Mediators of inflammation and their interaction with sleep: relevance for chronic fatigue syndrome and related conditions

Sickness behavior, its mechanisms and significance

Recent studies have begun to clarify the pathogenesis of sickness behavior. Cytokines released by macrophages, dendritic cells and mast cells act on the brain to trigger behavioral changes in infected animals. The major cytokines, interleukin-1, tumor necrosis factor alpha, and others, all act on the hypothalamus to provoke alterations in the normal homeostatic condition. These include elevated body temperature, increased sleep, and loss of appetite as well as major alterations in lipid and protein metabolism leading to significant weight loss. Some of these changes are clearly directed towards enhancing the normal immune responses. The benefits of others such as appetite loss are unclear. It is also important to recognize that other animals may recognize sickness behavior as a sign of weakness and mark the victim out for targeting by predators. As a result, some prey species may work very hard to mask their sickness, a response that serves to complicate veterinary diagnosis.

Therapeutic options for reducing sleep impairment in allergic rhinitis, rhinosinusitis, and nasal polyposis

BACKGROUND

Patients with inflammatory disorders of the upper airways, such as allergic rhinitis, rhinosinusitis, and nasal polyposis, often have significant sleep disturbances. Poor sleep can lead to fatigue, daytime somnolence, impaired daytime functioning as reflected in lower levels of productivity at work or school, and a reduced quality of life. Although the exact mechanisms by which these inflammatory nasal conditions disturb sleep is not fully understood, congestion appears to be a key factor and is generally the most common and bothersome symptom for patients with these conditions. Successful therapy should improve patients' sleep and well-being without introducing any negative effects on sleep. SCOPE OF LITERATURE SEARCH: Literature searches of Medline, Embase, and abstracts from medical/scientific conferences were conducted for the period of 1995 through mid-2006 for primary and review articles and conference presentations about sleep disturbance related to allergic rhinitis, rhinosinusitis, and nasal polyposis. These searches also sought to identify articles examining how treatments for those diseases improved sleep and, consequently, patients' quality of life. Surveys of the impact of congestion on patients' quality of life and their sleep also were consulted. Clinical studies were selected for discussion if they were randomized, double-blind, and placebo-controlled. Limitations of this review include the absence of any direct comparisons of the effectiveness of different drugs on improving sleep and shortcomings in the statistical methods of the patient surveys.

FINDINGS

Intranasal corticosteroids (INSs) are the most effective medication for reducing congestion in patients with inflammatory nasal conditions. There is a growing amount of evidence that a reduction in congestion with INSs is associated with improved sleep, reduced daytime sleepiness, and enhanced patient quality of life.

CONCLUSION

Relief of sleep impairment associated with inflammatory disorders of the nose and sinuses can be addressed with INS therapy.

The classification of fibromyalgia syndrome

As has been shown by a number of working groups, primary fibromyalgia syndrome does not represent a single clinical entity. It is possible to distinguish between a subgroup with high pain sensitivity and no associated psychiatric condition, a second and a third subgroup characterized by depression associated with fibromyalgia syndrome, and a fourth group with somatoform pain disorder of the fibromyalgia type. Mild inflammatory processes must be considered as the cause in the first group, while depression is combined with fibromyalgia in the second and the third group. In the fourth group, serious previous or still existing psychological problems or also insufficient coping with illness symptoms must be regarded as the reason for pain chronification. Group 1 benefits from a blocking of the 5-HT3 receptors by means of tropisetron, for example. This does not only affect pain chronification but also the inflammatory process itself. Group 2 and 3 needs antidepressant treatment, whereas the focus should be on psychotherapy in group 4. Groups 1, 2 and 3 will also profit from multimodal physical treatment programs, to a certain extent this applies to group 4 as well. So-called mixed types require a combination of therapeutic measures.

Allergic rhinitis and its effect on sleep, fatigue, and daytime somnolence

OBJECTIVE

To examine the adverse effects of sleep impairment on the quality of life of patients with the disorder and how these effects can be treated with therapies targeted at the underlying problems that influence sleep.

