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

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.

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.

Health phenome of Parkinson's patients reveals prominent mood-sleep cluster

Background

Associations between phenotypic traits, environmental exposures, and Parkinson's disease have largely been evaluated one-by-one, piecemeal, and pre-selections. A comprehensive picture of comorbidities, phenotypes, exposures, and polypharmacy characterizing the complexity and heterogeneity of real-world patients presenting to academic movement disorders clinics in the US is missing.

Objectives

To portrait the complexity of features associated with patients with Parkinson's disease in a study of 933 cases and 291 controls enrolled in the Harvard Biomarkers Study.

Methods

The primary analysis evaluated 64 health features for associations with Parkinson's using logistic regression adjusting for age and sex. We adjusted for multiple testing using the false discovery rate (FDR) with £ 0.05 indicating statistical significance. Exploratory analyses examined feature correlation clusters and feature combinations.

Results

Depression (OR = 3.11, 95% CI 2.1 to 4.71), anxiety (OR = 3.31, 95% CI 2.01-5.75), sleep apnea (OR 2.58, 95% CI 1.47-4.92), and restless leg syndrome (RLS; OR 4.12, 95% CI 1.81-12.1) were significantly more common in patients with Parkinson's than in controls adjusting for age and sex with FDR £ 0.05. The prevalence of depression, anxiety, sleep apnea, and RLS were correlated, and these diseases formed part of a larger cluster of mood traits and sleep traits linked to PD. Exposures to pesticides (OR 1.87, 95% CI 1.37-2.6), head trauma (OR 2.33, 95% CI 1.51-3.73), and smoking (OR 0.57, 95% CI 0.43-0.75) were significantly associated with the disease consistent with previous studies. Vitamin supplementation with cholecalciferol (OR 2.18, 95% CI 1.4-3.45) and coenzyme Q10 (OR 2.98, 95% CI 1.89-4.92) was more commonly used by patients than controls. Cumulatively, 43% (398 of 933) of Parkinson's patients had at least one psychiatric or sleep disorder, compared to 21% (60 of 291) of healthy controls.

Conclusions

43% of Parkinson's patients seen at Harvard-affiliated teaching hospitals have depression, anxiety, and disordered sleep. This syndromic cluster of mood and sleep traits may be pathophysiologically linked and clinically important.

A primate nigrostriatal atlas of neuronal vulnerability and resilience in a model of Parkinson's disease

The degenerative process in Parkinson's disease (PD) causes a progressive loss of dopaminergic neurons (DaNs) in the nigrostriatal system. Resolving the differences in neuronal susceptibility warrants an amenable PD model that, in comparison to post-mortem human specimens, controls for environmental and genetic differences in PD pathogenesis. Here we generated high-quality profiles for 250,173 cells from the substantia nigra (SN) and putamen (PT) of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced parkinsonian macaques and matched controls. Our primate model of parkinsonism recapitulates important pathologic features in nature PD and provides an unbiased view of the axis of neuronal vulnerability and resistance. We identified seven molecularly defined subtypes of nigral DaNs which manifested a gradient of vulnerability and were confirmed by fluorescence-activated nuclei sorting. Neuronal resilience was associated with a FOXP2-centered regulatory pathway shared between PD-resistant DaNs and glutamatergic excitatory neurons, as well as between humans and nonhuman primates. We also discovered activation of immune response common to glial cells of SN and PT, indicating concurrently activated pathways in the nigrostriatal system. Our study provides a unique resource to understand the mechanistic connections between neuronal susceptibility and PD pathophysiology, and to facilitate future biomarker discovery and targeted cell therapy.

Probable Parasomnias and Mortality: A Prospective Study in US Men

OBJECTIVE

To examine the association between parasomnias, including rapid eye movement sleep behavior disorder (RBD) and sleep walking (SW), and mortality risk in a large-scale population-based cohort.

METHODS

This prospective cohort study was based on 25,695 participants from the Health Professionals Follow-up Study, a population-based cohort of male health professionals in the United States. Probable SW (pSW) and probable RBD (pRBD) were measured by questions adapted from the Mayo Sleep Questionnaire in 2012. All-cause mortality and cause-specific mortality were ascertained through the national registry, reports by the families, and the postal system from January 1, 2012, through June 30, 2018.

RESULTS

Of the studied population, 223 reported pSW and 2720 reported pRBD. During 6 years of follow-up (2012 to 2018), 4743 mortality cases were documented. The co-occurrence of both probable parasomnias was associated with higher all-cause mortality risk (Ptrend=.008), and the adjusted hazard ratio (HR) of mortality was 1.65 (95% CI, 1.20 to 2.28) compared with participants without either probable parasomnia after adjustment for major lifestyle, sleep, and metabolic risk factors, and chronic diseases. Significant associations were found for mortality attributed to neurodegenerative diseases (adjusted HR for both parasomnias vs none, 4.57; 95% CI, 2.62 to 7.97) and accidents (adjusted HR for both parasomnias vs none, 7.36; 95% CI, 2.95 to 18.4). Having pSW alone was associated with all-cause mortality, and pSW and pRBD were individually associated with mortality attributed to neurodegenerative diseases and accidents too (P<.05 for all).

CONCLUSION

Probable parasomnia was associated with a higher risk of all-cause mortality and mortality attributed to neurodegenerative diseases and accidents.

A genome-wide association study coupled with machine learning approaches to identify influential demographic and genomic factors underlying Parkinson's disease

Background: Despite the recent success of genome-wide association studies (GWAS) in identifying 90 independent risk loci for Parkinson's disease (PD), the genomic underpinning of PD is still largely unknown. At the same time, accurate and reliable predictive models utilizing genomic or demographic features are desired in the clinic for predicting the risk of Parkinson's disease. Methods: To identify influential demographic and genomic factors associated with PD and to further develop predictive models, we utilized demographic data, incorporating 200 variables across 33,473 participants, along with genomic data involving 447,089 SNPs across 8,840 samples, both derived from the Fox Insight online study. We first applied correlation and GWAS analyses to find the top demographic and genomic factors associated with PD, respectively. We further developed and compared a variety of machine learning (ML) models for predicting PD. From the developed ML models, we performed feature importance analysis to reveal the predictability of each demographic or the genomic input feature for PD. Finally, we performed gene set enrichment analysis on our GWAS results to identify PD-associated pathways. Results: In our study, we identified both novel and well-known demographic and genetic factors (along with the enriched pathways) related to PD. In addition, we developed predictive models that performed robustly, with AUC = 0.89 for demographic data and AUC = 0.74 for genomic data. Our GWAS analysis identified several novel and significant variants and gene loci, including three intron variants in LMNA (p-values smaller than 4.0e-21) and one missense variant in SEMA4A (p-value = 1.11e-26). Our feature importance analysis from the PD-predictive ML models highlighted some significant and novel variants from our GWAS analysis (e.g., the intron variant rs1749409 in the RIT1 gene) and helped identify potentially causative variants that were missed by GWAS, such as rs11264300, a missense variant in the gene DCST1, and rs11584630, an intron variant in the gene KCNN3. Conclusion: In summary, by combining a GWAS with advanced machine learning models, we identified both known and novel demographic and genomic factors as well as built well-performing ML models for predicting Parkinson's disease.

