[Immune outcomes of sleep disorders: the hypothalamic-pituitary-adrenal axis as a modulatory factor]

OBJECTIVE

To review the literature on the interaction between sleep and the immune system.

METHOD

A search on Web of Science and Pubmed database including the keywords sleep, sleep deprivation, stress, hypothalamic-pituitary-adrenal axis, immune system, and autoimmune diseases.

RESULTS

On Web of Science, 588 publications were retrieved; 61 references, more significant and closer to our objective, were used, including original articles and review papers.

CONCLUSION

Sleep deprivation and immune system exert a bidirectional influence on each other. Since sleep deprivation is considered a stressor, inasmuch as it induces elevation of cortisol or corticosterone levels in humans and rodents, respectively, and given the well-known immunosuppressive effect of glucocorticoids, we propose that increased activation of the hypothalamic-pituitary-adrenal axis is a major mediator of the immune alterations observed in patients with insomnia or in sleep deprived subjects.

Background patterns and sleep-wake cycles on amplitude-integrated electroencephalography in preterms younger than 30 weeks gestational age with peri-/intraventricular haemorrhage

AIM

The objective of this prospective study was to evaluate the influence of peri-/intraventricular haemorrhage (PIVH) grades I-IV on amplitude-integrated electroencephalographic (aEEG) activity in preterm infants<30 weeks gestational age (GA).

METHODS

The aEEG tracings of the first 2 weeks of life of 56 preterm infants younger than 30 weeks GA (2 groups: group A=23-26 weeks GA, group B=27-29 weeks GA) born during a 4-year period with PIVH grades I-IV were assessed for the relative duration of four background aEEG activity patterns (continuous pattern, discontinuous high-voltage pattern, discontinuous low-voltage pattern and nearly isoelectric pattern), the presence of seizure activity and the appearance of sleep-wake cycles and compared to the tracings of 75 neurologically healthy preterms without PIVH.

RESULTS

Analysis of aEEG background activity showed a decrease of continuous activity whereas discontinuous activity increased in both groups with larger haemorrhages (grades III and IV) and when compared to controls. Suspected seizure activity was more common with increasing degree of bleeding in group A (50% with PIVH I or II, 75% with PIVH III or IV) and when compared to controls and was the same with increasing degree of bleeding in group B (47% with PIVH I or II, 45% with PIVH III or IV). Sleep-wake cycles were less common with larger haemorrhages in both groups (group A: 41% with PIVH I or II, 25% with PIVH III or IV; group B: 52% with PIVH I or II, 9% with PIVH III or IV) and when compared to controls.

CONCLUSIONS

The aEEG characteristics of severe PIVH consist in a combination of a more discontinuous background pattern, a lack of sleep-wake cycles and a higher likelihood of seizure activity when compared to age-matched controls.

Does night-shift work induce apnea events in obstructive sleep apnea patients?

The aim of the present study was to determine the direct effect of night-work on the occurrence of obstructive apneas during sleep after a night shift in fast-rotating shift workers with sleep-related breathing disorders. Eight obstructive sleep apnea patients were examined with the use of a polysomnograph during sleep under two conditions: after day-shift work and after night-shift work. Both sleep studies were conducted within 2 to 3 weeks of each other. In four of the 8 subjects, during sleep after a night-shift, an increase in apnea/hypopnea index was found. Night work significantly increased several breathing variables: total duration of obstructive apneas during REM sleep, mean duration of obstructive apneas during arousal, and apnea index during arousal. We conclude that in a subpopulation of sleep apnea patients, acute sleep deprivation may worsen obstructive sleep apnea index.

