Leukocytosis and natural killer cell function parallel neurobehavioral fatigue induced by 64 hours of sleep deprivation

Sleep-dependent activity of T cells and regulatory T cells

A number of immunological functions are dependent on circadian rhythms and regular sleep. This has impact on the type and magnitude of immune responses following antigenic challenge, for example in vaccination. Little is known about the underlying mechanisms. One possibility may be the circadian and sleep-dependent modulation of CD4(+)CD25(-) T cell responses by CD4(+)CD25(+) natural regulatory T cells (nT(reg)). In a variety of studies, nT(reg) have been shown to regulate T cell responses negatively. Thus, we investigated the influence of sleep and circadian rhythm on the number and function of nT(reg) as well as on the function of CD4(+)CD25(-) T cells. Seven healthy young men were examined under defined conditions on two occasions, i.e. during sleep and sleep deprivation. Venous blood was drawn periodically; numbers of nT(reg), suppressive activity of nT(reg), interleukin-2 production and proliferation of CD4(+)CD25(-) T cells were explored in vitro. nT(reg) counts revealed a significant circadian rhythm with highest levels during the night (mean 95 nT(reg)/microl) and lowest levels during the day (mean 55 nT(reg)/microl). During normal sleep, the suppressive activity of nT(reg) was highest at 02.00 h and somewhat lower at 15.00 h. Surprisingly, almost no suppressive activity was present at 07.00 h. Deprivation of sleep abrogated this rhythm. CD4(+)CD25(-) T cell proliferation was dampened significantly by sleep deprivation. This is the first study in human cells to show that nT(reg) number and function follow a rhythm across the 24-h period. Furthermore, sleep deprivation severely disturbs the functional rhythm of nT(reg) and CD4(+)CD25(-) T cells.

Cardiovascular, inflammatory, and metabolic consequences of sleep deprivation

That insufficient sleep is associated with poor attention and performance deficits is becoming widely recognized. Fewer people are aware that chronic sleep complaints in epidemiologic studies have also been associated with an increase in overall mortality and morbidity. This article summarizes findings of known effects of insufficient sleep on cardiovascular risk factors including blood pressure, glucose metabolism, hormonal regulation, and inflammation with particular emphasis on experimental sleep loss, using models of total and partial sleep deprivation, in healthy individuals who normally sleep in the range of 7 to 8 hours and have no sleep disorders. These studies show that insufficient sleep alters established cardiovascular risk factors in a direction that is known to increase the risk of cardiac morbidity.

Assessment of the Potential Role of Tryptophan as the Precursor of Serotonin and Melatonin for the Aged Sleep-wake Cycle and Immune Function: Streptopelia Risoria as a Model

In the present review we summarize the relationship between the amino acid, tryptophan, the neurotransmitter, serotonin, and the indole, melatonin, with the rhythms of sleep/wake and the immune response along with the possible connections between the alterations in these rhythms due to aging and the so-called “serotonin and melatonin deficiency state.” The decrease associated with aging of the brain and circulating levels of serotonin and melatonin seemingly contributes to the alterations of both the sleep/wake cycle and the immune response that typically accompany old age. The supplemental administration of tryptophan, e.g. the inclusion of tryptophan-enriched food in the diet, might help to remediate these age-related alterations due to its capacity of raise the serotonin and melatonin levels in the brain and blood. Herein, we also summarize a set of studies related to the potential role that tryptophan, and its derived product melatonin, may play in the restoration of the aged circadian rhythms of sleep/wake and immune response, taking the ringdove (Streptopeliarisoria) as a suitable model.

Phagocyte migration and cellular stress induced in liver, lung, and intestine during sleep loss and sleep recovery

Sleep is understood to possess recuperative properties and, conversely, sleep loss is associated with disease and shortened life span. Despite these critical attributes, the mechanisms and functions by which sleep and sleep loss impact health still are speculative. One of the most consistent, if largely overlooked, signs of sleep loss in both humans and laboratory rats is a progressive increase in circulating phagocytic cells, mainly neutrophils. The destination, if any, of the increased circulating populations has been unknown and, therefore, its medical significance has been uncertain. The purpose of the present experiment was to determine the content and location of neutrophils in liver and lung tissue of sleep-deprived rats. These are two principal sites affected by neutrophil migration during systemic inflammatory illness. The content of neutrophils in the intestine also was determined. Sleep deprivation in rats was produced for 5 and 10 days by the Bergmann-Rechtschaffen disk method, which has been validated for its high selectivity under freely moving conditions and which was tolerated and accompanied by a deep negative energy balance. Comparison groups included basal conditions and 48 h of sleep recovery after 10 days of sleep loss. Myeloperoxidase (MPO), an enzyme constituent of neutrophils, was extracted from liver, lung, and intestinal tissues, and its activity was determined by spectrophotometry. Leukocytes were located in vasculature and interstitial spaces in the liver and the lung by immunohistochemistry. Heme oxygenase-1, also known as heat shock protein-32 and a marker of cellular stress, and corticosterone also were measured. The results indicate neutrophil migration into extravascular liver and lung tissue concurrent with cell stress and consistent with tissue injury or infection induced by sleep loss. Plasma corticosterone was unchanged. Recovery sleep was marked by increased lung heme oxygenase-1, increased intestinal MPO activity, and abnormally low corticosterone, suggesting ongoing reactive processes as a result of prior sleep deprivation.

Insomnia symptoms in a multiethnic sample of American women

BACKGROUND

Ethnic disparities in socioeconomic factors, risk markers, and coping styles affect health status. This study examined whether those factors influence insomnia symptoms in a multiethnic sample of urban American women.

METHODS

Women (n = 1440, average age = 59.5 +/- 6.45 years) participating in the study were recruited using a stratified, cluster sampling technique. The sample comprises African Americans (22%), English-speaking Caribbeans (22%), Haitians (22%), Dominicans (12%), Eastern Europeans (11%), and European Americans (11%). Trained staff conducted face-to-face interviews lasting 1.5 hours acquiring demographic, health, and sleep data.

RESULTS

Analysis indicated significant ethnic differences in socioeconomics, risk markers, and health characteristics. The prevalence of insomnia symptoms (defined as either difficulty initiating sleep, difficulty maintaining sleep, or early morning awakening) among African Americans was 71%, English-speaking Caribbeans 34%, Haitians 33%, Dominicans 73%, Eastern Europeans 77%, and European Americans 70%. Hierarchical regression results showed that ethnicity explained 20% of the variance in the insomnia variable. Sociodemographic factors explained 5% of the variance, risk markers explained 5%, medical factors 20%, and coping styles 1%. Goodness-of-fit test indicated the model was reliable [chi-square = 276, p < 0.001], explaining 51% of the variance.

CONCLUSIONS

Findings show interethnic heterogeneity in insomnia symptoms, even among groups previously assumed to be homogeneous. Different factors seemingly influence rates of insomnia symptoms within each ethnic group examined. These findings have direct relevance in the management of sleep problems among women of different ethnic backgrounds. Understanding of ethnic/cultural factors affecting the sleep experience is important in interpreting subjective sleep data.

