more likely to cause life style-related diseases.

The hypothalamic-pituitary-adrenal axis in the pathogenesis of rheumatic diseases

Many studies have demonstrated altered HPA axis activity in patients with rheumatic diseases. In the case of autoimmune inflammatory diseases, circumstantial evidence suggests that failure of the neuroendocrine-immune regulatory loop may lead to insufficient production of endogenous glucocorticoid. Nevertheless, in human autoimmune disease, it is not possible to determine if altered HPA axis activity predates the onset of chronic inflammation. Animal studies and some early genetic studies in RA patients lend credibility to the argument that insufficient HPA axis response to inflammatory stimuli may increase susceptibility to, or severity of, these diseases. Most patients with rheumatic diseases complain of musculoskeletal pain. There is evidence of HPA axis involvement in acute and chronic pain. In the case of FM, pain cannot be explained on the basis of inflammation or altered musculoskeletal anatomy. This has led to the hypothesis that central nervous system mechanisms contribute to the symptom of somatic pain. Again, it is unclear if the observed HPA axis abnormalities reflect pre-existing vulnerability to the FM spectrum of disease, or whether chronic somatic symptoms alter HPA axis activity. Availability of technology to study better central components of the HPA axis may shed further light on its role in the pathogenesis of inflammatory autoimmune rheumatic diseases and musculoskeletal pain syndromes.

A dose-response relationship between short sleeping hours and childhood obesity: results of the Toyama Birth Cohort Study

BACKGROUND

Short sleeping hours could cause obesity through increased sympathetic activity, elevated cortisol secretion and decreased glucose tolerance. The aim of this study was to clarify parental and lifestyle factors, particularly sleeping habits, associated with obesity in Japanese children.

METHODS

Between June and July 1996, 8274 children (4194 males and 4080 females) aged 6-7 years living in Toyama prefecture, Japan, were investigated by questionnaire survey and the collection of anthropometric data. Subjects with a body mass index (BMI; weight in kg divided by square of height in m) greater than the age- and sex-specific cut-off points linked to adulthood overweight (BMI of 25 kg/m2 or more) were defined as obese subjects. Parental obesity was defined as a BMI of 25 kg/m2 or more. Logistic regression analysis was performed to evaluate the strength of the relationships between parental obesity or lifestyle factors and childhood obesity, adjusted for possible confounding factors.

RESULTS

Parental obesity, long hours of TV watching and physical inactivity were significantly associated with childhood obesity. Although wake-up time was not related to obesity, there was a significant dose-response relationship between late bedtime or short sleeping hours and childhood obesity. Compared with children with 10 or more hours of sleep, the adjusted odds ratio was 1.49 (95% confidence interval 1.08-2.14) for those with 9-10 h sleep, 1.89 (1.34-2.73) for those with 8-9 h sleep and 2.87 (1.61-5.05) for those with <8 h sleep, after adjustment for age, sex, parental obesity and other lifestyle factors.

CONCLUSION

A strong inverse association was observed in the relationship between sleeping hours and childhood obesity. Longitudinal research will be required to confirm this causality.

Sleep deprivation reduces total plasma homocysteine levels in rats

Hyperhomocysteinemia has been associated with pathological and stressful conditions and is a risk factor for cardiovascular disease. Since sleep deprivation is a stressful condition that is associated with disruption of various physiological processes, we investigated whether it would also be associated with increases in plasma homocysteine levels. Further, since hyperhomocysteinemia may promote oxidative stress, and we had previously found evidence of oxidative stress in brain following sleep deprivation, we also searched for evidence of systemic oxidative stress by measuring glutathione and thiobarbituric acid reactive substance levels. Rats were sleep deprived for 96 h using the platform technique. A group was killed after sleep deprivation and another two groups were allowed to undergo sleep recovery for 24 or 48 h. Contrary to expectation, plasma homocysteine was reduced in sleep-deprived rats as compared with the control group and did not revert to normal levels after 24 or 48 h of sleep recovery. A trend was observed towards decreased glutathione and increased thiobarbituric acid reactive substance levels in sleep-deprived rats. It is possible that the observed decreases in homocysteine levels may represent a self-correcting response to depleted glutathione in sleep-deprived animals, which would contribute to the attenuation of the deleterious effects of sleep deprivation.

