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

Adenosine A2A receptors and sleep

Adenosine, a known endogenous somnogen, induces sleep via A1 and A2A receptors. In this chapter, we review the current knowledge regarding the role of the adenosine A2A receptor and its agonists, antagonists, and allosteric modulators in sleep-wake regulation. Although many adenosine A2A receptor agonists, antagonists, and allosteric modulators have been identified, only a few have been tested to see if they can promote sleep or wakefulness. In addition, the growing popularity of natural sleep aids has led to an investigation of natural compounds that may improve sleep by activating the adenosine A2A receptor. Finally, we discuss the potential therapeutic advantage of allosteric modulators of adenosine A2A receptors over classic agonists and antagonists for treating sleep and neurologic disorders.

Analysis of post COVID-19 condition and its overlap with myalgic encephalomyelitis/chronic fatigue syndrome

BACKGROUND

The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) disease (COVID-19) triggers the development of numerous pathologies and infection-linked complications and exacerbates existing pathologies in nearly all body systems. Aside from the primarily targeted respiratory organs, adverse SARS-CoV-2 effects were observed in nervous, cardiovascular, gastrointestinal/metabolic, immune, and other systems in COVID-19 survivors. Long-term effects of this viral infection have been recently observed and represent distressing sequelae recognised by the World Health Organisation (WHO) as a distinct clinical entity defined as post-COVID-19 condition. Considering the pandemic is still ongoing, more time is required to confirm post COVID-19 condition diagnosis in the COVID-19 infected cohorts, although many reported post COVID-19 symptoms overlap with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS).

AIMS OF REVIEW

In this study, COVID-19 clinical presentation and associated post-infection sequelae (post-COVID-19 condition) were reviewed and compared with ME/CFS symptomatology.

KEY SCIENTIFIC CONCEPTS OF REVIEW

The onset, progression, and symptom profile of post COVID-19 condition patients have considerable overlap with ME/CFS. Considering the large scope and range of pro-inflammatory effects of this virus, it is reasonable to expect development of post COVID-19 clinical complications in a proportion of the affected population. There are reports of a later debilitating syndrome onset three months post COVID-19 infection (often described as long-COVID-19), marked by the presence of fatigue, headache, cognitive dysfunction, post-exertional malaise, orthostatic intolerance, and dyspnoea. Acute inflammation, oxidative stress, and increased levels of interleukin-6 (IL-6) and tumor necrosis factor α (TNFα), have been reported in SARS-CoV-2 infected patients. Longitudinal monitoring of post COVID-19 patients is warranted to understand the long-term effects of SARS-CoV-2 infection and the pathomechanism of post COVID-19 condition.

[Cognitive disorders and sleep disturbances in long COVID]

Hintergrund

In den letzten 2 Jahren der COVID-19(„coronavirus disease 2019“)-Pandemie ist das Wissen um Langzeitfolgen der Erkrankung, das sog. „Long-COVID“, rapide gewachsen. Es bleiben jedoch noch viele Fragen offen, v. a. was die Ursachen überdauernder Beschwerden und ihre Prognose betrifft. Kognitive Störungen und Schlafstörungen gehören zu den häufig beklagten Beschwerden. Beide gehen mit starkem Leidensdruck und deutlicher Alltagsbeeinträchtigung einher.

Ziel der Arbeit

Wie ist die Datenlage zum Auftreten kognitiver Störungen und Schlafstörungen bei Long-COVID? Welches sind Einflussfaktoren und was ist bekannt zum Verlauf und zu möglichen zugrunde liegenden Mechanismen? Welche Therapieoptionen gibt es?

Material und Methode

In einem narrativen Review werden die wichtigsten Befunde zu kognitiven Störungen und Schlafstörungen bei Long-COVID dargestellt. Es wird ein Überblick gegeben über die Kohortenstudien mit Daten zu Prävalenz und Einflussfaktoren beider Symptomkomplexe. Es werden derzeitige Kenntnisse und Hypothesen zu pathophysiologischen Mechanismen dargestellt und ein Ausblick auf Behandlungsansätze gegeben.

Ergebnisse

Etwa ein Fünftel der Betroffenen berichtet mehr als 3 Monate nach einer SARS-CoV-2(„severe acute respiratory syndrome coronavirus 2“)-Infektion über kognitive Einschränkungen, etwa ein Drittel über Schlafstörungen, wobei es neben insomnischen auch zu hypersomnische Beschwerden kommt. Kognitive Störungen und Schlafstörungen treten bei Betroffenen aller Schweregrade auf. Es gibt Hinweise auf eine Besserung kognitiver Defizite im Verlauf, allerdings sind weitere Längsschnittstudien notwendig.

Diskussion

Neben der Prognose sind die zugrunde liegenden Krankheitsmechanismen noch unzureichend verstanden. Zudem besteht großer Forschungsbedarf zur Wirksamkeit und zu spezifischen Wirkfaktoren therapeutischer Interventionen.

Involvement of Probiotics and Postbiotics in the Immune System Modulation

Intestinal microbiota interacts with other systems, especially the immune system, which is responsible for protecting the body by recognizing “stranger” (pathogen associated molecular patterns-PAMPs) and “danger” (damage-associated molecular patterns-DAMPs) molecular motifs. In this manner, it plays an important role in the pathogenesis of various diseases and health. Despite the use of probiotics that modulate the intestinal microbiota in providing health benefits and in the treatment of diseases, there are some possible concerns about the possibility of developing adverse effects, especially in people with suppressed immune systems. Since probiotics provide health benefits with bioactive compounds, studies are carried out on the use of products containing non-living probiotic microorganisms (paraprobiotics) and/or their metabolites (postbiotics) instead of probiotic products. It is even reported that these microbial compounds have more immunomodulatory activities than living microorganisms via some possible mechanism and eliminates some disadvantages of probiotics. Considering the increasing use of functional foods in health and disease, further studies are needed with respect to the benefits and advantages of parabiotic and/or postbiotic use in the food and pharmaceutical industry as well as immune system modulation. Although probiotics have been extensive studied for a long time, it seems that postbiotics are promising tools for future research and applications according to the recent literature. This review aimed to evaluate the interaction of probiotics and postbiotics with the immune systems and also their advantages and disadvantages in the area of food-pharmaceutical industry and immune system modulation.