Daily changes in cardiac and vascular blood pressure components during breath holding episodes in obstructive sleep apnea patients after day-shift and night-shift work

We evaluated daily variability in the cardiovascular response to arterial chemoreceptors activation during breath holding in shift workers who were obstructive sleep apnea patients. Ten patients and 10 weight and age-matched control subjects were enrolled in the study. The experimental sessions consisted of 10 episodes of breath holding on inspiration interspersed with 1 min free breathing periods, repeated every 6 h: at 0.00, 6.00, 12.00, 18.00 hours. The subjects were examined under two experimental protocols: after day-shift work and after night-shift work (36 h of sleep deprivation). Blood pressure (System Portapres), ECG, and arterial hemoglobin oxygen saturation were monitored continuously. Data analysis were based on Smietanowski procedures written in the 4-th generation script language of MATLAB environment. The two methods introduced by Smietanowski a enabled symbolic description of cardiovascular regulatory mechanisms as cardiac, vascular, or mixed type control (BBC), and allowed quantifying relative contributions of cardiac and vascular components in the blood pressure variability. During the part of the study conducted after day-shift work, repetitive apneas led to a significantly greater increase in blood pressure in the sleep apnea patients, as compared with the controls. BBC analysis demonstrated that in the patients the domination of vascular influences during breath holding periods reached 70+/-2.0% and was significantly greater in comparison with the control group: 56+/-2.8 (P<0.01). However, contribution of cardiac component in the blood pressure response to breath holding was greater in the control group: 32+/-2% as compared with the 18+/-2% in the group of patients (P<0.01). Under the conditions of sleep deprivation (night-work shift), greater blood pressure responses to breath holding were observed in all subjects, but they were larger in the group of sleep apnea patients. The cardiovascular responses to hypoxia during breath holding showed daily variability: greater responses at 12.00 and 18.00 declined at 0.00 and 6.00 h. BBC analysis indicated a greater domination of vascular component in the blood pressure response in patients: 71+/-2.8% vs. 58+/-2% in controls. The contribution of cardiac component predominated in the control group: 27+/-3% vs. 19+/-1% in patients.

Circadian rhythmicity and the pharmacologic management of insomnia

The circadian clock modulates timing of sleep and wakefulness. In certain situations, the circadian potentiation of wakefulness may interfere with desired sleep-scheduling, particularly in the elderly and shift workers. Known abnormalities of circadian regulation are defined by their impact on sleep-wake state expression. In delayed sleep phase syndrome, patients have trouble going to sleep and arising at reasonable hours and are alert in the evening and sleepy in the morning. Patients with advanced sleep phase syndrome are sleepy in the evening and awaken very early and alert in the morning. In shift-work sleep disorder, individuals attempt to wake and sleep out of phase with the circadian clock. As with jet lag, the clock is functioning normally, but the requirements on the clock are abnormal. Typical insomnia can also be associated with circadian rhythm alterations. Practice guidelines and clinical studies data are needed to lead appropriate therapy selection and effective management.

Unrecognized GERD symptoms are associated with excessive daytime sleepiness in patients undergoing sleep studies

Sleep disturbances are commonly reported by patients who suffer from gastroesophageal reflux disease (GERD) but it is uncertain if GERD plays a role in patients with sleep disorders of undetermined origin. The prevalence of GERD in patients with sleep disorders of unknown etiology is uncertain; the aim of this study was to determine this prevalence. Three hundred eighty-five consecutive patients reporting to an outpatient clinic for evaluation of sleep disorders were assessed for their sleepiness in relation to reflux symptom intensity. Reflux symptoms that met the survey criteria for a diagnosis of GERD were present in 45 of the 385 subjects (12.8%). These subjects did not have a diagnosis of GERD and were not being treated. Multiple regression analysis showed that excessive sleepiness was associated with intensity of GERD symptoms. Patients with GERD had significantly higher Epworth sleep scores than patients without GERD (12.8 vs. 10.6; p=0.007), indicating more daytime sleepiness. We conclude that unrecognized and untreated GERD are present in many patients presenting with sleep disorders. Patients with GERD had significantly greater sleepiness. Further studies of the impact of GERD treatment in this population are necessary.

[Depression and sleep]

More than 80% of depressive patients have complaints about sleepiness and insomnia. Physiological researches demonstrate changes in sleep architecture and circadian rhythm in depressive patients. These researches suggest the enhancement of arousal function in daytime and nighttime and circadian changes in cholinergic and catecholaminergic neural system. Pharmacological therapy might be selected in considering the mechanism of these neural changes. The research about sleep deprivation therapy may give us the new advances in the further treatment.