An overview of the effects of levodopa and dopaminergic agonists on sleep disorders in Parkinson's disease

Sleep disorders are among the most common nonmotor symptoms in Parkinson's disease and are associated with reduced cognition and health-related quality of life. Disturbed sleep can often present in the prodromal or early stages of this neurodegenerative disease, rendering it crucial to manage and treat these symptoms. Levodopa and dopaminergic agonists are frequently prescribed to treat motor symptoms in Parkinson's disease, and there is increasing interest in how these pharmacological agents affect sleep and their effect on concomitant sleep disturbances and disorders. In this review, we discuss the role of dopamine in regulating the sleep-wake state and the impact of neurodegeneration on sleep. We provide an overview of the effects of levodopa and dopaminergic agonists on sleep architecture, insomnia, excessive daytime sleepiness, sleep-disordered breathing, rapid eye movement sleep behavior disorder, and restless legs syndrome in Parkinson's disease. Levodopa and dopaminergic drugs may have different effects, beneficial or adverse, depending on dosing, method of administration, and differential effects on the different dopamine receptors. Future research in this area should focus on elucidating the specific mechanisms by which these drugs affect sleep in order to better understand the pathophysiology of sleep disorders in Parkinson's disease and aid in developing suitable therapies and treatment regimens.

CITATION

Scanga A, Lafontaine A-L, Kaminska M. An overview of the effects of levodopa and dopaminergic agonists on sleep disorders in Parkinson's disease. J Clin Sleep Med. 2023;19(6):1133-1144.

Widening the Spectrum of Risk Factors, Comorbidities, and Prodromal Features of Parkinson Disease

Importance

The prodromal phase of Parkinson disease (PD) may last for more than 10 years. Recognition of the spectrum and occurrence of risk factors, comorbidities, and prodromal features of PD can increase understanding of the causes and development of the disease and help identify individuals at risk.

Objective

To identify the association of a subsequent diagnosis of PD with a range of risk factors and prodromal features, including lifestyle factors, comorbidities, and potential extracerebral manifestations of PD.

Design, Setting, and Participants

This was a case-control study using insurance claims of outpatient consultations of patients with German statutory health insurance between January 1, 2011, and December 31, 2020. Included were patients with incident diagnosis of PD without a previous diagnosis of parkinsonism or dementia and controls matched 1:2 for age, sex, region, and earliest year of outpatient encounter.

Exposures

Exposures were selected based on previous systematic reviews, case-control and cohort studies reporting on risk factors, comorbidities, and prodromal features of PD.

Main Outcomes and Measures

Previously postulated risk factors and prodromal features of PD, using the International Statistical Classification of Diseases and Related Health Problems, Tenth Revision (ICD-10) coding.

Results

A total of 138 345 patients with incident PD (mean [SD] age, 75.1 [9.8] years; 73 720 male [53.3%]) and 276 690 matched controls (mean [SD] age, 75.1 (9.8) years; 147 440 male [53.3%]) were identified. Study participants were followed up for a mean (SD) of 6.0 (2.0) years. Consistent with previous reports, risk factors and prodromal features associated with PD included traumatic brain injury, odds ratio (OR), 1.62; 95% CI, 1.36-1.92; alcohol misuse, OR, 1.32; 95% CI, 1.21-1.44; hypertension, OR, 1.29; 95% CI, 1.26-1.31; anosmia, OR, 2.16; 95% CI, 1.59-2.93; and parasomnias (including RBD), OR, 1.62; 95% CI, 1.42-1.84. In addition, there were associations with restless legs syndrome (OR, 4.19; 95% CI, 3.91-4.50), sleep apnea (OR, 1.45; 95% CI, 1.37-1.54), epilepsy (OR, 2.26; 95% CI, 2.07-2.46), migraine (OR, 1.21; 95% CI, 1.12-1.29), bipolar disorder (OR, 3.81; 95% CI, 3.11-4.67), and schizophrenia (OR, 4.48; 95% CI, 3.82-5.25). The following diagnoses were also found to be associated with PD: sensory impairments beyond anosmia, such as hearing loss (OR, 1.14; 95% CI, 1.09-1.20) and changes of skin sensation (OR, 1.31; 95% CI, 1.21-1.43). There were also positive associations with skin disorders (eg, seborrheic dermatitis, OR, 1.30; 95% CI, 1.15-1.46; psoriasis, OR, 1.13; 95% CI, 1.05-1.21), gastrointestinal disorders (eg, gastroesophageal reflux, OR, 1.29; 95% CI, 1.25-1.33; gastritis, OR, 1.28; 95% CI, 1.24-1.33), conditions with a potential inflammatory component (eg, seronegative osteoarthritis, OR, 1.21; 95% CI, 1.03-1.43), and diabetes types 1 (OR, 1.32; 95% CI, 1.21-1.43) and 2 (OR, 1.24; 95% CI, 1.20-1.27). Associations even 5 to 10 years before diagnosis included tremor (odds ratio [OR], 4.49; 95% CI, 3.98-5.06), restless legs syndrome (OR, 3.73; 95% CI, 3.39-4.09), bipolar disorder (OR, 3.80; 95% CI, 2.82-5.14), and schizophrenia (OR, 4.00; 95% CI, 3.31-4.85).

Conclusions and Relevance

Results of this case-control study suggest that the associations found between PD and certain risk factors, comorbidities, and prodromal symptoms in a representative population may reflect possible early extrastriatal and extracerebral pathology of PD. This may be due to shared genetic risk with PD, medication exposure, or direct causation, or represent pathophysiologically relevant factors contributing to the pathogenesis of PD.

Restless Legs Symptoms and Periodic Leg Movements in Sleep Among Patients with Parkinson's Disease

BACKGROUND

The association between restless legs syndrome (RLS) and Parkinson's disease (PD) remains controversial, with epidemiologic and descriptive evidence suggesting some potential overlap while mechanistic/genetic studies suggesting relative independence of the conditions.

OBJECTIVE

To examine a known, objectively measured endophenotype for RLS, periodic leg movements (PLMS) in sleep, in patients with PD and relate that objective finding to restless legs symptoms.

METHODS

We performed polysomnography for one (n = 8) or two (n = 67) consecutive nights in 75 PD patients and examined the association of PLMS with restless legs symptoms.