Acute sleep deprivation is associated with increased electrocardiographic P-wave dispersion in healthy young men and women

BACKGROUND

Sleep deprivation (SD) is associated with worse cardiovascular outcome including mortality. Prolonged P-wave duration and P-wave dispersion (Pd) are known to represent inhomogeneous conduction of sinus impulses and are known to be electrophysiologic predictors of atrial fibrillation. Pd in normal subjects has been reported to be influenced by the autonomic tone. Because autonomic tone is affected by sleep and sleep duration, we evaluated the effect of acute SD on P-wave duration and Pd in healthy young adults and whether the effect was gender selective.

METHODS

We obtained electrocardiograms of 37 healthy young volunteers (age: 28.45 +/- 7.97; 11 women) after a night of regular sleep and repeated after a night with sleep debt. We measured minimum and maximum P-wave durations (Pmin, Pmax) and Pd in milliseconds.

RESULTS

Average sleep time of the subjects were 7.7 +/- 0.8 hours during regular sleep and 1.7 +/- 1.6 hours during a night of sleep debt (P < 0.001). Subjects had significantly lower values of Pmin in milliseconds after a night of sleep debt when compared to regular sleep (65.13 +/- 8.03 vs 74.86 +/- 10.95; P < 0.001), whereas they had significantly higher values of Pmax and Pd (102.16 +/- 9.46 vs 95.13 +/- 11.21; P < 0.001 and 37.02 +/- 8.11 vs 20.27 +/- 11.42; P < 0.001, respectively). In Pearson's correlation analysis Pmin was positively and Pmax and Pd were negatively correlated with sleep time (P < 0.001, r = 0.465; P = 0.003, r =-0.336 and P < 0.001, r =-0.698 respectively). Effect of SD on P-wave duration and Pd was similar for both men and women.

CONCLUSIONS

In conclusion, prolongation of Pmax and Pd in acute SD suggests that acute SD might contribute to development and/or recurrence of atrial fibrillation.

Sleep and inflammation

Among adults in the United States, sleep durations appear to have decreased in recent years. Inadequate sleep and sleep deprivation cause numerous neurobehavioral and physiological changes. A number of recent studies have reported associations between disrupted sleep/sleep deprivation and inflammatory responses, although the physiological mechanisms underlying these relationships remain unclear. Alterations in sleep due to lifestyle factors, the aging process, and disease states have all been associated with increases in a range of inflammatory markers. Several of these inflammatory processes have been associated with reduced health status (e.g., C-reactive protein and cardiovascular disease). Thus, maintaining adequate sleep duration and quality through good sleep habits and treatment of sleep disorders may reduce inflammatory processes associated with aging and increase the wellness phenotype.

[Individual differences and sleep deprivation effects]

Contemporary lifestyle and different life circumstances often require that individuals restrict their sleep duration and change their sleep schedule. That often leads to sleep deprivation. Former studies showed that sleep deprivation effects on the physiological and psychological functioning of an individual depended on numerous factors such as type of sleep deprivation, previous sleep duration, time of day when the effects were examined, characteristics of tasks performed, and the subject's motivation. This paper discusses the effects of sleep deprivation and the existence of stable individual differences in those effects, named "vulnerability to sleep loss". Recent studies indicate that some characteristics of the subjects could help predict systematic and robust sleep deprivation effects, such as age, sex and personality characteristics. Furthermore, the article discusses the importance of individual differences in specific characteristics related to sleep and wakefulness like those in preferred circadian phase, sleep need, individual level of sleepiness, and the ability to fall asleep quickly. So far, studies of individual characteristics did not result in consistent conclusions about their predictive importance for vulnerability to sleep loss. Further studies directed at this problem could help identify individuals who are more vulnerable to sleep loss, and contribute to personal and public safety of night work.

The effects of 40 hours of total sleep deprivation on inflammatory markers in healthy young adults

Inflammatory cytokines are released in response to stress, tissue damage, and infection. Acutely, this response is adaptive; however, chronic elevation of inflammatory proteins can contribute to health problems including cardiovascular, endocrine, mood, and sleep disorders. Few studies have examined how sleep deprivation acutely affects inflammatory markers, which was the aim of the current study. Nineteen healthy men and women aged 28.05+/-8.56 (mean+/-SD) were totally sleep deprived for 40 h under constant routine conditions. Pro-inflammatory markers: intracellular adhesion molecule-1 (ICAM-1), E-selectin, vascular adhesion molecule-1 (VCAM-1), c-reactive protein (CRP), interleukin-6 (IL-6), and interleukin-1beta (IL-1beta), and the anti-inflammatory cytokine interleukin-1 receptor antagonist (IL-1ra) were assayed in plasma. Daytime levels during baseline (hours 1-15 of scheduled wakefulness) were compared to daytime levels during sleep deprivation (hours 25-39 of scheduled wakefulness), thus controlling for circadian phase within an individual. Repeated measures ANOVA with planned comparisons showed that 40 h of total sleep deprivation induced a significant increase in E-selectin, ICAM-1, IL-1beta, and IL-1ra, a significant decrease in CRP and IL-6, and no significant change in VCAM-1. Alterations in circulating levels of pro- and anti-inflammatory cytokines and cell adhesion molecules during sleep deprivation were consistent with both increased and decreased inflammation. These findings suggest that one night of sleep loss triggers a stress response that includes stimulation of both pro- and anti-inflammatory proteins in the healthy young subjects tested under our experimental conditions.

Behavioral and physiological consequences of sleep restriction

Adequate sleep is essential for general healthy functioning. This paper reviews recent research on the effects of chronic sleep restriction on neurobehavioral and physiological functioning and discusses implications for health and lifestyle. Restricting sleep below an individual's optimal time in bed (TIB) can cause a range of neurobehavioral deficits, including lapses of attention, slowed working memory, reduced cognitive throughput, depressed mood, and perseveration of thought. Neurobehavioral deficits accumulate across days of partial sleep loss to levels equivalent to those found after 1 to 3 nights of total sleep loss. Recent experiments reveal that following days of chronic restriction of sleep duration below 7 hours per night, significant daytime cognitive dysfunction accumulates to levels comparable to that found after severe acute total sleep deprivation. Additionally, individual variability in neurobehavioral responses to sleep restriction appears to be stable, suggesting a trait-like (possibly genetic) differential vulnerability or compensatory changes in the neurobiological systems involved in cognition. A causal role for reduced sleep duration in adverse health outcomes remains unclear, but laboratory studies of healthy adults subjected to sleep restriction have found adverse effects on endocrine functions, metabolic and inflammatory responses, suggesting that sleep restriction produces physiological consequences that may be unhealthy.

