Changes in cerebral and autonomic activity heralding periodic limb movements in sleep

A pilot study to understand the relationship between cortical arousals and leg movements during sleep

Leg movements during sleep occur in patients with sleep pathology and healthy individuals. Some (but not all) leg movements during sleep are related to cortical arousals which occur without conscious awareness but have a significant effect of sleep fragmentation. Detecting leg movements during sleep that are associated with cortical arousals can provide unique insight into the nature and quality of sleep. In this study, a novel leg movement monitor that uses a unique capacitive displacement sensor and 6-axis inertial measurement unit, is used in conjunction with polysomnography to understand the relationship between leg movement and electroencephalogram (EEG) defined cortical arousals. In an approach that we call neuro-extremity analysis, directed connectivity metrics are used to interrogate causal linkages between EEG and leg movements measured by the leg movement sensors. The capacitive displacement measures were more closely related to EEG-defined cortical arousals than inertial measurements. Second, the neuro-extremity analysis reveals a temporally evolving connectivity pattern that is consistent with a model of cortical arousals in which brainstem dysfunction leads to near-instantaneous leg movements and a delayed, filtered signal to the cortex leading to the cortical arousal during sleep.

Periodic limb movement index and severity of obstructive sleep apnea

Background

Periodic limb movements during sleep (PLMS) and obstructive sleep apnea syndrome (OSAS) are two frequent coincident sleep disorders. The association of PLMS with OSAS severity and predictors of PLMS in OSAS patients were investigated.

Material and method

This is a retrospective study that enrolled adult patients ≥ 16 years old who visited the sleep unit at Mouwasat Hospital, Saudi Arabia, between January 2021 and October 2021. All were subjected to full medical history, clinical examination, Epworth Sleepiness (ESS), STOP-Bang questionnaires, and standard overnight polysomnography. Subjects were subdivided into two groups based on PSG findings: group I, OSA patients (153). Patients were classified into mild n = 57 (AHI ≥ 5 and < 15), moderate n = 35 (AHI ≥ 15 and < 30), and severe n = 61 (AHI ≥ 30). Group II, control group included 100 subjects.

Result

There was a higher frequency of PLMS in OSA patients vs control group (with a statistically significant value). The study showed a statistically significantly positive correlation between PLMI and each of AHI, hypopnea index, desaturation index, and PLMs with arousal index, in contrast; it had a statistically significantly negative correlation with BMI among the OSA group. By performing multivariate logistic regression to predict the possible factors associated with the existence of PLMS among the OSA group, it was showed that the apnea index and desaturation index were statistically significant predictors.

Conclusion

The present study showed that OSA patients with PLM were older; had greater AHI, hypopnea index, desaturation index, and PLMs with arousal index; and had lower BMI. Further studies are needed for better understanding this complex relationship.

Patients with a Higher Number of Periodic Limb Movements Have Higher Nocturnal Blood Pressure

There is growing evidence that periodic limb movements in sleep (PLMS) may lead to increased blood pressure (BP) values during the night. The aim of this study was to assess if patients with disordered sleep and an increased number of PLMS have higher BP values at night. We analyzed 100 polysomnographic (PSG) recordings of patients with disordered sleep, with the exclusion of sleep-related breathing disorders. Patients also registered beat-to-beat blood pressure during PSG. We compared the BP of patients with an increased number of PLMS (more than 5 PLMS per hour of sleep) during the night (examined group, n = 50) to the BP of patients with a PLMS number within the normal range (up to 5 PLMS per hour of sleep) (control group, n = 50). Patients from the examined group had significantly higher values of systolic BP during the night (119.7 mmHg vs. 113.3 mmHg, p = 0.04), sleep (119.0 mmHg vs. 113.3 mmHg, p = 0.04), and wake (122.5 mmHg vs. 117.2 mmHg, p = 0.04) periods and of diastolic BP during the night (75.5 mmHg vs. 70.6 mmHg, p = 0.04) and wake (77.6 mmHg vs. 71.5 mmHg, p = 0.01) periods. Our results suggest a relationship between the number of PLMS during the night and the values of nocturnal blood pressure. It is possible that their treatment could lower nocturnal BP in patients with sleep disorders, therefore improving their vascular risk profile.

Sex Differences in Excessive Daytime Sleepiness Among Patients With Obstructive Sleep Apnea

BACKGROUND AND PURPOSE

To identify sex differences in daytime sleepiness associated with apnea severity and periodic limb movements during sleep (PLMS) in subjects with obstructive sleep apnea (OSA).

METHODS

This study used the Epworth Sleepiness Scale (ESS), Beck Depression Inventory (BDI), and Sleep Hygiene Index (SHI) in logistic regression analyses with interaction terms. Severe OSA, excessive daytime sleepiness (EDS), and PLMS were defined as an apnea-hypopnea index of ≥30, an ESS score of ≥11, and a periodic limb movements index of >15, respectively.

RESULTS

The 1,624 subjects with OSA (males, 79.1%) comprised 45.3%, 38.2%, and 16.4% with severe OSA, EDS, and PLMS, respectively. Multiple logistic regression without interaction terms showed that sex, severe OSA, and PLMS were not significantly associated with EDS. However, significant interactions were noted between sex and severe OSA and PLMS in EDS in both crude and adjusted models (all p values<0.05). In the adjusted model, severe OSA was associated with EDS in males (p=0.009) but not in females. PLMS were more likely to be associated with EDS in females (p=0.013), whereas PLMS were less likely to be associated with EDS in males (p=0.041). The models were adjusted by the BDI score, SHI, and presence of medical comorbidities.