Subjective sleep problems in later life as predictors of cognitive decline. Report from the Maastricht Ageing Study (MAAS)

BACKGROUND

Although biological sleep criteria seem to be associated with cognitive changes in older people, it is not clear if subjective sleep parameters are related to cognitive decline in later life.

OBJECTIVES

The aim of this study was to determine whether subjective sleep complaints in a population-based sample of 838 middle aged and older adults (>or= 50 years) predicted cognitive decline over a period of 3 years.

METHODS

Sleep complaints at baseline, assessed with the subscale Sleep Problems of the Symptoms Checklist-90, were used as a predictor variable. Cognitive performance at follow-up, measured with the Mini Mental Status Examination, was employed as a dependent variable.

RESULTS

Controlling for the effects of age, gender, length of follow-up interval, systemic diseases, and cognitive function at baseline, subjective sleep complaints were negatively associated with cognitive performance at follow-up.

CONCLUSION

Subjective sleep complaints predict cognitive decline in middle aged and older adults. Mechanisms behind the effect of subjective sleep complaints on cognitive performance are discussed.

Sleep disturbance after burn injury

This study describes sleep disturbance and related factors in a group of 74 patients at 1 week after discharge using a sleep problems questionnaire developed by the authors. Results indicated that a significant proportion of patients reported a problem with their sleep (73%). Several items were identified as highly prevalent, including frequent nighttime awakenings (87%), napping during the daytime (65%), sleeping alone (64%), experiencing pain during the night (62%), and difficulties with sleep onset (62%). Results suggest numerous possible interventions to improve patients' sleep quality. The usefulness of a more extensive questionnaire was also indicated.

Sleep-related breathing disorders, loud snoring and excessive daytime sleepiness in obese subjects

OBJECTIVE

To investigate the prevalence of sleep breathing disorders, loud snoring and excessive daytime sleepiness in a group of obese subjects, and to identify the predictors of obstructive sleep apnea (OSA) severity in these patients.

SUBJECTS

A total of 161 consecutive obese patients (body mass index (BMI)> or =30.0 kg/m(2)), ranging between 30.0 and 67.3, represented by 57 men and 104 women, aged 16-75 y. Forty (15 men and 25 women) age-matched (20-70 y) nonobese (BMI<27 kg/m(2)) volunteers were also recruited for the study.

MEASUREMENTS

Respiratory function parameters, nocturnal sleep quality (evaluated by a specific questionnaire), nocturnal hypoventilation and OSA (evaluated by night polysomnography) were examined in all subjects. Anthropometric parameters (neck circumference, waist circumference, waist-to-hip ratio) were also investigated.

RESULTS

Eighty-three obese patients (51.5% of the obese group) had a respiratory disturbance index (RDI)> or =10, corresponding to a moderate or severe sleep apnea. In particular, 24.8% (40/161), ie a quarter of all obese patients, were affected by severe OSA and this alteration was present in 42.1% of obese men (24/57) and in 15.4% (16/104) of obese women. When a stepwise multiple regression analysis was performed, neck circumference in men and BMI in women were shown to be the strongest predictors of sleep apnea. Twenty-nine percent of all obese subjects (40.3% of men and 23.1% of women) showed nocturnal hypoventilation; however, it was present as a unique breathing alteration in only 5% of the obese population. The percentage of patients having excessive daytime sleepiness was significantly higher than in nonobese subjects, even when only nonapneic obese patients were considered (P<0.001).

CONCLUSION

This study shows that OSA is present in more than 50% of a population of obese patients with a mean BMI higher than 40.0, this percentage being much higher than that commonly reported in previous studies, particularly in women. Neck circumference in men and BMI in women seem to be the strongest predictors of the severity of OSA in obese patients. Nocturnal hypoventilation seems to be present in more than 29% of a severe obese population. Moreover, this study indicates that morbid obesity can be associated with excessive daytime sleepiness even in the absence of sleep apnea.

Sleep disturbance in association with elevated pulse rate for prediction of mortality--consequences of mental strain?

OBJECTIVES

Sleep deprivation has experimentally been shown to adversely influence glucose metabolism, endocrine function and sympathovagal balance in young men without known serious disease. We investigated the impact of sleep problems and resting heart rate in a large sample of self-reported, healthy middle-aged men and women on long-term mortality.