The Association Between Obstructive Sleep Apnea and Allergic Rhinitis: Current Literature Review

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Sleep-disordered breathing (SDB) is now a significant health problem in today's culture. It ranges from a spectrum of abnormal conditions during sleep from the primary snorer to mild, moderate, or severe obstructive sleep apnea (OSA). SDB also comprises other conditions, such as sleep-related hypoventilation, sleep-related hypoxemia, and central sleep apnea syndromes.

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One of the components of the pathophysiology of OSA that remain unclear is the association of allergic rhinitis (AR) in the evolution of OSA. Several studies relate the co-existence of OSA and AR in the common clinical practice, but its correlation was not clear. This review article aimed to review the pathophysiological relationship between OSA and AR in terms of the role of chemical mediators and the effect of AR treatment in support of OSA.

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The symptoms of AR further accelerate the clinical progression to OSA development. Inflammatory mediators such as histamine, cysteinyl leukotrienes, and interleukins are found at a high level in AR, which can aggravate AR symptoms such as nasal obstruction, rhinorrhea, and itchiness, which can then lead to sleep disruption in OSA patients. In addition, OSA patients also have increased chemical mediators such as tumor necrosis factor, interleukin 6, and 1, which would activate the T helper 2 phenotypes that can aggravate AR symptoms. This vicious cycle can potentiate each other and worsen the condition. Few studies have shown that treatment of AR can improve OSA, especially the use of intranasal steroid and leukotriene receptor antagonists.

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A detailed evaluation of rhinitis symptoms should be made for OSA patients so that they can benefit not only from the improvement of AR but also the good sleep quality.

House Dust Mite Related Allergic Rhinitis and REM Sleep Disturbances

PURPOSE

Sleep disturbances are common in patients with allergic rhinitis (AR). Perennial allergens like house dust mites (HDM) are difficult to avoid and have nocturnal impacts on the respiratory system and Quality of Life (QOL). The Rapid Eye Movement (REM) sleep stage is associated with memory, cognition, dreams, and overall restfulness, which can be impaired in AR patients with Sleep Disordered Breathing (SDB) even when normal all-night apnea-hypopnea (AHI) or respiratory disturbance (RDI) indices are noted on polysomnography (PSG). We hypothesized that AR HDM allergen positive patients would show REM-specific SDB reflected in their objectively elevated REM-RDI values.

MATERIALS AND METHODS

This retrospective analysis of 100 patients included 47 with HDM positive allergy testing. All patients underwent PSG testing calculating the RDI during REM. Multivariate logistic regression models evaluated relationships between allergic statuses and sleep parameters while controlling for potential confounders.

RESULTS

Compared with allergy negative patients, HDM allergen positive patients were significantly more likely (OR 4.29, 95%CI 1.26-14.62) to have a REM-RDI in the moderate/severe range (≥15 events/h).

CONCLUSIONS

Our study highlighted the significance of respiratory allergies to HDM in patients with SDB. We revealed a significant relationship between HDM allergen positivity and SDB characterized by elevated REM-RDI regardless of all-night AHI, RDI, or REM-AHI values. Clinical implications of knowing about disturbed REM and/or HDM allergenicity include better preparation, treatment, outcomes, and QOL for allergic, SDB, and upper airway surgery patients.

Diagnosis of Obstructive Sleep Apnea in Patients with Allergic and Non-Allergic Rhinitis

Background and objectives: Rhinitis could be considered a risk factor for obstructive sleep apnea (OSA). Studies were conducted to evaluate the relation between OSA and Allergic rhinitis (AR). Non-allergic rhinitis with eosinophilia syndrome (NARES) is a condition with a symptomatology apparently similar to AR. The aim of this study was to evaluate the different presence of OSA in patients suffering from NARES and AR. Materials and Methods: Sixty patients were enrolled and subdivided into NARES, AR and control groups. NARES and AR diagnosis were performed using ARIA (Allergic Rhinitis and its Impact on Asthma) protocol. All patients were screened for OSA with home sleep apnea testing (HSAT) exam analyzing AHI (Apnea Hypopnea Index) values. Results: Results showed that 60% of patients affected by NARES presented OSA. On the contrary, altered AHI was found only in 35% of patients affected by AR and in 10% of patients belonging to the control group. Conclusions: In conclusion, data showed that there was an increased risk of OSA in NARES patients respect to AR patients and healthy patients.

Sleep problems in advanced cancer patients and their caregivers: Who is disturbing whom?

Background The aims of the study were to understand sleep problems and their effects in advanced cancer patients and spousal and intimate partner caregivers and to examine the directionality of the link between patients' and caregivers' sleep problems. Methods Fifty-four advanced cancer patients and their spousal and intimate partners were administered a battery of questionnaires that included the Pittsburgh Sleep Quality Index and the Center for Epidemiological Studies at the patients' cancer diagnosis and at 2, 4, and 6 months after diagnosis. Results Patients' and caregivers' sleep duration was significantly related. Using cross-lagged panel analyses, caregivers' sleep quality significantly predicted patients' sleep quality and patients' sleep quality subsequently predicted caregivers' sleep quality. Patients' sleep latency significantly was found to significantly predict caregivers' sleep latency. Conclusion Patients diagnosed with cancer and their intimate partners have poor sleep quality and sleep patterns are related.

Impact of mast cells in fibromyalgia and low-grade chronic inflammation: Can IL-37 play a role?

Fibromyalgia (FM) is a disease characterized by chronic widespread pain, fatigue, aches, joint stiffness, depression, cognitive dysfunction, and nonrestorative sleep. In FM, neurotransmission and glial activation can occur with an increase in inflammatory cytokines and involvement of mast cells (MCs) in the skin. FM skin biopsies show an increase in the number of MCs, as well as the production of corticotropin releasing hormone and substance P (SP) by the neurons, which in turn activate MCs to release neurosensitizing proinflammatory substances, such as cytokines, secreted preformed mediators, and lipids, which can exacerbate low-grade inflammation. In fact, certain proinflammatory cytokines are higher in FM and mediate muscle pain, the mechanism of which is not yet clear. MC-derived tumor necrosis factor (TNF) induces nerve growth factor (NGF) and participates in nerve fiber elongation in skin hypersensitivity. IL-37 is an inhibitor of proinflammatory IL-1 family members, which are generated and released by MCs. The goal of this article is to demonstrate that inflammatory cytokines and MC products play a role in FM and that inflammation may be inhibited by IL-37. Here, we propose IL-37 as a cytokine that contributes to improve the pathogenesis of FM by blocking IL-1 family members.