CONCLUSIONS

There are significant sex differences in subjective daytime sleepiness in subjects with severe OSA and PLMS. Severe OSA and PLMS may influence daytime sleepiness more in males and females, respectively.

Periodic limb movements during sleep: a narrative review

Objective

Using narrative review techniques, this paper evaluates the evidence for separable underlying patho-mechanisms of periodic limb movements (PLMs) to separable PLM motor patterns and phenotypes, in order to elucidate potential new treatment modalities.

Background

Periodic limb movement disorder (PLMD) is estimated to occur in 5–8% of the paediatric population and 4–11% of the general adult population. Due to significant sleep fragmentation, PLMD can lead to functional impairment, including hyperactivity and delayed language development in children, and poor concentration and work performance in adults. Longitudinal data demonstrate that those with PLMD are at greater risk of depression and anxiety, and a 4-fold greater risk of developing dementia. PLMD has been extensively studied over the past two decades, and several key insights into the genetic, pathophysiological, and neural correlates have been proposed. Amongst these proposals is the concept of separable PLM phenotypes, proposed on the basis of nocturnal features such as the ratio of limb movements and distribution throughout the night. PLM phenotype and presentation, however, varies significantly depending on the scoring utilized and the nocturnal features examined, across age, and co-morbid clinical conditions. Furthermore, associations between these phenotypes with major neurologic and psychiatric disorders remain controversial.

Methods

In order to elucidate potential divergent biological pathways that may help clarify important new treatment modalities, this paper utilizes narrative review and evaluates the evidence linking PLM motor patterns and phenotypes with hypothesised underlying patho-mechanisms. Distinctive, underlying patho-mechanisms include: a pure motor mechanism originating in the spinal cord, iron deficiency, dopamine system dysfunction, thalamic glutamatergic hyperactivity, and a more cortical-subcortical interplay. In support of the latter hypothesis, PLM rhythmicity appears tightly linked to the microarchitecture of sleep, not dissimilarly to the apnoeic/hypopneic events seen in obstructive sleep apnea (OSA).

Conclusions

This review closes with a proposal for greater investigation into the identification of potential, divergent biological pathways. To do so would require prospective, multimodal imaging clinical studies which may delineate differential responses to treatment in restless legs syndrome (RLS) without PLMS and PLMS without RLS. This could pave the way toward important new treatment modalities.

Heart rate change and clinical characteristics in patients with neck myoclonus: An observational study

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Heart rates increased with neck myoclonus events.

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The rate of increase was higher for neck myoclonus with cortical arousal than for those without.

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Neck myoclonus may be associated with excessive daytime sleepiness or abnormal behaviors during REM sleep.

Objective

This study was conducted to evaluate heart rate (HR) change and clinical characteristics in patients with neck myoclonus (NM), a physiological motor phenomenon occurring during sleep.

Methods

For 18 consecutive patients in whom NM was confirmed from video-polysomnography, we analyzed 576 NMs. Change rate of HR at each 1 sec point towards the averaged HR in prior 5 sec period was calculated before and after all NM events.

Results

Findings show NM events as more prevalent during REM sleep than during NREM sleep (83.9% vs. 16.1%). For NM without cortical arousal in REM and NREM sleep, the respective HR increased 20 s before NM (p < 0.05); the change rate was up to 13%. For NM with cortical arousal in REM sleep, the HR increased 50 s before NM (p < 0.05); the change rate reached 18%. Three NM subjects showed abnormal vocalization or shouting during REM. Six NM subjects had excessive daytime sleepiness without sleep disorder.

Conclusion

HR increased before NM events, which may be associated with pathophysiology of NM. NM may possibly be associated with excessive daytime sleepiness or abnormal behaviors during REM sleep.

Significance

HR increase is associated with pathophysiology of NM and clinical symptoms.

A systematic review and meta-analysis of the cyclic alternating pattern across the lifespan

BACKGROUND

Cyclic alternating pattern (CAP) is the electroencephalogram (EEG) pattern described as a marker of sleep instability and assessed by NREM transient episodes in sleep EEG. It has been associated with brain maturation. The aim of this review was to evaluate the normative data of CAP parameters according to the aging process in healthy subjects through a systematic review and meta-analysis.

METHODS

Two authors independently searched databases using PRISMA guidelines. Discrepancies were reconciled by a third reviewer. Subgroup analysis and tests for heterogeneity were conducted.

RESULTS

Of 286 studies, 10 submitted a total of 168 healthy individuals to CAP analysis. Scoring of CAP can begin at 3 months of life, when K-complexes, delta bursts, or spindles can be recognized. Rate of CAP increased with age, mainly during the first 2 years of life, then decreased in adolescence, and increased in the elderly. The A1 CAP subtype and CAP rate were high in school-aged children during slow-wave sleep (SWS). A1 CAP subtypes were significantly more numerous in adolescents compared with other groups, while the elderly showed the highest amounts of A2 and A3 CAP subtypes. Our meta-analysis registered the lowest CAP rate in infants younger than 2 years old and the highest in the elderly.

CONCLUSIONS

This review summarized the normative data of CAP in NREM sleep during the aging process. The CAP rate increased with age and sleep depth, especially during SWS. Parameters of CAP may reflect gender hormonal effects and neuroplasticity. More reports on CAP subtypes are needed for their reference values establishment.

