Prevalence and clinical profile of restless legs syndrome in Parkinson's disease

Prevalence and clinical profile of patients with restless legs syndrome in Parkinson's disease: A meta-analysis

INTRODUCTION

Restless legs syndrome (RLS) is a sensorimotor disorder of sleep/wake regulation characterized by an urge to move the legs accompanied by a wide range of sensory symptoms, mainly affecting the lower limbs. An increased incidence of RLS has been demonstrated in Parkinson's disease (PD) and has been associated with severe motor and non-motor manifestations. We aimed to provide a reliable estimate of RLS prevalence and the clinical features associated with its occurrence in PD (PD-RLS).

METHODS

We performed a systematic literature search up to January 2024 using PubMed, Scopus, and PsycINFO databases. Articles were included if they provided data on PD patients with or without RLS, and these proportions were used to estimate the prevalence of PD-RLS. Clinical profile associated with PD-RLS was explored by comparing the clinical characteristics of PD patients with and without RLS.

RESULTS

Forty-six studies were included in the meta-analysis. Pooled RLS prevalence was 20 % of a total sample of 6990 PD patients and was associated with female sex, mixed motor phenotype, worse motor disturbances and functional disability, and a wide range of non-motor symptoms such as sleep disorders, cognitive and autonomic dysfunctions, and more severe neuropsychiatric manifestations. Sensitivity analyses indicated significant associations of PD-RLS with variables related to dopaminergic therapy. No association was found with serum ferritin, serum iron and hemoglobin levels.

CONCLUSIONS

The prevalence of PD-RLS exceeds that reported in the general population, suggesting the existence of a relationship between the two disorders. Dopaminergic treatment seems to play an ambivalent role relieving, worsening or "mimicking" RLS manifestations. However, the clinical profile of PD-RLS patients, characterized by a greater severity of non-motor symptoms, also suggests that neurotransmitter systems other than the dopaminergic one are involved in PD-RLS etiology.

Machine Learning Models for Parkinson Disease: Systematic Review

Background

With the increasing availability of data, computing resources, and easier-to-use software libraries, machine learning (ML) is increasingly used in disease detection and prediction, including for Parkinson disease (PD). Despite the large number of studies published every year, very few ML systems have been adopted for real-world use. In particular, a lack of external validity may result in poor performance of these systems in clinical practice. Additional methodological issues in ML design and reporting can also hinder clinical adoption, even for applications that would benefit from such data-driven systems.

Objective

To sample the current ML practices in PD applications, we conducted a systematic review of studies published in 2020 and 2021 that used ML models to diagnose PD or track PD progression.

Methods

We conducted a systematic literature review in accordance with PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines in PubMed between January 2020 and April 2021, using the following exact string: "Parkinson's" AND ("ML" OR "prediction" OR "classification" OR "detection" or "artificial intelligence" OR "AI"). The search resulted in 1085 publications. After a search query and review, we found 113 publications that used ML for the classification or regression-based prediction of PD or PD-related symptoms.

Results

Only 65.5% (74/113) of studies used a holdout test set to avoid potentially inflated accuracies, and approximately half (25/46, 54%) of the studies without a holdout test set did not state this as a potential concern. Surprisingly, 38.9% (44/113) of studies did not report on how or if models were tuned, and an additional 27.4% (31/113) used ad hoc model tuning, which is generally frowned upon in ML model optimization. Only 15% (17/113) of studies performed direct comparisons of results with other models, severely limiting the interpretation of results.

Conclusions

This review highlights the notable limitations of current ML systems and techniques that may contribute to a gap between reported performance in research and the real-life applicability of ML models aiming to detect and predict diseases such as PD.

Animal Approaches to Studying Risk Factors for Parkinson's Disease: A Narrative Review

Despite recent efforts to search for biomarkers for the pre-symptomatic diagnosis of Parkinson's disease (PD), the presence of risk factors, prodromal signs, and family history still support the classification of individuals at risk for this disease. Human epidemiological studies are useful in this search but fail to provide causality. The study of well-known risk factors for PD in animal models can help elucidate mechanisms related to the disease's etiology and contribute to future prevention or treatment approaches. This narrative review aims to discuss animal studies that investigated four of the main risk factors and/or prodromal signs related to PD: advanced age, male sex, sleep alterations, and depression. Different databases were used to search the studies, which were included based on their relevance to the topic. Although still in a reduced number, such studies are of great relevance in the search for evidence that leads to a possible early diagnosis and improvements in methods of prevention and treatment.

Predicting neurodegeneration from sleep related biofluid changes

Sleep-wake disturbances are common in neurodegenerative diseases and may occur years before the clinical diagnosis, potentially either representing an early stage of the disease itself or acting as a pathophysiological driver. Therefore, discovering biomarkers that identify individuals with sleep-wake disturbances who are at risk of developing neurodegenerative diseases will allow early diagnosis and intervention. Given the association between sleep and neurodegeneration, the most frequently analyzed fluid biomarkers in people with sleep-wake disturbances to date include those directly associated with neurodegeneration itself, such as neurofilament light chain, phosphorylated tau, amyloid-beta and alpha-synuclein. Abnormalities in these biomarkers in patients with sleep-wake disturbances are considered as evidence of an underlying neurodegenerative process. Levels of hormonal sleep-related biomarkers such as melatonin, cortisol and orexin are often abnormal in patients with clinical neurodegenerative diseases, but their relationships with the more standard neurodegenerative biomarkers remain unclear. Similarly, it is unclear whether other chronobiological/circadian biomarkers, such as disrupted clock gene expression, are causal factors or a consequence of neurodegeneration. Current data would suggest that a combination of fluid biomarkers may identify sleep-wake disturbances that are most predictive for the risk of developing neurodegenerative disease with more optimal sensitivity and specificity.