Anti-Inflammatory Diets and Fatigue

Accumulating data indicates a link between a pro-inflammatory status and occurrence of chronic disease-related fatigue. The questions are whether the observed inflammatory profile can be (a) improved by anti-inflammatory diets, and (b) if this improvement can in turn be translated into a significant fatigue reduction. The aim of this narrative review was to investigate the effect of anti-inflammatory nutrients, foods, and diets on inflammatory markers and fatigue in various patient populations. Next to observational and epidemiological studies, a total of 21 human trials have been evaluated in this work. Current available research is indicative, rather than evident, regarding the effectiveness of individuals’ use of single nutrients with anti-inflammatory and fatigue-reducing effects. In contrast, clinical studies demonstrate that a balanced diet with whole grains high in fibers, polyphenol-rich vegetables, and omega-3 fatty acid-rich foods might be able to improve disease-related fatigue symptoms. Nonetheless, further research is needed to clarify conflicting results in the literature and substantiate the promising results from human trials on fatigue.

Fatigue, Sleep, and Autoimmune and Related Disorders

Profound and debilitating fatigue is the most common complaint reported among individuals with autoimmune disease, such as systemic lupus erythematosus, multiple sclerosis, type 1 diabetes, celiac disease, chronic fatigue syndrome, and rheumatoid arthritis. Fatigue is multi-faceted and broadly defined, which makes understanding the cause of its manifestations especially difficult in conditions with diverse pathology including autoimmune diseases. In general, fatigue is defined by debilitating periods of exhaustion that interfere with normal activities. The severity and duration of fatigue episodes vary, but fatigue can cause difficulty for even simple tasks like climbing stairs or crossing the room. The exact mechanisms of fatigue are not well-understood, perhaps due to its broad definition. Nevertheless, physiological processes known to play a role in fatigue include oxygen/nutrient supply, metabolism, mood, motivation, and sleepiness-all which are affected by inflammation. Additionally, an important contributing element to fatigue is the central nervous system-a region impacted either directly or indirectly in numerous autoimmune and related disorders. This review describes how inflammation and the central nervous system contribute to fatigue and suggests potential mechanisms involved in fatigue that are likely exhibited in autoimmune and related diseases.

Gating and the Need for Sleep: Dissociable Effects of Adenosine A1 and A2A Receptors

Roughly one-third of the human lifetime is spent in sleep, yet the reason for sleep remains unclear. Understanding the physiologic function of sleep is crucial toward establishing optimal health. Several proposed concepts address different aspects of sleep physiology, including humoral and circuit-based theories of sleep-wake regulation, the homeostatic two-process model of sleep regulation, the theory of sleep as a state of adaptive inactivity, and observations that arousal state and sleep homeostasis can be dissociated in pathologic disorders. Currently, there is no model that places the regulation of arousal and sleep homeostasis in a unified conceptual framework. Adenosine is well known as a somnogenic substance that affects normal sleep-wake patterns through several mechanisms in various brain locations via A₁ or A_2A receptors (A₁Rs or A_2ARs). Many cells and processes appear to play a role in modulating the extracellular concentration of adenosine at neuronal A₁R or A_2AR sites. Emerging evidence suggests that A₁Rs and A_2ARs have different roles in the regulation of sleep. In this review, we propose a model in which A_2ARs allow the brain to sleep, i.e., these receptors provide sleep gating, whereas A₁Rs modulate the function of sleep, i.e., these receptors are essential for the expression and resolution of sleep need. In this model, sleep is considered a brain state established in the absence of arousing inputs.

Precision Medicine: The Role of the MSIDS Model in Defining, Diagnosing, and Treating Chronic Lyme Disease/Post Treatment Lyme Disease Syndrome and Other Chronic Illness: Part 2

We present a precision medical perspective to assist in the definition, diagnosis, and management of Post Treatment Lyme Disease Syndrome (PTLDS)/chronic Lyme disease. PTLDS represents a small subset of patients treated for an erythema migrans (EM) rash with persistent or recurrent symptoms and functional decline. The larger population with chronic Lyme disease is less understood and well defined. Multiple Systemic Infectious Disease Syndrome (MSIDS) is a multifactorial model for treating chronic disease(s), which identifies up to 16 overlapping sources of inflammation and their downstream effects. A patient symptom survey and a retrospective chart review of 200 patients was therefore performed on those patients with chronic Lyme disease/PTLDS to identify those variables on the MSIDS model with the greatest potential effect on regaining health. Results indicate that dapsone combination therapy decreased the severity of eight major Lyme symptoms, and multiple sources of inflammation (other infections, immune dysfunction, autoimmunity, food allergies/sensitivities, leaky gut, mineral deficiencies, environmental toxins with detoxification problems, and sleep disorders) along with downstream effects of inflammation may all affect chronic symptomatology. In part two of our observational study and review paper, we postulate that the use of this model can represent an important and needed paradigm shift in the diagnosis and treatment of chronic disease.

Associations between sleep quality and inflammatory markers in patients with schizophrenia

Sleep disorder is a risk factor for several systemic inflammation-related diseases and there are extensive data showing that schizophrenia is associated with chronic low-grade systemic inflammation. This study investigated the associations between sleep quality and inflammatory markers in patients with schizophrenia, which has not been examined before. Sleep quality (total sleep time, sleep efficiency, sleep onset latency, total activity counts, wake after sleep onset, number of awakening, and average length of awakening) was measured using actigraphy in 199 schizophrenia inpatients. The state of inflammation was measured using blood concentration of white blood cells (WBC) and neutrophils, together with neutrophil-lymphocyte ratio (NLR), and platelet-lymphocyte ratio (PLR). The results showed that total sleep time was negatively associated with NLR and PLR, and sleep efficiency was negatively associated with neutrophil counts and NLR. Sleep onset latency, total activity counts, wake after sleep onset, and number of awakening were positively associated with WBC and neutrophil counts. The average length of awakening was positively associated with NLR and PLR. This is the first report to suggest that improving sleep quality may modulate the state of inflammation in patients with schizophrenia.

