Impact of sleep debt on metabolic and endocrine function

Subjective sleep quality in cystic fibrosis

OBJECTIVES

To evaluate sleep quality in patients with cystic fibrosis (CF).

METHODS

The Pittsburgh Sleep Quality Index (PSQI) questionnaire was administered to 37 CF patients with moderate to severe lung disease in a clinically stable state. Sleep studies were performed concurrently. PSQI scores were correlated with results of anthropometric variables, arterial blood gas tensions, lung function variables, and polysomnographic variables. Potential differences in objective measurements between patients with high and low scores on the PSQI were assessed.

RESULTS

Thirty-seven patients with CF were studied, aged 27+/-8 (mean+/-1 SD) years and forced expiratory volume in 1 s (FEV(1)) 36+/-12% predicted. The mean PSQI was 5.7+/-4.0. Fourteen of the 37 patients had a high PSQI, i.e. >5. Significant correlations between objective variables and both component scores and total PSQI were as follows: age and 'subjective sleep quality' (r=0.4, P<0.05), age and 'sleep duration' (r=0.3, P<0.05), FEV(1) % predicted and 'subjective sleep quality' (r=-0.4, P<0.05), carbon monoxide transferred per litre of lung volume (KCO) % predicted and 'daytime dysfunction' (r=-0.4, P<0.01), PaCO(2) and 'sleep latency' (r=0.4, P<0.01), arterial carbon dioxide tension (PaCO(2)) and 'habitual sleep efficiency' (r=0.3, P<0.05), PaCO(2) and total PSQI (r=0.4, P<0.05), absolute minimum sleep oxyhemoglobin saturation by pulse oximetry (SpO(2) %) and 'sleep latency' (r=-0.4, P<0.05), absolute minimum sleep SpO(2) % and 'sleep duration' (r=-0.4, P<0.05), absolute minimum sleep SpO(2) % and total PSQI (r=-0.4, P<0.05) and awake transcutaneous CO(2) and 'sleep duration' (r=0.45, P<0.05). Better sleep efficiency (P<0.05) and a greater % of rapid eye movement (REM) sleep (P<0.05) were found in those patients with a PSQI of < or =5.

CONCLUSIONS

A number of CF patients reported poor sleep quality. A relationship was shown between subjective sleep quality and physiological variables describing disease severity. Better sleep efficiency and % REM sleep were seen in patients with low PSQI scores. These results suggest a useful role for the PSQI in assessing sleep quality in patients with CF.

Sleep duration and mortality: The effect of short or long sleep duration on cardiovascular and all-cause mortality in working men and women

BACKGROUND

There is evidence to suggest that insufficient sleep may have an adverse effect on physical and psychological health. Previous studies have reported that when adjusting for major risk factors for cardiovascular disease and a number of demographic and social variables, sleeping 7-8 h each night is associated with lower mortality. These studies, however, have excluded any consideration of stress, which is known to be related to a number of behavioural risk factors for disease and, like sleep, may influence neurochemical, hormonal and immunological functioning.

METHODS

This study revisits the associations between sleep duration, cardiovascular disease risk factors and mortality, taking into account the perceived stress of individuals. The data come from a cohort of working Scottish men and women recruited between 1970 and 1973; approximately half of the cohort was screened for a second time, 4-7 years after the baseline examination.

RESULTS

For both men and women, higher self-perceived stress was associated with a reduction in the hours of sleep reported. The pattern of mortality from all causes and the pattern of mortality from cardiovascular disease were consistent for both men and women. When sleep was measured on one occasion only, the risk of dying was reduced for men sleeping more than 8 h in every 24 h compared with those sleeping 7-8 h over the same period. This was after adjustment had been made for age, marital status, social class, cardiovascular risk factors and stress. The risk of dying was increased for women sleeping less than 7 h in every 24 h compared with those sleeping 7-8 h over the same period, after similar adjustments. When the data from the 1st and 2nd screening were considered longitudinally, both men and women who reported that they slept less than 7 h on both occasions that they were questioned, had a greater risk of dying from any cause than those who had reported sleeping 7-8 h at both screenings, after adjusting for age, marital status, social class and stress.

CONCLUSIONS

Short sleep over a prolonged period may be associated with an increased risk of mortality: men and women who reported sleeping fewer than 7 h in 24 on two occasions between 4 and 7 years apart, had greater risk of dying from any cause over a 25 year period than those who reported sleeping 7-8 h on both occasions that they were questioned.

Seventh report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure

The National High Blood Pressure Education Program presents the complete Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure. Like its predecessors, the purpose is to provide an evidence-based approach to the prevention and management of hypertension. The key messages of this report are these: in those older than age 50, systolic blood pressure (BP) of greater than 140 mm Hg is a more important cardiovascular disease (CVD) risk factor than diastolic BP; beginning at 115/75 mm Hg, CVD risk doubles for each increment of 20/10 mm Hg; those who are normotensive at 55 years of age will have a 90% lifetime risk of developing hypertension; prehypertensive individuals (systolic BP 120-139 mm Hg or diastolic BP 80-89 mm Hg) require health-promoting lifestyle modifications to prevent the progressive rise in blood pressure and CVD; for uncomplicated hypertension, thiazide diuretic should be used in drug treatment for most, either alone or combined with drugs from other classes; this report delineates specific high-risk conditions that are compelling indications for the use of other antihypertensive drug classes (angiotensin-converting enzyme inhibitors, angiotensin-receptor blockers, beta-blockers, calcium channel blockers); two or more antihypertensive medications will be required to achieve goal BP (<140/90 mm Hg, or <130/80 mm Hg) for patients with diabetes and chronic kidney disease; for patients whose BP is more than 20 mm Hg above the systolic BP goal or more than 10 mm Hg above the diastolic BP goal, initiation of therapy using two agents, one of which usually will be a thiazide diuretic, should be considered; regardless of therapy or care, hypertension will be controlled only if patients are motivated to stay on their treatment plan. Positive experiences, trust in the clinician, and empathy improve patient motivation and satisfaction. This report serves as a guide, and the committee continues to recognize that the responsible physician's judgment remains paramount.