RESULTS

We found no association between restless legs symptoms and PLMS in PD. Prevalence of both was similar to data reported previously in other PD samples.

CONCLUSION

We interpret these results as suggesting that restless legs symptoms in PD patients may represent a different phenomenon and pathophysiology than RLS in the non-PD population.

Longitudinal Studies of Sleep Disturbances in Parkinson's Disease

PURPOSE OF REVIEW

Sleep disorders are among the most common non-motor symptoms in Parkinson's disease (PD). Recent longitudinal studies of sleep in PD have utilized validated sleep questionnaires and video-polysomnography performed over multiple time points. This review summarizes existing longitudinal studies focusing on the prevalence, associations, and changes of sleep disorders in PD over time, as well as the methodologies used in these studies.

RECENT FINDINGS

Fifty-three longitudinal studies of sleep in PD were identified: excessive daytime sleepiness, insomnia, obstructive sleep apnea, rapid eye movement sleep behavior disorder (RBD), restless legs syndrome, and shift work disorder were studied in addition to other studies that had focused on either multiple sleep disorders or broadly on sleep disorders as a whole. The prevalence of sleep disorders increases over time and are associated particularly with non-motor features of disease. RBD is now considered an established prodromal feature of PD, but other sleep disorders do not clearly increase risk of subsequent PD. Further work is necessary to determine if treatment of sleep disorders in PD alters disease symptom and their progression or reduces PD risk. Longitudinal studies of sleep in PD have demonstrated a high prevalence of sleep disorders that are associated with non-motor features of PD which can increase over time. More work is necessary to determine if treatment of sleep disorders can alter the course of PD.

Sleep Disorders and Future Diagnosis of Parkinsonism: A Prospective Study Using the Canadian Longitudinal Study on Aging

BACKGROUND

Earlier detection of parkinsonism, specifically during its prodromal stage, may be key to preventing its progression. Previous studies have produced contradictory results on the association between sleep symptoms and prodromal parkinsonism.

OBJECTIVE

We conducted a prospective study within the Canadian Longitudinal Study on Aging (CLSA) to determine whether self-reported symptoms of insomnia, somnolence, apnea, and restless legs syndrome predate the diagnosis of parkinsonism after three years of follow-up.

METHODS

At baseline, amongst other information, participants completed a questionnaire for difficulty initiating or maintaining sleep, daytime somnolence, snoring or stopping breathing during sleep, and symptoms of restless legs syndrome. After 3 years of follow-up, baseline responses from participants who self-reported a new diagnosis of parkinsonism (cases) were compared to those who did not (controls). For each case, 10 controls were individually matched by age, sex, education, BMI, caffeine, smoking, and alcohol. Binary unconditional logistic regression models were used to estimate the association between sleep symptoms and new-onset parkinsonism, adjusting for age, sex, education, BMI, smoking, alcohol, and caffeine.

RESULTS

We identified 58 incident-parkinsonism cases and 580 matched controls (65.5%male, mean age = 69.60, SD = 8.0). Baseline symptoms of sleep-onset insomnia (12.1%vs. 13.0%, Adjusted OR[95%CI] = 0.87[0.32,2.33]), sleep-maintenance insomnia (24.1%vs. 20.2%, AOR = 1.01[0.46,2.20]), daytime somnolence (8.6%vs. 7.4%, AOR = 1.11[0.37,3.39]), obstructive sleep apnea (27.3%vs. 26.2%, AOR = 0.84[0.40,1.79]), and restless leg syndrome (20.6%vs. 9.9%, AOR = 1.34[0.42,4.25]) were similar among those who developed parkinsonism and those who did not.

CONCLUSION

Symptoms of insomnia, somnolence, apnea, and restless legs did not predate a new diagnosis of parkinsonism over 3 years.

Hippocampal and Reticulo-Thalamic Parvalbumin Interneurons and Synaptic Re-Organization during Sleep Disorders in the Rat Models of Parkinson's Disease Neuropathology

We investigated the alterations of hippocampal and reticulo-thalamic (RT) GABAergic parvalbumin (PV) interneurons and their synaptic re-organizations underlying the prodromal local sleep disorders in the distinct rat models of Parkinson’s disease (PD). We demonstrated for the first time that REM sleep is a predisposing state for the high-voltage sleep spindles (HVS) induction in all experimental models of PD, particularly during hippocampal REM sleep in the hemiparkinsonian models. There were the opposite underlying alterations of the hippocampal and RT GABAergic PV+ interneurons along with the distinct MAP2 and PSD-95 expressions. Whereas the PD cholinopathy enhanced the number of PV+ interneurons and suppressed the MAP2/PSD-95 expression, the hemiparkinsonism with PD cholinopathy reduced the number of PV+ interneurons and enhanced the MAP2/PSD-95 expression in the hippocampus. Whereas the PD cholinopathy did not alter PV+ interneurons but partially enhanced MAP2 and suppressed PSD-95 expression remotely in the RT, the hemiparkinsonism with PD cholinopathy reduced the PV+ interneurons, enhanced MAP2, and did not change PSD-95 expression remotely in the RT. Our study demonstrates for the first time an important regulatory role of the hippocampal and RT GABAergic PV+ interneurons and the synaptic protein dynamic alterations in the distinct rat models of PD neuropathology.

Association of Circadian Abnormalities in Older Adults With an Increased Risk of Developing Parkinson Disease

Importance

Disruption in circadian activity rhythms is very common in older adults, particularly among those with neurodegenerative diseases, including Parkinson disease (PD). However, whether circadian disruption could be a prodrome for PD is unclear.

Objective

To determine the association between rest-activity rhythm (RAR) and risk of incident PD and to explore whether this association is independent of nighttime sleep disturbances.

Design, Setting, and Participants

The ancillary sleep study of the longitudinal cohort Osteoporotic Fractures in Men Study (MrOS) was conducted from December 1, 2003, to March 31, 2005. Of the 3135 community-dwelling men enrolled in the MrOS sleep study, 3049 had technically adequate RAR data; of these, 119 were excluded for having prevalent PD or missing incident data, leaving 2930 men without PD at baseline. Data were analyzed from February 1 through August 31, 2019.

Exposures

Twenty four-hour RAR parameters (amplitude, mesor, robustness, and acrophase) generated by wrist actigraphy-extended cosinor analysis.

Main Outcomes and Measures

Incident PD based on physician diagnosis. Multivariable logistic regression was used to determine the association between quartiles of RAR parameters and risk of incident PD.