Artificial intelligence in neurodegenerative diseases: A review of available tools with a focus on machine learning techniques

Neurodegenerative diseases have shown an increasing incidence in the older population in recent years. A significant amount of research has been conducted to characterize these diseases. Computational methods, and particularly machine learning techniques, are now very useful tools in helping and improving the diagnosis as well as the disease monitoring process. In this paper, we provide an in-depth review on existing computational approaches used in the whole neurodegenerative spectrum, namely for Alzheimer's, Parkinson's, and Huntington's Diseases, Amyotrophic Lateral Sclerosis, and Multiple System Atrophy. We propose a taxonomy of the specific clinical features, and of the existing computational methods. We provide a detailed analysis of the various modalities and decision systems employed for each disease. We identify and present the sleep disorders which are present in various diseases and which represent an important asset for onset detection. We overview the existing data set resources and evaluation metrics. Finally, we identify current remaining open challenges and discuss future perspectives.

Brain regions associated with periodic leg movements during sleep in restless legs syndrome

The neural substrates related to periodic leg movements during sleep (PLMS) remain uncertain, and the specific brain regions involved in PLMS have not been evaluated. We investigated the brain regions associated with PLMS and their severity using the electroencephalographic (EEG) source localization method. Polysomnographic data, including electromyographic, electrocardiographic, and 19-channel EEG signals, of 15 patients with restless legs syndrome were analyzed. We first identified the source locations of delta-band (2–4 Hz) spectral power prior to the onset of PLMS using a standardized low-resolution brain electromagnetic tomography method. Next, correlation analysis was conducted between current densities and PLMS index. Delta power initially and most prominently increased before leg movement (LM) onset in the PLMS series. Sources of delta power at −4~−3 seconds were located in the right pericentral, bilateral dorsolateral prefrontal, and cingulate regions. PLMS index was correlated with current densities at the right inferior parietal, temporoparietal junction, and middle frontal regions. In conclusion, our results suggest that the brain regions activated before periodic LM onset or associated with their severity are the large-scale motor network and provide insight into the cortical contribution of PLMS pathomechanism.

Restless legs syndrome, periodic limb movements during sleep and cardiovascular risk

Multiple mechanisms may modulate an association between restless legs syndrome/Willis-Ekbom disease (RLS/WED) and cardiovascular disease (CVD), including chronic sleep deprivation, intermittent, periodic limb movements in sleep (PLMS)-related autonomic fluctuations and possible autonomic dysfunction intrinsically associated with RLS per se. The purpose of this paper is to review the existing RLS/WED literature focusing on the pathophysiologic evidence for possible associations between RLS/WED and PLMS with CVD and events (CVE). Specific intrinsic dysautonomic aspects of the disease, which may contribute to generating CVD, are separately discussed. The association between RLS/WED and both CV risk factors and CVD still remains elusive. Although several shared pathophysiological causes could explain these possible relationships, the emerging body of literature focusing on these disorders remains controversial. Not only longitudinal population-based studies and meta-analyses, but also more animal models and therapeutic interventions are needed in order to build a sufficiently robust body of evidence on this topic.

Basal sympathetic predominance in periodic limb movements in sleep after continuous positive airway pressure

PURPOSE

This study investigated the basal autonomic regulation in patients with obstructive sleep apnea (OSA) showing periodic limb movements in sleep (PLMS) emerging after therapy with continuous positive airway pressure (CPAP).

METHODS

Data of patients with OSA undergoing a first polysomnography for diagnosis and a second polysomnography for therapy with CPAP were reviewed. Patients with OSA showing PLMS on the first polysomnography were excluded. By using heart rate variability analysis, epochs without any sleep events and continuous effects from the second polysomnography were retrospectively analyzed.

RESULTS

Of 125 eligible patients, 30 with PLMS after therapy with CPAP (PLMS group) and 30 not showing PLMS on both polysomnography (non-PLMS group) were randomly selected for the analysis. No significant differences in the demographic characteristics and variables of polysomnographies were identified between the groups. Although one trend of low root mean square of successive differences (RMSSD) between intervals of adjacent normal heart beats (NN intervals) in the PLMS group was observed, patients in the PLMS group had significantly low normalized high-frequency (n-HF) and high-frequency (HF) values, but high normalized low frequency (n-LF) and high ratio of LF to HF (LF/HF ratio). After adjustment for confounding variables, PLMS on the second polysomnography was significantly associated with RMSSD (β = - 6.7587, p = 0.0338), n-LF (β = 0.0907, p = 0.0148), n-HF (β = - 0.0895, p = 0.0163), log LF/HF ratio (β = 0.4923, p = 0.0090), and log HF (β = - 0.6134, p = 0.0199).

CONCLUSIONS

Patients with OSA showing PLMS emerging after therapy with CPAP may have a basal sympathetic predominance with potential negative cardiovascular effects.

EEG Functional Connectivity Prior to Sleepwalking: Evidence of Interplay Between Sleep and Wakefulness

Study Objectives

Although sleepwalking (somnambulism) affects up to 4% of adults, its pathophysiology remains poorly understood. Sleepwalking can be preceded by fluctuations in slow-wave sleep EEG signals, but the significance of these pre-episode changes remains unknown and methods based on EEG functional connectivity have yet to be used to better comprehend the disorder.

Methods

We investigated the sleep EEG of 27 adult sleepwalkers (mean age: 29 ± 7.6 years) who experienced a somnambulistic episode during slow-wave sleep. The 20-second segment of sleep EEG immediately preceding each patient's episode was compared with the 20-second segment occurring 2 minutes prior to episode onset.

Results

Results from spectral analyses revealed increased delta and theta spectral power in the 20 seconds preceding the episodes' onset as compared to the 20 seconds occurring 2 minutes before the episodes. The imaginary part of the coherence immediately prior to episode onset revealed (1) decreased delta EEG functional connectivity in parietal and occipital regions, (2) increased alpha connectivity over a fronto-parietal network, and (3) increased beta connectivity involving symmetric inter-hemispheric networks implicating frontotemporal, parietal and occipital areas.