Chrononutrition applied to formula milks to consolidate infants' sleep/wake cycle

Some 30% of pre-weaning infants present problems of sleep during the night, especially those who are bottle-fed. The solution is for them to be breast-fed for as long as possible, or, if this is not possible, for the formula milk to reproduce breast-milk's natural circadian variations in the concentrations of tryptophan and those nucleotides which have a beneficial effect in consolidating the circadian sleep-wake cycle.

OBJECTIVE

To study in pre-weaning infants the effect on nocturnal sleep of the administration of formula milk dissociated into its day/night components.

MATERIALS AND METHODS

A prospective study was carried out on 30 pre-weaning infants of 4-20 weeks in age who preferentially showed sleep problems. The day dissociated formula, administered from 06:00-18:00, had lower levels of tryptophan and carbohydrates, and higher levels of proteins together with cytosine-5P, guanosine-5P, and inosine-5P. The night dissociated formula, administered from 18:00-06:00, had lower levels of proteins and medium-chain triglycerides, higher levels of tryptophan and carbohydrates, together with adenosine-5P and uridine-5P. In a random, double-blind, design, three one-week diets were administered: Diet A (Control): normal initiation milk; Diet B: 06:00-18:00 normal initiation milk, 18:00-06:00 dissociated night formula; and Diet C: day/night formulas with the schedule given above. The sleep patterns were analyzed by means of actimeters (Actiwatch). Statistical analysis consisted of an ANOVA with a Scheffe F-test, taking a value of p<0.05 to be statistically significant.

RESULTS

The children receiving the week of Diet C (with the day/night formulas in synchrony with the environment) showed increased hours of actual sleep (7.68 +/- 0.54 h vs. 6.77 +/- 0.12 h for the Diet A control) and improved sleep latency (0.44 +/- 0.04 h vs. 0.60 +/- 0.08 h for the Diet A control). The same children receiving the Diet B in another different week showed an improvement in sleep efficiency (76.43 +/- 3.4% vs. the Diet A control 69.86 +/- 0.94%) and sleep latency (0.45 +/- 0.04 h vs. the Diet A control 0.60 +/- 0.08h) The parents also reported, in response to follow-up questions, an improvement in the sleep of their infants during the Diet C week.

CONCLUSION

Day/night infant formula milks designed according to the principles of chrononutrition help to consolidate the sleep/wake rhythm in bottle-fed infants.

Pediatric Insomnia: A Behavioral Approach

This article discusses the two common causes of insomnia in children, behavioral insomnia of childhood and delayed sleep phase syndrome. Both of these conditions are primarily treated with behavioral interventions that can be initiated and managed by the primary care provider. A review of these behavioral interventions is provided.

A systematic review of the neurobehavioural and physiological effects of shiftwork systems

Shiftwork is a common experience for many workers. There are a wide range of shift systems in use, with a number of general approaches and myriad variations of each one. Many aspects of shift systems have been studied, but attempts to reach definitive conclusions about appropriate designs have been hampered by a number of methodological issues. The aim of this systematic review was to provide evidence-based recommendations on the effect of various shift systems on neurobehavioural and physiological functioning and to identify areas which are lacking in appropriate evidence. Two main aspects of shift design were able to be considered-the direction of shift rotation and extended shift length (mainly 12-h shifts). Other areas for which there was at least one relevant paper of adequate methodology were the use of naps during night shifts, the starting time of shifts, and several other specific shift issues. Overall, the review found there is insufficient evidence to support definitive conclusions regarding any of these factors. However, the analysis provides support for the use of forward rotating shift systems in preference to backward rotating shift systems, at last as far as 8-h shifts are concerned. There are many unanswered questions in shift design. For these questions to be answered, it is important that the methodological shortcomings present in most of the studies published to date be overcome.

