Autonomic response to periodic leg movements during sleep in narcolepsy-cataplexy

Progress of autonomic disturbances in narcolepsy type 1

Narcolepsy type 1 is a kind of sleep disorder characterized by a specific loss of hypocretin neurons in the lateral hypothalamus and reduced levels of hypocretin-1 in the cerebrospinal fluid. Hypocretin deficiency is associated with autonomic disorders. This article summarizes the autonomic disorders and possible mechanisms associated with narcolepsy type 1. Patients with narcolepsy type 1 often have various systemic autonomic symptoms, including non-dipping blood pressure, reduced heart rate variability, dynamic cerebral autoregulation impairment, reduced gastric motility and emptying, sleep-related erectile dysfunction, skin temperature abnormalities, and blunted pupillary light reflex. Similar findings should strengthen the recognition and intervention of these disturbances in clinical practice. In addition to hypocretin deficiency, current evidence also indicates that pharmacological therapy (including psychostimulants and anti-cataplectic drugs) and comorbidities may contribute to the alterations of autonomic system observed in narcolepsy type 1.

Heart rate changes associated with the different types of leg movements during sleep in children, adolescents and adults with restless legs syndrome

The objective of this study was to describe in detail the heart rate changes accompanying short-interval leg movements during sleep, periodic leg movements during sleep, and isolated leg movements during sleep in children and adolescents with restless legs syndrome, and to compare them with the same findings in adults with restless legs syndrome. We analysed time series of R-R intervals synchronized to the onset of short-interval leg movements during sleep, periodic leg movements during sleep or isolated leg movements during sleep that entailed an arousal during non-rapid-eye-movement sleep. We assessed cardiac activation based on the heart rate changes with respect to baseline during non-rapid-eye-movement sleep without leg movements. All types of leg movements recorded during sleep were accompanied by important heart rate changes also in children, with an overall impact similar to that observed in adults. In all age groups, heart rate changes accompanying short-interval leg movements during sleep were constituted by a tachycardia, without a subsequent relative bradycardia, that was instead evident for periodic leg movements during sleep and isolated leg movements during sleep. Moreover, an age-related decline of the relative bradycardia following the heart rate increase, in association with periodic leg movements during sleep and isolated leg movements during sleep, was observed. Our findings show that important heart rate changes accompany all leg movements during sleep at all ages in restless legs syndrome, with significant age-related differences. This information represents an important contribution to the ongoing scientific debate on the possibility and opportunity to treat periodic leg movements during sleep.

Cardiovascular disorders in narcolepsy: Review of associations and determinants

Narcolepsy type 1 (NT1) is a lifelong disorder of sleep-wake dysregulation defined by clinical symptoms, neurophysiological findings, and low hypocretin levels. Besides a role in sleep, hypocretins are also involved in regulation of heart rate and blood pressure. This literature review examines data on the autonomic effects of hypocretin deficiency and evidence about how narcolepsy is associated with multiple cardiovascular risk factors and comorbidities, including cardiovascular disease. An important impact in NT1 is lack of nocturnal blood pressure dipping, which has been associated with mortality in the general population. Hypertension is also prevalent in NT1. Furthermore, disrupted nighttime sleep and excessive daytime sleepiness, which are characteristic of narcolepsy, may increase cardiovascular risk. Patients with narcolepsy also often present with other comorbidities (eg, obesity, diabetes, depression, other sleep disorders) that may contribute to increased cardiovascular risk. Management of multimorbidity in patients with narcolepsy should include regular assessment of cardiovascular health (including ambulatory blood pressure monitoring), mitigation of cardiovascular risk factors (eg, cessation of smoking and other lifestyle changes, sleep hygiene, and pharmacotherapy), and prescription of a regimen of narcolepsy medications that balances symptomatic benefits with cardiovascular safety.