Residential environments and cardiovascular risk

The article begins with a discussion of the rationale for studying the relationship between residential environments and cardiovascular health. Existing empirical research relating residential environments to cardiovascular outcomes and risk factors is summarized. The research areas discussed include neighborhood socioeconomic characteristics and cardiovascular disease, the effects of residential environments on physical activity, and the effects of residential environments on diet. Other mechanisms through which residential environments may affect cardiovascular health are also briefly noted. Key challenges in investigating the relationship between residential environments and health are discussed. These challenges include characterizing environments (including definition and geographic scale as well as conceptualization and measurement of relevant features), the limitations of observational studies, and the need to evaluate the health impact of interventions or "naturally" occurring changes in local environments. The need for interdisciplinary work is emphasized.

Obesity and obstructive sleep apnea

There is a very high prevalence of OSA in obese individuals and a high prevalence of obesity in patients with OSA. The pathophysiology of OSA is intimately linked to obesity. Anatomic and functional considerations of the pharyngeal airway, the CNS, central obesity, and leptin likely interact in the development of OSA in obese individuals. OSA may itself predispose individuals to worsening obesity because of sleep deprivation, daytime somnolence, and disrupted metabolism. The diagnosis of OSA requires the clinician's awareness of its potential to cause a spectrum of acute and chronic neurocognitive, psychiatric, and nonspecific symptoms in patients who may be unaware that their sleep is disturbed. Symptoms and examination findings help predict which obese individuals have OSA, and polysomnography is the gold standard by which to make the diagnosis and assess the effects of treatment. Numerous disease states are associated with both OSA and obesity, and it is becoming clear that the relationships are mediated by complex interrelated mechanisms. Common diseases and disease mechanisms in OSA and obesity suggest that conditions related to obesity may be better managed if patients, particularly those who are morbidly obese, are evaluated and treated for previously undiagnosed OSA. OSA is cured in only specific cases with craniofacial or upper airway surgery, and the general application of UVP is not efficacious. OSA also can be cured with sufficient lifestyle-mediated or surgical weight loss; however, in the absence of long-term weight maintenance, OSA returns with weight gain. Although not curative, nasal CPAP is the initial treatment of choice for most patients because of its noninvasive approach and technical efficacy. It is limited, however, by patient acceptance and long-term compliance. Advances in mask comfort and use of humidified air should increase its acceptance. Future management strategies include newer generations of positive airway devices that automatically titrate pressures (which are not yet recommended by expert organizations) and multidisciplinary approaches to managing the care of patients with OSA.

Searching for sleep mutants of Drosophila melanogaster

The functions of sleep are still unknown, but are probably related to cellular and molecular aspects of neural function. To better understand the benefits that sleep may bring at the cellular level, recent studies have employed Drosophila melanogaster as a model system and shown that fruit flies share the fundamental features of mammalian sleep. As in mammals, sleep in Drosophila is characterized by increased arousal threshold and by changes in brain electrical activity. Fly sleep is homeostatically regulated independent of the circadian clock, is modulated by stimulants and hypnotics, and is affected by age. Also, fly sleep is associated with changes in brain gene expression similar to those observed in mammals. While Drosophila neurobiology is sufficiently complex to permit meaningful generalizations to mammals and humans, Drosophila genetics is simple enough to allow a rapid mutagenesis screening. An ongoing mutagenesis study has screened approximately 5000 mutant Drosophila lines and found that sleep amount, sleep pattern, and the homeostatic regulation of sleep are highly conserved phenotypes in flies. So far, this study has identified 10 short sleeper lines and 4 lines that show no sleep rebound after sleep deprivation. Ultimately, the characterization of these lines should help identifying crucial cellular pathways involved in the regulatory mechanisms of sleep and its functional consequences.

Insulin resistance and obstructive sleep apnea: is increased sympathetic stimulation the link?

The science of sleep is in early stages of development, and the biochemical consequences of obstructive sleep apnea (OSA) are slowly being identified. Only recently have investigators begun to identify the commonalities and interaction between OSA and insulin resistance, the underlying pathology of type 2 diabetes. Obesity and increasing age play important parts in the natural history of both conditions, which frequently coexist. The purpose of this article is, first, to examine the extent and strength of studies that have investigated the association between OSA and increased insulin resistance or type 2 diabetes and, second, to propose a model that explains the association and cyclical interaction between OSA, obesity, and insulin resistance.

Sleep and its homeostatic regulation in mice lacking the adenosine A1 receptor

Sleep deprivation (SD) increases extracellular adenosine levels in the basal forebrain, and pharmacological manipulations that increase extracellular adenosine in the same area promote sleep. As pharmacological evidence indicates that the effect is mediated through adenosine A1 receptors (A1R), we expected A1R knockout (KO) mice to have reduced rebound sleep after SD. Male homozygous A1R KO mice, wild-type (WT) mice, and heterozygotes (HET) from a mixed 129/C57BL background were implanted during anesthesia with electrodes for electroencephalography (EEG) and electromyography (EMG). After 1 week of recovery, they were allowed to adapt to recording leads for 2 weeks. EEG and EMG were recorded continuously. All genotypes had a pronounced diurnal sleep/wake rhythm after 2 weeks of adaptation. We then analyzed 24 h of baseline recording, 6 h of SD starting at light onset, and 42 h of recovery recording. Neither rapid eye movement sleep (REM sleep) nor non-REM sleep (NREMS) amounts differed significantly between the groups. SD for 6 h induced a strong NREMS rebound in all three groups. NREMS time and accumulated EEG delta power were equal in WT, HET and KO. Systemic administration of the selective A1R antagonist 8-cyclopentyltheophylline (8-CPT) inhibited sleep for 30 min in WT, whereas saline and 8-CPT both inhibited sleep in KO. We conclude that constitutional lack of adenosine A1R does not prevent the homeostatic regulation of sleep.