Chronobiology of sleep in humans

Periodic circadian (24-h) cycles play an important role in daily hormonal and behavioural rhythms. Usually our sleep/wake cycle, temperature and melatonin rhythms are internally synchronized with a stable phase relationship. When there is a desynchrony between the sleep/wake cycle and circadian rhythm, sleep disorders such as advanced and delayed sleep phase syndrome can arise as well as transient chronobiologic disturbances, for example from jet lag and shift work. Appropriately timed bright light is effective in re-timing the circadian rhythm and sleep pattern to a more desired time, ameliorating these disturbances. Other less potent retiming effects may also be obtained from the judicious use of melatonin and exercise.

Constant light housing during nursing causes human DSPS (delayed sleep phase syndrome) behaviour in Clock-mutant mice

Delayed sleep phase syndrome (DSPS) is very often seen among patients with sleep-wake rhythm disorders. Humans with the 3111C allele of the human Clock gene tend to demonstrate a higher evening preference on the morningness-eveningness (ME) preference test. DSPS is thought to be an extreme form of this evening preference. Clock-mutant mice have been proposed as an animal model of evening preference. In this study, we looked at whether constant light (LL) housing of Clock-mutant mice during lactation would result in evening preference and/or DSPS. Housed under light-dark (LD) or constant dark (DD) conditions during the lactation period, both wild-type and Clock-mutant mice did not show a phase-delay in the locomotor activity measured under light-dark conditions, whereas constant light housing during lactation significantly caused a delayed onset. The magnitude of the delay during the light-dark cycle was positively associated with free-running period measured during constant darkness. Among wild, heterozygote, and homozygote pups born from heterozygous dams, only homozygote pups showed a delayed onset. Constant light-housed Clock-mutant mice exhibited a lower number and delayed peak of phospho-MAPK-immunoreactive cells in core regions of the suprachiasmatic nucleus (SCN) compared to light-dark housed wild-type or Clock-mutant mice. Activity onset returned to normal with daily melatonin injection at the lights-off time for 5 days. The present results demonstrate that Clock-mutant mice exposed to constant light during lactation can function as an animal model of DSPS and can be used to gain an understanding of the ethological aspects of DSPS as well as to find medication for its treatment.

Elevated plasma homocysteine in older shift-workers: a potential risk factor for cardiovascular morbidity

There is evidence supporting an association between shift work and cardiovascular morbidity, but the underlying mechanisms are unknown. The present paper investigated the levels of cardiovascular biochemical risk factors in shift-workers both with (n=26) and without (n=103) sleep complaints, and in day-workers (n=173) working in the same plant. Blood samples were taken in the morning after an overnight fast and analyzed for homocysteine, C-reactive protein, and lipid profile. Biochemical data were compared among groups after stratifying workers by age (i.e., <40 and > or = 40 yrs). Shift-workers who complained about sleep disturbances and who were > or = 40 years of age had significantly higher levels of homocysteine than did their younger counterparts - shift-workers who did not complain of sleep disturbances and day-workers. There were no other between-group differences in any of the biochemical variables. The results of this investigation demonstrate an association between sleep disturbances in older shift-workers and mild hyperhomocysteinemia. The elevated homocysteine levels may play a role in the increased rates of cardiovascular morbidity in shift-workers, and they may have practical implications regarding the nutrition of shift-workers.

Role of sleep-wake cycle on blood pressure circadian rhythms and hypertension

Stages of different depth characterize the temporal organization of sleep. Each stage exerts an effect on blood pressure (BP) regulation and contributes to its 24-h variation. The main determinant of the circadian influences of sleep and wakefulness on BP is the daytime sympathetic and nighttime parasympathetic prevalence, but many other physiologic mechanisms known either to induce sleep or determine arousal may play an important role in the mediation of sleep influences on BP. Alteration of one or more of such mechanisms may be reflected in altered circadian BP rhythms. Sleep- and arousal-related mechanisms and phenomena that affect circadian BP rhythms include neurohumoral sleep factors (arginine vasopressin, vasoactive intestinal peptide, somatotropin, insulin, steroid hormones and metabolites, and serotonin among others) and waking factors (corticotropin-releasing factor, adrenocorticotropin, thyrotropin-releasing hormone, endogenous opioids, and prostaglandin (E(2))). Pathologic respiratory variations (sleep-disordered breathing) and insomnia are major causes of the sleep-related alteration of the circadian BP profile, including loss of the expected normal decline in BP by 10-20% from the daytime level. A great number of medical disorders can cause insomnia, but objective sleep studies have been performed only in a minority of them. Overall, the sleep-related pathophysiological mechanisms actually involved in causing altered circadian BP rhythms in different normotensive and hypertensive conditions are not completely understood. In any case, changes in the circadian BP rhythm are known to be strongly related to one's risk of cardiovascular morbidity and mortality, thus representing strong prognostic indicators worthy of further investigation.