METHODS

In all 22,444 men and 10,902 women participated in a population-based health screening (71% mean attendance), including blood sampling and examination of blood pressure (BP) and pulse rate after 10 min supine rest, as well as a self-administered questionnaire on sleep problems. Mortality was assessed from national death registers.

RESULTS

Sleep disturbances were related to increased cardiovascular risk factor levels at baseline in both sexes, and predicted total and cause-specific mortality after a mean of 12 years (women) and 17 years (men) of follow-up. In men, self-reported healthy at baseline, total mortality during follow-up was independently predicted by both sleep problems and increased resting heart rate, also after adjustment for smoking, body mass index (BMI), systolic BP, cholesterol, smoking and problematic alcohol drinking habits. A step-wise increased total mortality was shown in men reporting successively worse sleep problems and higher heart rate, highest hazard ratio 2.7 [95% confidence interval (CI) = 2.1-3.4] after adjustments, compared with men free from sleep problems and with normal heart rate.

CONCLUSIONS

Sleep disturbance is a predictor of total and cause-specific mortality in both sexes, but only interacts with increased resting heart rate for this prediction in healthy men. Sleep problems correlated cross-sectional with disturbances in lipid and glucose metabolism, even after adjustment for degree of obesity and smoking. Sleep disturbance is a symptom for a biological pathway that is correlated to premature mortality. One possible explanation would be that it acts in concert with sympathetic nervous activation (SNA), both being consequences of chronic stress exposure.

Sleep deprivation elevates plasma corticosterone levels in neonatal rats

Plasma corticosterone (CORT) levels were measured after short periods of sleep deprivation in rats at postnatal days 12, 16, 20, and 24. There was an age-dependent increase in basal CORT levels and sleep deprivation significantly elevated CORT at all ages compared to non-sleep deprived controls. The levels of CORT after sleep deprivation in P16, P20 and P24 animals were similar, resulting in an age-dependent decrease of the magnitude of the response. Sleep deprived P12 animals had lower levels of CORT. However, the observed response to sleep deprivation suggests that sleep loss is a significant stressor at this age. These observations suggest that younger animals are more sensitive to the effects of mild sleep deprivation than older ones.

Is there an association between shift work and having a metabolic syndrome? Results from a population based study of 27,485 people

OBJECTIVES

To explore how metabolic risk factors for cardiovascular disease (CVD) differ between shift workers and day workers in a defined population. Shift work has been associated with an increased risk of CVD. Risk factors and causal pathways for this association are only partly known.

METHODS

A working population of 27,485 people from the Västerbotten intervention program (VIP) has been analysed. Cross sectional data, including blood sampling and questionnaires were collected in a health survey.

RESULTS

Obesity was more prevalent among shift workers in all age strata of women, but only in two out of four age groups in men. Increased triglycerides (>1.7 mmol/l) were more common among two age groups of shift working women but not among men. Low concentrations of high density lipoprotein (HDL) cholesterol (men<0.9 and women<1.0 mmol/l) were present in the youngest age group of shift workers in both men and women. Impaired glucose tolerance was more often found among 60 year old women shift workers. Obesity and high triglycerides persisted as risk factors in shift working men and women after adjusting for age and socioeconomic factors, with an OR of 1.4 for obesity and 1.1 for high triglyceride concentrations. The relative risks for women working shifts versus days with one, two, and three metabolic variables were 1.06, 1.20, and 1.71, respectively. The corresponding relative risks for men were 0.99, 1.30, and 1.63, respectively.

CONCLUSIONS

In this study, obesity, high triglycerides, and low concentrations of HDL cholesterol seem to cluster together more often in shift workers than in day workers, which might indicate an association between shift work and the metabolic syndrome.

Health in a 24-h society

With increasing economic and social demands, we are rapidly evolving into a 24-h society. In any urban economy, about 20% of the population are required to work outside the regular 0800-1700 h working day and this figure is likely to increase. Although the increase in shiftwork has led to greater flexibility in work schedules, the ability to provide goods and services throughout the day and night, and possibly greater employment opportunities, the negative effects of shiftwork and chronic sleep loss on health and productivity are now being appreciated. For example, sleepiness surpasses alcohol and drugs as the greatest identifiable and preventable cause of accidents in all modes of transport. Industrial accidents associated with night work are common, perhaps the most famous being Chernobyl, Three Mile Island, and Bhopal.