Conclusions

Taken together, these modifications in EEG functional connectivity suggest that somnambulistic episodes are preceded by brain processes characterized by the co-existence of arousal and deep sleep.

Heart rate variability in restless legs syndrome and periodic limb movements of Sleep

INTRODUCTION

The relationship between the autonomic nervous system and restless legs syndrome (RLS) and periodic limb movements of sleep (PLMS) consists of varied and somewhat conflicting reports. In order to further elucidate these complexities, a retrospective analysis of polysomnography (PSG) records and clinical data was performed.

METHODS

Records from 233 adult subjects were randomly selected and organized into one of four groups ("non-RLS/PLMS" [n=61], "RLS" [n=60], "PLMS" [n=58], and "RLS/PLMS" [n=54]). Heart rate variability (HRV) analysis was based on 5-minute samples of 2-lead electrocardiogram data isolated from PSG recordings during wakefulness and NREM sleep, and included mean RR interval (labeled "NN") and standard deviation of the RR intervals (labeled "SDNN"), and HRV power, very low frequency (VLF), low frequency (LF), and high frequency (HF) spectral bands.

RESULTS

A significant reduction in the VLF band in the PLMS group as compared to the non-RLS/PLMS group (542±674 vs. 969±1025 ms², p=0.038) was found in wakefulness. Statistically significant differences were seen in the PLMS group as compared to the non-RLS/PLMS group with a reduction in SDNN (p=0.001) and the HF (p=0.001) band, and an increase in HRV power (p=0.001), and the VLF (p=0.005) and LF (p=0.001) bands in NREM sleep.

CONCLUSIONS

The PLMS group exhibited reduced basal sympathetic activity in wakefulness, but basal sympathetic predominance during NREM sleep, distinguishing this group from the RLS and RLS/PLMS groups.

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.

Periodic limb movements in sleep are followed by increases in EEG activity, blood pressure, and heart rate during sleep

Purpose

Periodic limb movements in sleep (PLMS) are related to arousal, sympathetic activation, and increases in blood pressure (BP), but whether they are part of the arousal process or causative of it is unclear. Our objective was to assess the temporal distribution of arousal-related measures around PLMS.

Methods

Polysomnographic recordings of six patients with restless legs syndrome were analyzed. We analyzed 15 PLMS, plus three 5-s epochs before and after each movement, for every patient. Mean values per epoch of blood pressure (BP), heart rate (HR), and electroencephalographic (EEG) power were calculated. For each patient, six 5-s epochs of undisturbed sleep were analyzed as controls.

Results

Alpha + beta EEG power, systolic BP, and HR were significantly increased following PLMS. The EEG power and HR increases were noticed in the first epoch after PLMS, whereas that of systolic BP was observed in the second and third epochs following a PLMS. No significant changes occurred in the epochs of undisturbed sleep.

Conclusions

The results suggest that PLMS are followed by arousal-related nervous system events. Given the high frequency of PLMS throughout the night, they could be a potential risk factor for nocturnal arrhythmias and hypertension, in addition to causing sleep deprivation.

The Comparisons of Cerebral Hemodynamics Induced by Obstructive Sleep Apnea with Arousal and Periodic Limb Movement with Arousal: A Pilot NIRS Study

Obstructive sleep apnea syndrome (OSA) and restless legs syndrome (RLS) with periodic limb movement during sleep (PLMS) are two sleep disorders characterized by repetitive respiratory or movement events associated with cortical arousals. We compared the cerebral hemodynamic changes linked to periodic apneas/hypopneas with arousals (AHA) in four OSA-patients with periodic limb movements (PLMA) with arousals in four patients with RLS-PLMS using near-infrared spectroscopy (NIRS). AHA induced homogenous pattern of periodic fluctuations in oxygenated (HbO2) and deoxygenated (HHb) hemoglobin, i.e., the decrease of HbO2 was accompanied by an increase of HHb during the respiratory event and resolved to reverse pattern when cortical arousal started. Blood volume (BV) showed the same pattern as HHb but with relative smaller amplitude in most of the AHA events.These changing patterns were significant as Wilcoxon signed-rank tests gave p < 0.001 when comparing the area under the curve of these hemodynamic parameters to zero. By contrast, in PLMA limb movements induced periodic increments in HbO2 and BV (Wilcoxon signed-rank tests, p < 0.001), but HHb changed more heterogeneously even during the events coming from the same patient. Heart rate (HR) also showed different patterns between AHA and PLMA. It significantly decreased during the respiratory event (Wilcoxon signed-rank test, p < 0.001) and then increased after the occurrence of cortical arousal (Wilcoxon signed-rank test, p < 0.001); while in PLMA HR first increased preceding the occurrence of cortical arousal (Wilcoxon signed-rank test, p < 0.001) and then decreased. The results of this preliminary study show that both AHA and PLMA induce changes in cerebral hemodynamics. The occurrence of cortical arousal is accompanied by increased HR in both events, but by different BV changes (i.e., decreased/increased BV in AHA/PLMA, respectively). HR changes may partially account for the increased cerebral hemodynamics during PLMA; whereas in AHA probable vasodilatation mediated by hypoxia/hypercapnia is more crucial for the post-arousal hemodynamics. The differences between changes of cerebral hemodynamics and HR may indicate different pathological mechanisms behind these two sleep disorder events.