Sleep disorders in Lewy body dementia: Mechanisms, clinical relevance, and unanswered questions

In Lewy body dementia (LBD), disturbances of sleep and/or arousal including insomnia, excessive daytime sleepiness, rapid eye movement (REM) sleep behavior disorder, obstructive sleep apnea, and restless leg syndrome are common. These disorders can each exert a significant negative impact on both patient and caregiver quality of life; however, their etiology is poorly understood. Little guidance is available for assessing and managing sleep disorders in LBD, and they remain under-diagnosed and under-treated. This review aims to (1) describe the specific sleep disorders which occur in LBD, considering their putative or potential mechanisms; (2) describe the history and diagnostic process for these disorders in LBD; and (3) summarize current evidence for their management in LBD and consider some of the ongoing and unanswered questions in this field and future research directions.

Restless Legs Syndrome in Parkinson's Disease

BACKGROUND

Restless legs syndrome (RLS) might worsen sleep quality and quality of life in people with Parkinson's disease (PwPD).

OBJECTIVE

The main aim of the present study is to explore the associations between RLS and sleep, quality of life and other non-motor symptoms (NMS) in a sample of PwPD.

METHODS

We compared the clinical features of 131 PwPD with and without RLS, in a cross-sectional study. We used several validated scales for assessment: the International Restless Legs Syndrome Study Group rating scale (IRLS), Parkinson's Disease Sleep Scale version 2 (PDSS-2), Parkinson's Disease Questionnaire (PDQ-39), Non-Motor Symptoms Questionnaire (NMSQ) and International Parkinson and Movement Disorder Society Non-Motor Rating Scale (MDS-NMS).

RESULTS

Thirty-five patients (26.71%) out of the total PwPD met the RLS diagnostic criteria, without significant differences between male (57.14%) and female (42.87%) (p = 0.431). Higher total scores of PDSS-2 were recorded among PwPD + RLS (p < 0.001), suggesting worse sleep quality. Significant correlations were observed between the diagnosis of RLS and some types of pain (especially nocturnal pain), physical fatigue and probable sleep-disordered breathing, according to the MDS-NMSS assessment.

CONCLUSIONS

RLS has a high frequency in PwPD and it requires proper management, considering its consequences on sleep and quality of life.

Association between Inflammatory Bowel Disease and Subsequent Development of Restless Legs Syndrome and Parkinson’s Disease: A Retrospective Cohort Study of 35,988 Primary Care Patients in Germany

Background: In addition to the gastrointestinal symptoms, inflammatory bowel disease (IBD), which includes Crohn’s disease (CD) and ulcerative colitis (UC), is associated with extraintestinal manifestations, including neurological disorders, which are gaining increasing attention due to a recently increased focus on the gut–brain axis. Here we aim to evaluate the association between IBD and restless legs syndrome (RLS) as well as Parkinson’s disease (PD) in a cohort of primary care patients in Germany. Methods: The study included 17,994 individuals with a diagnosis of IBD (7544 with CD and 10,450 with UC) and 17,994 propensity-score-matched individuals without IBD from the Disease Analyzer database (IQVIA). An initial diagnosis of RLS or PD was assessed as a function of IBD. Associations between CD and UC with RLS and PD were analyzed using Cox regression models. Results: During the 10-year observation period, 3.6% of CD patients vs. 1.9% of matched non-IBD pairs (p < 0.001) and 3.2% of UC patients vs. 2.7% of matched pairs (p < 0.001) were diagnosed with RLS. The results were confirmed by Cox regression analysis, which showed a significant association between UC (HR: 1.26; 95% CI: 1.02–1.55) and CD (HR: 1.60; 95% CI: 1.23–2.09) and subsequent RLS. The incidence of PD in IBD patients was not significantly increased. However, we observed a non-significant trend towards a higher incidence of PD in male patients with CD but not UC (HR: 1.55; 95%CI: 0.98–2.45, p = 0.064). Conclusions: The present analysis suggests a significant association between IBD and the subsequent development of RLS. These findings should stimulate further pathophysiological research and may eventually lead to specific screening measures in patients with IBD.

Sleep and circadian rhythms in Parkinson's disease and preclinical models

The use of animals as models of human physiology is, and has been for many years, an indispensable tool for understanding the mechanisms of human disease. In Parkinson's disease, various mouse models form the cornerstone of these investigations. Early models were developed to reflect the traditional histological features and motor symptoms of Parkinson's disease. However, it is important that models accurately encompass important facets of the disease to allow for comprehensive mechanistic understanding and translational significance. Circadian rhythm and sleep issues are tightly correlated to Parkinson's disease, and often arise prior to the presentation of typical motor deficits. It is essential that models used to understand Parkinson's disease reflect these dysfunctions in circadian rhythms and sleep, both to facilitate investigations into mechanistic interplay between sleep and disease, and to assist in the development of circadian rhythm-facing therapeutic treatments. This review describes the extent to which various genetically- and neurotoxically-induced murine models of Parkinson's reflect the sleep and circadian abnormalities of Parkinson's disease observed in the clinic.

Excessive Daytime Sleepiness in Parkinson's Disease

Excessive daytime sleepiness (EDS) is one of the most common sleep disorders in Parkinson's disease (PD). It has attracted much attention due to high morbidity, poor quality of life, increased risk for accidents, obscure mechanisms, comorbidity with PD and limited therapeutic approaches. In this review, we summarize the current literature on epidemiology of EDS in PD to address the discrepancy between subjective and objective measures and clarify the reason for the inconsistent prevalence in previous studies. Besides, we focus on the effects of commonly used antiparkinsonian drugs on EDS and related pharmacological mechanisms to provide evidence for rational clinical medication in sleepy PD patients. More importantly, degeneration of wake-promoting nuclei owing to primary neurodegenerative process of PD is the underlying pathogenesis of EDS. Accordingly, altered wake-promoting nerve nuclei and neurotransmitter systems in PD patients are highlighted to providing clues for identifying EDS-causing targets in the sleep and wake cycles. Future mechanistic studies toward this direction will hopefully advance the development of novel and specific interventions for EDS in PD patients.