Knowledge Gaps in the Perioperative Management of Adults With Narcolepsy: A Call for Further Research

There is increasing awareness that sleep disorders may be associated with increased perioperative risk. The Society of Anesthesia and Sleep Medicine created the Narcolepsy Perioperative Task Force: (1) to investigate the current state of knowledge of the perioperative risk for patients with narcolepsy, (2) to determine the viability of developing perioperative guidelines for the management of patients with narcolepsy, and (3) to delineate future research goals and clinically relevant outcomes. The Narcolepsy Perioperative Task Force established that there is evidence for increased perioperative risk in patients with narcolepsy; however, this evidence is sparse and based on case reviews, case series, and retrospective reviews. Mechanistically, there are a number of potential mechanisms by which patients with narcolepsy could be at increased risk for perioperative complications. These include aggravation of the disease itself, dysautonomia, narcolepsy-related medications, anesthesia interactions, and withdrawal of narcolepsy-related medications. At this time, there is inadequate research to develop an expert consensus or guidelines for the perioperative management of patients with narcolepsy. The paucity of available literature highlights the critical need to determine if patients with narcolepsy are at an increased perioperative risk and to establish appropriate research protocols and clearly delineated patient-centered outcomes. There is a real need for collaborative research among sleep medicine specialists, surgeons, anesthesiologists, and perioperative providers. This future research will become the foundation for the development of guidelines, or at a minimum, a better understanding how to optimize the perioperative care of patients with narcolepsy.

Moderate to severe but not mild RLS is associated with greater sleep-related sympathetic autonomic activation than healthy adults without RLS

INTRODUCTION

Restless legs syndrome (RLS) patients have been found to have high rates of transitory increases in the activity of the sympathetic autonomic nervous system with increases in heart rate and blood pressure. These were identified by evaluating heart rate or blood pressure changes independent of any leg movement analyses. There has been an implicit assumption this high rate of sympathetic activations is abnormal, but there has been no direct comparison for similar measures with a healthy population free of RLS. Thus, it is not known if during sleep the rates of sympathetic nervous system activation are greater for RLS than for a healthy population. The objectives of this study were to determine if: (1) RLS patients compared to healthy controls have a greater frequency of sympathetic nervous system activation (significant heart rate increases) with a higher percentage of leg movements associated with these activations; (2) the sympathetic activation frequency and its relation to leg movements correlate significantly with RLS severity in RLS patients; and (3) there is some minimum threshold for RLS severity defining an RLS population where most (eg 85%) have abnormally high rates of sympathetic activation.

METHODS

Sleep data on 32 RLS patients and 21 matched healthy controls were obtained from a prior study. All leg movements during sleep (LMS) and periodic leg movements in sleep (PLMS) were identified following the new WASM criteria; LMS that were not PLMS were considered isolated leg movements in sleep (ILMS). All episodes with significant heart rate increases were identified following procedures established by Cassel et al., (2016, see further on for citation) ie a slope of linear regression ≥2.5 beats per minute over five consecutive heartbeats. Severity of RLS was evaluated using the International Restless Legs Study Group Scale (IRLS).

RESULTS

RLS patients had significantly more heart rate increases than controls (67.88/hr vs. 9.87/hr). RLS patients had a significantly greater percentage of both LMS and PLMS occurring with heart rate increases than controls (44% vs. 30%; 48% vs. 18%, respectively). These measures correlated significantly with IRLS and also PLMS/hr. 85% of the RLS patients with IRLS scores >22 or PLMS >50/hr had rates of sympathetic activation that were >90th percentile for the healthy controls.

CONCLUSION

This is the first paper documenting that RLS patients showed clearly increased sympathetic activation when identified independent of PLMS. This, however, occurs for more severe RLS and not milder RLS. It has been proposed that the abnormally high rate of sympathetic activation for RLS patients relates to development of adverse cardiovascular health consequences observed in some studies. Thus, these data may provide a basic standard for possible use in epidemiological studies to identify the level of RLS severity more likely to have adverse health consequences (eg, cardiovascular disease). Since two-thirds of RLS patients have mild to even intermittent disease, including all RLS is likely to miss the potential health consequences of RLS.

Impact of acute administration of sodium oxybate on heart rate variability in children with type 1 narcolepsy

BACKGROUND

Currently, cardiovascular measurements in children affected with type 1 narcolepsy (NT1) have never been investigated, and neither have their modulation by the administration of sodium oxybate (SO).

METHODS

Twelve drug-naïve NT1 children (four males, eight females) with a mean age of 11 ± 3.16 years underwent a nocturnal polysomnography, at baseline and during the first night of SO administration. Data were contrasted with those recorded in 23 age-matched healthy controls. Heart rate variability (HRV) analysis was performed by analyzing the electrocardiogram signal for automatic detection of R waves with a computer program calculating a series of standard time-domain measures and obtaining spectral parameters, by means of a Fast-Fourier Transform.