Potential role for peripheral circadian clock dyssynchrony in the pathogenesis of cardiovascular dysfunction

Circadian clocks are intracellular molecular mechanisms designed to allow the cell, organ, and organism to prepare for an anticipated stimulus prior to its onset. In order for circadian clocks to maintain their selective advantage, they must be entrained to the environment. Light, sound, temperature, physical activity (including sleep/wake transitions), and food intake are among the strongest environmental factors influencing mammalian circadian clocks. Normal circadian rhythmicities in these environmental factors have become severely disrupted in our modern day society, concomitant with increased incidence of type 2 diabetes mellitus, obesity, and cardiovascular disease. Here, we review our current knowledge regarding the roles of peripheral circadian clocks, concentrating on those found within tissues directly involved in metabolic homeostasis and cardiovascular function. We propose that both inter- and intra-organ dyssynchronization, through alteration/impairment of peripheral circadian clocks, accelerates the development of cardiovascular disease risk factors associated with cardiometabolic syndrome.

A circadian sleep disorder reveals a complex clock

Circadian rhythms are established by transcription of clock genes and autoregulatory transcriptional feedback loops. In this issue, Xu et al. (2007) characterize mice expressing a human Per2 mutation identified in patients with familial advanced sleep phase syndrome. Their results reveal that PER2 phosphorylation, by CK1delta and other kinases, is surprisingly complex and has opposite effects on PER2 levels and period length.

Circadian rhythm sleep disorders

Humans exhibit endogenous circadian rhythms that are regulated by the master circadian clock of the body, the suprachiasmatic nucleus. These endogenous circadian rhythms are aligned to the outside world by social and environmental cues. Circadian rhythm sleep disorders (CRSD) occur when there is an alteration of the internal timing mechanism or a misalignment between sleep and the 24-h social and physical environment. CRSD are often underrecognized yet should be considered in the differential of patients presenting with symptoms of insomnia and/or hypersomnia. Because behavioral and environmental factors often are involved in the development and maintenance of these conditions, a multimodal treatment approach of behavioral and/or pharmacologic approaches is usually required to synchronize a patient's circadian rhythm to the 24-h environment, consolidate sleep, and improve alertness. Rapid advances in our understanding of the physiologic, cellular, and molecular basis of circadian rhythm and sleep regulation will likely lead to improved diagnostic tools and treatments for CRSD.

Biological Rhythms Workshop IC: sleep and rhythms

Rhythms of sleep and wakefulness (typically measured as rest/activity rhythms) are among the most prominent of biological rhythms and therefore were among the first to be recorded in early chronobiological studies. These rhythms can provide useful information about the central biological clock, although an appreciation of the problems associated with using rest/activity to infer central clock function is important in the design and interpretation of chronobiological experiments in both animals and humans. Here, we review the anatomical and neurophysiologic bases of sleep regulation in mammals as well as similarities and differences between the sleep of humans and that of other organisms. We outline how human sleep is measured, the role of the circadian system in models of human sleep regulation, and human circadian rhythm sleep disorders. Although the function of sleep is still not completely understood, sleep has a critical role for human health, and we have attempted to outline the role that the circadian timing system has in regulating human sleep and in contributing to sleep disorders.