SLEEP DISRUPTION IN OLDER ADULTS

Insomnia is not a normal part of aging, but nighttime sleep in older adults is often disrupted, leading to excessive daytime sleepiness and other physical, psychological, and cognitive changes that affect overall health. Even so, clinicians often pay little attention to sleep in this population. The sleep of older adults tends to be less deep than that of younger people, and coexisting conditions and treatment effects can more easily disrupt sleep. This article reviews the current literature on sleep disruption in older adults and suggests ways that nurses can apply the information in intervening to improve sleep in their older patients.

Subjective poor sleep and white blood cell count in male Japanese workers

Sleep deprivation has been shown to be associated with an increase in inflammatory makers such as interleukin-6 and C-reactive protein. The purpose of the present study was to investigate the relation between subjective poor sleep and white blood cell (WBC) count, an inflammatory marker. The subjects were 208 male Japanese workers in a synthetic fiber-manufacturing plant, who responded to a cross-sectional survey of a questionnaire on basic attributes, life style, and sleep. All male workers in the plant took an annual health checkup. WBC count was also examined in the checkup. The WBC count was greater in shift workers than in daytime workers. Shift workers complained of poor sleep more frequently, though their sleeping hours were longer. Multiple regression analysis showed that poor sleep as well as smoking habit, BMI and age were independent factors for an increase in WBC count, while sleeping hours and work pattern (shift work) were not significant factors. The present finding that poor sleep was associated with higher WBC count in male workers might suggest the importance of quality of sleep, particularly among shift workers.

Sleep, fatigue, and NK cell activity in healthy volunteers: significant relationships revealed by within subject analyses

Poor sleep is thought to compromise health partially through its effect on immune function. Although experimental studies have shown that sleep deprivation reduces natural killer cell activity (NKCA) within individuals, cross-sectional studies of individuals in ordinary life have often failed to find such a relationship. The current study compared cross-sectional and longitudinal approaches to explore the association between sleep and NKCA. The relationship between NKCA and fatigue was also studied since individuals who are highly fatigued due to various clinical conditions often exhibit reduced NKCA. In the present study, fatigue and amount of sleep were assessed by self-report, and NKCA was assessed in peripheral blood samples collected from each of 45 healthy women at two time points approximately one month apart. Using cross-sectional analysis for each of the two sessions, sleep was related to NKCA only in the second session. Fatigue was not related to NKCA at either session. A within-subject design, however, revealed that an increase in the amount of sleep and decrease in levels of fatigue were related to an increase in NKCA. The current findings suggest that NKCA varies with amount of sleep or fatigue within an individual, and that this relationship may often be masked by large interpersonal differences in cross-sectional studies.

Sleep deprivation: Impact on cognitive performance

Today, prolonged wakefulness is a widespread phenomenon. Nevertheless, in the field of sleep and wakefulness, several unanswered questions remain. Prolonged wakefulness can be due to acute total sleep deprivation (SD) or to chronic partial sleep restriction. Although the latter is more common in everyday life, the effects of total SD have been examined more thoroughly. Both total and partial SD induce adverse changes in cognitive performance. First and foremost, total SD impairs attention and working memory, but it also affects other functions, such as long-term memory and decision-making. Partial SD is found to influence attention, especially vigilance. Studies on its effects on more demanding cognitive functions are lacking. Coping with SD depends on several factors, especially aging and gender. Also interindividual differences in responses are substantial. In addition to coping with SD, recovering from it also deserves attention. Cognitive recovery processes, although insufficiently studied, seem to be more demanding in partial sleep restriction than in total SD.

Dolphin continuous auditory vigilance for five days

The present report describes the first study of continuous vigilance in dolphins. Two adult bottlenose dolphins (Tursiops truncatus), WEN (male) and SAY (female), maintained a very high detection rate of randomly presented, infrequent, 1.5-s target tones in a background of frequent 0.5-s equal-amplitude tones over five continuous 120-h sessions. The animals were able to maintain high levels (WEN 97, 87, 99%; SAY 93, 96%) of target detection without signs of sleep deprivation as indicated by behavior, blood indices or marked sleep rebound during 24 h of continuous post-experiment observation. Target response time overall (F = 0.384; P = 0.816) did not change between day 1 and day 5. However, response time was significantly slower (F = 21.566, P = 0.019) during the night (21.00-04.00 h) when the dolphins would have ordinarily been resting or asleep.

Effects of sleep deprivation on the development of autoimmune disease in an experimental model of systemic lupus erythematosus

Sleep is hypothesized to play a restorative role on immune system. In addition, disturbed sleep is thought to impair host defense mechanisms. Chronic sleep deprivation is a common occurrence in modern society and has been observed in a number of chronic inflammatory conditions, such as systemic lupus erythematosus (SLE). New Zealand Black/New Zealand White (NZB/NZW) F1mice develop an autoimmune disease that strongly resembles SLE in humans, exhibiting high titers of antinuclear antibodies associated with the development of rapidly progressive and lethal glomerulonephritis. On the basis of this evidence, the present study examined the onset and progress of lupus in as-yet healthy female mice submitted to sleep deprivation. Sleep deprivation was accomplished by two 96-h periods in the multiple-platform method when mice were 10 wk old, and they were observed until 28 wk of age. Blood samples were collected from the orbital plexus fortnightly to evaluate serum antinuclear antibodies and anti-double-stranded DNA. Proteinuria and longevity as well as body weight were also assessed. The results indicated that mice submitted to sleep deprivation exhibited an earlier onset of the disease, as reflected by the increased number of antinuclear antibodies. However, no statistical difference was found in the other parameters analyzed. According to these results, sleep deprivation could be considered as a risk factor for the onset but not for the evolution of the disease.

Changes in brain gene expression after long-term sleep deprivation

Long-term sleep deprivation in rats produces dramatic physiological changes including increase in energy expenditure, decrease in body weight, and death after 2-3 weeks. Despite several studies, the sleep deprivation syndrome remains largely unexplained. Here, to elucidate how prolonged sleep loss affects brain cells we used microarrays and screened the expression of > 26 000 transcripts in the cerebral cortex. Rats were sleep deprived using the disk-over-water method for 1 week. Seventy-five transcripts showed increased expression in these animals relative to controls that had been spontaneously awake or sleep deprived for a few hours. Most of them were induced as a result of chronic sleep loss and not non-specific effects of the disk stimulation. They include transcripts coding for several immunoglobulins, stress response proteins (macrophage inhibitor factor-related protein 14, heat-shock protein 27, alpha-B-crystallin), minoxidil sulfotransferase, globins and cortistatin. Twenty-eight transcripts decreased their expression in long-term sleep-deprived rats. Sixteen of them were specifically decreased as a result of chronic sleep loss, including those coding for type I procollagen and dihydrolipoamide acetyltransferase. We also compared sleeping rats to short-term and long-term sleep-deprived rats, and found that acute and chronic sleep loss led to some differences at the molecular level. Several plasticity-related genes were strongly induced after acute sleep deprivation only, and several glial genes were down-regulated in both sleep deprivation conditions, but to a different extent. These findings suggest that sustained sleep loss may trigger a generalized inflammatory and stress response in the brain.