RESULTS

In sleep stages N2 and N3, NT1 children showed increased power in the low-frequency (LF) and very-LF (VLF) ranges, when compared to controls. In addition, HRV (as measured by time domain parameters) during all sleep stages tended to be slightly higher in patients when compared to controls. Treatment with SO did not change significantly any parameter, but an overall trend to mildly decreased HRV that reached a significant value only during R sleep.

CONCLUSIONS

HRV during all sleep stages tended to be slightly higher in young patients when compared to controls, confirming the presence of a slight sympathovagal system imbalance even in NT1 children. SO tends to decrease these values especially during REM sleep and in that regard, further studies supporting these preliminary findings and considering the long-term effects of SO on heart rate parameters are warranted.

The Clinical Importance of Periodic Leg Movements in Sleep

OPINION STATEMENT

Periodic leg movements during sleep (PLMS) are commonly found in patients with restless leg syndrome (RLS), but they may occur in other sleep disorders and several medical conditions. Their prevalence increases with age, but they can also be observed in children. During the last decades, very active research has been devoted to determine and understand the pathophysiology, associated events, and clinical significance of PLMS. This chapter tries to sum up the most relevant PLMS-related findings, focusing on the relationship between PLMS and the cardiovascular system, in order to understand the clinical implication of this complex motor phenomenon. PLMS have been associated with sympathetic overactivity, namely surges in nocturnal blood pressure and heart rate, without modification in global autonomic balance. Also, PLMS have been related to inflammatory cellular pathways, with elevated level of inflammatory markers, which are associated with cardiovascular risk. The PLMS-related modulation of the autonomic system and of inflammation may increase cardiovascular and cerebrovascular risk in subjects with frequent PLMS. Moreover, also, comorbidities associated with PLMS may play a synergic role in worsening the cardiovascular risk and the consequent mortality and morbidity. Furthermore, little is known about pathophysiological correlates in children with PLMS and their chronic implication on the cardiovascular and cerebrovascular systems. A few studies have suggested that treating PLMS with dopaminergic drugs may reduce their associated sympathetic overactivity and modify disease progression. Definitely, further research is needed to assess the clinical impact of PLMS, associated or not with RLS, and above all the long-term impact of treating PLMS on cardiovascular risk, morbidity, and mortality.

Diurnal and nocturnal cardiovascular variability and heart rate arousal response in idiopathic hypersomnia

OBJECTIVES

Autonomic nervous system dysfunction has been described in narcolepsy with cataplexy affecting sympathetic functions. In this study we analyzed whether altered diurnal and nocturnal cardiovascular control is present in idiopathic hypersomnia (IH).

METHODS

Fourteen drug-free patients aged 26.2 ± 7 years and 14 age-matched controls were examined. Clinical data, 24-h polysomnography, heart rate (HR) variability, and the HR response to spontaneous arousal were available.

RESULTS

Sleep macrostructure was comparable between controls and patients, with the latter having significantly longer sleep time, a higher number of sleep cycles (p < 0.0001), and low sleep efficiency (p < 0.01). The HR variability indices did not differ between groups, except for the rise of high frequency (HF) and HFnu in patients (p < 0.05) associated with blunted sympathetic indices (p < 0.01). These parasympathetic alterations were present for light, slow wave, and rapid eye-movement sleep and persisted for all sleep cycles. Compared to controls, the HR arousal response was significantly higher (p < 0.01) in patients starting before the arousal onset and persisting into the post-arousal period.

CONCLUSIONS

In IH patients a dysfunction of the parasympathetic activity during awake and sleep and an altered autonomic response to arousals are present. These findings suggest an impaired parasympathetic function that may explain some vegetative symptoms present in this type of central hypersomnia.

Prevalence of periodical leg movements in patients with narcolepsy in an outpatient facility in São Paulo

Studies have pointed out that approximately 50–60% of narcolepsy patients may demonstrate higher prevalence of periodical leg movements. However, we highlight that the prevalence studies and the effects of periodical leg movements in patients with narcolepsy are limited and with conflicting results. The objective of this study was that of describing and discussing the prevalence of periodical leg movements in patients with narcolepsy in the outpatient facility of diurnal excessive sleepiness of the Federal University of São Paulo, Brazil.