Submarine watch schedules: underway evaluation of rotating (contemporary) and compressed (alternative) schedules

INTRODUCTION

With a desire to increase health, cognitive performance effectiveness, and quality of life for submarine watch-standers underway, we performed an evaluation comparing an alternative, compressed-work (ALT) schedule, designed to enhance circadian rhythm entrainment and sleep hygiene, to the contemporary submarine (SUB) forward rotating schedule, aboard the ballistic-missile submarine, USS Henry M. Jackson (SSBN-730 Gold).

METHODS

We assessed a compressed close-6 watch-schedule ("ALT") relative to the existing backward rotating 6-hr on, 12-hr off 18-hr watch schedule ("SUB") employed underway aboard submarines. We monitored 40 subjects' sleep, and temperature and salivary cortisol from 10 of the 40 for approximately two weeks on each respective schedule underway.

RESULTS

The cortisol cosinor mesors (midline estimating statistic of rhythm), and amplitudes did not differ significantly between conditions. The temperature cosinor mesors, and the cosinor amplitude were not significantly different, while the cosine curve fit accounted for significantly more variance in the ALT condition than in the SUB condition. The SUB schedule garnered significantly more sleep (7.1 +/- 0.2 hours) than that of the ALTMID schedule (6.3 +/- 0.3 hours). Surveys revealed that 52% of respondents preferred the SUB schedule, 15% preferred the ALT, and 33% were either indifferent or submitted uninterpretable surveys.

CONCLUSIONS

The ALT schedule was not superior to the existing SUB schedule by physiological or subjective measures and was incompatible to accommodating operational constraints.

Insomnia in circadian dysrhythmias

Insomnia is one of the most common symptoms of disordered sleep. The etiology of insomnia is multifaceted, and the correct diagnosis will lead to effective treatment. One cause of insomnia that is often overlooked results from a conflict in schedules and desynchronization between the intrinsic sleep-wake propensity of a person and his or her 24-hour physical and social environment. Sleep propensity is governed by the complex interactions of an oscillating circadian rhythm and a monotonous homeostatic process. This review describes the basic physiology of the circadian system and, based on these understandings, discusses the various clinical manifestations of and treatments for circadian rhythm sleep disorders.

Melatonin in mood disorders

The cyclic nature of depressive illness, the diurnal variations in its symptomatology and the existence of disturbed sleep-wake and core body temperature rhythms, all suggest that dysfunction of the circadian time keeping system may underlie the pathophysiology of depression. As a rhythm-regulating factor, the study of melatonin in various depressive illnesses has gained attention. Melatonin can be both a 'state marker' and a 'trait marker' of mood disorders. Measurement of melatonin either in saliva or plasma, or of its main metabolite 6-sulfatoxymelatonin in urine, have documented significant alterations in melatonin secretion in depressive patients during the acute phase of illness. Not only the levels but also the timing of melatonin secretion is altered in bipolar affective disorder and in patients with seasonal affective disorder (SAD). A phase delay of melatonin secretion takes place in SAD, as well as changes in the onset, duration and offset of melatonin secretion. Bright light treatment, that suppresses melatonin production, is effective in treating bipolar affective disorder and SAD, winter type. This review discusses the role of melatonin in the pathophysiology of bipolar disorder and SAD.

Sleep and the metabolic syndrome

The metabolic syndrome represents a clustering of several interrelated risk factors of metabolic origin that are thought to increase cardiovascular risk. It is still uncertain whether this clustering results from multiple underlying risk factors or whether it has a single cause. One metabolic abnormality that may underlie several clinical characteristics of the metabolic syndrome is insulin resistance. This review discusses the evidence that sleep disturbances (obstructive sleep apnoea, sleep deprivation and shift work) may independently lead to the development of both insulin resistance and individual clinical components of the metabolic syndrome. The converse may also be true, in that metabolic abnormalities associated with the metabolic syndrome and insulin resistance may potentially exacerbate sleep disorders. The notion that sleep disturbances exert detrimental metabolic effects may help explain the increasing prevalence of the metabolic syndrome and insulin resistance in the general population and may have important implications for population-based approaches to combat the increasing epidemic of metabolic and cardiovascular disease.