Cytokine mRNA expression in patients with multiple sclerosis and fatigue

Background: Fatigue is one of the most common disabling symptoms in patients with multiple sclerosis (MS), but the putative role of proinflammatory cytokines remains to be elucidated. Methods: Thirty-seven patients (27 women, 10 men) with relapsing-remitting (n =29) and secondary progressive (n =8) MS, aged 41.0 ± 10.2 years, were studied. Fatigue was assessed by Krupp’s Fatigue Severity Scale (FSS). C ytokine mRNA expression for interferon (IFN)-g, tumor necro sis factor (TNF)-a and interleukin (IL)-10 were measured by real time RT PC R. A utonomic function was evaluated by standard tests for parasympathetic and sympathetic function, as well as by serum levels of norepinephrine and epinephrine. Results: Median levels of TNF-a mRNA expression were significantly higher in MS patients with (FSS]-4.0 and]-5.0, n=26 and n=14, respectively) than in those without fatigue (FSSB-4.0, n =11). No differences were seen for IFN-g and IL-10 mRNA expression. C ytokine levels were not correlated to autonomic tests or to serum catecho lamine levels. Conclusions: These results suggest that TNF-a, as a principal proinflammatory mediator, is associated with MS-related fatigue. This is in support of a patho genic role of the MS-related inflammatory process in the development of fatigue.

Polyunsaturated fatty acids moderate the effect of poor sleep on depression risk

Although potentially modifiable risk factors for interferon-alpha (IFN-α)-associated depression (IFN-MDD) have been identified, it is not currently known how they interact to confer risk. In the present study we prospectively investigated interactions among poor sleep quality, high-stress, pre-existing depressive symptoms, and polyunsaturated fatty acid status. Non-depressed hepatitis C patients (n=104) were followed prospectively during IFN-α therapy. IFN-MDD occurs in 20-40% of patients and was diagnosed using the Structured Clinical Interview of DSM-IV (SCID-IV), with incidence examined using Cox regression. Baseline Pittsburgh Sleep Quality Inventory (PSQI), Perceived Stress Scale (PSS), Beck Depression Inventory (BDI), and a range of plasma long-chain fatty acid levels were measured (gas chromatography) - focusing on the ratio of arachidonic acid (AA) to docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) (AA/EPA+DHA). The AA/EPA+DHA ratio (Β=0.40 ± 0.16; p=0.006), PSQI (Β=0.12 ± 0.04; p=0.001), PSS (Β=0.07 ± 0.02; p<0.001), and baseline BDI (Β=0.05 ± 0.02; p<0.001) each individually predicted IFN-MDD incidence. In step-wise Cox regression eliminating non-significant variables, two interactions remained significantly predictive: PSQI*AA/EPA+DHA (p=0.008) and PSS*AA/EPA+DHA (p=0.01). Receiver Operator Curves (ROC) were used to examine the specificity and sensitivity of IFN-MDD prediction. When sleep was normal (PSQI<5), AA/EPA+DHA was strongly predictive of IFN-MDD (AUC=91 ± 6; p=0.002). For example, among those with AA/EPA+DHA less than the median (4.15), none with PSQI<5 developed depression. Conversely, neither PSS nor PSQI was statistically associated with depression risk in those with an elevated AA/EPA+DHA ratio. These data demonstrate that the AA/EPA+DHA ratio moderates the effect of poor sleep on risk for developing IFN-MDD and may have broader implications for predicting and preventing MDD associated with inflammation.

Napping and the risk of type 2 diabetes: a population-based prospective study

OBJECTIVE

Some studies indicate an association between napping and increased risk of type 2 diabetes. We studied this prospectively in a sample representative of general population.

METHODS

A questionnaire was administered to the Finnish Twin Cohort in 1990 (response rate 77%, age 33-60 years). The study population included 12,244 subjects who replied to the question "Do you sleep during the daytime (take naps)?" with five response alternatives ranging from "no need" to "every or almost every day." Information on incident cases of diabetes was obtained by linkage to nationwide registers. Logistic regression models were used to obtain odds ratios (ORs) (95% confidence intervals) for incident type 2 diabetes risk in 1991-2004 by napping category. Adjustments were made for 11 socio-demographic and lifestyle covariates. For subjects aged 33-45 years at baseline, a questionnaire in 2011 provided information on prevalent diabetes.

RESULTS

Thirty-four per cent had no need for napping, and 15% did so on ≥3 days weekly. There were 356 incident type 2 diabetes cases during the follow-up. Using the 'no need' category as the reference, the risk of type 2 diabetes was significantly increased only among those napping most frequently [OR 1.86 (1.29-2.67), age- and sex-adjusted]. After adjusting for other covariates, the results were essentially the same, but when adjusted for body mass index, the association decreased (to about 1.3) and was statistically non-significant. Analysis of 2011 self-reported type 2 diabetes was in line with the register data.

CONCLUSIONS

Frequent napping is associated with future risk of type 2 diabetes. This association is largely explained by obesity.

Risk factors for sleep impairment in adult patients with chronic rhinosinusitis

OBJECTIVE

Although sleep impairment is reported by patients with chronic rhinosinusitis, the associated factors have not been well studied. Therefore, we determined the associated risk factors for sleep impairment in patients with chronic rhinosinusitis (CRS).

METHODS

This study was a prospective cohort study. A total of 572 adult patients (171 women, 401 men; mean age, 49.0 years; range, 18-64 years) who completed a questionnaire, had a clinical examination, and underwent endoscopic sinus surgery were analyzed using stepwise multiple linear regression.

RESULTS

With regard to subjective symptoms, nasal obstruction (beta coef., 0.27; p<0.001), anterior nasal drainage (beta coef., 0.13; p=0.004), facial pain/pressure (beta coef., 0.09; p=0.048), headache (beta coef., 0.10; p=0.010), and cough (beta coef., 0.14; p<0.001) were predictors of an increased risk of sleep impairment of CRS (adjusted R(2), 0.240; p=0.048). In the matter of background parameters, total polyp score (polyp grading system) (beta coef., 0.16; p<0.001) and allergic rhinitis (beta coef., 0.09; p=0.034) were predictors of an increased risk of sleep impairment of CRS (adjusted R(2), 0.029; p=0.034).

CONCLUSION

These results suggest that sleep impairment in these patients is caused by the various mechanisms associated with nasal symptoms themselves, CRS and allergic rhinitis. However, the specific pathophysiology has not been clarified yet; further studies are expected to elucidate that of sleep impairment in patients with CRS.