We revised 59 files of patients with the clinical and electrophysiological diagnosis of narcolepsy according to the American Academy of Sleep Medicine.

Of these 59 cases of patients with narcolepsy, 12 (20.3%) demonstrated periodical leg movements. Thirty five patients (59.3%) had history of cataplexy and 38 patients (64.4%) had the presence of the allele HLA-DQB1⁎0602. There was a higher prevalence of periodical leg movements in patients with cataplexy (p<0.0001) and in patients with the presence of the allele HLA-DQB1⁎0602 (p<0.0001).

Our study characterized the higher prevalence of periodical leg movement in patients with narcolepsy, mainly in patients with cataplexy and with the presence of the allele HLA-DQB1⁎0602.

Morbidities in rapid eye movement sleep behavior disorder

Idiopathic rapid eye movement (REM) sleep behavior disorder (iRBD, RBD without any obvious comorbid major neurological disease), is strongly associated with numerous comorbid conditions. The most prominent is that with neurodegenerative disorders, especially synuclein-mediated disorders, above all Parkinson disease (PD). Idiopathic RBD is an important risk factor for the development of synucleinopathies. Comorbidity studies suggest that iRBD is associated with a number of other potential pre-motor manifestations of synucleinopathies such as, cognitive and olfactory impairment, reduced autonomic function, neuropsychiatric manifestations and sleep complaints. Furthermore, patients with PD and RBD may have worse prognosis in terms of impaired cognitive function and overall morbidity/mortality; in dementia, the presence of RBD is strongly associated with clinical hallmarks and pathological findings of dementia with Lewy bodies. These findings underline the progressive disease process, suggesting involvement of more brain regions in patients with a more advanced disease stage. RBD is also associated with narcolepsy, and it is likely that RBD associated with narcolepsy is a distinct subtype associated with different comorbidities. RBD is also associated with antidepressant medications, autoimmune conditions, and, in rare cases, brainstem lesions.

Attenuated heart rate response is associated with hypocretin deficiency in patients with narcolepsy

STUDY OBJECTIVE

Several studies have suggested that hypocretin-1 may influence the cerebral control of the cardiovascular system. We analyzed whether hypocretin-1 deficiency in narcolepsy patients may result in a reduced heart rate response.

DESIGN

We analyzed the heart rate response during various sleep stages from a 1-night polysomnography in patients with narcolepsy and healthy controls. The narcolepsy group was subdivided by the presence of +/- cataplexy and +/- hypocretin-1 deficiency.

SETTING

Sleep laboratory studies conducted from 2001-2011.

PARTICIPANTS

In total 67 narcolepsy patients and 22 control subjects were included in the study. Cataplexy was present in 46 patients and hypocretin-1 deficiency in 38 patients.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

All patients with narcolepsy had a significantly reduced heart rate response associated with arousals and leg movements (P < 0.05). Heart rate response associated with arousals was significantly lower in the hypocretin-1 deficiency and cataplexy groups compared with patients with normal hypocretin-1 levels (P < 0.04) and patients without cataplexy (P < 0.04). Only hypocretin-1 deficiency significantly predicted the heart rate response associated with arousals in both REM and non-REM in a multivariate linear regression.

CONCLUSIONS

Our results show that autonomic dysfunction is part of the narcoleptic phenotype, and that hypocretin-1 deficiency is the primary predictor of this dysfunction. This finding suggests that the hypocretin system participates in the modulation of cardiovascular function at rest.