"Sleep is not tangible" or what the Hebrew tradition has to say about sleep

Much of what is known about sleep disorders has been uncovered in the last forty years. As scientists, we consider these discoveries to be landmarks. Yet there is a tremendous amount of information written about sleep in the Bible and its commentaries. Sleep, and even sleep disorders, are referred to in many instances and can be directly interpreted by what we know today. Our forefathers and foremothers generally viewed sleep as both pleasant and necessary and were aware that sleep was not one continuous stage. They referred to the function of sleep as being restorative. They deplored sleep deprivation, believing that it impaired life. They felt that excessive sleepiness was harmful. They understood that insomnia could be caused by stress and anxiety and by excessive alcohol, and that physical activity (exercise) and drinking milk could improve sleep. They suggested cures for insomnia, including some of the ideas included in today's sleep hygiene rules. They understood that there was a rhythm or timing to sleep. They even understood that it is easier to delay the circadian rhythm that to advance it. Although naps are not recommended, they sometimes took naps in the afternoon, but suggested just how long that nap should last-about one-half hour. And they knew that with age, although sleep is advanced, healthy elderly do not have difficulty sleeping. Although we think we have discovered many new features about sleep disorders, much of what we know today was suggested thousands of years ago and documented in the Bible and the Talmud.

Adenosine, prolonged wakefulness, and A1-activated NF-kappaB DNA binding in the basal forebrain of the rat

There is considerable evidence to suggest that adenosine is a modulator of behavioral state. Our previous reports showed that perfusion of adenosine into the basal forebrain decreased wakefulness. Furthermore, prolonged wakefulness resulted in increased levels of extracellular adenosine in the basal forebrain of cats and rats. However, the longer-term consequences of prolonged wakefulness and increased adenosine are largely unknown. We report here an increase in the DNA binding activity of the transcription factor, nuclear factor-kappa B (NF-kappaB) following 3 h of sustained wakefulness in the rat basal forebrain. Moreover, this treatment led to the appearance of the p65 subunit of NF-kappaB in the nucleus, as determined by western blot analysis of nuclear proteins. This contrasted with undetectable levels in the sleeping controls. A concomitant disappearance of I-kappaB in cytoplasm suggested the degradation of this inhibitor of NF-kappaB. In the acute in vitro basal forebrain slice preparation, perfusion of adenosine increased NF-kappaB DNA binding while pretreatment of the slices with the A1 adenosine receptor antagonist, cyclopentyl-1-3-dimethylxanthine, significantly reduced NF-kappaB DNA binding. These results are compatible with the hypothesis that increases in the levels of adenosine in the basal forebrain, that occur during prolonged wakefulness, act through an A1 adenosine receptor and a second messenger system to increase the activity of the transcription factor NF-kappaB. We further hypothesize that some of the long duration effects of prolonged wakefulness/sleep deprivation on performance and physiology, often termed 'sleep debt', might be mediated through adenosine and its activation of NF-kappaB, which is known to alter the expression of several behavioral state regulatory factors.

Sleep deprivation decreases phase-shift responses of circadian rhythms to light in the mouse: role of serotonergic and metabolic signals

The circadian pacemaker in the suprachiasmatic nuclei is primarily synchronized to the daily light-dark cycle. The phase-shifting and synchronizing effects of light can be modulated by non-photic factors, such as behavioral, metabolic or serotonergic cues. The present experiments examine the effects of sleep deprivation on the response of the circadian pacemaker to light and test the possible involvement of serotonergic and/or metabolic cues in mediating the effects of sleep deprivation. Photic phase-shifting of the locomotor activity rhythm was analyzed in mice transferred from a light-dark cycle to constant darkness, and sleep-deprived for 8 h from Zeitgeber Time 6 to Zeitgeber Time 14. Phase-delays in response to a 10-min light pulse at Zeitgeber Time 14 were reduced by 30% in sleep-deprived mice compared to control mice, while sleep deprivation without light exposure induced no significant phase-shifts. Stimulation of serotonin neurotransmission by fluoxetine (10 mg/kg), a serotonin reuptake inhibitor that decreases light-induced phase-delays in non-deprived mice, did not further reduce light-induced phase-delays in sleep-deprived mice. Impairment of serotonin neurotransmission with p-chloroamphetamine (three injections of 10 mg/kg), which did not increase light-induced phase-delays in non-deprived mice significantly, partially normalized light-induced phase-delays in sleep-deprived mice. Injections of glucose increased light-induced phase-delays in control and sleep-deprived mice. Chemical damage of the ventromedial hypothalamus by gold-thioglucose (600 mg/kg) prevented the reduction of light-induced phase-delays in sleep-deprived mice, without altering phase-delays in control mice. Taken together, the present results indicate that sleep deprivation can reduce the light-induced phase-shifts of the mouse suprachiasmatic pacemaker, due to serotonergic and metabolic changes associated with the loss of sleep.