Sleep quality and the treatment of intestinal microbiota imbalance in Chronic Fatigue Syndrome: A pilot study

Chronic Fatigue Syndrome (CFS) is a multisystem illness, which may be associated with imbalances in gut microbiota. This study builds on recent evidence that sleep may be influenced by gut microbiota, by assessing whether changes to microbiota in a clinical population known to have both poor sleep and high rates of colonization with gram-positive faecal Streptococcus, can improve sleep. Twenty-one CFS participants completed a 22- day open label trial. Faecal microbiota analysis was performed at baseline and at the end of the trial. Participants were administered erythromycin 400 mg b.d. for 6 days. Actigraphy and questionnaires were used to monitor sleep, symptoms and mood. Changes in patients who showed a clinically significant change in faecal Streptococcus after treatment (responders; defined as post-therapy distribution<6%) were compared to participants who did not respond to treatment. In the seven responders, there was a significant increase in actigraphic total sleep time (p=0.028) from baseline to follow up, compared with non-responders. Improved vigour scores were associated with a lower Streptococcus count (ρ=-0.90, p=0.037). For both the responders and the whole group, poorer mood was associated with higher Lactobacillus. Short term antibiotic treatment appears to be insufficient to effect sustainable changes in the gut ecosystem in most CFS participants. Some improvement in objective sleep parameters and mood were found in participants with reduced levels of gram-positive gut microbiota after antibiotic treatment, which is encouraging. Further study of possible links between gut microorganisms and sleep and mood disturbances is warranted.

How genetically engineered systems are helping to define, and in some cases redefine, the neurobiological basis of sleep and wake

The advent of genetically engineered systems, including transgenic animals and recombinant viral vectors, has facilitated a more detailed understanding of the molecular and cellular substrates regulating brain function. In this review we highlight some of the most recent molecular biology and genetic technologies in the experimental "systems neurosciences," many of which are rapidly becoming a methodological standard, and focus in particular on those tools and techniques that permit the reversible and cell-type specific manipulation of neurons in behaving animals. These newer techniques encompass a wide range of approaches including conditional deletion of genes based on Cre/loxP technology, gene silencing using RNA interference, cell-type specific mapping or ablation and reversible manipulation (silencing and activation) of neurons in vivo. Combining these approaches with viral vector delivery systems, in particular adeno-associated viruses (AAV), has extended, in some instances greatly, the utility of these tools. For example, the spatially- and/or temporally-restricted transduction of specific neuronal cell populations is now routinely achieved using the combination of Cre-driver mice and stereotaxic-based delivery of AAV expressing Cre-dependent cassettes. We predict that the experimental application of these tools, including creative combinatorial approaches and the development of even newer reagents, will prove necessary for a complete understanding of the neuronal circuits subserving most neurobiological functions, including the regulation of sleep and wake.

The roles of prostaglandin E2 and D2 in lipopolysaccharide-mediated changes in sleep

When living organisms become sick as a result of a bacterial infection, a suite of brain-mediated responses occur, including fever, anorexia and sleepiness. Systemic administration of lipopolysaccharide (LPS), a common constituent of bacterial cell walls, increases body temperature and non-rapid eye movement (NREM) sleep in animals and induces the production of pro-inflammatory prostaglandins (PGs). PGE2 is the principal mediator of fever, and both PGE2 and PGD2 regulate sleep-wake behavior. The extent to which PGE2 and PGD2 are involved in the effect of LPS on NREM sleep remains to be clarified. Therefore, we examined LPS-induced changes in body temperature and NREM sleep in mice with nervous system-specific knockouts (KO) for the PGE2 receptors type EP3 or EP4, in mice with total body KO of microsomal PGE synthase-1 or the PGD2 receptor type DP, and in mice treated with the cyclooxygenase (COX) inhibitor meloxicam. We observed that LPS-induced NREM sleep was slightly attenuated in mice lacking EP4 receptors in the nervous system, but was not affected in any of the other KO mice or in mice pretreated with the COX inhibitor. These results suggest that the effect of LPS on NREM sleep is partially dependent on PGs and is likely mediated mainly by other pro-inflammatory substances. In addition, our data show that the main effect of LPS on body temperature is hypothermia in the absence of nervous system EP3 receptors or in the presence of a COX inhibitor.

Assessment of sleep problems in children with familial Mediterranean fever

AIMS

This study aimed to investigate sleep patterns, sleep disturbances and possible factors that are associated with sleep disturbances among children with familial Mediterranean fever (FMF).

PATIENTS AND METHODS

Fifty-one patients with FMF and 84 age- and sex-matched healthy controls were enrolled in the study. The patients who had an attack during the last 2 weeks were not included. Demographic data, FMF symptoms, disease duration, dose of colchicine, disease severity score, number of attacks in the last year, MEFV mutation and serum C-reactive protein (CRP) levels were recorded for each patient. A Children's Sleep Habits Questionnaire was performed.

RESULTS

The total sleep scores of the patients with FMF were significantly higher than the control group. Total sleep durations were similar between FMF patients and controls. Children with FMF had significantly higher scores regarding sleep-onset delay, sleep anxiety, night wakings and sleep-disordered breathing when compared to healthy controls. There was a significant positive correlation between number of attacks in the last year and sleep onset delay, night wakings and sleep disordered-breathing. Disease severity score and CRP levels were not associated with any of the subscale scores. The patients with exertional leg pain had significantly higher total sleep scores than the ones without. Furthermore, patients with exertional leg pain had significantly higher subscale scores regarding sleep onset delay, parasomnias and sleep-disordered breathing.

CONCLUSION

This study showed for the first time that children with FMF had more sleep disturbances than their healthy peers. Higher numbers of attacks and exertional leg pain were associated with poor sleep quality. In conclusion, this study underlines the need to assess and manage sleep problems in children with FMF.

Allergy and sleep-disordered breathing

PURPOSE OF REVIEW

An inconsistent link between sleep-disordered breathing (SDB) and allergic rhinitis has been reported in the literature for decades. This review attempts to highlight some of the recent epidemiological studies purporting and refuting this connection, discuss possible mechanisms for this relationship and discuss how treatment of allergic rhinitis can help ameliorate SDB.