Results

Among the 2930 men included in the analysis (mean [SD] age, 76.3 [5.5] years), 78 (2.7%) developed PD during 11 years of follow-up. After accounting for all covariates, the risk of PD increased with decreasing circadian amplitude (strength of the rhythm) (odds ratio [OR] per 1-SD decrease, 1.77; 95% CI, 1.30-2.41), mesor (mean level of activity) (OR per 1-SD decrease, 1.64; 95% CI, 1.22-2.21), or robustness (how closely activity follows a cosine 24-hour pattern) (OR per 1-SD decrease, 1.54; 95% CI, 1.14-2.07) (P < .005 for trend). Those in the lowest quartile of amplitude, mesor, or robustness had approximately 3 times the risk of developing PD compared with those in the highest quartile of amplitude (OR, 3.11; 95% CI, 1.54-6.29), mesor (OR, 3.04; 95% CI, 1.54-6.01), and robustness (OR, 2.65; 95% CI, 1.24-5.66). The association remained after further adjustment for nighttime sleep disturbances and duration in the lowest compared with the highest quartile (OR for amplitude, 3.56 [95% CI, 1.68-7.56]; OR for mesor, 3.24 [95% CI, 1.52-6.92]; and OR for robustness, 3.34 [95% CI, 1.45-7.67]). These associations were somewhat attenuated, but the pattern remained similar after excluding PD cases developed within 2 years after baseline in the lowest compared with the highest quartile (OR for amplitude, 2.40 [95% CI, 1.15-5.00]; OR for mesor, 2.76 [95% CI, 1.35-5.67]; and OR for robustness, 2.33 [95% CI, 1.07-5.07]). Acrophase was not significantly associated with risk of PD.

Conclusions and Relevance

In this cohort study, reduced circadian rhythmicity was associated with an increased risk of incident PD, suggesting it may represent an important prodromal feature for PD. Future studies are needed to determine whether circadian disruption could also be a risk factor for PD and whether strategies to improve circadian function affect the risk of PD.

Restless legs syndrome and perceived olfactory and taste dysfunction: A community-based study

BACKGROUND AND PURPOSE

Restless legs syndrome (RLS) has been suggested as a prodromal symptom of Parkinson disease (PD). Olfactory or taste dysfunction can also occur preceding PD diagnosis. However, whether RLS is associated with chemosensory dysfunction remains unknown. We thus aim to investigate the association between RLS and perceived olfactory and taste dysfunction.

METHODS

We performed a cross-sectional analysis including 90,337 Chinese adults free of neurodegenerative diseases in the Kailuan study in 2016. Presence of RLS was defined using revised RLS diagnostic criteria or the Cambridge-Hopkins questionnaire for RLS. Perceived olfactory and taste dysfunction was collected via a questionnaire. The association between RLS and perceived olfactory and taste dysfunction was assessed using logistic regression model, adjusting for potential cofounders such as age, sex, and medical history.

RESULTS

RLS was associated with high odds of having perceived olfactory and/or taste dysfunction (adjusted odds ratio = 5.92, 95% confidence interval = 3.11-11.3). The significant association persisted when using the Cambridge-Hopkins questionnaire (adjusted odds ratio = 5.55, 95% confidence interval = 2.37-13.0) or when excluding participants with major chronic diseases.

CONCLUSIONS

RLS was associated with increased odds of perceived olfactory and taste dysfunction.

Lack of Causal Effects or Genetic Correlation between Restless Legs Syndrome and Parkinson's Disease

BACKGROUND

Epidemiological studies have reported an association between Parkinson's disease (PD) and restless legs syndrome.

OBJECTIVES

We aimed to use genetic data to study whether these 2 disorders are causally linked or share genetic architecture.

METHODS

We performed two-sample Mendelian randomization and linkage disequilibrium score regression using summary statistics from recent genome-wide meta-analyses of PD and restless legs syndrome.

RESULTS

We found no evidence for a causal relationship between restless legs syndrome (as the exposure) and PD (as the outcome, inverse variance-weighted; b = -0.003, SE = 0.031, P = 0.916; F statistic = 217.5). Reverse Mendelian randomization also did not demonstrate any causal effect of PD on restless legs syndrome (inverse variance-weighted; b = -0.012, SE = 0.023, P = 0.592; F statistic = 191.7). Linkage disequilibrium score regression analysis demonstrated lack of genetic correlation between restless legs syndrome and PD (rg = -0.028, SE = 0.042, P = 0.507).

CONCLUSIONS

There was no evidence for a causal relationship or genetic correlation between restless legs syndrome and PD. The associations observed in epidemiological studies could be attributed, in part, to confounding or nongenetic determinants. © 2021 International Parkinson and Movement Disorder Society.

Melatonin as a Chronobiotic and Cytoprotective Agent in Parkinson's Disease

This article discusses the role that melatonin may have in the prevention and treatment of Parkinson’s disease (PD). In parkinsonian patients circulating melatonin levels are consistently disrupted and the potential therapeutic value of melatonin on sleep disorders in PD was examined in a limited number of clinical studies using 2–5 mg/day melatonin at bedtime. The low levels of melatonin MT1 and MT2 receptor density in substantia nigra and amygdala found in PD patients supported the hypothesis that the altered sleep/wake cycle seen in PD could be due to a disrupted melatonergic system. Motor symptomatology is seen in PD patients when about 75% of the dopaminergic cells in the substantia nigra pars compacta region degenerate. Nevertheless, symptoms like rapid eye movement (REM) sleep behavior disorder (RBD), hyposmia or depression may precede the onset of motor symptoms in PD for years and are index of worse prognosis. Indeed, RBD patients may evolve to an α-synucleinopathy within 10 years of RBD onset. Daily bedtime administration of 3–12 mg of melatonin has been demonstrated effective in RDB treatment and may halt neurodegeneration to PD. In studies on animal models of PD melatonin was effective to curtail symptomatology in doses that allometrically projected to humans were in the 40–100 mg/day range, rarely employed clinically. Therefore, double-blind, placebo-controlled clinical studies are urgently needed in this respect.

Association of Sleepwalking and REM Sleep Behavior Disorder With Parkinson Disease in Men

IMPORTANCE

Previous studies conducted among patients with Parkinson disease (PD) reported that parasomnias other than rapid eye movement (REM) sleep behavior disorder (RBD), particularly sleepwalking (SW), are associated with PD severity. However, it remains unclear whether the presence of SW is associated with altered odds of having PD in a population-based study.

OBJECTIVE

To evaluate whether probable SW, either alone or co-occurring with probable RBD, is associated with higher odds of PD in men.

DESIGN, SETTING, AND PARTICIPANTS

This cross-sectional study included 25 694 men from the Health Professionals Follow-up Study, a population-based cohort of male health professionals in the US with information on probable SW and probable RBD. Data collection took place between January 2012 and June 2018, and data analysis took place from July 2020 to October 2020.