Characteristic lifestyles in 6-year-old children with obese parents: Results of the toyama birth cohort study

OBJECTIVE

The aim of this study was to identify characteristic lifestyles in children with obese parents.

METHODS

8,030 children (4,072 males and 3,958 females) aged 6 to 7 years were investigated. A questionnaire relating to the lifestyles of children was distributed through elementary schools for completion by parents. The heights and weights of parents were self-reported. A parent with a body mass index (weight in kilograms divided by the square of height in meters) greater than the 90th percentile for gender (26.7 kg/m(2) for fathers and 24.3 kg/m(2) for mothers) was defined as an obese parent. A chi-square test for each trend was applied to evaluate an increasing trend in the frequency or level of each lifestyle in children with obese parents.

RESULTS

Children with obese parents were significantly associated with increasing trends in the proportions categorized by irregular intake of breakfast, faster eating, longer TV watching, and shorter sleeping hours.

CONCLUSIONS

These lifestyles are considered to be possible risk factors for the development of obesity. These characteristic lifestyles observed in children with obese parents could strengthen the relationship between child and parental body compositions, in addition to the genetic predisposition to obesity in children with obese parents. These findings indicate that education with lifestyle modification for obese parents will be required to prevent further weight gain in children with obese parents.

Sleep deprivation and hypothalamic-pituitary-adrenal (HPA) axis activity in depressed patients

In the present study we investigated HPA axis activity in depressed patients treated with partial sleep deprivation (PSD) in order to identify endocrinological characteristics related to PSD responsiveness. Thirty-three drug-free patients (14 men, 19 women) suffering from major depression according to DSM-IV criteria were treated with PSD. Response to PSD was defined as a reduction of at least 30% according to the 6-item version of the Hamilton Depression Scale (6-HAMD). Subsequently, the combined dexamethasone-suppression/CRH-stimulation test (DEX/CRH test) was performed. Patients were pretreated with 1.5 mg dexamethasone (DEX) at 23:00 h and challenged with 100 microg corticotropin-releasing hormone (CRH) the following day. Postdexamethasone cortisol concentrations (before CRH administration) served as parameters for the DST status (dexamethasone suppression test). The cortisol stimulation after CRH was used as measurement for the DEX/CRH test status. Of the depressive patients, 54.5% (18 out of 33) responded to PSD. DST suppressors (postdexamethasone cortisol levels < 15 ng/ml) showed a significantly greater reduction in 6-HAMD scores after PSD than DST nonsuppressors. Furthermore, a significant negative correlation between postdexamethasone cortisol levels and reduction in 6-HAMD scores after PSD could be established. However, there was no relationship between the cortisol stimulation following CRH challenge and response to PSD. Although the combined DEX/CRH challenge test is a more sensitive marker for HPA axis dysregulation in depression than the standard DST, the negative feedback of the HPA system reflected by the DST status is apparently more closely associated with response to partial sleep deprivation in major depressive disorder.