The Impact of Subthalamic Deep Brain Stimulation on Restless Legs Syndrome in Parkinson's Disease

INTRODUCTION

The study aimed at evaluating the effect of subthalamic deep brain stimulation (DBS-STN) on restless legs syndrome (RLS) in Parkinson's disease (PD) patients.

MATERIALS AND METHODS

We assessed the presence of RLS before, 6 and 12 months after surgery in 36 patients. Differences between patients with RLS, without RLS, and with remission of RLS in terms of sleep measures (interview and validated questionnaires) and nonmotor symptoms (NMS). Polysomnography (PSG) was performed in 24 patients. Simple and multiple regression models were used to identify potential predictors of RLS outcome after DBS-STN.

RESULTS

Before DBS-STN 14 of the 36 patients (39%) were diagnosed with RLS. DBS-STN resulted in the resolution of RLS in 43% (n = 6) and the emergence of RLS in 2 (9%) patients. During the study, 20 patients remained without RLS and the patients with unremitting RLS (n = 8) experienced alleviation of symptoms. At baseline patients with RLS had higher Non-Motor Symptoms Scale (NMSS) total and sleep domain, Unified Parkinson's Disease Rating Scale (UPDRS) part IV and lower Parkinson's Disease Sleep Scale (PDSS) scores. There were no differences between the groups without and with RLS in terms of PSG recordings.

CONCLUSION

DBS-STN provided relief of symptoms in most of the patients with PD and RLS. We found that RLS was associated with worse subjective sleep quality, more severe NMS, and complications of levodopa therapy. DBS-STN may have direct impact on RLS rather than related indirectly through post-surgery change in medications.

Sleep Disorders in Parkinson Disease

Sleep disorders in Parkinson disease have attracted the attention of clinicians and researchers for decades. Recently, major advances in their clinical characterization, polysomnographic description, pathophysiologic understanding, and treatment took place. Parkinson disease encompasses the whole spectrum of sleep medicine: every category of sleep disorder can be observed in these patients. Video polysomnography frequently is indicated, sometimes followed by multiple sleep latency/maintenance of wakefulness tests. Additional studies may include actigraphy, cardiorespiratory polygraphy, and dim light melatonin assessment. Treatment needs to be specific to the underlying sleep disorder and can include medications and nondrug treatments, for example, behavioral therapy and light therapy.

Sleep Disorders and Cognitive Dysfunctions in Parkinson's Disease: A Meta-Analytic Study

A relationship between sleep disorders and cognitive dysfunctions was reported in Parkinson's Disease (PD), however, some studies did not confirm the link. A meta-analytic study was performed to investigate the relationship between sleep disorders and cognitive dysfunctions, and to clarify the evolution of cognitive status in PD patients with sleep disorders.The systematic literature search was performed up to November 2020 using PubMed, Scopus, and PsycINFO databases. We included studies published in peer-reviewed journals in English providing results about neuropsychological comparison between patients with or without sleep disorders. Meta-analysis on cross-sectional data included 54 studies for REM Sleep Behavior Disorder (RBD), 22 for Excessive Daytime Sleepiness (EDS), 7 for Obstructive Sleep Apnea (OSA), 13 for Restless Legs Syndrome (RLS), and 5 for insomnia, the meta-analysis on longitudinal data included 7 studies.RBD was related to deficits of global cognitive functioning, memory, executive functions, attention/working memory, language, and visuospatial abilities. EDS was associated with deficits of global cognitive functioning and attention and working memory abilities, whereas RLS and OSA were related to global cognitive dysfunction. Moreover, we revealed that PD patients with RBD and those with EDS performed worse than PD patients without sleep disorders at follow-up rather than baseline evaluation. Our results suggest that sleep disorders are associated with cognitive deficits supporting indirectly that these, especially the REM Sleep Behavior Disorder, reflect abnormalities of frontal networks and posterior cortical areas. Sleep disorders in patients with PD seem to also increase the risk for long-term cognitive decline.

Is restless legs syndrome in Parkinson disease patients associated with any specific factor?

BACKGROUND

Restless legs syndrome or Willis-Ekbom disease is a disorder characterized by unpleasant sensations associated with the need to mobilize the lower limbs. In Parkinson disease patients, restless legs syndrome is associated with worse quality of life and excessive sleepiness. Regarding other factors, results of different studies are controversial.

OBJECTIVE

To determine the factors associated with the restless legs syndrome presence in Parkinson disease patients.

METHODS

A cross-sectional study was conducted in 88 consecutive Parkinson disease patients from the outpatient clinic for 21 months. Participants underwent a clinical interview, assessment based on standardized scales (Epworth Sleepiness Scale, Parkinson Disease Questionnaire - 39, Pittsburgh Sleep Quality Index, International Restless Legs Syndrome Study Group rating scale), and video-polysomnography.

RESULTS

Out of the 88 participants, 25 had restless legs syndrome. In the multivariate analysis, restless legs syndrome in Parkinson disease has been associated with the symptom of smell loss and quality of sleep and life. In the univariate analysis, restless legs syndrome in Parkinson disease has occurred more frequently in women with higher frequency of insomnia, constipation, and anosmia than in the group without restless legs syndrome.

CONCLUSION

Restless legs syndrome is a prevalent condition in patients with Parkinson disease and is associated with specific characteristics in this group of patients.

[Restless legs syndrome in Parkinson's disease]

Disturbances in sleep and wakefulness are important symptoms of Parkinson's disease (PD) and are associated with negative effects on patients' quality of life. The analysis of literature on the relationship between RLS and PD revealed three main hypotheses explaining the relatively high incidence of RLS in PD: (1) RLS can be considered as an early (prodromal) manifestation or a predictor of PD that can outpace its main symptoms by several years (by analogy with conduct disorder during sleep with REM); (2) the high incidence of RLS in the advanced stage of PD may be associated with augmentation of previously latent RLS symptoms during prolonged dopaminergic therapy of PD; (3) a significant proportion of RLS cases in PD patients are not «classical» RLS, but represent, for example, manifestations of motor or non-motor fluctuations or a special form of stereotypy in the legs. Further research is needed to determine if any of these statements are true.