Endothelial function in obstructive sleep apnea and response to treatment

Impaired endothelium-dependent vascular relaxation is a prognostic marker of atherosclerosis and cardiovascular disease. We evaluated endothelium-dependent flow-mediated dilation (FMD) and endothelium-independent nitroglycerin (NTG)-induced dilation of the brachial artery with Doppler ultrasound in 28 men with obstructive sleep apnea (OSA) and 12 men without OSA. Subjects with OSA (apnea-hypopnea index; mean +/- SD, 46.0 +/- 14.5) had lower FMD compared with subjects without OSA (5.3 +/- 1.7% vs. 8.3 +/- 1.0%, p < 0.001), and major determinants of FMD were the apnea-hypopnea index and age. There was no significant difference in NTG-induced dilation. Subjects with OSA were randomized to nasal continuous positive airway pressure (nCPAP) or observation for 4 weeks. Subjects on nCPAP had significant increase in FMD, whereas those on observation had no change (4.4% vs. -0.8%, difference of 5.2%, p < 0.001). Neither group showed significant change in NTG-induced vasodilation. Eight subjects who used nCPAP for over 3 months were reassessed on withdrawing treatment for 1 week. On nCPAP withdrawal, FMD became lower than during treatment (p = 0.02) and were similar to baseline values. Our findings demonstrated that men with moderate/severe OSA have endothelial dysfunction and treatment with nCPAP could reverse the dysfunction; the effect, however, was dependent on ongoing use.

Four-year follow-up study of sleep and psychiatric symptoms in preadolescents: relationship of persistent and temporary sleep problems to psychiatric symptoms

The course of sleep disturbances in preadolescents was assessed during a 4-year follow-up, and psychiatric problems associated with persistent and temporary sleep problems were investigated in an epidemiological setting. A representative random sample of 1,290 children, their parents, and school teachers filled out various questionnaires when the children were aged 8 and 12 years. Response rates to the relevant items varied between 66.8% and 81.2%. Parental reports of sleep problems decreased from 23.4% to 9.1% during the 4-year period, whereas children's reports remained steady at 18%. Persistent sleep disturbances were found in 12% of children, and 33.3% of sleep problems reported at age 8 were continued. Both current and persistent sleep disturbances were associated with the broad range of mental health problems reported by teachers. However, multivariate modeling suggested that especially current sleep problems were associated with an increased risk for psychiatric problems (odds ratio [OR] 2.45; 95% confidence interval [CI] 1.20-4.99), particularly emotional problems (OR 2.92; 95% CI 1.58-5.38).

The effects of nocturnal life on endocrine circadian patterns in healthy adults

We observed the 24-hour patterns of endocrine in medical students who lived either a diurnal life or nocturnal life. Nocturnal life was designed by skipping their breakfast but consuming much (>50% of their daily food intake) in the evening and at night with the sleep from 0130 h to 0830 h the next morning. After 3 weeks in the experimental life, the 24-hour plasma concentrations of melatonin, leptin, glucose and insulin were measured every three hours. Both plasma melatonin and leptin showed peaks at 0300 h in the diurnal lifestyle group, and the night peaks decreased in the nocturnal lifestyle group. The changes in the patterns of melatonin and leptin were highly consistent with that of night-eating syndrome (NES). Plasma glucose increased after all meals in both groups. Its concentration maintained a high level in the nocturnal lifestyle group between midnight and early morning while insulin secretion decreased markedly during this period. Furthermore, the strong association between glucose and insulin in the diurnal lifestyle group after meals was damaged in the nocturnal lifestyle group. It was suggested that nocturnal life leads to the impairment of insulin response to glucose. Taking these results together, nocturnal life is likely to be one of the risk factors to health of modern people, including NES, obesity and diabetes.

Serum amyloid a in obstructive sleep apnea

BACKGROUND

Patients with severe obstructive sleep apnea (OSA) may have increased risk for cardiovascular and cerebrovascular diseases. Serum amyloid A (SAA) protein has recently been linked to the development of atherosclerosis, stroke, diabetes, and dementia. We tested the hypothesis that plasma SAA levels are increased in otherwise healthy subjects with OSA.

METHODS AND RESULTS

Plasma SAA levels were measured in 10 male patients with moderate to severe OSA before sleep, after 5 hours of untreated OSA, and in the morning after effective continuous positive airway pressure treatment. SAA levels were also measured in 10 closely matched control subjects at similar time points. Baseline plasma SAA levels before sleep were strikingly higher in patients with moderate to severe OSA than in controls (18.8+/-2.6 versus 7.2+/-2.6 microg/mL, respectively; P=0.005) and remained unchanged in both groups throughout the night. SAA levels in 10 male patients with mild OSA were comparable with controls (P=0.46). Plasma SAA in 7 female patients with moderate to severe OSA was also markedly higher compared with matched control female subjects (24.1+/-2.4 versus 10.2+/-2.4 microg/mL, respectively; P=0.0013) but was not different from male patients with moderate to severe OSA (P=0.3). There was a significant positive correlation between SAA and apnea-hypopnea index (r=0.40, P=0.03).

CONCLUSIONS

Plasma SAA levels are more than 2-fold greater in patients with moderate to severe OSA compared with subjects with mild OSA or healthy controls regardless of gender. Elevated SAA may contribute to any increased risk for cardiovascular and neuronal dysfunction in patients with OSA.

Palatable solutions during paradoxical sleep deprivation: reduction of hypothalamic-pituitary-adrenal axis activity and lack of effect on energy imbalance

Paradoxical sleep deprivation (PSD) induces increased energy expenditure in rats, insofar as rats eat more but loose weight throughout the deprivation period. In the present study, rats were offered water, saccharin or sucrose to drink during the deprivation period, since it has been proposed that carbohydrates reduce the hypothalamic-pituitary-adrenal (HPA) axis response to stress. Rats were submitted to the flower pot technique for 96 h. During the PSD period, they were weighed daily and food and fluid intake was assessed twice a day. At the end of the PSD period, rats were killed and plasma concentrations of glucose, adrenocorticotropic hormone (ACTH) and corticosterone were assayed. Compared to their control counterparts, all paradoxical sleep-deprived rats consumed more food, but lost weight. Paradoxical sleep-deprived rats given sucrose drank more than their control counterparts (especially in the light phase of the light/dark cycle). Paradoxical sleep-deprived rats showed increased food intake during all periods throughout the experiment, with peak intake during the dark phase and nadir during the light phase of the light/dark cycle. All paradoxical sleep-deprived rats showed lower glucose plasma levels than control rats and increased relative adrenal weight. However, when given saccharin or sucrose, paradoxical sleep-deprived rats showed lower concentrations of ACTH and corticosterone than their water-provided counterparts, indicating that palatable fluids were capable of lowering HPA axis activation produced by PSD. The fact that PSD induced energy imbalance regardless of the relative attenuation of the HPA axis activity produced by saccharin or sucrose suggests that the HPA axis may play only a secondary role in this phenomenon, and that other mechanisms may account for this effect. The data also suggest that supply of palatable fluids can be an additional modification to reduce the stress of the flower pot method.