Hypothalamo-pituitary-adrenal axis activity is related to the level of central arousal: effect of sleep deprivation on the association of high-frequency waking electroencephalogram with cortisol release

The temporal and quantitative interrelationships between the hypothalamo-pituitary-adrenal (HPA) axis activity and the level of central arousal were studied in 10 healthy young men during daytime wakefulness. Two experimental sessions were conducted randomly between 09.00 and 18.00 h, once after nocturnal sleep and once after a night of total sleep deprivation. Spectral analysis of serial waking electroencephalography (EEG) from a short target fixation task repeated every 10 min was undertaken, along with an estimation of cortisol secretory profiles by deconvolution of plasma radioimmunoassay measures obtained from continuous blood withdrawal with regular sampling at a 10-min interval. Following nocturnal sleep, a temporal association between the HPA axis activity and the waking EEG activity was found, cortisol secretory rate following changes in frontal gamma (20-45 Hz) band power by 10 min (average R = 0.458, p < 0.001). Although it remained significant (average R = 0.276, p < 0.05), the association strength decreased significantly following total sleep deprivation (p < 0.05, Wilcoxon test). Cortisol plasma level, secretory rate and pulse amplitude were increased as well as waking EEG power in the delta (0.5-5.5 Hz), theta (5.5-8.5 Hz) and gamma frequency bands (all p values <0.05, Student t tests). The sleep deprivation-related increases in cortisol secretory rate and waking EEG gamma activity were quantitatively associated (R = 0.504, p < 0.05). These results support the existence of a common ultradian regulatory mechanism, co-ordinating HPA axis activity to the level of central arousal in man, which seems involved in the sleep deprivation-induced hyper-arousal.

Prolonged sedation with propofol in the rat does not result in sleep deprivation

The use of propofol provides sedation without prolonging emergence in patients in the Intensive Care Unit. When prolonged, however, continuous sedation may overlap with naturally occurring sleep periods and potentially increase the risk of sleep deprivation. We modified an established rat model of sleep to determine whether prolonged, continuous sedation results in sleep deprivation. Rats were continuously sedated for a 12-h period overlapping completely with their normal sleep phase. Electroencephalogram (EEG) and movement data were collected before and after the sedation period. Rats were evaluated for EEG and movement evidence of sleep deprivation after sedation. When compared with baseline, the time spent in rapid eye movement (REM) and non-REM sleep was decreased during the first 4 h after sedation. The duration of non-REM sleep bouts was not altered. Power in the delta band (0.5-4 Hz) during non-REM sleep was diminished during the first 2 h only. Movements were reduced during the first hour after emergence from sedation only. In summary, no EEG or behavioral evidence of sleep deprivation was observed on emergence from sedation. These results imply that sedation is associated with a restorative process reversing the natural accumulation of sleep need that occurs during wakefulness.

IMPLICATIONS

Prolonged sedation in the Intensive Care Unit may alter the restorative effects of naturally occurring sleep. We sedated rats during their sleep phase to determine whether sedation interferes with sleep. Upon emergence, no evidence of sleep deprivation was observed. Sedation may thus be associated with a restorative effect similar to sleep.

Somatic and psychological complaints and their correlates with insomnia in the Japanese general population

OBJECTIVE

This cross-sectional study was conducted to estimate the prevalence of somatic and psychological complaints (SPCs) and to investigate the association of SPCs with insomnia in a sample of the general adult population of Japan.

METHODS

We randomly selected 4000 adult residents (-20 years old) from five areas of Japan using stratified sampling and conducted interviews using a structured questionnaire. The questionnaire solicited information about eight somatic symptoms, eight psychological symptoms, three sleep problems, and demographic and health-related information. A total of 3,030 subjects completed questionnaires, giving a response rate of 75.8%.

RESULTS

Stiff neck/shoulder (45.3%), backache (35.1%), and fatigue (31.4%) were the most common complaints in this population. In general, SPCs were more prevalent in younger persons and in women. Logistic regression analyses, controlling for other factors, showed that insomnia was significantly associated with a number of SPCs: backache (odds ratio [OR] = 1.4, 95% confidence interval [CI] = 1.1-1.6), epigastric discomfort (OR = 1.7, 95% CI = 1.3-2.2), weight loss (OR = 2.0, 95% CI = 1.2-3.3), headache (OR = 1.7, 95% CI = 1.3-2.2), fatigue (OR = 1.7, 95% CI = 1.4-2.1), worrying (OR = 1.6, 95% CI = 1.1-2.3), irritability (OR = 1.4, 95% CI = 1.1-1.7), and loss of interest (OR = 1.8, 95% CI = 1.2-2.7).

CONCLUSIONS

SPCs were common and were largely associated with insomnia in the general adult population of Japan. Further study is needed to examine the causal links between SPCs and insomnia.