Rapid eye movement sleep behavior disorder and rapid eye movement sleep without atonia in narcolepsy

Narcolepsy is a rare disabling hypersomnia disorder that may include cataplexy, sleep paralysis, hypnagogic hallucinations, and sleep-onset rapid eye movement (REM) periods, but also disrupted nighttime sleep by nocturnal awakenings, and REM sleep behavior disorder (RBD). RBD is characterized by dream-enacting behavior and impaired motor inhibition during REM sleep (REM sleep without atonia, RSWA). RBD is commonly associated with neurodegenerative disorders including Parkinsonisms, but is also reported in narcolepsy in up to 60% of patients. RBD in patients with narcolepsy is, however, a distinct phenotype with respect to other RBD patients and characterized also by absence of gender predominance, elementary rather than complex movements, less violent behavior and earlier age at onset of motor events, and strong association to narcolepsy with cataplexy/hypocretin deficiency. Patients with narcolepsy often present dissociated sleep features including RSWA, increased density of phasic chin EMG and frequent shift from REM to NREM sleep, with or without associated clinical RBD. Most patients with narcolepsy with cataplexy lack the hypocretin neurons in the lateral hypothalamus. Tonic and phasic motor activities in REM sleep and dream-enacting behavior are mostly reported in presence of cataplexy. Narcolepsy without cataplexy is a condition rarely associated with hypocretin deficiency. We proposed that hypocretin neurons are centrally involved in motor control during wakefulness and sleep in humans, and that hypocretin deficiency causes a functional defect in the motor control involved in the development of cataplexy during wakefulness and RBD/RSWA/phasic motor activity during REM sleep.

Non-dipping blood pressure profile in narcolepsy with cataplexy

BACKGROUND

Patients with narcolepsy-cataplexy (NC) mostly exhibit undetectable hypocretin levels. Hypocretin system is one of the key players in the complex interaction between sleep and the cardiovascular system. We tested the hypothesis that hypocretin deficiency affects cardiovascular risk factors by measuring nighttime and daytime ambulatory blood pressure (BP) and the night-to-day BP ratio as well as endothelial dysfunction by the digital pulse amplitude response in drug-free patients with NC compared to controls.

METHODOLOGY

Sleep, clinical and biological cardiovascular risk factors, fingertip peripheral arterial tonometry, and 24-hour ambulatory BP monitoring were recorded in 50 drug-free patients with NC and 42 healthy control subjects, except for BP monitoring available in all controls but in 36 patients with NC.

PRINCIPAL FINDINGS

More patients than controls were smokers, obese and with dyslipidemia. One-third of patients with NC were "non-dippers" (defined as <10% drop in BP during sleep) compared to only 3% of controls. The diastolic non-dipper BP profile had up to 12-fold higher odds of being associated with NC. We noted negative correlations between mean diastolic BP fall during night, REM sleep percentage and number of sleep onset REM periods, and a positive correlation with mean sleep latency on the MSLT. The digital pulse amplitude response measured by fingertip was similar between NC and controls.

CONCLUSION

We found a high percentage of non-dippers in patients with NC with association with REM sleep dysregulation. The blunted sleep-related BP dip in NC may be of clinical relevance, as it may indicate increased risk for cardiovascular events.

Abnormal sleep-cardiovascular system interaction in narcolepsy with cataplexy: effects of hypocretin deficiency in humans

STUDY OBJECTIVE

Narcolepsy with cataplexy (NC) is associated with loss of hypocretin neurons in the lateral hypothalamus involved in the circadian timing of sleep and wakefulness, and many biologic functions including autonomic control. The authors investigated whether chronic lack of hypocretin signaling alters cardiovascular control during sleep in humans.

DESIGN

Comparison of 24-hr circadian rhythms, day-night, time- and state-dependent changes of blood pressure (BP) and heart rate (HR) in drug-free patients with NC and control subjects.

SETTING

University hospital.

PATIENTS OR PARTICIPANTS

Ten drug-free patients with NC (9 men, 1 woman) and 12 control subjects (9 men, 3 women).

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

Daytime BP was comparable in patients with NC and controls, but patients with NC displayed a nighttime nondipping BP pattern. The 24-hr circadian rhythmicity of BP and HR was normal in both groups. Systolic BP during nighttime rapid eye movement sleep was significantly increased in the NC group. The 24-hr HR was significantly higher in the NC group but the day-night and state-dependent HR modulations were intact. The nighttime BP pattern coupled in the NC group with increased sleep fragmentation and a higher prevalence of arousals, periodic limb movements in sleep (PLMS), and PLMS arousals. In an analysis of the sleep/cardiovascular interaction in the periods after sleep onset and preceding morning awakening, only PLMS were consistently associated with the blunted nighttime decrease in BP in the NC group.