Sleep loss reduces diurnal rhythm amplitude of leptin in healthy men

The aim of the current study was to investigate the effects of sleep loss on the diurnal rhythm of circulating leptin levels. An indwelling forearm catheter was used to sample blood at 90-min intervals for a total of 120 h, which included 88 h of sustained sleeplessness, in 10 healthy men. The diurnal amplitude of leptin was reduced during total sleep deprivation and returned toward normal during the period of recovery sleep. This finding provides evidence that sleep influences the nocturnal leptin profile, and may have implications for the understanding of the role of sleep in metabolic regulation and the aetiologies of obesity and the night eating syndrome.

Family caregivers' sleep loss and depression over time

Depression is a normal response when a family member receives a diagnosis of cancer. However, this response may be exacerbated by other factors such as chronic sleep loss that are amenable to intervention. This pilot study described caregiver sleep and depression patterns over time and explored the feasibility of data collection methods and instruments. The stress and coping framework of Lazarus and Folkman guided this study. A descriptive correlational design was used for this 10-week pilot study. Ten adult family caregivers of patients with cancer were recruited from outpatient oncology clinics. Sleep quality and depression were measured weekly. Actigraphs were worn for 72 hours during weeks 1, 5, and 10. Individual sleep quality and depression scores were generated. Actigraph latency, duration, and efficiency scores were generated. Actigraph and sleep quality scores were compared. Individual caregiver sleep and depression plots show large variance over time. Discrepancies were noted between Actigraph and sleep quality latency, duration, and efficiency scores. Sleep and depressive symptoms fluctuate widely over time. Therefore, accurate assessment and treatment of caregiver problems require repeated assessments. Self-reports of sleep and depression appear to underestimate problems and must be evaluated carefully within this context.

Mood disorders and allostatic load

The brain controls both the physiologic and the behavioral coping responses to daily events as well as major stressors, and the nervous system is itself a target of the mediators of those responses through circulating hormones. The amygdala and hippocampus interpret what is stressful and regulate appropriate responses. The amygdala becomes hyperactive in posttraumatic stress disorder (PTSD) and depressive illness, and hypertrophy of amygdala nerve cells is reported after repeated stress in an animal model. The hippocampus expresses adrenal steroid receptors. It undergoes atrophy in several psychiatric disorders and responds to repeated stressors with decreased dendritic branching and reduction in number of neurons in the dentate gyrus. Stress promotes adaptation ("allostasis"), but a perturbed diurnal rhythm or failed shutoff of mediators after stress ("allostatic state") leads, over time, to wear and tear on the body ("allostatic load"). Neural changes mirror the pattern seen in the cardiovascular, metabolic, and immune systems, that is, short-term adaptation versus long-term damage. Allostatic load leads to impaired immunity, atherosclerosis, obesity, bone demineralization, and atrophy of nerve cells in brain. Allostatic load is seen in major depressive illness and may also be expressed in other chronic anxiety disorders such as PTSD and should be documented.

Facilitation of ejaculation after methamphetamine administration in paradoxical sleep deprived rats

This study investigated the effects of methamphetamine (MA) on genital reflexes in paradoxical sleep deprived (PSD) rats. Different doses of MA (0, 4, 16 and 64 mg/kg) were acutely given after PSD or the equivalent time to control animals. We observed enhancement of spontaneous ejaculation in PSD rats with larger doses of MA, the highest of which induced ejaculation in 100% of the PSD rats. This was significantly higher than the 30% in the control. Although testosterone exerts motivational effects on male sexual behavior, our data shows that testosterone levels were lower after the PSD period in saline and in the 64 mg/kg MA groups, which present ejaculation at different rates (20% and 100%, respectively). Progesterone levels were significantly higher in PSD-saline in relation to control group and in the 16 and 64 mg/kg of MA groups compared to the other doses. Since PSD induces dopaminergic alterations and dopamine (DA) has a key role in male sexual behavior, plasma DA was also measured. The DA concentration was enhanced in all PSD groups compared with their control group. The mechanism that activates steroid hormones may represent an important physiological effect through which neurotransmitters can affect behavioral events. These data show that MA facilitates ejaculation in PSD rats, however, further studies need to be carried out in order to clarify the hormonal-neurochemical mechanisms involved.

Sleep-disordered breathing, glucose intolerance, and insulin resistance

Sleep-disordered breathing (SDB) is a common condition with prevalence estimates of 2-4% in the general population. Epidemiological data suggest that SDB is an independent risk factor for cardiovascular disease. Glucose intolerance and insulin resistance are also well-recognized risk factors for the development of cardiovascular disease. A number of recent clinic-based studies suggest that, independent of obesity, SDB may adversely affect glucose tolerance and insulin sensitivity. The purpose of this study was to systematically review the evidence for the link between SDB, glucose intolerance, and insulin resistance. A MEDLINE search for SDB and metabolic disorders was performed and 24 articles that met the inclusion criteria were identified. Population-based studies indicate that habitual snoring is independently associated with glucose intolerance and insulin resistance. Studies that have used objective measures of SDB (e.g. polysomnography) provide further support for an independent link between SDB, glucose intolerance, and insulin resistance. However, studies on the treatment of SDB with continuous positive airway pressure (CPAP) have yielded inconsistent results and overall do not reveal an improvement in the metabolic disturbance after treatment. Although population-based prospective data on the metabolic implications of SDB are still lacking, current data point to an independent association between SDB and impaired glucose homeostasis. Potential mediators of this association include altered adrenergic function, the direct effects of hypoxemia on glucose regulation, and release of proinflammatory cytokines that affect metabolism.