DATA SOURCES

Medline and Ovid search for sleep and rhinitis.

STUDY SELECTION

All literature on this topic were reviewed, and, if significant, were incorporated into this review.

RESULTS

Intranasal corticosteroids used as treatment for allergic rhinitis have been shown to reduce the nasal congestion characteristic of the disorder. Data on sleep-related end points from clinical trials on intranasal corticosteroids also reveal that the treatment's effectiveness in alleviating nasal congestion leads to better sleep, reduced daytime somnolence, and improved quality of life.

CONCLUSION

Further research, specifically using sleep measurements as primary end points, is needed to definitively show that intranasal corticosteroids reduce nasal congestion, thereby improving sleep and, consequently, quality of life in patients with allergic rhinitis. These future trials will serve to identify the most effective therapies that target the adverse effects of sleep impairment in this disorder.

The importance of rhinitis on sleep, daytime somnolence, productivity and fatigue

PURPOSE OF REVIEW

The goal of treatment of allergic rhinitis should include improvement of daytime and nighttime symptoms, sleep, and quality of life. Congestion from allergic rhinitis is associated with decreased learning and productivity at work and school and a reduced quality of life. The release of inflammatory mediators and activation of inflammatory cells results in nasal congestion, causing disrupted sleep and subsequent daytime somnolence.

RECENT FINDINGS

This review presents evidence that allergic rhinitis causes sleep disruption, and discusses the pathophysiology of this process. The medications used to treat allergic rhinitis and their ability to improve sleep in patients with allergic rhinitis are reviewed.

SUMMARY

Some allergic rhinitis medications can be sedating; therefore, it is important to treat allergic rhinitis with medications that improve symptoms while producing few adverse effects. Medications such as the second-generation antihistamines and anticholinergic drugs are well tolerated, but have little effect on congestion. Intranasal corticosteroids reduce congestion, improve sleep and sleep problems, and reduce daytime sleepiness, fatigue, and inflammation. Recently, montelukast, a leukotriene receptor antagonist, has been added to the therapies approved for allergic rhinitis. Montelukast significantly improves both daytime and nighttime symptoms.

Fatigue in liver disease: pathophysiology and clinical management

Fatigue is the most commonly encountered symptom in patients with liver disease, and it has a significant impact on their quality of life. However, although some progress has been made with regard to the understanding of the processes which may generate fatigue in general, the underlying cause(s) of liver disease-associated fatigue remain incompletely understood. The present review describes recent advances which have been made in our ability to measure fatigue in patients with liver disease in the clinical setting, as well as in our understanding of potential pathways which are likely important in the pathogenesis of fatigue associated with liver disease. Specifically, experimental findings suggest that fatigue associated with liver disease likely occurs as a result of changes in neurotransmission within the brain. In conclusion, a reasonable approach to help guide in the management of the fatigued patient with liver disease is presented.

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.

Psychosocial Stress and Cardiovascular Risk: What is the Role of Daily Experience?

We describe an ecological momentary assessment (EMA) protocol designed to measure daily life experiences along several psychosocial dimensions (Social Conflict, Task Demand, Decisional Control, Negative Affect, and Arousal) hypothesized to be relevant for cardiovascular disease risk. In a large community sample, these assessments have been administered in conjunction with ambulatory blood pressure (ABP) monitoring and measures of subclinical cardiovascular disease. Several results have emerged that support the promise of this approach. First of all, each of these dimensions of experience appears to be a trigger for cardiovascular activation, with movement on each scale being associated with significant within-person changes in heart rate and blood pressure in the natural environment. Second, there appear to be individual differences in physiological responsiveness to these dimensions of daily experience, with such differences being associated in some cases with laboratory-based assessments of cardiovascular reactivity, as might be expected. Third, EMA ratings are associated in several instances with (between-person) stable individual differences in ABP readings. And finally, we have found that some of the characteristics defined by our EMA ratings are related to measures of subclinical atherosclerosis. Such effects appear to be mediated, in part, by ABP. The advantages of using EMA measures for capturing the effects of psychosocial stressors are highlighted by comparing the predictive validity of these daily life assessments to traditional global self-reports. We conclude by describing future plans for use of this type of assessment protocol for helping us to characterize psychosocial characteristics relevant to cardiovascular disease risk. Personality and social processes during daily living may have an important impact not only on psychological functioning but also on physical health and disease. In this article we review our recent work involving the assessment of daily experience as a means of better understanding the role of psychosocial stress in cardiovascular disease risk. First, we outline the rationale for our interest in daily experience sampling for examining these processes, and we describe the methods we have adopted for this purpose. Next, we review findings from a recent study in which we have used these approaches to examine the role of psychosocial stress on ABP and atherosclerosis in a community-dwelling sample. We compare our approach to more traditional (global self-report and laboratory-observation) methods for examining these relationships in humans, and we discuss potential future directions for use of daily experience sampling in studies of health and behavior.