Does restless legs syndrome impact cognitive function via sleep quality in adults with Parkinson's disease?

Purpose: Restless legs syndrome (RLS) is a sleep disorder that results in sleep dysfunction. Sleep disruption can have profound negative consequences in adults with Parkinson's disease (PD), potentially including cognitive dysfunction. This study examined the relationships among RLS, cognition, and sleep quality in persons with PD.Materials and methods: Participants (N = 79) with idiopathic PD completed six questionnaires evaluating RLS, sleep quality, daytime sleepiness, global cognitive function, sleep apnea risk, and depression. Participants were further examined for body mass index composition and motor symptom severity (MDS-UPDRS Part III).Results: Persons with RLS (n = 25) had significantly worse cognitive function (p = 0.035, d = -0.56) and sleep quality (p < 0.0001, d = -1.19), and more daytime sleepiness (p = 0.009, d = 0.67) than those without RLS (n = 54). Cognitive function was not significantly correlated with sleep quality (rs = 0.113) or daytime sleepiness (rs = -0.001). The association between RLS and cognition was not attenuated by controlling for sleep quality or daytime sleepiness.Conclusions: This study is unique as it is the first to consider the possibility that RLS in PD may be associated with cognitive deficits through a pathway involving sleep quality. Persons with RLS and PD have greater deficits in both sleep quality and cognitive function than individuals without RLS; however, cognitive dysfunction among those with PD and RLS in this sample is not accounted for by sleep quality.

Sleep in Parkinson's disease

Sleep disturbances are common in Parkinson's disease and comprise the entire spectrum of sleep disorders. On the one hand regulation of sleep and wakefulness is affected in Parkinson's disease, leading to the development of disorders, such as insomnia and daytime sleepiness. While on the other hand control of motor activity during sleep is impaired, with subsequent manifestation of parasomnias (mainly REM sleep behavior disorders, but also, albeit more rarely, sleepwalking, and overlap parasomnia). Restless legs syndrome has been reported to be frequent in patients with Parkinson's disease, although there is no consensus on whether it is more frequent in Parkinson's disease than in the general population. The same is true for sleep-related breathing disorders. Regarding the diagnosis of sleep disorders in patients with Parkinson's disease, one of the main challenges is correctly identifying excessive daytime sleepiness as there are many potential confounding factors, for example it is necessary to distinguish sleep-related breathing disorders from medication effects, and to distinguish restless legs syndrome from the concomitant presence of potential mimics specific to Parkinson's disease, such as akathisia, nocturnal leg cramps, nocturnal hypokinesia, early morning dystonia, etc. The correct diagnosis of REM sleep behavior disorder is also not always easy, and video-polysomnography should be performed in order to exclude mimic-like movements at the end of sleep apneas or violent periodic leg movements of sleep. These aspects and specific considerations about diagnosis and treatment of sleep disorders in patients with Parkinson's disease will be reviewed.

The Parkinson's disease and restless legs syndrome/Willis-Ekbom disorder link: evidences, biases and clinical relevance

Parkinson's disease (PD) and restless legs syndrome/Willis-Ekbom disorder (RLS/WED) are relatively common diseases in the realm of movement disorders. The fact that both may, as expected, co-occur and typically share a similar remarkable response to dopaminergic treatment raised the interest in exploration of additional shared features that throughout the years cruised fields as diverse as phenomenology, epidemiology, genetics, pathology, and clinical studies. In this review, we describe and critically examine the evidence and biases of a conceivable overlap of these two disorders, trying to shed light onto two main sources of confusion: (1) are PD and RLS/WED reciprocal risk factors? and (2) what are the main mimics of RLS/WED in PD?

Genetic risk of Parkinson disease and progression:: An analysis of 13 longitudinal cohorts

OBJECTIVE

To determine if any association between previously identified alleles that confer risk for Parkinson disease and variables measuring disease progression.

METHODS

We evaluated the association between 31 risk variants and variables measuring disease progression. A total of 23,423 visits by 4,307 patients of European ancestry from 13 longitudinal cohorts in Europe, North America, and Australia were analyzed.

RESULTS

We confirmed the importance of GBA on phenotypes. GBA variants were associated with the development of daytime sleepiness (p.N370S: hazard ratio [HR] 3.28 [1.69-6.34]) and possible REM sleep behavior (p.T408M: odds ratio 6.48 [2.04-20.60]). We also replicated previously reported associations of GBA variants with motor/cognitive declines. The other genotype-phenotype associations include an intergenic variant near LRRK2 and the faster development of motor symptom (Hoehn and Yahr scale 3.0 HR 1.33 [1.16-1.52] for the C allele of rs76904798) and an intronic variant in PMVK and the development of wearing-off effects (HR 1.66 [1.19-2.31] for the C allele of rs114138760). Age at onset was associated with TMEM175 variant p.M393T (-0.72 [-1.21 to -0.23] in years), the C allele of rs199347 (intronic region of GPNMB, 0.70 [0.27-1.14]), and G allele of rs1106180 (intronic region of CCDC62, 0.62 [0.21-1.03]).

CONCLUSIONS

This study provides evidence that alleles associated with Parkinson disease risk, in particular GBA variants, also contribute to the heterogeneity of multiple motor and nonmotor aspects. Accounting for genetic variability will be a useful factor in understanding disease course and in minimizing heterogeneity in clinical trials.

Probable RBD Associates with the Development of RLS in Parkinson's Disease: A Cross-Sectional Study

Objectives

We aimed to investigate the prevalence of restless leg syndrome (RLS) and exploring the contributing factors that affect the development of RLS in Parkinson's disease (PD) patients.

Methods

A cross-sectional study was conducted consisting of 178 consecutive PD patients from our hospital between October 2015 and August 2016. We divided the participants into two groups, which were PD with RLS and PD with non-RLS. Then, we recorded their demographics and clinical data to draw a comparison between PD with RLS and PD with non-RLS.