EXPOSURES

Probable SW and probable RBD were measured by questions adapted from the Mayo Sleep Questionnaire in 2012.

MAIN OUTCOMES AND MEASURES

PD, confirmed after review of medical records by a movement disorder specialist.

RESULTS

Of the 25 694 studied men (mean [SD] age, 75.6 [7.4] years), 223 (0.9%) had probable SW, 2720 (10.6%) had probable RBD, and 257 (1.0%) had PD. After adjusting for potential confounders (eg, age, smoking, caffeine intake, chronic disease status, and other sleep disorders), compared with individuals without probable SW and probable RBD, participants with probable SW, probable RBD, and both probable SW and probable RBD had higher odds of PD, (probable SW: odds ratio [OR], 4.80; 95% CI, 1.61-14.26; probable RBD: OR, 6.36; 95% CI, 4.83-8.37; both probable SW and probable RBD: OR, 8.44; 95% CI, 3.90-18.27).

CONCLUSIONS AND RELEVANCE

In this cross-sectional study of a male population, probable sleep parasomnias, including both SW and RBD, were associated with higher odds of having PD. PD-related neurodegeneration may impair arousal regulation during sleep.

Association of BST1 polymorphism with idiopathic restless legs syndrome in Chinese population

BACKGROUND

Parkinson's disease (PD) and restless legs syndrome/Willis-Ekbom disease (RLS/WED) are both common movement disorders. Based on their clinical overlap, association studies of PD and RLS/WED have been conducted for many years.

OBJECTIVE

To investigate whether or not the genetic risk factor of PD was also associated with RLS/WED.

SUBJECTS AND METHODS

We included 102 idiopathic RLS/WED patients and 189 matched controls from southeast China. The clinical data included the International Restless Legs Syndrome Study Group Rating Scale, the subtypes of RLS/WED symptoms (painful or other discomfort), the comorbidities, the pregnancy history of female patients, the Hamilton Depression Scale (HAMD), and the Pittsburgh Sleep Quality Index (PSQI) questionnaire. Risk gene analysis between RLS/WED and control groups including 21 SNPs (single nucleotide polymorphisms) was conducted. Genotyping was done by Sanger sequencing.

RESULTS

We found that rs4273468 polymorphism of BST1 gene increased the risk of idiopathic RLS/WED patients in southeastern Chinese population (P = <0.001, OR = 2.85, p = 0.019 after Bonferroni correction). Moreover, the haplotype of G-G (rs4698412-rs4273468) was significantly associated with Chinese RLS/WED patients (p = <0.001).

CONCLUSION

BST1 may contribute to the development of RLS/WED. Further studies on larger cohorts are needed to confirm these findings.

Sleep Issues in Parkinson's Disease and Their Management

Parkinson's disease (PD) is an alpha-synucleinopathy that leads to prominent motor symptoms including tremor, bradykinesia, and postural instability. Nonmotor symptoms including autonomic, neurocognitive, psychiatric symptoms, and sleep disturbances are also seen frequently in PD. The impact of PD on sleep is related to motor and nonmotor symptoms, in addition to the disruption of the pathways regulating sleep by central nervous system pathology. Rapid eye movement sleep behavior disorder is a parasomnia that can lead to self-injury and/or injury to partners at night. Restless legs syndrome is a subjective sensation of discomfort and urge to move the legs prior to falling asleep and can lead to insomnia and reduced sleep quality. Excessive daytime sleepiness is common in PD and exerts a negative impact on quality of life in addition to increasing the risk of falls. Obstructive sleep apnea is a breathing disorder during sleep that can cause frequent awakenings and excessive daytime sleepiness. Circadian rhythm dysfunction can lead to an advanced or delayed onset of sleep in patients and create disruption of normal sleep and wake times. All of these disorders are common in PD and can significantly reduce sleep quantity, sleep quality, or quality of life for patients and caretakers. Treatment approaches for each of these disorders are distinct and should be individualized to the patient. We review the literature regarding these common sleep issues encountered in PD and their treatment options.

Contribution of the GABAergic System to Non-Motor Manifestations in Premotor and Early Stages of Parkinson's Disease

Non-motor symptoms are common in Parkinson’s disease (PD) and they represent a major source of disease burden. Several non-motor manifestations, such as rapid eye movement sleep behavior disorder, olfactory loss, gastrointestinal abnormalities, visual alterations, cognitive and mood disorders, are known to precede the onset of motor signs. Nonetheless, the mechanisms mediating these alterations are poorly understood and probably involve several neurotransmitter systems. The dysregulation of GABAergic system has received little attention in PD, although the spectrum of non-motor symptoms might be linked to this pathway. This Mini Review aims to provide up-to-date information about the involvement of the GABAergic system for explaining non-motor manifestations in early stages of PD. Therefore, special attention is paid to the clinical data derived from patients with isolated REM sleep behavior disorder or drug-naïve patients with PD, as they represent prodromal and early stages of the disease, respectively. This, in combination with animal studies, might help us to understand how the disturbance of the GABAergic system is related to non-motor manifestations of PD.

Leg restlessness preceding the onset of motor symptoms of Parkinson disease: A case series of 5 patients

Patients with Parkinson disease (PD) often show restless legs syndrome (RLS), leg motor restlessness (LMR) and other leg restlessness (OLR) related to sensorimotor symptoms.Here, we describe 5 patients who presented with leg restlessness as an early manifestation of PD.In case 1, the patient had leg restlessness that was not LMR or RLS and preceded the onset of motor symptoms by 1 year. In case 2, LMR preceded motor symptoms by 2 years. Case 3 had unilateral RLS symptoms on the left side of the body for 33 years. Two and a half years after the spread of RLS symptoms to the right leg with increased frequency of left-sided RLS symptoms, the patient developed PD at the age of 58 years. In cases 4 and 5, RLS symptoms preceded motor symptoms by 3 months and 1 month, respectively. All patients developed Parkinsonism within 3 years (median, 1.0 year; range 0.083-2.5 years) after initial onset or exacerbation of leg restlessness. All patients had frequent leg restlessness symptoms (6-7 days per week). In our series, the preceding leg restlessness was unilateral and confined to the dominant side of the subsequent Parkinsonism, or preceding leg restlessness was bilateral but dominant on the dominant side of the subsequent Parkinsonism.Clinicians should be aware that late-onset leg restlessness (>50 years of age) including RLS, LMR, and OLR, particularly if frequent and asymmetrical, can be an early nonmotor manifestation of PD.