Reducing disruption of circadian temperature rhythm following surgery

Temperature and other circadian rhythms are disrupted following surgery and other traumatic events. During recovery, coordination between temperature rhythms and other rhythmic physiologic processes is reduced. Studies of animals and humans have shown that return of synchrony is not immediate, but that it is important in the recovery process. The purpose of this study was to test a combination of cues that have been shown to adjust the timing of circadian temperature rhythm. The combined cues consisted of timed ingestion of caffeine and protein foods and adjustment of the sleep/wake cycle. The intervention was tested in 26 age- and gender-matched maxillofacial surgery patients. Patients were randomly assigned to control or experimental groups. Circadian temperature rhythm was measured by continuous monitoring with axillary probes and miniature recorders before and after surgery. Following surgery, both experimental and control subjects displayed 24-hour circadian temperature rhythms; however, the peak-to-trough difference was decreased more following surgery in the control subjects than in the subjects who had prepared for surgery by practicing the intervention. Control subjects also had less day-to-day stability in the phase of their rhythms following surgery. These results suggest that the intervention reduced circadian disruption following surgery and provides a way for patients to prepare themselves to resist rhythm changes.

How much sleep do we need?

There is increasing concern for sleeplessness-related risks in modern society. Some recent epidemiological data seem to support the view that many segments of the adult population have chronically inadequate sleep. On the other hand, some experts have claimed that our core, basic amount of sleep is around 6 h per night, and that the rest of our sleep can be easily curtailed, being unnecessary to fulfill any sleep need. However, experimental data on the effects of both acute and cumulative partial sleep deprivation (PSD) consistently point out that sleep restriction has substantial negative effects on sleepiness, motor and cognitive performance and mood, as well as on some metabolic, hormonal and immunological variables. As chronic PSD may have serious long-term adverse health effects, it should be avoided in the general population. In the short-term, the effects of sleep curtailment seem to accumulate linearly, while the effects of long-term PSD should be further investigated, as the few available studies are flawed by methodological weaknesses. On the other hand, there is evidence that extending sleep by 2-3 h beyond the norm produces only marginal benefits for an average individual. Finally, it is underlined that, as large individual differences do exist in the need for sleep, the search for the sleep need may be vain. A somnotypology, taking into account age, gender and the position in both the sleep-alert and the morningness-eveningness continuum, should help in the search for the actual individual sleep need. 2001 Harcourt Publishers Ltd

A stochastic differential equation model of diurnal cortisol patterns

Circadian modulation of episodic bursts is recognized as the normal physiological pattern of diurnal variation in plasma cortisol levels. The primary physiological factors underlying these diurnal patterns are the ultradian timing of secretory events, circadian modulation of the amplitude of secretory events, infusion of the hormone from the adrenal gland into the plasma, and clearance of the hormone from the plasma by the liver. Each measured plasma cortisol level has an error arising from the cortisol immunoassay. We demonstrate that all of these three physiological principles can be succinctly summarized in a single stochastic differential equation plus measurement error model and show that physiologically consistent ranges of the model parameters can be determined from published reports. We summarize the model parameters in terms of the multivariate Gaussian probability density and establish the plausibility of the model with a series of simulation studies. Our framework makes possible a sensitivity analysis in which all model parameters are allowed to vary simultaneously. The model offers an approach for simultaneously representing cortisol's ultradian, circadian, and kinetic properties. Our modeling paradigm provides a framework for simulation studies and data analysis that should be readily adaptable to the analysis of other endocrine hormone systems.

Sleep patterns and mortality among elderly patients in a geriatric hospital

BACKGROUND

Sleep disturbance is one of the major and unsolved problems in older people. Most of the previous sleep studies rely on self-reported documents, and memory disturbance in older people might bias sleep complaints and health status.

OBJECTIVE

Sleep disturbances were studied as a mortality risk.

METHODS

In 272 patients who were aged, infirmed and chronically institutionalized in a skilled-care geriatric hospital, the presence or absence of sleep disturbances were examined by hourly observations of patients over 2 weeks at baseline, and they were prospectively followed up for 2 years to assess mortality.

RESULTS

Mortality after 2 years was significantly higher in the nighttime insomnia, daytime sleepiness, and sleep-onset delay groups. Further, adjusted for age, gender and activities of daily living status, the presence of nighttime insomnia and sleep-onset delay remained associated with a higher risk of mortality.