Metabolic disturbances in obesity versus sleep apnoea: the importance of visceral obesity and insulin resistance

Obstructive sleep apnoea (OSA) is a very prevalent disorder particularly amongst middle-aged, obese men, although its existence in women as well as in lean individuals is increasingly recognized. Despite the early recognition of the strong association between OSA and obesity, and OSA and cardiovascular problems, sleep apnoea has been treated as a 'local abnormality' of the respiratory track rather than as a 'systemic illness'. In 1997, we first reported that the pro-inflammatory cytokines interleukin (IL)-6 and tumour necrosis factor-alpha (TNF alpha) were elevated in patients with disorders of excessive daytime sleepiness (EDS) and proposed that these cytokines were mediators of daytime sleepiness. Also, we reported a positive correlation between IL-6 or TNF alpha plasma levels and the body mass index (BMI). In subsequent studies, we showed that IL-6, TNF alpha, leptin and insulin levels were elevated in sleep apnoea independently of obesity and that visceral fat, was the primary parameter linked with sleep apnoea. The association of OSA with insulin resistance and diabetes type 2 has been confirmed since then in several epidemiological and clinical studies. Furthermore, our findings that women with polycystic ovary syndrome (PCOS, a condition associated with hyperandrogenism and insulin resistance) were much more likely than controls to have sleep disordered breathing (SDB) and daytime sleepiness support the pathogenetic role of insulin resistance in OSA. Other findings that support the view that sleep apnoea and sleepiness may be manifestations of a serious metabolic disorder, namely the Metabolic or Visceral Obesity Syndrome, include: obesity without sleep apnoea is associated with daytime sleepiness; PCOS and diabetes type 2 are independently associated with EDS after controlling for SDB, obesity and age; and increased prevalence of sleep apnoea in postmenopausal women, with hormonal replacement therapy associated with a significantly reduced risk for OSA. In conclusion, accumulating evidence provides support to our model of the bi-directional, feedforward, pernicious association between sleep apnoea, sleepiness, inflammation and insulin resistance, all promoting atherosclerosis and cardiovascular disease.

Sleep as restitution: an introduction

This paper summarizes a symposium that has shown that sleep is a state of altered metabolism, and that disturbances and curtailing of sleep have far-reaching effects on endocrinology, immunology and metabolism, changes that may be linked to disease. As yet, the entire causal chain is weak but there are indications that, in particular, the risk of type 2 diabetes and cardiovascular disease may result from disturbed sleep. It is hypothesized that both insulin resistance and chronic low-grade inflammation may be involved.

Community stress, demoralization, and body mass index: evidence for social signal transduction

Quantification of the relationship between community-level chronic stress from neighborhood conditions and individual morale has rarely been reported. In this work, pregnant women were recruited at the prenatal clinics of Harlem Hospital and Columbia Presbyterian Medical Center in the USA, and given an initial questionnaire that included all 27 questions of the Dohrenwend demoralization instrument, as well as questions about household economics and health. An index of chronic community stress (ICCS) was compiled for each of the health areas of the study zone by standardizing and weighting each stressor significantly associated with low birthweight rate and summing the standardized, weighted values. Health areas were divided into ICCS quintiles. The graph of the quintile weighted averages of the index vs. the quintile averages of the demoralization score was an asymmetric inverted 'U' shape that fitted well to a stochastic resonance signal transduction model (adjusted R2=0.73). On average, the women in the worst three quintiles were much heavier than those of the two best quintiles. Women reporting household economic deprivations were significantly more demoralized than the others. Median health area rents were strongly negatively associated with the ICCS. The worst average demoralization score occurred in the middle quintile, a state of coping with both poor community conditions and an economically strained household. Rents bridge community conditions and household economics.

Socioeconomic status and stress-related biological responses over the working day

OBJECTIVES

The influence of low socioeconomic status on cardiovascular disease may be mediated in part by sustained activation of stress-related autonomic and neuroendocrine processes. We hypothesized that low socioeconomic status would be associated with heightened ambulatory blood pressure and cortisol output over the working day.

METHODS

One hundred eight men and 94 women from the Whitehall II epidemiological cohort participated. Blood pressure and heart rate were monitored every 20 minutes over a working day and evening, and salivary cortisol was sampled on waking up and at 2-hour intervals. Measures were also taken under resting laboratory conditions. Socioeconomic status was indexed by grade of employment.

RESULTS

Resting blood pressure, heart rate, and cortisol did not differ by grade. Ambulatory systolic pressure was greater in the morning in the lower (128.9 +/- 15.7 mm Hg) than the intermediate (122.6 +/- 12.5 mm Hg) and higher grades (123.3 +/- 12.7 mm Hg) after adjustment for age, sex, smoking, and alcohol intake (p =.019). Heart rate was also raised in the morning in the lower grade participants. Differences in morning systolic pressure and heart rate were independent of concurrent physical activity. Cortisol concentration was greater in lower than higher grade men (9.54 +/- 4.1 vs. 7.38 +/- 2.8 nmol/liter, p =.008) but was more elevated in higher than lower grade women (7.84 +/- 2.5 vs. 6.35 +/- 1.9 nmol/liter, p =.014). Differences remained significant after adjustment for age, time of awakening, smoking, and alcohol intake.

CONCLUSIONS

Socioeconomic differences in blood pressure and cortisol may reflect stress-related activation of biological pathways that contribute to variations in disease risk.

Salivary cortisol patterns and cognitive speed in major depression: a comparison with allergic rhinitis and healthy control subjects

Few studies have investigated the relationship between cortisol and cognitive functions other than memory in depression. This study investigated daily salivary cortisol patterns (basal cortisol levels at 08:00, 16:00, and 21:00 h and flatness of the diurnal curve) in relation to cognitive speed and memory. Twenty-seven unmedicated outpatients with major depressive disorder (MDD) were compared with 36 healthy controls and with 20 allergic rhinitis patients, to determine whether effects should be ascribed to MDD or to more general disease-related processes. MDD patients were characterised by a flatter diurnal cortisol curve and by reduced cognitive speed. Flatter cortisol curves were associated with cognitive slowness. However, this relationship is unlikely to be causal; after control for depressive symptoms and group membership, flatness of the diurnal cortisol curve was no longer a significant predictor of cognitive slowness. Thus, MDD and related depressive symptoms appeared to be independently associated with altered cortisol secretory patterns and with decrements in cognitive speed.