Results

23 (12.92%) were diagnosed with RLS among all the enrolled PD patients. Unified Parkinson's Disease Rating Scale III (UPDRS III) and Hamilton Depression Scale (HAMD) scores, probable rapid eye movement sleep behavior disorder (PRBD), and daily levodopa equivalent dose (LED) in the PD with the RLS group were significantly different from those in the PD with the non-RLS group. Daily LED and the scores of UPDRS III and HAMD in PD patients with RLS were all higher than those in PD patients with non-RLS. PRBD, daily LED, and HAMD scores were significantly independent factors contributing to the development of RLS (OR = 4.678, 95% CI 1.372~15.944, P = 0.014; OR = 1.003, 95% CI 1.001~1.005, P = 0.019; OR = 1.094, 95% CI 1.002~1.193, P = 0.045). The severity of RLS was positively correlated with the duration of PD and daily LED (r = 0.438, P = 0.036; r = 0.637, P = 0.001).

Conclusion

PRBD existence, daily LED, and HAMD scores are independent factors for developing RLS in PD patients. PRBD existence is firstly proposed as an independent factor in developing RLS among PD patients. RLS severity in PD patients are positively associated with the duration of PD and daily LED.

Restless Legs Syndrome and Parkinson Disease: A Causal Relationship Between the Two Disorders?

Restless Legs Syndrome/Willis-Ekbom Disease (RLS/WED) is a common sleep related movement disorder that can be idiopathic or occurs in comorbidity with other medical conditions such as polyneuropathy, iron deficiency anemia, multiple sclerosis, hypertension and cardiovascular diseases. In recent years, a growing body of literature investigated the association between RLS/WED and Parkinson's Disease (PD). Several questions regarding the comorbidity between these two disorders are still unanswered. If the insurgence of RLS/WED may precede the onset of PD, or if RLS/WED could represent a secondary condition of PD and if impaired dopaminergic pathway may represent a bridge between these two conditions are still debatable issues. In this review, we critically discuss the relationship between RLS/WED and PD by reviewing cross sectional and longitudinal studies, as well as the role of dopamine in these disorders. A twofold interpretation have to be taken into account: dopaminergic therapy may have a crucial role in the development of RLS/WED in PD patients or RLS/WED can be conceived as an early manifestation of PD rather than a risk factor. Several studies showed a high prevalence of RLS/WED in PD patients and several findings related to dopaminergic and iron alterations in both disorders, however up to now it is difficult to find a point of agreement between studies. A greater number of systematic and strongly controlled longitudinal studies as well as basic pathophysiological investigations particularly in RLS/WED are needed to clarify this complex relationship.

An overview of sleep and circadian dysfunction in Parkinson's disease

Sleep and circadian alterations are amongst the very first symptoms experienced in Parkinson's disease, and sleep alterations are present in the majority of patients with overt clinical manifestation of Parkinson's disease. However, the magnitude of sleep and circadian dysfunction in Parkinson's disease, and its influence on the pathophysiology of Parkinson's disease remains often unclear and a matter of debate. In particular, the confounding influences of dopaminergic therapy on sleep and circadian dysfunction are a major challenge, and need to be more carefully addressed in clinical studies. The scope of this narrative review is to summarise the current knowledge around both sleep and circadian alterations in Parkinson's disease. We provide an overview on the frequency of excessive daytime sleepiness, insomnia, restless legs, obstructive apnea and nocturia in Parkinson's disease, as well as addressing sleep structure, rapid eye movement sleep behaviour disorder and circadian features in Parkinson's disease. Sleep and circadian disorders have been linked to pathological conditions that are often co-morbid in Parkinson's disease, including cognitive decline, memory impairment and neurodegeneration. Therefore, targeting sleep and circadian alterations could be one of the earliest and most promising opportunities to slow disease progression. We hope that this review will contribute to advance the discussion and inform new research efforts to progress our knowledge in this field.

Association of Restless Legs Syndrome With Incident Parkinson's Disease

Study Objectives

The association between restless legs syndrome (RLS) and Parkinson's disease (PD) has been extensively studied with inconclusive results; therefore, we prospectively examined the associations of the presence of RLS with development of incident PD.

Methods

From a nationally representative prospective cohort of almost 3.5 million US veterans (age: 60 ± 14 years, 93% male, median follow-up time of 7.8 years [interquartile range: 6.4-8.4 years]), we created a propensity-matched cohort of 100882 PD-free patients and examined the association between prevalent RLS and incident PD. This association was also assessed in the entire cohort. Associations were examined using Cox models.

Results

There were 68 incident PD events (0.13%, incidence rate 1.87 [1.48-2.37]/10000 patient-years) in the RLS-negative group, and 185 incident PD events (0.37%, incidence rate 4.72 [4.09-5.45]/10000 patient-years) in the RLS-positive group in the propensity-matched cohort. Prevalent RLS was associated with more than twofold higher risk of incident PD (hazard ratio [HR]: 2.57, 95% confidence interval [CI]: 1.95-3.39) compared to RLS-negative patients. Qualitatively similar results were found when we examined the entire 3.5 million cohort: Prevalent RLS was associated with more than twofold higher risk of incident PD (multivariable adjusted HR: 2.81, 95%CI: 2.41-3.27).

Conclusion

RLS and PD share common risk factors. In this large cohort of US veterans, we found that prevalent RLS is associated with higher risk of incident PD during 8 years of follow-up, suggesting that RLS could be an early clinical feature of incident PD.

A systematic review of the literature on disorders of sleep and wakefulness in Parkinson's disease from 2005 to 2015

Sleep disorders are among the most common non-motor manifestations in Parkinson's disease (PD) and have a significant negative impact on quality of life. While sleep disorders in PD share most characteristics with those that occur in the general population, there are several considerations specific to this patient population regarding diagnosis, management, and implications. The available research on these disorders is expanding rapidly, but many questions remain unanswered. We thus conducted a systematic review of the literature published from 2005 to 2015 on the following disorders of sleep and wakefulness in PD: REM sleep behavior disorder, insomnia, nocturia, restless legs syndrome and periodic limb movements, sleep disordered breathing, excessive daytime sleepiness, and circadian rhythm disorders. We discuss the epidemiology, etiology, clinical implications, associated features, evaluation measures, and management of these disorders. The influence on sleep of medications used in the treatment of motor and non-motor symptoms of PD is detailed. Additionally, we suggest areas in need of further research.