Duration of sleep and breast cancer risk in a large population-based case–control study

One important function of sleep may be its contribution to the maintenance of the immune system and regulation of the circadian rhythms by melatonin. Researchers have speculated that disruption of immune functions involving cortisol levels and natural killer cell activity may increase breast cancer risk whereas increased melatonin exposure may protect against breast cancer. We conducted a multistate population-based case-control study of 4,033 women with invasive breast cancer and 5,314 community women without breast cancer in which we inquired about women's sleep habits in the recent past and during adult lifetime. Relative to women who slept 7.0-7.9 h/night, the multivariate odds ratio for developing breast cancer among women who slept an average of 9 h or more per night approximately 2 years prior to interview was 1.13 (95% CI 0.93-1.37). The multivariate-adjusted odds ratio for the continuous term was 1.06 (95% CI 1.01-1.11), suggesting a 6% increase in risk for every additional hour of sleep. Similar patterns were observed for average lifetime adult sleep duration. We found little evidence that sleeping few hours per night was associated with breast cancer risk. The results of this study suggest that increasing sleep duration is modestly associated with an increased breast cancer risk. In contrast, short duration of sleep (<7 h/night) is not substantially associated with increased risk. Further research in this area is warranted.

Seven days’ around the clock exhaustive physical exertion combined with energy depletion and sleep deprivation primes circulating leukocytes

Both exhaustive physical exertion and starvation have been reported to induce depression of immune function. The aim of the present study was to investigate the inflammatory environment and state of activation and mediator-producing potential of circulating leukocytes during prolonged physical activity with concomitant energy and sleep deprivation. Eight well-trained males were studied during 7 days of semi-continuous physical activity. Sleep was restricted to about 1 h/24 h, energy intake to 1.5- 3.0 MJ/24 h. Blood was drawn at 07.00 A.M.: on days 0, 2, 4, and 7. Plasma levels of inflammation markers were measured. The response of circulating leukocytes to lipopolysaccharide (LPS; 1 microg mL(-1)), and the effect of added hydrocortisone (10 and 100 nmol L(-1)), were measured in the supernatant after 3 h of incubation in an ex vivo whole blood model. Activation of leukocytes steadily increased as measured by plasma matrix metalloproteinase-9, tumour necrosis factor-alpha, interleukin-1beta, and interleukin-6. Inhibitors of systemic inflammation were either unaltered (tissue inhibitor of matrix metalloproteinase-1) or elevated (plasma interleukin-1 receptor antagonist). Cortisol levels increased on days 2 and 4, but thereafter reverted to baseline values. The leukocytes responded to LPS activation with increasing release of inflammatory cytokines throughout the study period. The anti-inflammatory potency of hydrocortisone decreased. Prolonged multifactorial stress thus activated circulating immune cells and primed them for an increased response to a subsequent microbial challenge.

Sleep in acute care units

Patients in the acute care units (ACU) are usually critically ill, making them more susceptible to the unfavorable atmosphere in the hospital. One of these unfavorable factors is sleep disruption and deprivation. Many factors may affect sleep in the ACU, including therapeutic interventions, diagnostic procedures, medications, the underlying disease process, and noise generated in the ACU environment. Many detrimental physiological effects can occur secondary to noise and sleep deprivation, including cardiovascular stimulation, increased gastric secretion, pituitary and adrenal stimulation, suppression of the immune system and wound healing, and possible contribution to delirium. Over the past few years, many studies have endeavored to objectively assess sleep in the ACUs, as well as the effect of mechanical ventilation and circadian rhythm changes critically ill patients. At this time, therefore, it is important to review published data regarding sleep in ACUs, in order to improve the knowledge and recognition of this problem by health care professionals. We have therefore reviewed the methods used to assess sleep in ACUs, factors that may affect sleep in the ACU environment, and the clinical implications of sleep disruption in the ACU.

Bidirectional communication between the brain and the immune system: implications for physiological sleep and disorders with disrupted sleep

This review describes mechanisms of immune-to-brain and brain-to-immune signaling involved in mediating physiological sleep and altered sleep with disease. The central nervous system (CNS) modulates immune function by signaling target cells of the immune system through autonomic and neuroendocrine pathways. Neurotransmitters and hormones produced and released by these pathways interact with immune cells to alter immune functions, including cytokine production. Cytokines produced by cells of the immune and nervous systems regulate sleep. Cytokines released by immune cells, particularly interleukin-1beta and tumor necrosis factor-alpha, signal neuroendocrine, autonomic, limbic and cortical areas of the CNS to affect neural activity and modify behaviors (including sleep), hormone release and autonomic function. In this manner, immune cells function as a sense organ, informing the CNS of peripheral events related to infection and injury. Equally important, homeostatic mechanisms, involving all levels of the neuroaxis, are needed, not only to turn off the immune response after a pathogen is cleared or tissue repair is completed, but also to restore and regulate natural diurnal fluctuations in cytokine production and sleep. The immune system's ability to affect behavior has important implications for understanding normal and pathological sleep. Sleep disorders are commonly associated with chronic inflammatory diseases and chronic age- or stress-related disorders. The best studied are rheumatoid arthritis, fibromyalgia and chronic fatigue syndromes. This article reviews our current understanding of neuroimmune interactions in normal sleep and sleep deprivation, and the influence of these interactions on selected disorders characterized by pathological sleep.

Mechanisms and functions of coupling between sleep and temperature rhythms

Energy metabolism is strongly linked to the circadian rhythms in sleep and body temperature. Both heat production and heat loss show a circadian modulation. Sleep preferably occurs during the circadian phase of decreased heat production and increased heat loss, the latter due to a profound increase in skin blood flow and, consequently, skin warming. The coupling of these rhythms may differ depending on whether they are assessed in experimental laboratory studies or in habitual sleeping conditions. In habitual sleeping conditions, skin blood flow is for a prolonged time increased to a level hardly ever seen during wakefulness. Possible mechanisms linking the rhythms in sleep and core body and skin temperature are discussed, with a focus on causal effects of changes in core and skin temperature on sleep regulation. It is shown that changes in skin temperature rather than in core temperature causally affect sleep propensity. Contrary to earlier suggestions of a functional role of sleep in heat loss, it is argued that sleep facilitates a condition of increased skin blood flow during a prolonged circadian phase, yet limits heat loss and the risk of hypothermia. Sleep-related behavior including the creation of an isolated microclimate of high temperature by means of warm clothing and bedding in humans and the curling up, huddling and cuddling in animals all help limit heat loss The increase in skin blood flow that characterizes the sleeping period may thus not primarily reflect a thermoregulatory drive. There is indirect support for an alternative role of the prolonged period of increased skin blood flow: it may support maintenance of the skin as a primary barrier in host defense.