A Data-Driven Analysis of the Rules Defining Bilateral Leg Movements during Sleep

STUDY OBJECTIVES

The aim of this study was to describe and analyze the association between bilateral leg movements (LMs) during sleep in subjects with restless legs syndrome (RLS), in order to eventually support or challenge the current scoring rules defining bilateral LMs.

METHODS

Polysomnographic recordings of 100 untreated patients with RLS (57 women and 43 males, mean age 57 y) were included. In each recording, we selected as reference all LMs that occurred during sleep and that were separated from another ipsilateral LM by at least 10 sec of EMG inactivity. For each reference LM and an evaluation interval from 5 sec before the onset to 5 sec after the offset of the reference LM, we evaluated (1) the presence or absence of contralateral leg movement activity and (2) the distribution of the onset-to-onset and (3) the offset-to-onset differences between bilateral LMs.

RESULTS

We selected a mean of 368 (± 222 standard deviation [SD]) reference LMs per subject. For 42% (± 22%) of the reference LMs no contralateral leg movement activity was observed within the evaluation interval. In 55% (± 22%) exactly one and in 3% (± 2%) more than one contralateral LM was observed. A further evaluation of events where exactly one contralateral LM was observed showed that in most (1) the two LMs were overlapping (93% ± 9% SD) and (2) were classified as bilateral according to the World Association of Sleep Medicine and the International Restless Legs Syndrome Study Group (WASM/ IRLSSG) (96% ± 6% SD) and (3) the American Academy of Sleep Medicine scoring rules (99% ± 2% SD). Although there was a systematic and statistically significant difference in standard LM indices during sleep based on the two different definitions of bilateral LMs, the size of the difference was not clinically meaningful (maximum individual, absolute difference in LM indices ± 2.5). In addition, we found that the duration of LMs within bilateral LM pairs was longer compared to monolateral LMs and that the duration of the single LMs in bilateral LM pairs tended to correlate.

CONCLUSIONS

The results of this study indicate that the two current standard scoring rules for the definition of bilateral LMs during sleep provide largely corresponding classifications in subjects with RLS and, in a clinical context, can be considered to be equivalent.

Prevalence and associations of respiratory-related leg movements: the MrOS sleep study

OBJECTIVES

Obstructive respiratory events often terminate with an associated respiratory-related leg movement (RRLM). Such leg movements are not scored as periodic leg movements (periodic limb movements during sleep, PLMS), although the criteria for distinguishing RRLM from PLMS differ between the American Academy of Sleep Medicine (AASM) and the World Association of Sleep Medicine (WASM)/ International Restless Legs Syndrome Study Group (IRLSSG) scoring manuals. Such LMs may be clinically significant in patients with obstructive sleep apnea (OSA). The prevalence and correlation of RRLM in men with OSA were examined.

METHODS

A case-control sample of 575 men was selected from all men with an apnea-hypopnea index (AHI, ≥3% desaturation criteria) ≥ 10 and good data from piezoelectric leg movement sensors at the first in-home sleep study in the MrOS cohort (mean age = 76.8 years). Sleep studies were rescored for RRLMs using five different RRLM definitions varying in both latency of leg movement onset from respiratory event termination and duration of the leg movement. The quartile of RRLM% (the number of RRLM/the number of hypopneas + apneas) was derived.

RESULTS

The nonparametric densities of RRLM% were most influenced by alterations in the latency rather than the duration of the LM. The most liberal RRLM definition (latency 0-5 s, duration 0.5-10 s) led to a median RRLM% of 23.4 (interquartile range 12.41, 37.12) in this sample. The average AHI and arousal index increased as the quartile of RRLM% increased, as well as the prevalence of chronic obstructive pulmonary disease (COPD). The prevalence of those with a history of hypertension decreased as RRLM% increased. The non-Caucasian race was associated with lower RRLM%.

CONCLUSION

Within an elderly sample with moderate to severe OSA, piezoelectric-defined RRLM% is associated with a number of sleep-related and demographic factors. Further study of the optimal definition, predictors, and consequences of RRLM is warranted.

The Role of Periodic Limb Movements During Sleep in Restless Legs Syndrome: A Selective Update

Periodic leg movements during sleep (PLMS) are a highly active research topic and accumulating recent evidence has led to reevaluation of key aspects on the role of PLMS in restless legs syndrome (RLS). This article summarizes the recent developments in 3 areas: the relationship of PLMS to cortical arousals in patients with RLS, the differential effect of dopaminergic and non-dopaminergic treatment on PLMS, and the possible emergence of PLMS as a sleep-related cardiovascular risk factor.

Basal sympathetic predominance in periodic limb movements in sleep with obstructive sleep apnea

Because the impact of periodic limb movements in sleep (PLMS) is controversial, no consensus has been reached on the therapeutic strategy for PLMS in obstructive sleep apnea (OSA). To verify the hypothesis that PLMS is related to a negative impact on the cardiovascular system in OSA patients, this study investigated the basal autonomic regulation by heart rate variability (HRV) analysis. Sixty patients with mild-to-moderate OSA who underwent polysomnography (PSG) and completed sleep questionnaires were analysed retrospectively and divided into the PLMS group (n = 30) and the non-PLMS group (n = 30). Epochs without any sleep events or continuous effects were evaluated using HRV analysis. No significant difference was observed in the demographic data, PSG parameters or sleep questionnaires between the PLMS and non-PLMS groups, except for age. Patients in the PLMS group had significantly lower normalized high frequency (n-HF), high frequency (HF), square root of the mean of the sum of the squares of difference between adjacent NN intervals (RMSSD) and standard deviation of all normal to normal intervals index (SDNN-I), but had a higher normalized low frequency (n-LF) and LF/HF ratio. There was no significant difference in the Epworth Sleepiness Scale, the Pittsburgh Sleep Quality Index, the Short-Form 36 and the Hospital Anxiety and Depression Scale between the two groups. After adjustment for confounding variables, PLMS remained an independent predictor of n-LF (β = 0.0901, P = 0.0081), LF/HF ratio (β = 0.5351, P = 0.0361), RMSSD (β = -20.1620, P = 0.0455) and n-HF (β = -0.0886, P = 0.0134). In conclusion, PLMS is related independently to basal sympathetic predominance and has a potentially negative impact on the cardiovascular system of OSA patients.