SLEEP AND CIRCADIAN RHYTHM DISORDERS IN PARKINSON'S DISEASE

Purpose of review

Sleep disorders are among the most challenging non-motor features of Parkinson's disease (PD) and significantly affect quality of life. Research in this field has gained recent interest among clinicians and scientists and is rapidly evolving. This review is dedicated to sleep and circadian dysfunction associated with PD.

Recent findings

Most primary sleep disorders may co-exist with PD; majority of these disorders have unique features when expressed in the PD population.

Summary

We discuss the specific considerations related to the common sleep problems in Parkinson's disease including insomnia, rapid eye movement sleep behavior disorder, restless legs syndrome, sleep disordered breathing, excessive daytime sleepiness and circadian rhythm disorders. Within each of these sleep disorders, we present updated definitions, epidemiology, etiology, diagnosis, clinical implications and management. Furthermore, areas of potential interest for further research are outlined.

Treatment of Sleep Dysfunction in Parkinson's Disease

OPINION STATEMENT

Impaired sleep and alertness affect the majority of Parkinson's disease (PD) patients, negatively impacting safety and quality of life. The etiology of impaired sleep-wake cycle in PD is multifactorial and encompasses medication side effects, nocturnal PD motor symptoms, and presence of co-existent sleep and neuropsychiatric disorders. The primary neurodegenerative process of PD involves brain regions that regulate the sleep-wake cycle, such as brainstem and hypothalamic nuclei. Sleep disorders in PD include insomnia, REM sleep behavior disorder (RBD), sleep disordered breathing (SDB), restless legs syndrome (RLS), and circadian disruption. Despite its high prevalence in the PD population, there is a paucity of clinical studies that have investigated treatment of sleep dysfunction associated with PD. Therefore, we aim to review available evidence and outline treatment strategies for improvement of disorders of sleep and wakefulness in PD patients. Evidence supporting the efficacy of pharmacological and non-pharmacological treatment strategies in PD is limited. There is thus a great need but also opportunity for development of well-designed clinical trials for impaired sleep and alertness in PD. Providing education about sleep hygiene and strategies for its implementation represents the initial step in management. Prompt diagnosis and treatment of co-existent primary sleep and psychiatric disorders are critical, as this may significantly improve sleep and alertness. While the optimal treatment for insomnia in PD has not been established, available strategies include cognitive-behavioral therapy, medications with soporific properties, and light therapy. Safety measures, clonazepam, and melatonin are the mainstay of treatment for RBD. Continuous positive airway pressure is an effective treatment for SDB in PD. The treatment algorithm for RLS associated with PD mirrors that used for idiopathic RLS. Circadian disruption has emerged as an important etiology of impaired sleep-wake cycles in PD, and circadian-based interventions hold promise for novel treatment approaches.

A Four-Year Longitudinal Study on Restless Legs Syndrome in Parkinson Disease

STUDY OBJECTIVES

Restless legs syndrome (RLS) prevalence estimates range from 0% to 52% in Parkinson disease (PD), but the causal relationship between the two disorders is still debated. The present study aims to evaluate RLS prevalence in de novo PD subjects, its incidence during the first 4 years from diagnosis, and possible relationships with clinical, laboratory, and neuroradiological data.

METHODS

One hundred nine newly diagnosed, drug-naïve PD subjects were evaluated at the time of PD diagnosis, and after 2- and 4-years. RLS diagnosis was performed with the RLS Diagnostic Index at each visit. Motor features, additional non-motor symptoms (NMS), and concomitant dopaminergic and nondopaminergic treatments were also gathered. Moreover, at baseline, 65 subjects were randomly selected to undergo a FP-CIT SPECT to study dopamine transporter availability.

RESULTS

RLS prevalence rose from 4.6% at baseline evaluation to 6.5% after 2 years and to 16.3% after 4 years (P = 0.007). A multinomial logistic stepwise regression model selected NMS Questionnaire items more likely to be associated with RLS at diagnosis (insomnia, OR = 15.555; P = 0.040) and with occurrence of RLS during follow-up (dizziness, OR = 1.153; P = 0.022; and daytime sleepiness; OR = 9.557; P = 0.001), as compared to patients without RLS. Older age was more likely associated to increased RLS occurrence during follow-up in a random effect logistic regression model (OR = 1.187; P = 0.036). A multinomial logistic stepwise model found increased dopaminergic transporter availability of affected caudate and putamen to be more likely associated with RLS presence at diagnosis (n = 5; OR = 75.711; P = 0.077), and RLS occurrence during follow-up (n = 16; OR = 12.004; P = 0.059), respectively, as compared to patients without RLS (n = 88).

CONCLUSIONS

RLS is present since PD diagnosis, and increases in prevalence during the course of PD. PD subjects with RLS have higher age at PD onset, more preserved dopaminergic pathways, and worse sleep and cardiovascular disturbances.

Restless Legs Syndrome and Leg Motor Restlessness in Parkinson's Disease

Sleep disturbances are important nonmotor symptoms in Parkinson's disease (PD) that are associated with a negative impact on quality of life. Restless legs syndrome (RLS), which is characterized by an urge to move the legs accompanied by abnormal leg sensations, can coexist with PD, although the pathophysiology of these disorders appears to be different. RLS and PD both respond favorably to dopaminergic treatment, and several investigators have reported a significant relationship between RLS and PD. Sensory symptoms, pain, motor restlessness, akathisia, and the wearing-off phenomenon observed in PD should be differentiated from RLS. RLS in PD may be confounded by chronic dopaminergic treatment; thus, more studies are needed to investigate RLS in drug-naïve patients with PD. Recently, leg motor restlessness (LMR), which is characterized by an urge to move the legs that does not fulfill the diagnostic criteria for RLS, has been reported to be observed more frequently in de novo patients with PD than in age-matched healthy controls, suggesting that LMR may be a part of sensorimotor symptoms intrinsic to PD. In this paper, we provide an overview of RLS, LMR, and PD and of the relationships among these disorders.