Sustained sleep restriction reduces emotional and physical well-being

BACKGROUND

Chronic insufficient sleep is a common finding in many pain-related and other medical diseases and is frequently experienced in the general population. Prolonged curtailment of nocturnal sleep has been studied for its adverse effect on cognitive functioning and subjective tiredness, but relatively little is known about its effect on mood and physical symptoms.

OBJECTIVE

In order to test whether sleep restriction to 50% of the habitual time over 12 days affects diurnal and day-to-day variation of subjective ratings of mood and physical symptoms, 108 adjectives and statements were self-rated using visual analog scales every 2h during the waking period.

DESIGN

Randomized, 16-day controlled in-laboratory study.

SETTING

General Clinical Research Center (GCRC).

PARTICIPANTS

Forty healthy subjects aged 21-40 years (14 females, 26 males).

INTERVENTION

Subjects were randomized to either 4h of sleep per night (11 pm-3 am, N=22) or 8h of sleep per night (11 pm-7 am, N=18) for 12 consecutive days.

MAIN OUTCOME MEASURE

Changes in the factor-derived variables optimism-sociability, tiredness-fatigue, anger-aggression, bodily discomfort, and items constituting bodily discomfort were compared between groups.

RESULTS

Optimism-sociability progressively declined over consecutive days of sleep restriction by 15%. Bodily discomfort showed a slight, but significant interindividual increase of 3% across days of sleep restriction due to significant increases of generalized body pain, back pain, and stomach pain. Optimism-sociability and tiredness-fatigue showed diurnal variations with a quadratic function period within each day in both conditions.

CONCLUSION

The data suggest that chronic insufficient sleep may contribute to the onset and amplification of pain and affect health by compromising optimistic outlook and psychosocial functioning.

Sleep and sedation in the pediatric intensive care unit

Sleep is an important and necessary function of the human body. Somatic growth and cellular repair occur during sleep. Critically ill children have disturbed sleep while in the pediatric intensive care unit related both to the illness itself and to light, noise, and caregiver activities disrupting an environment conducive to sleep. Medications administered in the pediatric intensive care unit can also disrupt sleep. This article reviews what is known about sleep in the pediatric intensive care unit and the effects of common sedation medications on sleep.

Clinical assessment of blood leukocytes, serum cytokines, and serum immunoglobulins as responses to sleep deprivation in laboratory rats

The specific systems and mechanisms affected by sleep deprivation that may perpetuate disease processes in humans still are speculative. In laboratory rats, prolonged sleep deprivation induces a state marked by abnormal control over indigenous bacteria that results in transient infections of internal tissues and eventual lethal septicemia. The present studies investigated changes in blood, serum, and bone marrow parameters that may provide diagnostic clues to immunopathology. Prolonged sleep deprivation was produced in rats by the disk-over-water method, a well-established and selective means that does not interfere with normal waking behaviors. Measurements included bone and blood differential white blood cell counts, multiple serum cytokines and chemokines, several major Ig classes and subclasses, and serum endotoxin concentrations. The results indicated mild, regenerative neutrophilia in sleep-deprived rats, initially accompanied by immature neutrophils and later by monocytosis. The corresponding serum cytokine profile revealed an evolving proinflammatory state, particularly by high incidence of interleukin-1β, implicating mononuclear phagocytes and resident tissue cells as main intermediary sources. In addition, multiple serum Ig classes were increased by sleep deprivation without experimental administration of an exogenous antigen. Despite this immune activation, there was failure to eradicate invading bacteria and toxins, suggesting competing anti-inflammatory processes or interference with immune effector functions during sleep deprivation. Nearly all of the immune-related events that emerged as responses to sleep deprivation have been implicated as etiological or provocative factors in other disease processes and may provide means by which sleep deprivation as a risk factor in disease may become understood.

Randomized study on the efficacy of cognitive-behavioral therapy for insomnia secondary to breast cancer, part II: Immunologic effects

PURPOSE

Cross-sectional studies suggest that clinical insomnia is associated with immune downregulation. However, there is a definite need for experimental studies on this question. The goal of this randomized controlled study was to assess the effect of an 8-week cognitive-behavioral therapy (CBT) for chronic insomnia on immune functioning of breast cancer survivors. Previous analyses of this study showed that CBT was associated with improved sleep and quality of life, and reduced psychological distress.

PATIENTS AND METHODS

Fifty-seven women with chronic insomnia secondary to breast cancer were randomly assigned to CBT (n = 27) or to a waiting-list control condition (WLC; n = 30). Peripheral-blood samples were taken at baseline and post-treatment (and postwaiting for WLC patients), as well as at 3-, 6-, and 12-month follow-up for immune measures, including enumeration of blood cell counts (ie, WBCs, monocytes, lymphocytes, CD3+, CD4+, CD8+, and CD16+/CD56+) and cytokine production (ie, interleukin-1-beta [IL-1beta] and interferon gamma [IFN-gamma]).

RESULTS

Patients treated with CBT had higher secretion of IFN-gamma and lower increase of lymphocytes at post-treatment compared with control patients. Pooled data from both treated groups indicated significantly increased levels of IFN-gamma and IL-1beta from pre- to post-treatment. In addition, significant changes in WBCs, lymphocytes, and IFN-gamma were found at follow-up compared with post-treatment.

CONCLUSION

This study provides some support to the hypothesis of a causal relationship between clinical insomnia and immune functioning. Future studies are needed to investigate the clinical impact of such immune alterations.

Sleep deprivation

The occurrence of chronic sleep deprivation in the population is commonplace. Both duration and quality of sleep are important to assess when evaluating a patient who has sleep complaints. Excessive sleepiness and decreased psychomotor performance have been demonstrated after sleep deprivation. Sleep loss may impact mood, autonomic function, and the immune system. Sleep-deprived adults may have impaired job performance and are prone to motor vehicle accidents. Simple interventions to ensure adequate sleep can help avoid these hazards.

Cognitive behavior therapy for chronic insomnia occurring within the context of medical and psychiatric disorders

Insomnia is a pervasive problem for many patients suffering from medical and psychiatric conditions. Even when the comorbid disorders are successfully treated, insomnia often fails to remit. In addition to compromising quality of life, untreated insomnia may also aggravate and complicate recovery from the comorbid disease. Cognitive behavior therapy for insomnia (CBT-I) has an established efficacy for primary insomnia, but less is known about its efficacy for insomnia occurring in the context of medical and psychiatric conditions. The purpose of this article is to present a rationale for using CBT-I in medical and psychiatric disorders, review the extant outcome literature, highlight considerations for adapting CBT-I procedures in specific populations, and suggest directions for future research. Outcome studies were identified for CBT-I in mixed medical and psychiatric conditions, cancer, chronic pain, HIV, depression, posttraumatic stress disorder, and alcoholism. Other disorders discussed include: bipolar disorder, eating disorders, generalized anxiety, and obsessive compulsive disorder. The available data demonstrate moderate to large treatment effects (Cohen's d, range=0.35-2.2) and indicate that CBT-I is a promising treatment for individuals with medical and psychiatric comorbidity. Although the literature reviewed here is limited by a paucity of randomized, controlled studies, the available data suggest that by improving sleep, CBT-I might also indirectly improve medical and psychological endpoints. This review underscores the need for future research to test the efficacy of adaptations of CBT-I to disease specific conditions and symptoms.