An Evidence-based Analysis of the Association between Periodic Leg Movements during Sleep and Arousals in Restless Legs Syndrome

STUDY OBJECTIVES

To analyze statistically the association between periodic leg movements during sleep (PLMS) and arousals, in order to eventually support or challenge the current scoring rules and to further understand their reciprocal influence.

SETTING

Sleep research center.

PATIENTS

Twenty untreated consecutive patients with restless legs syndrome (RLS) (13 women and 7 males, mean age 60.9 y).

METHODS

In each recording, we selected all PLMS/arousal pairs that met the following inclusion criteria: (a) PLMS events that were separated from another PLMS event (preceding or following) by at least 10 s of EMG inactivity; (b) arousal events separated from another arousal event (preceding or following) by at least 10 s of stable EEG baseline activity; (c) PLMS/arousal pairs were then selected among events identified according to the previous two criteria, when PLMS and arousals were separated (offset-to-onset) by no more than 10 s, regardless of which was first.

MEASUREMENTS AND RESULTS

We selected a mean of 46.1 (SD 25.55) PLMS/arousal pairs per subject; in these pairs, average PLMS duration was 3.2 s (0.65) and average arousal duration was 6.5 s (0.92). Within these event pairs, the great majority (on average 98.4%, SD 3.88) was separated by less than 0.5 s (i.e., between the end of one event and the onset of the other, regardless of which was first). Arousal onsets preceded PLMS onset in 41.2% of pairs, while the opposite was true for the remaining 58.8% of pairs. A significant correlation between PLMS duration and arousal duration was also found (r = 0.447, P < 0.000001).

CONCLUSION

The results of this study support the current rule for the definition of the association between periodic leg movements during sleep (PLMS) and arousals. The tight time relationship between PLMS and arousals and their correlated durations seem to indicate that both events might be regulated by a complex mechanism, rather than being connected by a simple reciprocal cause/effect relationship.

Frequent periodic leg movement during sleep is an unrecognized risk factor for progression of atrial fibrillation

Sleep apnea has been recognized as a factor predisposing to atrial fibrillation recurrence and progression. The effect of other sleep-disturbing conditions on atrial fibrillation progression is not known. We sought to determine whether frequent periodic leg movement during sleep is a risk factor for progression of atrial fibrillation. In this retrospective study, patients with atrial fibrillation and a clinical suspicion of restless legs syndrome who were referred for polysomnography were divided into two groups based on severity of periodic leg movement during sleep: frequent (periodic movement index >35/h) and infrequent (≤35/h). Progression of atrial fibrillation to persistent or permanent forms between the two groups was compared using Wilcoxon rank-sum test, chi-square tests and logistic regression analysis. Of 373 patients with atrial fibrillation (77% paroxysmal, 23% persistent), 108 (29%) progressed to persistent or permanent atrial fibrillation during follow-up (median, 33 months; interquartile range, 16-50). Compared to patients with infrequent periodic leg movement during sleep (n=168), patients with frequent periodic leg movement during sleep (n=205) had a higher rate of atrial fibrillation progression (23% vs. 34%; p=0.01). Patients with frequent periodic leg movement during sleep were older and predominantly male; however, there were no significant differences at baseline in clinical factors that promote atrial fibrillation progression between both groups. On multivariate analysis, independent predictors of atrial fibrillation progression were persistent atrial fibrillation at baseline, female gender, hypertension and frequent periodic leg movement during sleep. In patients with frequent periodic leg movement during sleep, dopaminergic therapy for control of leg movements in patients with restless legs syndrome reduced risk of atrial fibrillation progression. Frequent leg movement during sleep in patients with restless legs syndrome is associated with progression of atrial fibrillation to persistent and permanent forms.

Change in heart rate variability precedes the occurrence of periodic leg movements during sleep: an observational study

BACKGROUND

Several reports have described that individual periodic leg movements during sleep (PLMS) activities are associated with autonomic nervous system activity occurring shortly before each PLMS activity. Nevertheless, no study has investigated dynamic changes of autonomic nervous system activity before the onset of PLMS. This study detected changes in heart rate variability (HRV) at the onset of the period with PLMS using complex demodulation method.

METHODS

This study enrolled 14 patients diagnosed as having idiopathic PLMS disorder (PLMD). In periods with and without PLMS during sleep stage 2, HRV-related variables and the spectral power of fluctuation of a high frequency (HF) band (FHFB) were analyzed and compared. The changes of those parameters during transition from the period without PLMS to that with PLMS were explored.

RESULTS

Spectral power in the low frequency (LF) band and very low frequency (VLF) band were higher in the period with PLMS. Additionally, the average frequency in FHFB was higher. The frequency in this band fluctuated during the period with PLMS with remarkable elevation of FHFB. Moreover, spectral powers in FHFB, LF, and VLF were remarkably elevated shortly before the beginning of the period with PLMS (FHFB, -65 s; LF, -53 s; and VLF, -45 s).