Sleep and risk of parkinsonism and Parkinson's disease: a population-based study

Sleep disturbances may signal presence of prodromal parkinsonism, including Parkinson's disease. Whether general sleep quality or duration in otherwise healthy subjects is related to the risk of parkinsonism remains unclear. We hypothesized that both worse self-reported sleep quality and duration, as well as a longitudinal deterioration in these measures, are associated with the risk of parkinsonism, including Parkinson's disease. In the prospective population-based Rotterdam Study, we assessed sleep quality and duration with the Pittsburgh Sleep Quality Index in 7726 subjects (mean age 65 years, 57% female) between 2002 and 2008, and again in 5450 subjects between 2009 and 2014. Participants were followed until 2015 for a diagnosis of parkinsonism and Parkinson's disease. Outcomes were assessed using multiple modalities: interviews, physical examination, and continuous monitoring of pharmacy records and medical records of general practitioners. We used Cox regression to associate sleep, and changes in sleep over time, with incident parkinsonism and Parkinson's disease, adjusting for age, sex, education and smoking status. Over 64 855 person-years in 13 years of follow-up (mean: 8.4 years), 75 participants developed parkinsonism, of whom 47 developed Parkinson's disease. We showed that within the first 2 years of follow-up, worse sleep quality {hazard ratio (HR) 2.38 per standard deviation increase [95% confidence interval (CI 0.91-6.23)]} and shorter sleep duration [HR 0.61 per standard deviation increase (95% CI 0.31-1.21)] related to a higher risk of parkinsonism. Associations of worse sleep quality [HR 3.86 (95% CI 1.19-12.47)] and shorter sleep duration [HR 0.48 (95% CI 0.23-0.99)] with Parkinson's disease were more pronounced, and statistically significant, compared to parkinsonism. This increased risk disappeared with longer follow-up duration. Worsening of sleep quality [HR 1.76 per standard deviation increase (95% CI 1.12-2.78)], as well as shortening of sleep duration [HR 1.72 per standard deviation decrease (95% CI 1.08-2.72)], were related to Parkinson's disease risk in the subsequent 6 years. Therefore, we argue that in the general population, deterioration of sleep quality and duration are markers of the prodromal phase of parkinsonism, including Parkinson's disease.

Use of botulinum toxin for movement disorders

The term movement disorders encompasses all disorders hypokinetic and hyperkinetic, which were previously known as extrapyramidal syndromes. With the definition of movement disorders and their diagnostic criteria and classifications, new studies for therapeutics could be performed. New drugs were launched, functional neurosurgery was developed, and the introduction of botulinum toxin (BoNT) for hyperkinesias was introduced. BoNT is an important therapy for dystonia, tics, myoclonus, and tremors. The aim of this review is to present the new and well-established uses of BoNT for movement disorders.

Association between restless legs syndrome and other movement disorders

OBJECTIVE

This review focuses on the possible association between restless legs syndrome (RLS) and movement disorders, including Parkinson disease (PD), other parkinsonian syndromes, essential tremor, choreic and dystonic syndromes, Tourette syndrome, and heredodegenerative ataxias.

METHODS

Review of PubMed from 1966 to September 2018 and identification of references of interest for the topic. A meta-analysis of eligible studies on the frequency of RLS in patients with PD and controls using Meta-DiSc1.1.1 software and using the PRISMA guidelines was performed.

RESULTS AND CONCLUSIONS

Although there are substantial clinical, neuroimaging, neuropathologic, and genetic differences between RLS and PD, many reports describe a higher than expected prevalence of RLS in patients with PD, when compared with the general population or with matched control groups; several studies have also suggested that RLS could be an early clinical feature of PD. RLS symptoms are frequent in multiple system atrophy, essential tremor, Tourette syndrome, Friedreich ataxia, and spinocerebellar ataxia type 3 as well. Finally, possible genetic links between PD and RLS (the presence of allele 2 of the complex microsatellite repeat Rep1 within the α-synuclein gene promoter) and between Tourette syndrome and RLS (several variants in the BTBD9 gene) have been reported in 2 case-control association studies, although these data, based on preliminary data with small sample sizes, need to be replicated in further studies.

Restless Legs Syndrome in Parkinson's Disease Patients: Clinical Features Including Motor and Nonmotor Symptoms

Background and Purpose

We investigated the frequency and clinical features of restless legs syndrome (RLS) in patients with Parkinson's disease (PD).

Methods

This study included 74 PD patients. RLS was diagnosed in face-to-face assessments of all of the subjects based on diagnostic criteria of the International Restless Legs Syndrome Study Group revised in 2003. We analyzed the clinical features of PD patients with and without RLS and compared the data to idiopathic RLS.

Results

The frequency of RLS in the cohort was 21.6% (n=16). Two (12.5%) of the patients with RLS were not treated with dopaminergic drugs, while 14 (24.1%) of the 58 patients without RLS received treatment with dopaminergic drugs. Anxiety, depression, and quality of life (QoL) were significantly worst in patients with RLS. PD patients with RLS had significantly worse sleep quality (p=0.003) and worse scores on the cardiovascular subscale of the Scales for Outcomes in Parkinson's Disease for Autonomic Symptoms (p=0.031) compared to those without RLS. In the group of PD patients with RLS, RLS preceding PD onset was related to a lower Hoehn and Yahr stage.

Conclusions

We found that the frequency of RLS in the present patients with PD was higher than that in our previous study of a general population of RLS subjects. Compared to the PD patients without RLS, the present PD patients with RLS suffered from worse sleep quality and QoL, depression, anxiety, and autonomic disturbances, especially those with cardiovascular problems.

[Increased frequency and spread of restlessness as the early manifestation of Parkinson's disease in a woman with restless legs syndrome]

A 57-year-old woman had been suffered from insomnia due to restlessness and abnormal sensation of the left side of the body for 33 years. Since the preceding year of the first visit frequency of the symptoms increased, and the abnormal sensation was spread to the right leg. Her daughter had restless legs syndrome (RLS) since age 20. Neurological examination showed no abnormality. Laboratory test results showed normal ferritin levels. There was no renal dysfunction or anemia. A diagnosis of RLS was made, and her symptoms responded well to pramipexole treatment. However, the patient developed right shoulder pain and right-hand tremor one year and one and a half year after the first visit, respectively. Based on clinical findings and the findings of dopamine transporter scan and cardiac ¹²³I-MIBG scintigraphy, the patient was diagnosed with Parkinson's disease (PD). Careful observation of changes in RLS symptoms is required as an increased frequency and spread of symptoms of RLS could be the early manifestation of PD.