CONCLUSIONS

Hypocretin deficiency in humans may couple with an altered nighttime BP regulation that can be associated with an increased cardiovascular risk. This finding may be the result not only of the hypocretinergic deficiency per se but also of the altered sleep/wake regulation characterizing NC.

Cluster headache and sleep, is there a connection? A review

PURPOSE OF REVIEW

Sleep and the chronobiological disease cluster headache are believed to be interconnected. Despite efforts, the precise nature of the relationship remains obscured. A better understanding of this relation may lead to more effective therapeutic regimes for patients suffering from this debilitating disease. This review aims to evaluate the existing literature on the subject of cluster headache and sleep.

LATEST FINDINGS

Several previous studies describe an association between episodic cluster headache and distinct macrostructural sleep phases. This association was not confirmed in a recent study of seven episodic cluster headache patients, but it was suggested that further studies into the correlation between cluster headache attacks and the microstructure of sleep are relevant. The connection between cluster headache and the hypocretins is currently under investigation.

SUMMARY

There is evidence in favour of an association between episodic cluster headache and REM sleep whereas no such relation to chronic cluster headache has been reported. Particular features in the microstructure of sleep and arousal mechanisms could play a role in the pathogenesis of cluster headache. Reports indicate that cluster headache and obstructive sleep apnoea are associated. Single cases show improvement upon treatment of sleep apnoea, but the causal relationship remains in question.

Control of cardiovascular variability during undisturbed wake-sleep behavior in hypocretin-deficient mice

The central neural mechanisms underlying differences in cardiovascular variability between wakefulness, non-rapid-eye-movement sleep (NREMS), and rapid-eye-movement sleep (REMS) remain poorly understood. These mechanisms may involve hypocretin (HCRT)/orexin signaling. HCRT signaling is linked to wake-sleep states, involved in central autonomic control, and impaired in narcoleptic patients. Thus, we investigated whether HCRT signaling plays a role in controlling cardiovascular variability during spontaneous behavior in HCRT-deficient mice. HCRT-ataxin3 transgenic mice lacking HCRT neurons (TG), knockout mice lacking HCRT peptides (KO), and wild-type controls (WT) were instrumented with electrodes for sleep recordings and a telemetric blood pressure transducer. Fluctuations of systolic blood pressure (SBP) and heart period (HP) during undisturbed wake-sleep behavior were analyzed with the sequence technique, cross-correlation functions, and coherent averaging of SBP surges. During NREMS, all mice had lower SBP variability, greater baroreflex contribution to HP control at low frequencies, and greater amplitude of the central autonomic and baroreflex changes in HP associated with SBP surges than during wakefulness. During REMS, all mice had higher SBP variability and depressed central autonomic and baroreflex HP controls relative to NREMS. HP variability during REMS was higher than during NREMS in WT only. TG and KO also had lower amplitude of the cardiac baroreflex response to SBP surges during REMS than WT. These results indicate that chronic lack of HCRT signaling may cause subtle alterations in the control of HP during spontaneous behavior. Conversely, the integrity of HCRT signaling is not necessary for the occurrence of physiological sleep-dependent changes in SBP variability.

Periodic leg movements during sleep in narcoleptic patients with or without restless legs syndrome

We compared periodic and non-periodic leg movements during sleep and polysomnography in patients with narcolepsy with cataplexy (NC) with or without restless legs syndrome (RLS) with matched idiopathic RLS (iRLS) and control subjects. We enrolled 100 patients with NC: 17 having RLS were compared with 34 sex- and age-matched patients without RLS and with 17 normal controls and 17 iRLS subjects. Periodic leg movements were highest in iRLS and lowest in controls, with those in NC with RLS very close to iRLS, but higher than those in NC without RLS. The periodicity indexes showed the highest value in iRLS followed by NC with or without RLS and, finally, by controls. The inter-leg movement intervals peaked between 10 and 50 s in NC with RLS and in iRLS, the former did not display the nocturnal gradual decrease of periodic leg movements typical of iRLS. Periodic leg movements during sleep and polysomnography displayed specific features in RLS and NC, respectively, with NC with RLS showing an intermediate pattern. Even if RLS is only detected by targeted interview in NC, its frequency and impact on night-time sleep architecture and continuity suggest that this condition should be routinely searched for in NC.