Postprandial responses of glucose, insulin and triglycerides: influence of the timing of meal intake during night work

The objective was to study the postprandial responses of glucose, insulin and triglycerides to meal intake at different clock times during night work. Eleven night shift working nurses participated. Identical test meals were ingested at 19:30, 23:30 and 03:30, and contained 440 kcal/1,860 kJ of energy (33 E% fat, 51 E% carbohydrate, 16 E% protein). The food intake was standardized three days before the first test meal. Blood samples were drawn just before the test meals were ingested and thereafter at 30, 60, 90, 120, 180 and 240 minutes. The postprandial responses were estimated as the total area under the curve (AUC) and significance testing was done using repeated measures ANOVA. The highest insulin level was found after meal intake at 23:30, and the lowest after meal intake 03:30. The glucose response showed the same pattern. The insulin response to food intake in night working nurses is more pronounced in the night compared with morning and evening. The results would have implications for metabolic and cardiovascular disorders in night workers.

Diabetes and sleep disturbances: findings from the Sleep Heart Health Study

OBJECTIVE

To test the hypothesis that diabetes is independently associated with sleep-disordered breathing (SDB), and in particular that diabetes is associated with sleep abnormalities of a central, rather than obstructive, nature.

RESEARCH DESIGN AND METHODS

Using baseline data from the Sleep Heart Health Study (SHHS), we related diabetes to 1). the respiratory disturbance index (RDI; number of apneas plus hypopneas per h of sleep); 2). obstructive apnea index (OAI; >or=3 apneas/h of sleep associated with obstruction of the upper airway); 3). percent of sleep time < 90% O(2) saturation; 4). central apnea index (CAI; >or=3 apneas [without respiratory effort]/h sleep); 5). occurrence of a periodic breathing (Cheyne Stokes) pattern; and 6) sleep stages. Initial analyses excluding persons with prevalent cardiovascular disease (CVD) were repeated including these participants.

RESULTS

Of the 5874 participants included in this report, 692 (11.8%) reported diabetes or were taking oral hypoglycemic medications or insulin and 1002 had prevalent CVD. Among the 4872 persons without CVD, 470 (9.6%) had diabetes. Diabetic participants had worse CVD risk factor profiles than their nondiabetic counterparts, including higher BMI, waist and neck circumferences, triglycerides, higher prevalence of hypertension, and lower HDL cholesterol (P < 0.001, all). Descriptive analyses indicated differences between diabetic and nondiabetic participants in RDI, sleep stages, sleep time <90% O(2) saturation, CAI, and periodic breathing (P < 0.05, all). However, multivariable regression analyses that adjusted for age, sex, BMI, race, and neck circumference eliminated these differences for all sleep measures except percent time in rapid eye movement (REM) sleep (19.0% among diabetic vs. 20.1% among nondiabetic subjects, P < 0.001) and prevalence of periodic breathing (odds ratio [OR] for diabetic subjects versus nondiabetic subjects 1.80, 95% CI 1.02-3.15). Additionally, adjusted analyses showed diabetes was associated with nonstatistically significant elevations in the odds of an increased central breathing index (OR 1.42, 95% CI 0.80-2.55). Addition to the analysis of the 1002 persons with prevalent CVD (including 222 people with diabetes) did not materially change these results.

CONCLUSIONS

These data suggest that diabetes is associated with periodic breathing, a respiratory abnormality associated with abnormalities in the central control of ventilation. Some sleep disturbances may result from diabetes through the deleterious effects of diabetes on central control of respiration. The high prevalence of SDB in diabetes, although largely explained by obesity and other confounders, suggests the presence of a potentially treatable risk factor for CVD in the diabetic population.

Compliance with saliva sampling protocols: electronic monitoring reveals invalid cortisol daytime profiles in noncompliant subjects

OBJECTIVE

Ambulatory saliva collections for subsequent analysis of free cortisol levels are now frequently applied to measure adrenocortical activity in healthy subjects and patient populations. Despite the prime importance of accurate timing of saliva collection outside the laboratory, no data are available on the compliance of study participants following a given sampling protocol. This study investigated how accurately subjects adhered to the instructions to collect six saliva samples throughout 1 day.

METHODS

Subjects were instructed to collect six saliva samples throughout 1 day (directly after awakening, 30 minutes after awakening, 11 AM, 3 PM, 8 PM, 10 PM). Objective compliance was measured using an electronic monitoring device given to the subjects either with ("informed" N = 23) or without ("noninformed" N = 24) their knowledge of the nature of the device. Data on subjective compliance were obtained by self-report.

RESULTS

Thirty-one subjects (74%) were found to comply with the sampling instructions, and 11 (26%) failed at least once to obtain the saliva sample at the correct time of day. Nine of the 11 noncompliant subjects (82%) had two or more noncompliant samples. Fifty-five percent (6 of 11) of the noncompliant subjects took sample 2 outside the sampling window. The circadian cortisol profile differed significantly between compliant and noncompliant subjects (F = 7.98, p =.007). The most important effect of compliance was seen in the rise of cortisol at awakening. Compliant subjects showed a robust increase, whereas noncompliant individuals had only minimal changes from baseline at 30 minutes after awakening (t = 2.89, p =.007). Thus the steepness of the circadian cortisol decline was greater for compliant subjects (t = 2.10, p =.043). Furthermore, the informed group adhered more closely to the sampling protocol than the noninformed subjects (p =.001). Self-reported compliance also differed significantly between study groups (p =.03). In the noninformed group, self-reported sampling accuracy was significantly higher than objectively measured compliance (p =.03); the two measures were similar in the informed group (p = NS).

CONCLUSIONS

A significant number of subjects did not obtain saliva samples reliably in an ambulatory setting. This can partially invalidate the cortisol results and mask potential differences between subject groups of interest. We therefore recommend the use of electronic monitoring devices or other suitable methods and that study participants be informed about the device when ambulatory saliva collection is performed.