Sleep quality in renal transplant patients: a never investigated problem

BACKGROUND

Despite the great prevalence of sleep disorders and the low quality of sleep in patients with renal diseases, to date no study has evaluated these problems in renal transplant patients.

METHODS

The aim of the study was to assess sleep quality (SQ) in 301 kidney graft recipients by the Pittsburgh Sleep Quality Index (PSQI, range 0-21, with higher scores indicating worse SQ), in comparison with PSQI of both patients on haemodialysis (HD) (n = 245) and normal control subjects (n = 169).

RESULTS

PSQI of renal transplant patients averaged 6.46+/-3.71, a value significantly lower than in HD patients (8.52+/-3.81, P<0.001), but higher than in control subjects (3.54+/-1.61, P<0.0001 vs both transplant and dialysis patients). No correlation was found between PSQI and the main biochemical parameters of transplant patients. When the patients were divided into 'good' (PSQI<5) or 'poor' (PSQI>5) sleepers, a significant risk of psychological problems was associated with the condition of 'poor sleeper' (OR: 2.3; P<0.02), with no further correlation detected in either of the two groups.

CONCLUSIONS

These data demonstrate that SQ in renal transplant patients is surprisingly low, despite a well preserved renal function, and that poor sleep in these patients is also secondary to psychological problems. The use of PSQI in such patients represents a useful tool for the investigation of SQ and quality of life.

Using Stress Models to Evaluate Immuno-Modulating Effects of Nutritional Intervention in Healthy Individuals

There is clear evidence that nutritional supplementation helps to restore immune function and contributes to optimal resistance to infections in malnourished people. However, the literature is less clear on the suggested benefits of dietary supplementation for immune function in healthy, well nourished subjects. Such studies are hampered by large variability in immune function markers and clinical outcome measures, which are known to be affected by factors such as genotype, age, gender, history of infections and vaccinations, and various stressors associated with lifestyle. Therefore, there appears to be a need to employ experimental models that control and/or manipulate the factors that are responsible for this variability. Conceivably, such a model could experimentally apply various forms of stress to physiologically suppress the immune system and assess whether nutritional intervention can (partially) compensate the deleterious effects. Here we review effects of psychological stress, physical exertion, and sleep deprivation on various aspects of immune function and susceptibility to common infections. We focus on the usefulness of such stress models to evaluate the putative beneficial role of diets/nutrients on immune function in healthy individuals.

Cellular adhesion molecule expression, nocturnal sleep, and partial night sleep deprivation

Sleep is hypothesized to have a role in the regulation of the immune system. This study evaluated the nocturnal expression of cellular adhesion molecules, Mac-1 and L-selectin on monocytes and lymphocytes during a full nights sleep and following a partial night of sleep deprivation (PSD). Healthy male subjects (n=16) had an increase in the percentage of Mac-1 positive lymphocytes across the baseline night. Whereas, the percentage of Mac-1 positive lymphocytes was reduced and L-selectin positive lymphocytes and monocytes were greater during the PSD night as compared to the baseline night. These data indicate that acute sleep disruption is associated with alterations in cellular adhesion molecule expression, with implications for the regulation of immune cell trafficking.

Pain, psychological variables, sleep quality, and natural killer cell activity in midlife women with and without fibromyalgia

In women with fibromyalgia (FM), central nervous system (CNS) dysfunction in pain, mood, and sleep processes could be associated with changes in immune system indicators. The primary purpose of this study was to compare pain, psychological variables, subjective and objective sleep quality, lymphocyte phenotypes and activation markers, and natural killer activity (NKA) in midlife women with and without FM. A secondary purpose was to explore relationships among these variables in a step-wise regression. Subjects had pain pressure tender points assessed, completed a psychiatric interview and questionnaires (Beck Depression Inventory, SCL-90, Profile of Mood States, subjective sleep), and underwent polysomnograhic assessment for two consecutive nights. Lymphocyte phenotypes, activation markers, and NKA were assessed from blood drawn the morning after sleep laboratory night 2. Compared to controls, women with FM had lower pain thresholds, more psychological distress, higher depression scores, and reduced subjective and objective sleep quality. They also had fewer NK cells (p <.009) and more NK cells that expressed the IL-2 receptor (p <.04), but these differences were not statistically significant after correction for multiple comparisons. NKA was not statistically significantly lower in the women with FM compared to controls. In a multiple regression of age, tender point threshold, depression, psychological distress, and sleep efficiency, only the effect of group was significant (F = 5.479, p <.03) on NKA. In conclusion, we found little evidence to support the hypothesis that pain, mood, and sleep symptoms are associated with changes in the enumeration of peripheral lymphocytes or function in FM.

Sleep monitoring in children during neuromuscular blockade in the pediatric intensive care unit: a pilot study

BACKGROUND

Sleep is an important physiologic process that is known to be disrupted in the intensive care unit. Nevertheless, there is little information on how intensive care unit admission affects sleep in children. Because laryngotracheoplasty is elective but entails 5-7 days of neuromuscular blockade following surgery, children undergoing this procedure present a unique opportunity to analyze sleep during neuromuscular blockade apart from confounding variables resulting from critical illness.

OBJECTIVE

To determine the feasibility of using polysomnography to assess sleep patterns in children during neuromuscular blockade.

METHODS

Polysomnography recordings were obtained continuously for 4 days (96 hrs) in two children following laryngotracheoplasty. Medication administration (neuromuscular blockades, sedatives) and time of suctioning were also recorded.

RESULTS

Both subjects had documented sleep. However, the proportion of time in each stage was markedly different from developmental norms, and a greater proportion of sleep occurred during the day. Furthermore, there was substantial day-night and day-to-day variability. Some rebound of consolidated sleep appeared by day 4. Sedative use varied considerably. However, neither bolus sedation administration nor endotracheal suctioning appeared to affect sleep. Few monitoring difficulties were encountered.

CONCLUSIONS

Sleep can be monitored with minimal difficulty in children undergoing neuromuscular blockade in the pediatric intensive care unit. Sleep occurred throughout the day, and there was considerable fragmentation. To fully assess sleep in the intensive care unit, monitoring needs to be continuous over several days, rather than only at night or for < or =24 hrs. Further research is needed in the area to determine typical sleep patterns in children undergoing neuromuscular blockade.

Effect of sleep loss on C-reactive protein, an inflammatory marker of cardiovascular risk

OBJECTIVES

We sought to investigate the effects of sleep loss on high-sensitivity C-reactive protein (CRP) levels.