Recognition and treatment of neuropsychiatric disturbances in Parkinson's disease

The non-motor symptoms of Parkinson's disease (PD) have been attracting increasing attention due to their ubiquitous nature and their often devastating effects on the quality of life. Behavioral problems in PD include dementia, depression, apathy, fatigue, anxiety, psychosis, akathisia, personality change, sleep disorders and impulse control disorders. Some of these are intrinsic to the neuropathology while others occur as an interplay between pathology, psychology and pharmacology. While few data exist for guiding therapy, enough is known to guide therapy in a rational manner.

The relationship between sleep and cognition in Parkinson's disease: A meta-analysis

It is well established that sleep disorders have neuropsychological consequences in otherwise healthy people. Studies of night-time sleep problems and cognition in Parkinson's disease (PD), however, paint a mixed picture, with many reporting no relationship between sleep problems and neuropsychological performance. This review aimed to meta-analyse this research and to examine the factors underlying these mixed results. A literature search was conducted of published and unpublished studies, resulting in 16 papers that met inclusion criteria. Data were analysed in the domains of: global cognitive function; memory (general, long-term verbal recognition, long-term verbal recall); and executive function (general, shifting, updating, inhibition, generativity, fluid reasoning). There was a significant effect of sleep on global cognitive function, long-term verbal recall, long-term verbal recognition, shifting, updating, generativity, and fluid reasoning. Although there are effects on memory and executive function associated with poor sleep in PD, the effects were driven by a small number of studies. Numerous methodological issues were identified. Further studies are needed reliably to determine whether disturbed sleep impacts on cognition via mechanisms of hypoxia, hypercapnia, sleep fragmentation, chronic sleep debt or decreased REM and/or slow wave sleep in PD, as this may have important clinical implications.

Restless legs syndrome in patients with Parkinson's disease: a comparative study on prevalence, clinical characteristics, quality of life and nutritional status

BACKGROUND

Restless legs syndrome (RLS) is a common neurological disorder that can coexist with Parkinson's disease (PD). However, the association between these two movement disorders is quite poorly explored and previous findings are controversial in different aspects.

OBJECTIVE

To compare prevalence of RLS in Iranian PD population with a matched control group and to investigate the impact of comorbid RLS on quality of life (QoL), nutritional status, and clinical characteristics in PD population.

METHODS

This study was conducted on 108 individuals with idiopathic PD (IPD) and 424 matched controls. RLS was diagnosed using the International Restless Legs Syndrome Study Group (IRLSSG) criteria. Further assessments were performed on clinical characteristics, PD severity scales, psychiatric features, nutritional status, fatigue, and QoL in PD patients with and without RLS.

RESULTS

Restless legs syndrome was significantly more common among the patients with IPD (14.8%) compared to the controls (7.5%) [OR = 2.1 (95% CI: 1.1-4.0)]. IPD subjects with RLS had significantly higher anxiety score [10.1 (SD = 5.1) vs 5.9 (SD = 5.0); P = 0.003], worse nutritional status [23.7 (SD = 2.7) vs 25.4 (SD = 3.7); P = 0.008], and poorer QoL [26.9 (SD = 13.1) vs 17.0 (SD = 13.2); P = 0.006]. The number of positive answers to the IRLSSG diagnostic criteria had significant direct correlation with unpredictability of the off periods and the presence of symptomatic orthostasis.

CONCLUSIONS

Our study demonstrated a higher prevalence of RLS in patients with PD compared to general population. PD patients with RLS suffer from more anxiety, worse nutritional status, and worse QoL. RLS negatively accompanies with psychiatric problems, emotional behaviors, stigma, and cognitive impairment.

Parkinson's disease and restless legs syndrome

AIMS

Various sleep-related complications are common in Parkinson's disease (PD). The prevalence of restless legs syndrome (RLS) and its association with other symptoms were studied.

METHODS

Altogether, 1,447 Parkinson patients, aged 43-89, participated in a questionnaire study.

RESULTS

The response rate was 59.0% and of these, 68% returned fully answered questionnaires (n = 577). RLS occurred in 20.3% of the PD subjects. In patients with RLS, the symptoms occurred in 81.9% at least once weekly. The degree of severity was moderate in 42.7%, severe in 23.9% and very severe in 15.4%. Daytime sleepiness, fatigue, chronic insomnia, sleep maintenance insomnia, intense dreaming, and low quality of life were more common in patients with RLS than in patients without RLS. The occurrence of early onset RLS (onset ≤ age of 45 years) was 4.2%. The occurrences of late onset (>45 years) drug naïve RLS and late onset RLS (with dopaminergic medication) were 5.4 and 10.4%, respectively.

CONCLUSION

In patients with PD, the early onset of RLS resembles idiopathic RLS with typical gender distribution and familial trait. Late onset of RLS is more common than idiopathic RLS.

Restless legs syndrome in Parkinson's disease

The Restless legs syndrome (RLS) and Parkinson's disease (PD) are two disorders that can co-exist, whether or not they share a common pathophysiology. If, and to what extent RLS and PD share the same pathophysiology, is still under debate. Sleep disturbances are prevalent in PD, and as PD progresses, nocturnal disturbances become even more evident, in association not only with motor symptoms but also with non-motor symptoms. Alertness to, and recognition of, RLS in PD patients with sleep disorders could improve customized treatment and quality of life of these patients. In this article the prevalence of RLS in PD, the clinical profile of RLS in PD, the PD profile of patients with RLS, RLS mimics specifically related to PD and impact of RLS in PD will be reviewed.