RECENT FINDINGS

Recently, a large systematic review that included 18 studies and 27 000 individuals of the association between allergic rhinitis and SDB in children was published supporting a correlation between SDB and allergic rhinitis.

SUMMARY

Although the evidence generally supports a connection between SDB and allergic rhinitis, this connection is not definitive and the mechanism linking these two diseases remains poorly understood. In addition to epidemiological studies, several small studies have demonstrated an improvement in SDB upon treatment of allergic rhinitis; however, large studies using objective measures to quantify SDB and allergic rhinitis are needed.

Chronic rhinosinusitis and sleep: a contemporary review

BACKGROUND

Patients with chronic rhinosinusitis (CRS) exhibit centrally mediated behavioral changes commonly referred to as "sickness behavior." Sleep alteration is a component of sickness behavior which is estimated to affect up to 70 million patients annually. Patients with CRS have poor sleep quality, and little is known about the underlying etiology and pathophysiology. This narrative review aims to further organize and present the current knowledge associating sleep and CRS.

METHODS

A literature search was conducted of the OVID MEDLINE database using key search words including: "chronic rhinosinusitis," "sleep," "sleep disorders," and "sleep dysfunction." Additional keywords "nasal obstruction," "nasal polyp," and "fatigue" were identified and used to further delineate relevant articles.

RESULTS

The articles that specifically addressed sleep and CRS were dissected and presented as follows: (1) chronic rhinosinusitis and sleep; (2) chronic rhinosinusitis and fatigue; (3) chronic rhinosinusitis, nasal obstruction, and sleep; and (4) pathophysiology of sleep in chronic rhinosinusitis (cytokines in both sleep and chronic rhinosinusitis and their association to the neuroimmune biology of chronic rhinosinusitis).

CONCLUSION

Patients with CRS have sleep dysfunction that is associated with their disease severity and overall quality of life. The etiology of sleep dysfunction in CRS is most likely multifactorial. Increasing evidence suggests sleep dysfunction in patients with CRS is partly due to the inflammatory disease process, and sleep physiology in patients with CRS may be actively regulated by the inflammatory component of the disease.

Sleep impairment and daytime sleepiness in patients with allergic rhinitis: the role of congestion and inflammation

OBJECTIVE

To investigate the association of rhinitis with stress, fatigue, decrease productivity, inflammation, and sleep disordered breathing.

DATA SOURCES

Medical literature obtained from OVID and PubMed searches in February 2013 using the search terms "sleep," "rhinitis," "allergic rhinitis," "somnolence," and "fatigue".

STUDY SELECTIONS

Studies were selected based on the US Preventive Services Task Force levels 1, 2, and 3.

RESULTS

Allergic rhinitis is a disease that severely affects patients' quality of life and is increasing in prevalence worldwide. Nasal congestion is reported as the most common and bothersome symptom; it is often associated with sleep-disordered breathing, a likely cause of sleep impairment in rhinitis-affected individuals. The end result is a reduced quality of life and productivity and an increase in daytime sleepiness, fatigue, and stress. Current treatment modalities include intranasal corticosteroids, which have been found to reduce nasal congestion. Clinical trials on intranasal corticosteroids have provided data on sleep-related end points, and these studies report that the improved nasal congestion is associated with improved quality of life with better sleep and reduced daytime fatigue. Alternate therapies, including montelukast, also decrease nasal congestion and positively influence sleep, but to a lesser extent.

CONCLUSION

This review examines nasal congestion and cytokine changes and the associated sleep impairment in allergic rhinitis patients and the effect on daytime performance. It elaborates the adverse effects of disturbed sleep on quality of life and how therapies directed at reducing nasal congestion can relieve such effects.

IL-1β, IL-6, IL-8, IL-10, IFN-γ, TNF-α and its relationship with lipid parameters in patients with major depression

There is some evidence that an immune response with an increased production of proinflammatory cytokines frequently accompanies major depression. The aim of this study was to determine the serum levels of interleukines (IL-1β, IL-6, IL-8, IL-10), tumor necrosis factor-alpha (TNF-α), interferon-gamma (IFN-γ) and immonuglobulines (IgG, IgA and IgM) levels and to examine the relationships between all above parameters and lipid parameters. The study group included 30 patients and 30 healthy volunteers. Although total cholesterol, HDL-cholesterol, and IgM levels were increased significantly (p < 0.05) in patients and compared to those of the controls, no statistically significant differences (p > 0.05) were observed with other parameters. IFN-γ were positively correlated with total cholesterol (r = 0.425; P = 0.019) and LDL-cholesterol (r = 0.391; P = 0.032) levels in patients. Other cytokines and immunoglobulins did not show any correlation with lipid parameters. It was concluded that although no differences was observed in cytokines and immunoglobulin levels in the present study, the dysregulation of the lipids and immune system including the cytokine network is associated with the etiology and pathophysiology of major depressive disorders.

Biomarkers: symptoms, survivorship, and quality of life

OBJECTIVES

To review the evidence on a number of biomarkers that show potential clinical utility in the prediction of and treatment responsiveness for the four most common symptoms associated with cancer and its treatment (ie, pain, fatigue, sleep disturbance, depression).

DATA SOURCES

Review and synthesis of review articles and data-based publications.

CONCLUSION

A growing body of evidence suggests that sensitive and specific biomarkers will be available to assist clinicians with the assessment and management of symptoms.

IMPLICATIONS FOR NURSING PRACTICE

Nurses will play a critical role in educating patients about their risk for specific symptoms based on an evaluation of specific biomarkers. Nurses will be involved in using biomarker data to titrate medications based on patient's responses to symptom management interventions.

Sleep in spousal Alzheimer caregivers: a longitudinal study with a focus on the effects of major patient transitions on sleep

STUDY OBJECTIVES

Findings on sleep disturbances in family dementia caregivers are conflicting. We studied the longitudinal effects of dementia caregiving and major transitions in the caregiving situation on caregivers' sleep and the effect of moderating variables.

DESIGN AND SETTING

Community-based longitudinal study with assessments about once a year for up to three years.

PARTICIPANTS

A sample of 109 elderly spousal Alzheimer caregivers and 48 non-caregiving age- and gender-matched controls.