BACKGROUND

Concentrations of high-sensitivity CRP are predictive of future cardiovascular morbidity. In epidemiologic studies, short sleep duration and sleep complaints have also been associated with increased cardiovascular morbidity. Two studies were undertaken to examine the effect of acute total and short-term partial sleep deprivation on concentrations of high-sensitivity CRP in healthy human subjects.

METHODS

In Experiment 1, 10 healthy adult subjects stayed awake for 88 continuous hours. Samples of high-sensitivity CRP were collected every 90 min for 5 consecutive days, encompassing the vigil. In Experiment 2, 10 subjects were randomly assigned to either 8.2 h (control) or 4.2 h (partial sleep deprivation) of nighttime sleep for 10 consecutive days. Hourly samples of high-sensitivity CRP were taken during a baseline night and on day 10 of the study protocol.

RESULTS

The CRP concentrations increased during both total and partial sleep deprivation conditions, but remained stable in the control condition. Systolic blood pressure increased across deprivation in Experiment 1, and heart rate increased in Experiment 2.

CONCLUSIONS

Both acute total and short-term partial sleep deprivation resulted in elevated high-sensitivity CRP concentrations, a stable marker of inflammation that has been shown to be predictive of cardiovascular morbidity. We propose that sleep loss may be one of the ways that inflammatory processes are activated and contribute to the association of sleep complaints, short sleep duration, and cardiovascular morbidity observed in epidemiologic surveys.

Nocturnal Care Interactions with Patients in Critical Care Units

• Background Sleep deprivation is common in critically ill patients and may have long-term effects on health outcomes and patients’ morbidity. Clustering nocturnal care has been recommended to improve patients’ sleep.

• Objectives To (1) examine the frequency, pattern, and types of nocturnal care interactions with patients in 4 critical care units; (2) analyze the relationships among these interactions and patients’ variables (age, sex, acuity) and site of admission to the intensive care unit; and (3) analyze the differences in patterns of nocturnal care activities among the 4 units.

• Methods A randomized retrospective review of the medical records of 50 patients was used to record care activities from 7 PM to 7 AM in 4 critical care units.

• Results Data consisted of interactions during 147 nights. The mean number of care interactions per night was 42.6 (SD 11.3). Interactions were most frequent at midnight and least frequent at 3 AM. Only 9 uninterrupted periods of 2 to 3 hours were available for sleep (6% of 147 nights studied). Frequency of interactions correlated significantly with patients’ acuity scores (r = 0.32, all Ps &lt; .05). A sleep-promoting intervention was documented for only 1 of the 147 nights, and 62% of routine daily baths were provided between 9 PM and 6 AM.

• Conclusions The high frequency of nocturnal care interactions left patients few uninterrupted periods for sleep. Interventions to expand the period around 3 AM when interactions are least common could increase opportunities for sleep.

Sleep management training for cancer patients with insomnia

Insomnia is a common phenomenon in cancer patients; nevertheless, there are only a few intervention results published covering this topic. We examined the effects of a multi-modal psychological sleep management programme combining relaxation techniques, sleep hygiene, cognitive techniques and advice in stimulus control technique on various sleep and quality-of-life variables. We compared two intervention groups up to 6 months after treatment, one with progressive muscle relaxation (n=80), the other with autogenic training (n=71). A control group (n=78) received only a standard rehabilitation programme. It was a heterogeneous sample of adult patients (mean age 58 years) predominantly with breast, kidney or prostate cancer staying for 3 or 4 weeks in an oncological rehabilitation clinic. In comparison to the control group, the analysis of variance for repeated measures (R-MANOVA) showed significant improvements over time, indicating that intervention group participants benefited with moderate- or large-scale effects on sleep latency (p<0.001), sleep duration (p<0.001), sleep efficiency (p<0.001), sleep quality (p<0.001), sleep medication (p<0.05) and daytime dysfunction (p<0.05). In quality-of-life subscales, there was mainly improvement over time. This may indicate a benefit of the rehabilitation treatment in general. No evidence was found for any differences between the two intervention groups. The results suggest that the use of a multi-modal psychological sleep intervention could enhance various sleep parameters and well being of patients. The efficacy on quality of life is still under review.

Sleep in the intensive care unit

Abnormalities of sleep are extremely common in critically ill patients, but the mechanisms are poorly understood. About half of total sleep time occurs during the daytime, and circadian rhythm is markedly diminished or lost. Judgments based on inspection consistently overestimate sleep time and do not detect sleep disruption. Accordingly, reliable polygraphic recordings are needed to measure sleep quantity and quality in critically ill patients. Critically ill patients exhibit more frequent arousals and awakenings than is normal, and decreases in rapid eye movement and slow wave sleep. The degree of sleep fragmentation is at least equivalent to that seen in patients with obstructive sleep apnea. About 20% of arousals and awakenings are related to noise, 10% are related to patient care activities, and the cause for the remainder is not known; severity of underlying disease is likely an important factor. Mechanical ventilation can cause sleep disruption, but the precise mechanism has not been defined. Sleep disruption can induce sympathetic activation and elevation of blood pressure, which may contribute to patient morbidity. In healthy subjects, sleep deprivation can decrease immune function and promote negative nitrogen balance. Measures to improve the quantity and quality of sleep in critically ill patients include careful attention to mode of mechanical ventilation, decreasing noise, and sedative agents (although the latter are double-edged swords).

Sleep Disturbance Symptoms in Patients With Heart Failure

Sleep disturbances have a major impact on physical functioning, emotional well-being, and quality of life, but are not well described in patients with heart failure (HF). Eighty-four HF patients completed a sleep survey and provided demographic and clinical data. Seventy percent of the patients were male with a mean age of 54 years and a mean left ventricular ejection fraction of 22%. Forty-seven patients (56%) reported trouble sleeping and one-third used sleeping medication. The most frequently reported problems were inability to sleep flat (51%), restless sleep (44%), trouble falling asleep (40%), and awakening early (39%). Using logistic regression, physiological variables were tested as predictors of sleep disturbance. Severity of HF, age, gender, etiology, obesity, smoking, and use of beta-blockers were not predictors of sleep disturbance. HF patients experience significant sleep disturbances, which are not predicted by severity of symptoms or clinical status. Problems with sleep are an important component of a clinical assessment in this vulnerable population.

Nocturnal catecholamines and immune function in insomniacs, depressed patients, and control subjects

Insomnia predicts cardiovascular and non-cardiovascular disease mortality. This study evaluated EEG sleep, nocturnal sympathetic activity, and daytime measures of immune function in subjects with primary insomnia (n = 17) and patients with current major depression (n = 14) as compared to controls (n = 31). Insomniacs showed disordered sleep continuity along with nocturnal increases of average levels of circulating norepinephrine and decreases of natural killer cell responses, whereas depressed patients showed declines of natural killer cell activity, but no differences of EEG sleep or nocturnal catecholamines as compared to controls. Impairments of sleep efficiency correlated with nocturnal elevations of norepinephrine in the insomniacs but not in the depressives or controls. These data indicate that insomnia is associated with nocturnal sympathetic arousal and declines of natural immunity, and further support the role of sleep in the regulation of sympathetic nervous and immune system functioning.