Restless legs syndrome: an early clinical feature of Parkinson disease in men

STUDY OBJECTIVE

The association between restless legs syndrome (RLS) and Parkinson disease has been extensively studied, but the temporal relationship between the two remains unclear. We thus conduct the first prospective study to examine the risk of developing Parkinson disease in RLS.

DESIGN

Prospective study from 2002-2010.

SETTING

United States.

PARTICIPANTS

There were 22,999 US male health professionals age 40-75 y enrolled in the Health Professionals Follow-up Study without Parkinson disease, arthritis, or diabetes mellitus at baseline.

MEASUREMENT AND RESULTS

RLS was assessed in 2002 using a set of standardized questions recommended by the International RLS Study Group. Incident Parkinson disease was identified by biennial questionnaires and then confirmed by review of participants' medical records by a movement disorder specialist. We documented 200 incident Parkinson disease cases during 8 y of follow-up. Compared to men without RLS, men with RLS symptoms who had symptoms greater than 15 times/mo had higher risk of Parkinson disease development (adjusted relative risk = 1.47; 95% confidence interval: 0.59, 3.65; P = 0.41). This was statistically significant only for cases diagnosed within 4 y of follow-up (adjusted relative risk = 2.77; 95% confidence interval: 1.08, 7.11; P = 0.03).

CONCLUSION

Severe restless legs syndrome may be an early feature of Parkinson disease.

A long-term prospective follow-up study of incident RLS in the course of chronic DAergic therapy in newly diagnosed untreated patients with Parkinson's disease

It is currently controversial if and in which terms Parkinson's disease (PD) and restless legs syndrome (RLS) are linked in co-morbid association. In a cohort of 106 de novo PD patients (67 male and 39 female, aged 42-83 years), 15 of them developed RLS, which was prospectively assessed at 6-month intervals from the starting of dopamine(DA)ergic therapy. The incidence rate of total RLS was 47 per 1,000 case/person per year and 37 per 1,000 case/person per year after the exclusion of possible "secondary" forms of the disorder (n = 3). These figures are higher than those reported in an incidence study conducted in German general population (Study of Health in Pomerania), in which the method of ascertainment of RLS similar to ours has been used. An incidence rate of total RLS significantly higher than that reported in the above-mentioned study was found in the age ranges 55-64 years and in the age range 45-74 years standardized to European general population 2013  (70 and 53 per 1,000 case/person per year, respectively, p < 0.01). Ten out of 12 patients (83.3 %) developed RLS within 24 months from the starting of DAergic medication (median latency 7.5 months). These findings support the view that sustained DAergic therapy could represent the critical factor inducing an increased incidence of RLS in patients with PD and that the latter disease should be regarded as the condition predisposing to the occurrence of the former and not viceversa as previously hypothesized. The mechanism underlying the increased incidence of RLS remains unclear and deserves further investigation.

No association between neuropathy and restless legs in Parkinson's disease

BACKGROUND

The prevalence of restless legs syndrome (RLS) has been studied extensively in Parkinson's disease (PD), with conflicting findings. More recently, both neuropathy and leg motor restlessness (LMR) have been found to be significantly more prevalent in PD patients than in controls.

AIMS

Our objective was to determine whether RLS or LMR may be secondary to neuropathy, or its currently postulated determinants, cumulative levodopa usage and vitamin B(12) metabolism, in patients with PD.

MATERIALS AND METHODS

We compared prevalence of RLS, LMR and neuropathy in 37 PD patients and 37 age- and gender-matched controls. Correlations between RLS/LMR and neuropathy and symptomatic neuropathy, cumulative levodopa usage and vitamin B(12) levels were ascertained.

RESULTS

RLS prevalence was comparable in PD patients and controls (16.2% vs 10.8%; P = 0.30). LMR was significantly more common in PD patients than in controls (40.5% vs 16.2%; P = 0.038), as was neuropathy (37.8% vs 8.1%; P = 0.005). Neither RLS, nor LMR correlated with neuropathy or symptomatic neuropathy, cumulative levodopa exposure or serum vitamin B(12) levels in patients with PD. There was a non-significant trend for a correlation between LMR and earlier age of onset of PD (P = 0.069).

CONCLUSIONS

RLS and LMR appear unrelated to neuropathy or symptomatic neuropathy, cumulative levodopa usage, or serum vitamin B(12) levels in patients with PD. The occurrence of LMR may relate to the earlier onset of PD, raising the possibility of common pathophysiological mechanisms for PD and RLS, of which LMR may be an early manifestation in some patients.

Restless legs syndrome in Korean patients with drug-naïve Parkinson's disease: a nation-wide study

BACKGROUND

Restless legs syndrome is a common neurologic disorder, and there is increasing evidence for a dopaminergic link between Parkinson's disease and restless legs syndrome. However, most previous studies did not take into account the effects of dopaminergic medication. We conducted a nation-wide, cross-sectional study to determine the prevalence and clinical characteristics of restless legs syndrome in Korean drug-naïve Parkinson's disease patients.

METHODS

One hundred and fifty-one drug-naïve patients with Parkinson's disease were enrolled from 18 centers in South Korea over the course of one year. Clinical profiles of parkinsonism, restless legs syndrome, psychiatric symptoms, and laboratory data were collected. The findings of subjects with and without restless legs syndrome were compared.

RESULTS

The prevalence of restless legs syndrome in drug-naïve patients with Parkinson's disease was 16.5%. Subjects with restless legs syndrome had a higher mean Hoehn and Yahr stage and more severe limb parkinsonism, especially tremor. There was, however, no difference in iron metabolism between patients with and without restless legs syndrome. Analysis demonstrated that Beck's depression inventory score was associated with the severity of restless legs syndrome.

CONCLUSION

Our study demonstrated an increased prevalence of restless leg syndrome in drug-naïve patients with Parkinson's disease than in the general population. Based on the association between parkinsonism and restless legs syndrome, and the unique characteristics of restless legs syndrome in patients with Parkinson's disease, we suggest that the pathophysiology of restless legs syndrome in Parkinson's disease differs from that in patients without Parkinson's disease.