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.

Catecholamines mediate stress-induced increases in peripheral and central inflammatory cytokines

Proinflammatory cytokines act at receptors in the CNS to alter physiological and behavioral responses. Exposure to stressors increases both peripheral and central proinflammatory cytokines, yet the mechanism(s) of induction remain unknown. Experiments here examined the role of catecholamines in the in vivo induction of proinflammatory cytokines following tailshock stress. Rats were pretreated i.p. with 2.0 mg/kg prazosin (alpha1-adrenoceptor antagonist), 10.0 mg/kg propranolol (beta-adrenoceptor antagonist), or 5.0 mg/kg labetalol (alpha1- and beta-adrenoceptor antagonist) 30 min prior to tailshock exposure and plasma interleukin-1beta (IL-1beta) and IL-6, along with tissue interleukin-1beta from the hypothalamus, hippocampus, and pituitary were measured immediately following stressor termination. Prazosin attenuated stress-induced plasma IL-1beta and IL-6, but had no effect on tissue IL-1beta levels, while propranolol attenuated plasma IL-6 and blocked tissue IL-1beta elevation, and labetalol, which cannot cross the blood-brain barrier, attenuated plasma IL-1beta and IL-6, blocked pituitary IL-1beta, but had no effect on central tissue IL-1beta levels. Furthermore, administration of 50.0 mg/kg N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine hydrochloride, a neurotoxin that lesions neural projections from the locus coeruleus, prevented stress-induced elevation in hippocampal IL-1beta, a region highly innervated by the locus coeruleus, but had no effect on hypothalamic IL-1beta, a region that receives few locus coeruleus projections. Finally, i.p. injection of 5.0 mg/kg isoproterenol (beta-adrenoceptor agonist) was sufficient to induce circulating IL-1 and IL-6, and tissue IL-1beta. These data suggest catecholamines play an important role in the induction of stress-induced proinflammatory cytokines and that beta-adrenoceptors are critical for tissue IL-1beta induction, while both alpha- and beta-adrenoceptors contribute to the induction of plasma cytokines.

The rhythm of rest and excess

There is a stark contrast between our attitudes to sleep and those of the pre-industrial age. In Shakespeare's Julius Caesar we are told to "Enjoy the honey-heavy dew of slumber". There seems little chance of this today, as we crave more, work more and expect more, and, in the process, abandon sleep. Our occupation of the night is having unanticipated costs for both our physical and mental health, which, if continued, might condemn whole sectors of our society to a dismal future.

Incidence of diabetes in middle-aged men is related to sleep disturbances

OBJECTIVE

Sleep deprivation in healthy men has been experimentally found to result in disturbances in glucose metabolism and in sympathovagal imbalance. The aim of the present study was to investigate whether sleep disturbances and elevated resting heart rate are associated with increased risk of developing diabetes.

RESEARCH DESIGN AND METHODS

A group of 6,599 initially healthy, nondiabetic men aged 44.5 +/- 4.0 years took part in a prospective, population-based study in Malmö, Sweden. The incidence of diabetes during a mean follow-up of 14.8 +/- 2.4 years was examined in relation to self-reported difficulties in falling asleep and resting heart rate at baseline. Diabetes was assessed at follow-up in all subjects by questionnaire and in a subgroup of 1,551 men by blood glucose measurement.