MEASUREMENTS AND RESULTS

Random regression models with fixed and time-variant effects for covariates known to affect sleep were used to evaluate changes in the Pittsburgh Sleep Quality Index (PSQI) and in four actigraphy measures over time in relation to caregiving status and transitions (i.e., nursing home placement or death of the Alzheimer disease spouse). Multivariate-adjusted sleep characteristics did not significantly differ between caregivers and non-caregivers over time. Spousal death increased caregivers' nighttime wake after sleep onset (WASO) by 23 min (P = 0.002) and daytime total sleep time (TST) by 29 min (P = 0.003), while nighttime sleep percent decreased by 3.2% (P = 0.009) and nighttime TST did not change. Placement of the spouse had no significant effect on caregivers' sleep. Older age, male gender, role overload, depressive symptoms, and proinflammatory cytokines variously emerged as significant moderators of the relationships between caregiving and transitions with poor subjective and objective sleep.

CONCLUSIONS

Alzheimer caregivers and non-caregiving controls had similar trajectories of sleep. However, there may be subgroups of caregivers who are vulnerable to develop sleep disturbances, including those whose spouses have died.

The effect of allergic rhinitis on the degree of stress, fatigue and quality of life in OSA patients

Both allergic rhinitis (AR) and obstructive sleep apnea (OSA) are known to increase stress and fatigue, but the result of their coexistence has not been studied. The objective of this study was to evaluate the amount of stress and fatigue when AR is combined with OSA. One hundred and twelve patients diagnosed with OSA by polysomnography were enrolled. Among them, 37 patients were diagnosed with AR by a skin prick test and symptoms (OSA-AR group) and 75 patients were classified into the OSA group since they tested negative for allergies. We evaluated the Epworth sleepiness scale (ESS), stress score, fatigue score, ability to cope with stress, and rhinosinusitis quality of life questionnaire (RQLQ) with questionnaires and statistically compared the scores of both groups. There were no significant differences in BMI and sleep parameters such as LSAT, AHI, and RERA between the two groups. However, the OSA-AR group showed a significantly higher ESS score compared to the OSA group (13.7 ± 4.7 vs. 9.3 ± 4.8). Fatigue scores were also significantly higher in the OSA-AR group than in the OSA group (39.8 ± 11.0 vs. 30.6 ± 5.4). The OSA-AR group had a significantly higher stress score (60.4 ± 18.6 vs. 51.2 ± 10.4). The ability to cope with stress was higher in the OSA group, although this difference was not statistically significant. RQLQ scores were higher in the OSA-AR group (60.2 ± 16.7 compared to 25.1 ± 13.9). In conclusion, management of allergic rhinitis is very important in treating OSA patients in order to eliminate stress and fatigue and to minimize daytime sleepiness and quality of life.

Differential pharmacotherapy for subgroups of fibromyalgia patients with specific consideration of 5-HT3 receptor antagonists

INTRODUCTION

The fibromyalgia syndrome (FMS) has a prevalence of about 2% and is characterized by generalized musculoskeletal pain, reduced pain threshold and autonomic and functional symptoms. It is a multifactorial syndrome with four different subgroups exhibiting pathophysiological and psychiatric findings. No precise treatment strategy is currently available for the different FMS subgroups.

AREAS COVERED

This article reviews the evidence for treatment options for the different FMS subgroups.

EXPERT OPINION

Therapy for the first subgroup of primary FMS, with high levels of pain but no psychopathological alterations, is targeted at nociceptors expressing serotonin (5-hydroxytryptamine-3; 5-HT3) receptors with 5-HT3 receptor antagonists. The second and third subgroups are characterized by depressive syndromes with a major indication for antidepressants. The fourth subgroup with psychosomatic syndromes requires psychotherapeutic treatment. Secondary FMS is similar to the primary syndromes but is triggered by a variety of other diseases and frequently responds to 5-HT3 receptor antagonist treatment. Different classes of drug, such as pregabalin, must be tested for efficacy and tolerance. FMS treatment strategies should be tailored after the identification of individual FMS subgroups. Although several groups of drug have been studied extensively, 5-HT3 receptor antagonists are most effective in patients without psychopathological alterations.

Congestion and sleep impairment in allergic rhinitis

Allergic rhinitis is a prevalent disease in developed nations, and its prevalence has been increasing throughout the world. Nasal congestion is the most common and bothersome symptoms of rhinitis. Congestion is associated with sleep-disordered breathing and is thought to be a key cause of sleep impairment in individuals with rhinitis. The end result is a decrease in quality of life and productivity and an increase in daytime sleepiness. Treatment with intranasal corticosteroids has been shown to reduce nasal congestion. Data on sleep-related end points from clinical trials of intranasal corticosteroids indicate that this reduction is associated with improved sleep, reduced daytime fatigue, and improved quality of life. Other therapies, such as montelukast, also have a positive influence on congestion and sleep. This review examines nasal congestion and the associated sleep impairment of allergic rhinitis patients. It explores the adverse effects of disturbed sleep on quality of life and how these conditions can be reduced by therapies that decrease congestion.

The impact of shift work induced chronic circadian disruption on IL-6 and TNF-alpha immune responses

AIM

Sleep disturbances induce proinflammatory immune responses, which might increase cardiovascular disease risk. So far the effects of acute sleep deprivation and chronic sleep illnesses on the immune system have been investigated. The particular impact of shift work induced chronic circadian disruption on specific immune responses has not been addressed so far.

Methods

Pittsburgh-Sleep-Quality-Index (PSQI) questionnaire and blood sampling was performed by 225 shift workers and 137 daytime workers. As possible markers the proinflammatory cytokines IL-6 and TNF-α and lymphocyte cell count were investigated. A medical examination was performed and biometrical data including age, gender, height, weight, waist and hip circumference and smoking habits were collected by a structured interview.

Results

Shift workers had a significantly higher mean PSQI score than day workers (6.73 vs. 4.66; p < 0.001). Day workers and shift workers had similar serum levels of IL-6 (2.30 vs. 2.67 resp.; p = 0.276), TNF-α (5.58 vs. 5.68, resp.; p = 0.841) or lymphocytes count (33.68 vs. 32.99, resp.; p = 0.404). Furthermore there were no differences in cytokine levels (IL-6 p = 0.761; TNF-α p = 0.759) or lymphocyte count (p = 0.593) comparing the sleep quality within the cohorts. When this calculation of sleep quality was stratified by shift and day workers irrespective of their sleep quality day workers and shift workers had similar serum levels of IL-6, TNF-α or lymphocytes count. Multiple linear regression analysis showed a significant correlation of lymphocytes count and smoking habits.