Comorbidities, treatment, and pathophysiology in restless legs syndrome

Restless legs syndrome, also known as Willis-Ekbom disease, is a common neurological condition whose manifestation is affected by complex environmental and genetic interactions. Restless legs syndrome can occur on its own, mostly at a young age, or with comorbidities such as cardiovascular disease, diabetes, and arterial hypertension, making it a difficult condition to properly diagnose. However, the concept of restless legs syndrome as being two entities, primary or secondary to another condition, has been challenged with genetic data providing further insight into the pathophysiology of the condition. Although dopaminergic treatment was formerly the first-line therapy, prolonged use can result in a serious worsening of symptoms known as augmentation. Clinical studies on pregabalin, gabapentin enacarbil, oxycodone-naloxone, and iron preparations have provided new treatment options, but most patients still report inadequate long-term management of symptoms. Studies of the hypoxic pathway activation and iron deficiency have provided valuable information about the pathophysiology of restless legs syndrome that should now be translated into new, more effective treatments for restless legs syndrome.

Advances in markers of prodromal Parkinson disease

Efforts to develop neuroprotective therapy for Parkinson disease (PD) are focusing on the early stages of disease, which offer the best opportunity to intervene. Early PD can be divided into preclinical, prodromal and clinical stages; in this Review, we focus on the prodromal stage and markers that can be used to identify prodromal PD. We consider the necessary properties of a marker, before providing an overview of the proven and potential markers of prodromal PD, including clinical nonmotor markers, clinical motor markers, neuroimaging markers and tissue biomarkers. Markers for which the ability to predict conversion to PD is supported by the strongest evidence include olfactory loss, REM sleep behaviour disorder and constipation. Markers with the highest diagnostic strength include REM sleep behaviour disorder, dopaminergic imaging and subtle motor parkinsonism. The lead time - the period between the appearance of a marker and conversion to PD - is highly variable between markers, ranging from 5 years for impaired motor performance to >20 years for autonomic symptoms. The cost of screening for these markers also varies dramatically: some require just questionnaires, whereas others require sophisticated scanning techniques. Finally, we summarize how prodromal and risk markers can be combined to estimate the probability that an individual has prodromal PD, with a focus on the International Parkinson Disease and Movement Disorders Society (MDS) Prodromal Parkinson Criteria.

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.

Restless legs syndrome is associated with major comorbidities in a population of Danish blood donors

BACKGROUND

Restless Legs Syndrome (RLS) is characterized by uncomfortable nocturnal sensations in the legs making sedentary activities and sleep difficult, and is thus linked with psychosocial distress. Due to the symptomatology and neurobiology of RLS (disrupting brain iron and dopamine) it is likely that RLS associates with poorer health-related quality of life (HRQL) and depressive disorder. The objective of this study was to investigate the RLS-HRQL and the RLS-depressive disorder links in a generally healthy population that is not biased by medications.

METHODS

Complete data, including the Cambridge-Hopkins RLS questionnaire, the 12-item short-form standardized health survey (SF-12), the Major Depression Inventory (MDI), body mass index, smoking status, alcohol consumption, and education were available for 24,707 participants enrolled in the Danish Blood Donor Study from May 1, 2015 to February 1, 2017. Information on quality of sleep was available for all RLS cases. T-tests and multivariable logistic regression models were applied to examine the associations of RLS and MDI scores, and the physical and mental component scores (PCS and MCS) of SF-12, respectively. Analyses were conducted separately for men and women.

RESULTS

RLS associated with poorer MCS and poorer PCS. Moreover, Participants with RLS were more likely to classify with depressive disorder. Poor quality of sleep was associated with depressive disorder and poorer MCS among RLS cases, and with poorer PCS in female RLS cases.

CONCLUSION

Thus, we demonstrated that RLS is associated with a significantly lower HRQL and a higher prevalence of depressive disorder among otherwise healthy individuals.

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.

Sleep disorders and Parkinson disease; lessons from genetics

Parkinson disease is a common, age-related neurodegenerative disorder, projected to afflict millions of individuals in the near future. Understanding its etiology and identifying clinical, genetic or biological markers for Parkinson disease onset and progression is therefore of major importance. Various sleep-related disorders are the most common group of non-motor symptoms in advanced Parkinson disease, but they can also occur during its prodromal phase. However, with the exception of REM sleep behavior disorder, it is unclear whether they are part of the early pathological process of Parkinson disease, or if they develop as Parkinson disease advances because of treatments and neurodegeneration progression. The advancements in genetic studies in the past two decades have generated a wealth of information, and recent genetic studies offer new insight on the association of sleep-related disorders with Parkinson disease. More specifically, comparing genetic data between Parkinson disease and sleep-related disorders can clarify their association, which may assist in determining whether they can serve as clinical markers for Parkinson disease risk or progression. In this review, we discuss the current knowledge on the genetics of sleep-related disorders in Parkinson disease context, and the potential implications on research, diagnosis, counseling and treatment.

Sleep-wake disturbances in the premotor and early stage of Parkinson's disease

PURPOSE OF REVIEW

Review of recent literature pertaining to frequency, associations, mechanisms, and overall significance of sleep--wake disturbances (SWD) in the premotor and early phase of Parkinson's disease.

RECENT FINDINGS

SWD are frequent in Parkinson's disease and their prevalence increases with disease progression. Recent studies confirm previous findings that SWD can appear as initial manifestation of Parkinson's disease even decades before motor signs appear and highlight their clinical associations in these early stages. More intriguingly, new evidence underpins their role as risk factors, predictors, or even as driving force for the neurodegenerative process. As our understanding of sleep--wake neurobiology increases, new hypotheses emerge concerning the pathophysiology of SWD in early Parkinson's disease stages involving dopaminergic and nondopaminergic mechanisms.

SUMMARY

SWD are predictors for the development of parkinsonian syndromes including Parkinson's disease. This may offer the opportunity of developing new preventive strategies and interventions at an early stage of this neurodegenerative disease.

Prospective study of restless legs syndrome and total and cardiovascular mortality among women

OBJECTIVE

We prospectively examined whether women with physician-diagnosed restless legs syndrome (RLS) had a higher risk of total and cardiovascular disease (CVD) mortality relative to those without RLS.

METHODS

The current study included 57,417 women (mean age 67 years) from the Nurses' Health Study without cancer, renal failure, and CVD at baseline (2002). Main outcomes were total and CVD mortality. We used the Cox proportional hazards model to calculate hazard ratios (HRs) and 95% confidence intervals (CIs) for all-cause and CVD-specific mortality based on RLS status, adjusting for age, presence of major chronic diseases, and other potential confounders.

RESULTS

We documented 6,448 deaths during 10 years of follow-up. We did not observe a significant association between presence of physician-diagnosed RLS and high risk of total mortality (adjusted HR 1.15, 95% CI 0.98-1.34). When cause-specific mortality was studied, participants with RLS had a significantly higher risk of CVD mortality (adjusted HR 1.43, 95% CI 1.02-2.00) relative to those without RLS after adjustment for potential confounders. Longer duration of RLS diagnosis was significantly associated with a higher risk of CVD mortality (p for trend = 0.04). Excluding participants with common RLS comorbidities strengthened the association between RLS and total (adjusted HR 1.43, 95% CI 1.03-1.97) and CVD mortality (adjusted HR 2.27, 95% CI 1.21-4.28). However, we did not find a significant association between RLS and mortality due to cancer and other causes.