Sleep enhances the human antibody response to hepatitis A vaccination

OBJECTIVE

The common belief that sleep supports immune defense has received surprisingly little direct experimental support. The antibody response to vaccination provides a valid tool to assess the influence of sleep on adaptive immune functioning in humans, which is also clinically relevant.

METHODS

Two groups of healthy humans (N = 19) not previously infected with hepatitis A virus (HAV) were studied. On the night after primary vaccination with inactivated HAV, which took place at 0900 hours, one group had regular sleep. The other group stayed awake, and did not sleep before 2100 hours the following day. HAV antibody titers were measured repeatedly until 28 days after vaccination. Plasma hormone concentrations and white blood cell (WBC) subset counts were determined on the night and day after vaccination.

RESULTS

Subjects who had regular sleep after vaccination, displayed a nearly two-fold higher HAV antibody titer after 4 weeks than subjects staying awake on this night (p=.018). Compared with wakefulness, sleep after vaccination distinctly increased release of several immune-stimulating hormones including growth hormone, prolactin, and dopamine (p <.01). Concentrations of thyrotropin, norepinephrine, and epinephrine were lowered by sleep (p <.02), whereas sleep only marginally influenced WBC subset counts.

CONCLUSIONS

Data suggest that sleep compared with sleep deprivation on the night after vaccination improves the formation of antigen-specific immune defense as reflected by antibody production in humans. Sleep presumably acts by inducing a hormonal environment in secondary lymphoid tissues, enhancing lymphocyte proliferation and differentiation and finally antibody synthesis. Results underscore the importance of sleep for immunocompetence.

Chronic insomnia and immune functioning

OBJECTIVE

The goal of this study was to investigate whether clinical insomnia is associated with immune alterations by comparing immune functioning between patients with chronic insomnia and good sleepers.

METHODS

The good sleepers group was composed of 19 adults with a regular sleep schedule and no complaint of sleep disturbances. The insomnia group was composed of 17 adults meeting criteria for a chronic primary insomnia disorder. Peripheral blood samples were taken at the interview (time 1) and before the second night of polysomnographic assessment (time 2) for immune measures, including enumeration of blood cell counts (ie, white blood cells, monocytes, lymphocytes, and CD3+, CD4+, CD8+, and CD16+/CD56+ cells), natural killer cell activity, and cytokine production (ie, interleukin-1beta, interleukin-2, and interferon gamma).

RESULTS

Significant between-group differences were observed for CD3+, CD4+, and CD8+ cells, with higher levels found in good sleepers. In addition, a significant group-by-time interaction was found on monocyte counts. Although this was the only significant interaction effect observed, between-group differences were greater at time 2.

CONCLUSIONS

This study suggests that chronic insomnia is associated with some immune alterations. More research is needed to determine the clinical significance of these findings.

Brain-immune interactions in sleep

This chapter discusses various levels of interactions between the brain and the immune system in sleep. Sleep-wake behavior and the architecture of sleep are influenced by microbial products and cytokines. On the other hand, sleep processes, and perhaps also specific sleep states, appear to promote the production and/or release of certain cytokines. The effects of immune factors such as endotoxin and cytokines on sleep reveal species specificity and usually strong dependence on parameters such as substance concentration, time relative to administration or infection with microbial products, and phase relation to sleep and/or the light-dark cycle. For instance, endotoxin increased SWS and EEG SWA in humans only at very low concentrations, whereas higher concentrations increased sleep stage 2 only, but not SWS. In animals, increases in NREM sleep and SWA were more consistent over a wide range of endotoxin doses. Also, administration of pro-inflammatory cytokines such as IL-6 and IFN-alpha in humans acutely disturbed sleep while in rats such cytokines enhanced SWS and sleep. Overall, the findings in humans indicate that strong nonspecific immune responses are acutely linked to an arousing effect. Although subjects feel subjectively tired, their sleep flattens. However, some observations indicate a delayed enhancing effect on sleep which could be related to the induction of secondary, perhaps T-cell-related factors. This would also fit with results in animals in which the T-cell-derived cytokine IL-2 enhanced sleep while cytokines with immunosuppressive functions like IL-4 and L-10 suppressed sleep. The most straightforward similarity in the cascade of events inducing sleep in both animals and humans is the enhancing effect of GHRH on SWS, and possibly the involvement of the pro-inflammatory cytokine systems of IL-1 beta and TNF-alpha. The precise mechanisms through which administered cytokines influence the central nervous system sleep processes are still unclear, although extensive research has identified the involvement of various molecular intermediates, neuropeptides, and neurotransmitters (cp. Fig. 5, Section III.B). Cytokines are not only released and found in peripheral blood mononuclear cells, but also in peripheral nerves and the brain (e.g., Hansen and Krueger, 1997; März et al., 1998). Cytokines are thereby able to influence the central nervous system sleep processes through different routes. In addition, neuronal and glial sources have been reported for various cytokines as well as for their soluble receptors (e.g., Kubota et al., 2001a). Links between the immune and endocrine systems represent a further important route through which cytokines influence sleep and, vice versa, sleep-associated processes, including variations in neurotransmitter and neuronal activity may influence cytokine levels. The ability of sleep to enhance the release and/or production of certain cytokines was also discussed. Most consistent results were found for IL-2, which may indicate a sleep-associated increase in activity of the specific immune system. Furthermore, in humans the primary response to antigens following viral challenge is enhanced by sleep. In animals results are less consistent and have focused on the secondary response. The sleep-associated modulation in cytokine levels may be mediated by endocrine parameters. Patterns of endocrine activity during sleep are probably essential for the enhancement of IL-2 and T-cell diurnal functions seen in humans: Whereas prolactin and GH release stimulate Th1-derived cytokines such as IL-2, cortisol which is decreased during the beginning of nocturnal sleep inhibits Th1-derived cytokines. The immunological function of neurotrophins, in particular NGF and BDNF, has received great interest. Effects of sleep and sleep deprivation on this cytokine family are particularly relevant in view of the effects these endogenous neurotrophins can have not only on specific immune functions and the development of immunological memories, but also on synaptic reorganization and neuronal memory formation.

Sleep in host defense

Sleep remains an important enigma in neurobiology; it has a robust adaptive value yet its function remains elusive. Changes in sleep are hallmarks of the acute phase response to infectious challenge. The molecular regulation of these responses involves a cytokine cascade within brain, including interleukin-1 and tumor necrosis factor, and several other substances such as growth hormone releasing hormone, prolactin, nitric oxide and nuclear factor kappaB. These substances are also involved in the regulation of normal spontaneous sleep. Fatigue and sleep disturbances are common in cancer patients and in those receiving cytokine therapy. Regardless, the role of sleep in cancer is relatively uninvestigated.