Conclusion

Shift work induces chronic sleep debt. Our data reveals that chronic sleep debt might not always lead to an activation of the immune system, as we did not observe differences in lymphocyte count or level of IL-6 or TNF-α serum concentration between shift workers and day workers. Therefore chronic sleep restriction might be eased by a long-term compensating immune regulation which (in healthy) protects against an overstimulation of proinflammatory immune mechanisms and moderates metabolic changes, as they are known from short-term sleep deprivation or sleep related breathing disorders.

Tyrosine hydroxylase, interleukin-1beta and tumor necrosis factor-alpha are overexpressed in peripheral blood mononuclear cells from schizophrenia patients as determined by semi-quantitative analysis

The aim of this study is to profile the peripheral biomarkers (tyrosine hydroxylase, TH; interleukin-1beta, IL-1beta; and tumor necrosis factor-alpha, TNF-alpha) for schizophrenia and explore their relations with clinical symptoms. Thirty-nine patients with schizophrenia were evaluated using the Positive and Negative Syndrome Scale (PANSS), and 25 siblings and 30 normal healthy subjects were used as controls. The mRNA expression levels of TH, IL-1beta and TNF-alpha in peripheral blood mononuclear cells, as determined with semi-quantitative reverse transcription-polymerase chain reaction, were all significantly increased in both patients (3-fold) and siblings (2-fold) as compared with normal control. Both IL-1beta and TNF-alpha were significantly correlated with scores on the general psychopathology subscale of the PANSS. A significant positive correlation between IL-1beta and TH expression was found in both sibling and normal controls, but not in patients, while a positive correlation between IL-1beta and TNF-alpha was significant in all the groups. These results suggest that TH, IL-1beta and TNF-alpha are overexpressed in the peripheral blood mononuclear cells of schizophrenia patients, perhaps due to the hereditary factors. IL-1beta and TNF-alpha may influence the symptoms of schizophrenia in the cognition dysfunction and anxiety/depression domains of the PANSS.

Circadian disruption, Per3, and human cytokine secretion

Circadian disruption has been linked with inflammation, an established cancer risk factor. Per3 clock gene polymorphisms have also been associated with circadian disruption and with increased cancer risk. Patients completed a questionnaire and provided a blood sample prior to undergoing a colonoscopy (n = 70). Adjusted mean serum cytokine concentrations (IL-6, TNF-alpha, gamma-INF, IL-1ra, IL-1-beta, VEGF) were compared among patients with high and low scores for fatigue (Multidimensional Fatigue Inventory), depressive symptoms (Beck Depression Inventory II), or sleep disruption (Pittsburgh Sleep Quality Index), or among patients with different Per3 clock gene variants. Poor sleep was associated with elevated VEGF, and fatigue-related reduced activity was associated with elevated TNF-alpha concentrations. Participants with the 4/5 or 5/5 Per3 variable tandem repeat sequence had elevated IL-6 concentrations compared to those with the 4/4 genotype. Biological processes linking circadian disruption with cancer remain to be elucidated. Increased inflammatory cytokine secretion may play a role.

Status of immune mediators in fibromyalgia

Fibromyalgia (FM) is a form of nonarticular rheumatism characterized by long-term (> 3 months) and widespread musculoskeletal pain. However, the biophysiology of FM has remained elusive, and the treatment remains mainly empirical. There are numerous hypotheses about the pathophysiology of chronic widespread pain and FM; one includes a possible role of cytokines. Cytokines play a role in diverse clinical processes and phenomena such as fatigue, fever, sleep, pain, stress, and aching. Cytokines related to acute or repetitive tissue injuries may be responsible for long-term activation of spinal cord glia and dorsal horn neurons, thus resulting in central sensitization. Pain, stiffness, and depression in FM could be associated with some signs of inflammatory response system activation. Illumination of the pathophysiologic secrets of FM will result in more effective treatment regimens. We review the role of immune mediators in the pathophysiology of FM.

Mechanical or inflammatory low back pain. What are the potential signs and symptoms?

Non-specific low back pain (NSLBP) is commonly conceptualised and managed as being inflammatory and/or mechanical in nature. This study was designed to identify common symptoms or signs that may allow discrimination between inflammatory low back pain (ILBP) and mechanical low back pain (MLBP). Experienced health professionals from five professions were surveyed using a questionnaire listing 27 signs/symptoms. Of 129 surveyed, 105 responded (81%). Morning pain on waking demonstrated high levels of agreement as an indicator of ILBP. Pain when lifting demonstrated high levels of agreement as an indicator of MLBP. Constant pain, pain that wakes, and stiffness after resting were generally considered as moderate indicators of ILBP, while intermittent pain during the day, pain that develops later in the day, pain on standing for a while, with lifting, bending forward a little, on trunk flexion or extension, doing a sit up, when driving long distances, getting out of a chair, and pain on repetitive bending, running, coughing or sneezing were all generally considered as moderate indicators of MLBP. This study identified two groups of factors that were generally considered as indicators of ILBP or MLBP. However, none of these factors were thought to strongly discriminate between ILBP and MLBP.

Sleep impairment in allergic rhinitis, rhinosinusitis, and nasal polyposis

Sleep impairment is a significant problem for patients with inflammatory disorders of the upper respiratory tract, such as allergic rhinitis, rhinosinusitis, and nasal polyposis. Nasal congestion, one of the most common and bothersome symptoms of these conditions, is associated with sleep-disordered breathing and is thought to be a key cause of sleep impairment. This review examines sleep impairment associated with allergic rhinitis, rhinosinusitis, and nasal polyposis. It explores the adverse effects of disturbed sleep on patients' quality of life and how these inflammatory nasal conditions can be reduced by therapies that address the underlying problems affecting sleep. Treatment with intranasal corticosteroids has been shown to reduce nasal congestion in inflammatory disorders of the upper respiratory tract. Data on sleep-related end points from clinical trials of intranasal corticosteroids indicate that this reduction is associated with improved sleep, reduced daytime fatigue, and improved quality of life. Further research using measures of sleep as primary end points is warranted, based on the potential of these agents to improve sleep and quality of life in patients with allergic rhinitis, acute rhinosinusitis, and nasal polyposis. Such trials will help to identify the most effective therapies for sleep impairment in these 3 nasal 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.