RESULTS

A total of 615 (9.3%) subjects reported either difficulties in falling asleep or regular use of hypnotics (seen as markers of sleep disturbances), and 158 (2.4%) subjects reported both of these. Altogether, 281 (4.3%) of the men developed diabetes during the follow-up period. Logistic regression models showed difficulties in falling asleep or regular use of hypnotics (odds ratio [OR] 1.52 [95% CI 1.05-2.20]) and resting heart rate (OR per 10 bpm 1.13 [0.99-1.30]) to be associated with development of diabetes when full adjustments were made for baseline age, biological risk factors, lifestyle, family history of diabetes, and social class.

CONCLUSIONS

The results suggest that sleep disturbances and, possibly, elevated resting heart rate, in middle-aged men, are associated with an increased risk of diabetes.

Influences of allergic rhinitis on sleep

BACKGROUND

Allergic rhinitis is classically characterized by sneezing, pruritus, rhinorrhea, and nasal congestion. These symptoms can lead to impaired nocturnal sleep, and this impairment results in daytime fatigue and somnolence, reducing both learning and work efficiency and decreasing quality of life.

STUDY DESIGN

In addition, the mediators of AR, including histamine, leukotrienes, cytokines, and prostaglandins, may play a role in sleep regulation and, thus, may be directly involved in this impairment independent of nasal obstruction. Recumbency and/or diurnal variation augments turbinate swelling, causing nasal blockage during nocturnal sleep. Medications directed toward reversal of nasal congestion often concomitantly work through suppression of inflammatory mediators and constitute the primary therapy for sleep disturbance associated with allergic rhinitis. Some pharmaceutical interventions that reduce nasal congestion have adverse effects on sleep. Decongestants effectively reduce nasal congestion but frequently produce stimulatory effects and even insomnia. Antihistamines reduce sneezing and pruritus, but are less effective in relieving congestion. Earlier, "first-generation" antihistamines are associated with significant sedation. They also have anticholinergic properties, which can cause dry mouth and make mouth breathing even more uncomfortable in the allergic individual with nasal obstruction. The absence of anticholinergic properties in second-generation, largely nonsedating antihistamines limits their efficacy in rhinorrhea. Azelastine, a topical antihistamine, significantly reduces rhinorrhea and congestion and improves subjective sleep quality, but is also associated with increased sedation. Intranasal corticosteroids and oral leukotriene receptor antagonists effectively reduce rhinorrhea, congestion, and inflammatory mediators.

CONCLUSIONS

The efficacy of these medications at improving subjective sleep quality has been established through multiple randomized, double-blind, placebo-controlled clinical trials.

A review of sleep in selected immune and autoimmune disorders

Evidence for the reciprocal role of the immune system in sleep is growing. Sleep disturbances are believed to be both a cause and a consequence of various immune and autoimmune conditions.

Polymorphisms of the tumor necrosis factor receptors: no association with narcolepsy in German patients

Narcolepsy is a debilitating sleep disorder characterized by daytime sleepiness and cataplexy. The strong association of narcolepsy with the HLA system suggests an autoimmune cause. Tumor necrosis factor is a cytokine involved in both regulation of immune mechanisms and sleep. Several studies were undertaken to determine a contribution of tumor necrosis factor and its receptors to the pathogenesis of narcolepsy. A significant increase in the 196R allele, a functionally relevant polymorphism in the TNFR2 gene, has been found in Japanese patients, indicating altered transduction of tumor necrosis factor signals. Here we explore polymorphisms in both tumor necrosis factor receptor genes as risk factors in a German population sample. Neither the polymorphism in the TNFR1 nor that in the TNFR2 gene was associated with narcolepsy. Our findings contrast to those previously published and thus provide evidence for genetic heterogeneity between different narcolepsy populations.