CONCLUSIONS

Elevation of sympathetic nervous system activity and mean frequency fluctuation in an HF band can occur several tens of seconds before the period with PLMS. Dynamic changes in the autonomic nervous system activity might be related to the vulnerability to PLMS occurrence during the night.

Periodic Limb Movements during Sleep: A New Sleep-Related Cardiovascular Risk Factor?

In recent years, a growing body of evidence suggests that periodic limb movements during sleep (PLMS) are associated with hypertension, cardiovascular, and cerebrovascular risk. However, several non-mutually exclusive mechanisms may determine a higher cardiovascular risk in patients with PLMS and the link between the two remains controversial. Prospective data are scant and the temporal relationship between PLMS and acute vascular events is difficult to ascertain because although PLMS may lead to acute vascular events such as stroke, stroke may also give rise to PLMS. This article describes the clinical and polygraphic features of PLMS and examines the literature evidence linking PLMS with an increased risk for the development and progression of cardiovascular diseases, discussing the possible pathways of this association.

Excessive daytime sleepiness in sleep disorders

Excessive daytime sleepiness is a significant public health problem, with prevalence in the community estimated to be as high as 18%. Sleepiness is caused by abnormal sleep quantity or sleep quality. Amongst others, multiple neurological, psychological, cardiac and pulmonary disorders may contribute. Risk factors for excessive sleepiness include obesity, depression, extremes of age and insufficient sleep. In the clinical setting, two of the most commonly encountered causes are obstructive sleep apnoea and periodic limb movement disorder. There is continuing discussion of the mechanisms by which these disorders cause daytime symptoms, with intermittent nocturnal hypoxia, sleep fragmentation and autonomic dysregulation identified as important factors. The increased prevalence of obstructive sleep apnoea in obese subjects does not fully account for the increased rates of daytime sleepiness in this population and there is evidence to suggest that it is caused by metabolic factors and chronic inflammation in obese individuals. Sleepiness is also more common in those reporting symptoms of depression or anxiety disorders and significantly impacts their quality of life. Clinicians should be aware of factors which put their patients at high risk of daytime sleepiness, as it is a debilitating and potentially dangerous symptom with medico-legal implications. Treatment option should address underlying contributors and promote sleep quantity and sleep quality by ensuring good sleep hygiene. However, stimulant medication may be indicated in some cases to allow for more normal daytime functioning.

Periodic limb movements and heart rate changes

Periodic limb movements (PLM) during sleep are believed to be under the control of the sympathetic nervous system and may cause interrupted sleep and daytime sleepiness. The present case highlights the close relationship between PLM and significant heart rate changes independent of the presence of arousals. Thus, in addition to the already known deleterious effect on sleep continuity, moderate-severe PLM may also affect cardiovascular health.

EEG delta oscillations as a correlate of basic homeostatic and motivational processes

Functional significance of delta oscillations is not fully understood. One way to approach this question would be from an evolutionary perspective. Delta oscillations dominate the EEG of waking reptiles. In humans, they are prominent only in early developmental stages and during slow-wave sleep. Increase of delta power has been documented in a wide array of developmental disorders and pathological conditions. Considerable evidence on the association between delta waves and autonomic and metabolic processes hints that they may be involved in integration of cerebral activity with homeostatic processes. Much evidence suggests the involvement of delta oscillations in motivation. They increase during hunger, sexual arousal, and in substance users. They also increase during panic attacks and sustained pain. In cognitive domain, they are implicated in attention, salience detection, and subliminal perception. This evidence shows that delta oscillations are associated with evolutionary old basic processes, which in waking adults are overshadowed by more advanced processes associated with higher frequency oscillations. The former processes rise in activity, however, when the latter are dysfunctional.

Periodic Limbic Movement Disorder during Sleep as Diabetes-Related Syndrome? A Polysomnographic Study

Introduction. Periodic limb movements during sleep (PLMs) is common in the elderly. When quality-of-life drops due to sleep disturbances, we speak about periodic limb movement disorder during sleep (PLMD). Another similar disorder, restless legs syndrome (RLS), is considered to be related to diabetes; RLS and PLMDs are genetically related. Our aim was to detect PLMDs in a population of diabetic patients and identify them as possible hallmarks of these autonomic disorders. Material and Methods. We selected 41 type-2 diabetics with no sleep comorbidity, and compared them with 38 healthy matched volunteers. All participants underwent the Epworth Sleepiness Scale (ESS) and polysomnography (PSG). A periodic limb movement (PLM) index >5, that is, the higher number of PLMs/sleep hour for the entire night, was considered as abnormal. Results. Diabetics showed lower sleep efficiency than controls on the ESS, lower proportions of REM and non-REM sleep, and higher arousal and PLM indexes, as assessed through PSG. PLMDs were diagnosed in 13 of 41 diabetic patients (31%); the latter showed lower sleep efficiency, lower non-REM slow-wave sleep, and increased arousal and PLM indexes. Conclusion. The relationship between PLMs-related sleep fragmentation and endocrine carbohydrate metabolism regulation might be casual or genetically determined. This deserves further investigations.

Prevalence and associated factors of restless legs in a 57-year-old urban population in northern Finland

OBJECTIVE

We examined the prevalence and associated factors of restless legs syndrome (RLS) in a 57-year-old unselected urban population in northern Finland.

METHODS

A health survey was conducted in 2002 that targeted persons born in 1945 and residing in the city of Oulu on 31 December, 2001. Their history of RLS, coronary heart disease (CHD), daytime sleepiness, depressive symptoms and snoring was assessed by means of questionnaires.