CONCLUSION

Sleep disturbance may be one of the symptoms indicating poor health or functional deficits, and be an independent risk factor for survival.

Shiftwork and cardiovascular disease: review of disease mechanisms

This paper reviews the main findings concerning mechanisms explaining the increased risk of coronary heart disease (CHD) in shiftworkers. We discuss a conceptual model, in which three main shiftwork pathways to CHD are postulated--social problems, behavioral change, and disturbed circadian rhythm. Social problems that are associated with shiftwork might lead to stress. Significant shiftwork-related behavioral problems are smoking and unhealthy food habits. Disturbed circadian rhythm might result in sleep deprivation. Unphysiologic timing of physical activity and food intake in relation to circadian rhythms is another possible explanation for the negative impact on the cardiovascular system.

Obesity and cortisol

Cortisol in obesity is a much-studied problem. Previous information indicates that cortisol secretion is elevated but that circulatory concentrations are normal or low, suggesting that peripheral disappearance rate is elevated. These studies have usually not taken into account the difference between central and peripheral types of obesity. Recent studies using saliva cortisol have indicated that the problem is complex with both high and low secretion of cortisol, perhaps depending on the status of the function of the hypothalamic-pituitary-adrenal gland axis. A significant background factor seems to be environmental stress. The results also suggest that the pattern of cortisol secretion may be important. Other neuroendocrine pathways are also involved, including the central sympathetic nervous system, the gonadal and growth hormone axes, and the leptin system. In concert, these abnormalities seem to be responsible for the abnormal metabolism often seen in central obesity. Several associated polymorphisms of candidate genes may provide a genetic background. Cortisol conversion to inactive metabolites may be a factor increasing central signals to secretion and may add to the increased secretion of cortisol induced by centrally acting factors. Perinatal factors have been found to be involved in the pathogenesis of obesity and its complications. The mechanism involved is not known, but available information suggests that programming of the hypothalamic-pituitary-adrenal axis may be responsible.

Adaptation of the 24-h growth hormone profile to a state of sleep debt

In normal men, the majority of GH secretion occurs in a single large postsleep onset pulse that is suppressed during total sleep deprivation. We examined the impact of semichronic partial sleep loss, a highly prevalent condition, on the 24-h growth hormone profile. Eleven young men were studied after six nights of restricted bedtimes (0100-0500) and after 7 nights of extended bedtimes (2100-0900). Slow-wave sleep (SWS) was estimated as the duration of stages III and IV. Slow-wave activity (SWA) was calculated as electroencephalogram power density in the 0.5- to 3-Hz frequency range. During the state of sleep debt, the GH secretory pattern was biphasic, with both a presleep onset "circadian" pulse and a postsleep onset pulse. Postsleep onset GH secretion was negatively related to presleep onset secretion and tended to be positively correlated with the amount of concomitant SWA. When sleep was restricted, both SWS and SWA were increased during early sleep. Unexpectedly, the increase in SWA affected the second, rather than the first, SWA cycle, suggesting that presleep onset GH secretion may have limited SWA in the first cycle, possibly via an inhibition of central GH-releasing hormone activity. Thus neither the GH profile nor the distribution of SWA conformed with predictions from acute sleep deprivation studies, indicating that adaptation mechanisms are operative during chronic partial sleep loss.

Sleep as a mediator of the relationship between socioeconomic status and health: a hypothesis

This article discusses the hypothesis that the adverse impact of low socioeconomic status (SES) on health may be partly mediated by decrements in sleep duration and quality. Low SES is frequently associated with a diminished opportunity to obtain sufficient sleep or with environmental conditions that compromise sleep quality. In a recent study, we examined carbohydrate metabolism, endocrine function, and sympatho-vagal balance in young, healthy adults studied after restricting sleep to four hours per night for six nights as compared to a fully rested condition obtained by extending the bed-time period to 12 hours per night for six nights. The state of sleep debt was associated with decreased glucose tolerance, elevated evening cortisol levels, and increased sympathetic activity. The alterations in glucose tolerance and hypothalamo-pituitary-adrenal function were qualitatively and quantitatively similar to those observed in normal aging. These results indicate that sleep loss can increase the "allostatic load" and facilitate the development of chronic conditions, such as obesity, diabetes, and hypertension, which have an increased prevalence in low SES groups.