Patterns of performance degradation and restoration during sleep restriction and subsequent recovery: a sleep dose-response study

Daytime performance changes were examined during chronic sleep restriction or augmentation and following subsequent recovery sleep. Sixty-six normal volunteers spent either 3 (n = 18), 5 (n= 16), 7 (n = 16), or 9 h (n = 16) daily time in bed (TIB) for 7 days (restriction/augmentation) followed by 3 days with 8 h daily TIB (recovery). In the 3-h group, speed (mean and fastest 10% of responses) on the psychomotor vigilance task (PVT) declined, and PVT lapses (reaction times greater than 500 ms) increased steadily across the 7 days of sleep restriction. In the 7- and 5-h groups speed initially declined, then appeared to stabilize at a reduced level; lapses were increased only in the 5-h group. In the 9-h group, speed and lapses remained at baseline levels. During recovery, PVT speed in the 7- and 5-h groups (and lapses in the 5-h group) remained at the stable, but reduced levels seen during the last days of the experimental phase, with no evidence of recovery. Speed and lapses in the 3-h group recovered rapidly following the first night of recovery sleep; however, recovery was incomplete with speed and lapses stabilizing at a level comparable with the 7- and 5-h groups. Performance in the 9-h group remained at baseline levels during the recovery phase. These results suggest that the brain adapts to chronic sleep restriction. In mild to moderate sleep restriction this adaptation is sufficient to stabilize performance, although at a reduced level. These adaptive changes are hypothesized to restrict brain operational capacity and to persist for several days after normal sleep duration is restored, delaying recovery.

Effects of sleep loss in men and women with insufficient sleep suffering from chronic disease: a model for supportive nursing care

This study evaluated self-reported subjective health and effects of sleep loss according to perceived interfering cognitive anxiety related to falling asleep in patients with and without insufficient sleep and gender differences in these aspects 5 years after coronary artery bypass graft and transluminal coronary angioplasty. A total of 145 patients, five years after intervention, responded to a mailed questionnaire. Nearly 60% had severe combined sleep disturbances; 35.9% of these had complained of insufficient sleep and 15% also perceived difficulty falling asleep related to cognitive anxiety. Measurable gender differences were small. A theoretical framework is presented which can increase understanding among nurses, patients and their relatives concerning the quality and quantity of sleep and sleep loss related to quality of life. These results suggest that there are significant relationships between sleep quality, resilience to stress and coping strategy in patients with a chronic disease, indicating the need for more individualised supportive nursing care.

Loneliness and pathways to disease

Social isolation predicts morbidity and mortality from cancer, cardiovascular disease, and a host of other causes. The mechanisms by which the social world impacts on health are poorly understood, in part because of lack of specificity in the conceptualization and operationalization of relevant aspects of social relationships and physiological processes. Perceived social isolation, commonly termed loneliness, may represent a link between the epidemiological and biological levels of analysis. Research is presented that investigates loneliness as a social factor of importance in three predisease pathways: health behaviors, excessive stress reactivity, and inadequate or inefficient physiological repair and maintenance processes. Empirical evidence of autonomic, endocrine, and immune functioning suggests that the physiological effects of loneliness unfold over a relatively long time period. For cancer patients, interventions should be aimed at providing instrumental support for the immediate demands of the disease.

A prospective study of self-reported sleep duration and incident diabetes in women

Short-term sleep restriction results in impaired glucose tolerance. To test whether habitually short sleep duration increases the risk of developing diabetes, we studied a cohort of 70,026 women enrolled in the Nurses Health Study, without diabetes at baseline, and who responded to a question about daily sleep duration in 1986. Subjects were followed until 1996 for the diagnosis of diabetes (1,969 cases). Long and short sleep durations were associated with an increased risk of diabetes diagnosis. The relative risks (RRs) for short (slept < or =5 h per day) and long (slept > or =9 h per day) sleepers were 1.57 (95% CI 1.28-1.92) and 1.47 (1.19-1.80), respectively. After adjustment for BMI and a variety of confounders, the RR was not significantly increased for short sleepers (1.18 [0.96-1.44]) but remained modestly increased for long sleepers (1.29 [1.05-1.59]). We then performed a similar analysis using only symptomatic cases (n = 1,187). Adjusted RRs for symptomatic diabetes were modestly elevated in both short (1.34 [1.04-1.72]) and long (1.35 [1.04-1.75]) sleepers. Our data suggest that the association between a reduced self-reported sleep duration and diabetes diagnosis could be due to confounding by BMI, or sleep restriction may mediate its effects on diabetes through weight gain. Sleep restriction may be an independent risk factor for developing symptomatic diabetes.

Sleep disorders and the failure to lower nocturnal blood pressure

PURPOSE OF REVIEW

The failure to lower systolic blood pressure at night (called non-dipping) and sleep apnea are both associated with adverse cardiovascular outcomes. Sleep apnea is a common cause of non-dipping blood pressure.

RECENT FINDINGS

Sleep apnea increases night time blood pressure through enhanced cardiac pre-load, sleep disturbance and hypoxia. Hypoxia elicits increased levels of norepinephrine, endothelin and erythropoetin. Patients with sleep apnea tend to be elderly and obese, so they have poor endothelial nitric oxide release and blunted baroreflexes. They thus have several stimuli for high blood pressure and poor compensatory mechanisms to lower blood pressure.

SUMMARY

Non-dipping patients without sleep apnea have evidence of volume overload and correct their blood pressure pattern in response to diuretics. Individuals with sleep apnea have evidence of increased cardiac pre-load from episodes of negative intrathoracic pressure. Their daytime blood pressure responds poorly to many drugs, but beta blockers may be effective. Their night time blood pressure responds only slightly to therapy of their sleep apnea with continuous positive airway pressure, even though continuous positive airway pressure decreases their norepinephrine, erythropoetin and endothelin levels.