RESULTS

Altogether 995 of 1332 eligible subjects (74%) participated (556 women, 439 men). The overall prevalence of RLS > or = 1 per week was 20% in women and 15% in men. In the fitted multiple logistic regression model, RLS was found to be associated with female gender (OR 1.64, 95% CI 0.98-2.72), CHD (OR 2.92, 95% CI 1.18-7.23), daytime sleepiness (OR 2.12, 95% CI 1.32-3.41), moderately elevated (31-45) or high (46-65) Zung sum scores (OR 1.95, 95% CI 1.09-3.48 and OR 3.67, 95% CI 1.71-7.90, respectively), antidepressant medication (OR 2.10, 95% CI 1.06-4.19) and arthropathy (OR 1.69, 95% CI 1.04-2.72). Insufficient evidence was found of an association between RLS and type 2 diabetes or impaired glucose regulation.

CONCLUSIONS

Restless legs syndrome is fairly common in subjects aged 57 years. A particularly strong positive association was observed between RLS and depressive symptoms and CHD.

Ropinirole in restless legs syndrome and periodic limb movement disorder

Restless legs syndrome and periodic limb movement disorder of sleep are now recognized as prevalent, distinct, yet overlapping disorders affecting all age groups. Although delineation of the mechanisms underlying these disorders continues to be the focus of very intense research efforts, it has become apparent that there is a prominent role for dopaminergic agents in the clinical management of these patients. Among the various dopaminergic drugs, ropinirole has undergone relatively intense and critical scrutiny, and appears to provide a safe and efficacious treatment option for patients with these two conditions. The more recent development of a controlled formulation for this drug is likely to yield additional benefits such as improved adherence and reduced fluctuations in daytime and nighttime symptoms. However, there is not enough evidence at this time to support such assumption.

Cardiovascular variability during periodic leg movements in sleep in children

STUDY OBJECTIVES

Periodic leg movements in sleep (PLMS) are episodes of repetitive and stereotypic leg movements occurring during sleep. In adults, research indicates that PLMS affects sleep quality and duration and are associated with a shift to relatively greater sympathetic influence over cardiovascular variables. However, little research has been performed to investigate the effect of PLMS episodes on cardiac autonomic control in children. This study aimed to quantify the effect of PLMS episodes during NREM2 sleep on heart rate variability (HRV) measures of sympathovagal balance in children.

PARTICIPANTS

Overnight polysomnography data from 20 children (7-12 y) referred for assessment of sleep disordered breathing (SDB) were analyzed retrospectively. Ten children with episodes of PLMS were matched for age and SDB severity with a control group of 10 children without PLMS episodes.

RESULTS

The LF/HF ratio was significantly higher in the PLM+ compared with both the PLM- periods from PLMS subjects (P < 0.001) and the periods from the control group (P < 0.001). However, this effect could not be parsimoniously interpreted due to the likelihood that leg movements had a direct effect on the lower frequencies. Analysis of the ratio PLM+ to PLM+ plus PLM- indicated parasympathetic inhibition during periods of periodic leg movement and the onset of individual leg movements were associated with cardiac acceleration followed by a return to pre-movement levels.

CONCLUSION

This study identified vagal inhibition in association with episodes of PLMS in children. Rapid cardiac acceleration occurring concurrently with the onset of individual leg movements also suggested decreased vagal activity associated with the movements.

Periodic limb movements both in non-REM and REM sleep: relationships between cerebral and autonomic activities

OBJECTIVE

To investigate the temporal relationship between cerebral and autonomic activities before and during periodic limb movements in NREM and REM sleep (PLMS).

METHODS

Patterns of EEG, cardiac and muscle activities associated with PLMS were drawn from polysomnographic recordings of 14 outpatients selected for the presence of PLMS both in NREM and REM sleep. PLMS were scored during all sleep stages from tibial EMG. Data from a bipolar EEG channel were analyzed by wavelet transform. Heart rate (HR) was evaluated from the electrocardiogram. EEG, HR and EMG activations were detected as transient increase of signal parameters and examined by analysis of variance and correlation analysis independently in NREM and REM sleep. Homologous parameters in REM and NREM sleep were compared by paired t-test.

RESULTS

The autonomic component, expressed by HR increase, took place before the motor phenomenon both in REM and NREM sleep, but it was significantly earlier during NREM. In NREM sleep, PLM onset was heralded by a significant activation of delta-EEG, followed by a progressive increase of all the other bands. No significant activations of delta EEG were found in REM sleep. HR and EEG activations positively correlated with high frequency EEG activations and negatively (in NREM) with slow frequency ones.

CONCLUSIONS

Our findings suggested a heralding role for delta band only in NREM sleep and for HR during both NREM and REM sleep. Differences in EEG and HR activation between REM and NREM sleep and correlative data suggested a different modulation of the global arousal response.

SIGNIFICANCE

In this study, time-frequency analysis and advanced statistical methods enabled an accurate comparison between brain and autonomic changes associated to PLM in NREM and REM sleep providing indications about interaction between autonomic and slow and fast EEG components of arousal response.

Sleep-associated movement disorders and heart failure

Sleep-associated movement disorders are a broad group of sleep disorders characterized by involuntary movements that may disrupt sleep. Relatively little is known about the clinical consequences of sleep-associated movement disorders on cardiovascular health. Because these disorders manifest mostly during sleep, recognizing a movement disorder can be particularly difficult. Nevertheless, patients can have frequent arousals and suffer from similar sleep deprivation, fragmentation, and autonomic disruption as occurs in sleep-disordered breathing. Subsequently, these disorders may have a serious impact on daytime function and perception of health in patients with chronic heart failure.