CONCLUSIONS

Women with RLS had a higher CVD mortality rate, which may not be fully explained by common co-occurring disorders of RLS.

Sleep fragmentation and Parkinson's disease pathology in older adults without Parkinson's disease

INTRODUCTION

Patients with Parkinson's disease (PD) frequently experience disrupted sleep, and several sleep abnormalities are associated with an increased risk of incident PD. However, there are few data concerning the relationship between objectively quantified sleep disruption and the cardinal histopathological features of PD, especially in individuals without clinical PD.

METHODS

We studied 269 older adults without PD who had participated in the Rush Memory and Aging Project and undergone uniform structured neuropathologic evaluations upon death. Sleep fragmentation was measured using actigraphy. Logistic regression models examined the associations of sleep fragmentation proximate to death with the burden of Lewy body pathology and substantia nigra neuron loss.

RESULTS

Greater sleep fragmentation was associated with the presence of Lewy body pathology (odds ratio 1.40; 95% confidence interval 1.05-1.86; P = .02) and substantia nigra neuron loss (odds ratio 1.43; 95% confidence interval 1.10-1.88; P = .008) and a higher odds of a pathological diagnosis of PD (odds ratio 2.04; 95% confidence interval 1.34-3.16; P = .0009). These associations were independent of motor features of parkinsonism, demographic characteristics, and a wide range of medical co-morbidities.

CONCLUSIONS

Sleep fragmentation is associated with PD pathology in older adults without PD. These results suggest that sleep fragmentation may be a marker of or risk factor for PD pathology in older adults without PD. © 2017 International Parkinson and Movement Disorder Society.

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.

Is there a Premotor Phase of Essential Tremor?

BACKGROUND

Essential tremor (ET) is the most common tremor disorder. In addition to its hallmark feature, kinetic tremor of the upper limbs, patients may have a number of non-motor symptoms and signs (NMS). Several lines of evidence suggest that ET is a neurodegenerative disorder and certain NMS may antedate the onset of tremor. This article comprehensively reviews the evidence for the existence of a "premotor phase" of ET, and discusses plausible biological explanations and implications.

METHODS

A PubMed search in May 2017 identified articles for this review.

RESULTS

The existence of a premotor phase of ET gains support primarily from longitudinal data. In individuals who develop incident ET, baseline (i.e., premotor) evaluations reveal greater cognitive dysfunction, a faster rate of cognitive decline, and the presence of a protective effect of education against dementia. In addition, baseline evaluations also reveal more self-reported depression, antidepressant medication use, and shorter sleep duration in individuals who eventually develop incident ET. In cross-sectional studies, certain personality traits and NMS (e.g., olfactory dysfunction) also suggest the existence of a premotor phase.

DISCUSSION

There is preliminary evidence supporting the existence of a premotor phase of ET. The mechanisms are unclear; however, the presence of Lewy bodies in some ET brains in autopsy studies and involvement of multiple neural networks in ET as evident from the neuroimaging studies, are possible contributors. Most evidence is from a longitudinal cohort (Neurological Disorders of Central Spain: NEDICES); additional longitudinal studies are warranted to gain better insights into the premotor phase of ET.

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.

Characterizing restless legs syndrome and leg motor restlessness in patients with Parkinson's disease: A multicenter case-controlled study

BACKGROUND

We investigated the prevalence and impact of restless legs syndrome (RLS) and leg motor restlessness (LMR) in patients with Parkinson's disease (PD) in a multicenter study.

METHODS

A total of 436 PD patients and 401 age- and sex-matched controls were included in this study. RLS was diagnosed based on four essential features. LMR was diagnosed when a participant exhibited the urge to move his or her legs but did not meet the four essential features of RLS.

RESULTS

The RLS prevalence did not differ between PD patients and controls (3.4% vs. 2.7%), while LMR prevalence was significantly higher in PD patients than in controls (12.8% vs. 4.5%). PD patients with RLS or LMR had a higher prevalence of excessive daytime sleepiness (EDS) (50.7%, vs. 6.9%), probable REM sleep behavior disorder (38.0% vs. 3.4%) and PD-related sleep problems (49.3% vs. 20.7%) than controls with RLS or LMR. RLS/LMR preceding PD onset was related to an older age of PD onset.

CONCLUSION

Our study revealed an increased prevalence of LMR but not RLS in PD patients. LMR could be an early manifestation of PD; however, whether LMR is within the range of RLS or whether LMR and RLS constitute different entities in PD requires further studies.

Prevalence and associated comorbidities of restless legs syndrome (RLS): Data from a large population-based door-to-door survey on 19176 adults in Tehran, Iran

BACKGROUND

Discrepancies have been reported in the prevalence rate of restless legs syndrome (RLS) among different ethnic groups and geographic populations. Furthermore, there are disagreements on determinant factors and associated comorbidities of RLS. We aimed to estimate prevalence of RLS and investigate its associated comorbid conditions and risk factors in a large population-based door-to-door survey.

METHODS

Following a multistage random sampling from the households lived in 22 urban districts of Tehran, Iran, 19176 participants with ≥30 years of age were recruited. Trained surveyors filled study checklist consisting of baseline characteristics, risk factors and comorbidity profile and the International RLS Study Group (IRLSSG) diagnostic criteria through face-to-face interviews.

RESULTS

In total, 1580 individuals were positively screened for RLS resulting in a standardized prevalence rate of 60.0/1000. There was a gradual increase in RLS prevalence by advancing age, however, sex difference disappeared after adjustment. Parkinsonism [adjusted odds' ratio (adj-OR) = 7.4 (95% CI: 5.3-10.4)], peripheral neuropathy [adj-OR = 3.7 (95% CI: 3.3-4.1)], subjective cognitive impairment (SCI) [adj-OR = 3.1 (95% CI: 2.7-3.4)], acting out dreams [adj-OR = 2.8 (95% CI: 2.5-3.2)], hyposmia [adj-OR = 2.5 (95% CI: 2.2-2.9)], active smoking [adj-OR = 1.5 (95% CI: 1.3-1.9)] and additional number of cardiometabolic diseases associated with higher risk of RLS [adj-OR = 1.6 (95% CI: 1.2-2.3)].

CONCLUSION

Our findings showed that neuro-cognitive co-morbidities such as parkinsonism, peripheral neuropathy, SCI, acting out dreams and hyposmia as well as cardio-metabolic risk factors and diseases were independent determinants of RLS. It is recommended to screen individuals with either these comorbid conditions for RLS or the ones with RLS for the accompanying diseases.