Nocturnal cortisol and melatonin secretion in primary insomnia

The present study investigated evening and nocturnal serum cortisol and melatonin concentrations in patients with primary insomnia to test if this clinical condition is accompanied by an increase of cortisol secretion and a simultaneous decrease of nocturnal melatonin production. Ten drug-free patients (4 males, 6 females) with primary insomnia (mean age+/-S.D.: 39.2+/-9.1 years) and 10 age- and gender-matched healthy controls participated in the study. All subjects spent three consecutive nights in the sleep laboratory with polysomnography. Measurement of cortisol and melatonin (from 19:00 h to 09:00 h) was performed prior to and during the last laboratory night. Contrary to expectation, cortisol secretion did not differ between healthy controls and insomniac patients. On the other hand, nocturnal melatonin production was significantly diminished in insomniac patients. Polysomnographically determined sleep patterns, in contrast to subjective ratings of sleep, demonstrated only minor alterations of sleep in the insomniac group. The lack of increased cortisol secretion in the patients with primary insomnia indicates that results from studies on the biological consequences of experimental sleep loss in healthy subjects cannot be applied to primary insomnia in general, especially if there are only minor objective sleep alterations. In spite of the negligible objective sleep disturbances in the present sample, nocturnal melatonin production was reduced, which tentatively suggests a role for this hormone in primary insomniacs. The pathophysiological significance of this finding is, however, still a matter of debate.

Sleep and methods of assessment

Sleep is a complex behavior; adequate sleep is essential for healthy functioning and even for survival. Poor sleep quality and insufficient sleep have been linked to increased risk for various illnesses, as well as with an increased prevalence of excessive daytime sleepiness and reduced quality of life. Daytime sleepiness can lead to dangerous outcomes associated with drowsy driving and has become an important public health issue. Routine health examinations that include questions about sleep habits, daytime sleepiness, and problems with sleep at night can help to educate people about the importance of good sleep habits. They provide a way to identify sleep disorders so that appropriate therapies can be instituted or proper referrals to a sleep specialist can be given.

Sleep and the endocrine system: new associations to old diseases

Sleep and sleep disorders play a prominent role in hormone regulation. Given that sleep disordered breathing (SDB) and diabetes mellitus (DM) are thought to result from obesity, it has been assumed that when the two coexist, the diabetes was caused by the obesity. However, new data has shed light on the effects that SDB, sleep deprivation, and snoring have on glucose regulation. It now appears that in addition to causing daytime drowsiness, cardiovascular disease, mood and memory disturbances, impotence, and car wrecks, obstructive sleep apnea (OSA) also promotes insulin resistance. Though data is still sketchy on the optimum management of coexisting DM and OSA, large-scale studies will most likely prove that homeostatic glucose control in patients with sleep apnea will require aggressive treatment of their SDB.

Is obesity associated with poor sleep quality in adolescents?

Obesity has reached epidemic proportions in the U.S. and more developed countries, particularly so among adolescents. A substantial impact on public health could be achieved if other factors causing obesity besides the conventional ones of diet and physical activity could be identified and acted upon. The present study investigates whether there is a link between low sleep quality and obesity in a tri-ethnic, cross-sectional sample (n = 383) of male and female adolescents ages 11-16 years old (Heartfelt Study). Sleep quality was expressed as two variables, total sleep time and sleep disturbance time obtained by 24-hour wrist actigraphy. Percent body fat and body mass index (BMI) were used together to define obesity. The potential influence of demographic and behavioral confounders were considered in models that described the relation of sleep to obesity occurrence. Obese adolescents experienced less sleep than nonobese adolescents (P < 0.01). For each hour of lost sleep, the odds of obesity increased by 80%. Sleep disturbance was not directly related to obesity in the sample, but influenced physical activity level (P < 0.01). Daytime physical activity diminished by 3% for every hour increase in sleep disturbance. The above observations were independent of potential confounding variables. Inadequate and poor sleep quality in adolescents may be important factors to consider in the prevention of childhood obesity.

A pilot study of the effects of expressive writing on psychological and behavioral adjustment in patients enrolled in a Phase II trial of vaccine therapy for metastatic renal cell carcinoma

Forty-two patients with metastatic renal cell carcinoma who were participating in a Phase II clinical trial were randomly assigned to an expressive writing (EW) or neutral writing (NW) group. Patients in the EW group wrote about their cancer, and patients in the NW group wrote about health behaviors. No statistically significant group differences were found in symptoms of distress, perceived stress, or mood disturbance, except for the Vigor subscale of the Profile of Mood States. However, patients in the EW group reported significantly less sleep disturbance, better sleep quality and sleep duration, and less daytime dysfunction compared with patients in the NW group. The results suggest that EW may have sleep-related health benefits in terminally ill cancer patients.

Sleeping with the hypothalamus: emerging therapeutic targets for sleep disorders

Delineating the basic mechanisms that regulate sleep will likely result in the development of better treatments for sleep disorders. The hypothalamus is now recognized as a key center for sleep regulation, with hypothalamic neurotransmitter systems providing the framework for therapeutic advances. An increased awareness of the close interaction between sleep and homeostatic systems is also emerging. Progress has occurred in the understanding of narcolepsy--molecular techniques have identified the lateral hypothalamic hypocretin (orexin) neuropeptide system as key to the disorder. Other sleep disorders are now being tackled in the same way and are likely to yield to efforts combining basic and clinical research. Here we highlight the role of the hypothalamus in sleep physiology and discuss neurotransmitter systems, such as adenosine, dopamine, GABA, histamine and hypocretin, that may have therapeutic applications for sleep disorders.

Adenosine induces inositol 1,4,5-trisphosphate receptor-mediated mobilization of intracellular calcium stores in basal forebrain cholinergic neurons

In the cholinergic basal forebrain, we found previously that the extracellular adenosine concentration increase that accompanies sleep deprivation, acting via the A1 receptor, led to activation of the transcription factor nuclear factor-kappaB and to the upregulation of A1 adenosine receptor mRNA. We thus began to examine intracellular signaling mechanisms. We report here that adenosine, acting in a dose-dependent manner and predominantly via A1 receptors, stimulated IP3 receptor-regulated calcium release from intracellular stores. To the best of our knowledge, this calcium signaling pathway effect is a novel action of the G(i)-coupled A1 adenosine receptor in neurons. Moreover, this calcium mobilization was not seen at all in noncholinergic neurons but was present in a large proportion of cholinergic neurons. These data suggest a potential role for a calcium-signaling pathway in adenosine-induced long-term effects of sleep deprivation and a key role for cholinergic neurons in this process.