Neuropsychological functioning in Parkinson's disease: Differential relationships with self-reported sleep-wake disturbances

Multiple sleep disturbances are associated with apathy in individuals with Parkinson's disease

Background

Parkinson's disease (PD) is associated with both sleep disturbances and apathy, and within PD, apathy has been associated with REM behavior disorder and excessive daytime sleepiness. Whether other forms of sleep disturbance are similarly associated with apathy in PD remains unclear. This study explored associations between a broad array of sleep disturbances and apathy in 50 individuals with idiopathic PD (PD) and 48 matched controls (MC).

Methods

Participants were adults aged 53-80 (Mdn = 67), 23 % female, and 96 % white. Sleep disturbances were measured with various questionnaires (ISI, PSQI, PROMIS-SD, ESS, PROMIS-SRI, RBDSQ). Mood was measured with the STAI and BDI-II. Apathy was evaluated using the Apathy Scale (AS). Spearman correlations and regression analyses were performed between measures of sleep disturbance and AS in the total sample and each group. Group correlations were compared using 2-sample Fisher's z test.

Results

The AS total score significantly correlated with PROMIS-SRI in the total sample and multiple measures of sleep disturbance in the PD group. The apathy subscales were each significantly correlated with sleep disturbance measures in the total sample, MC, and PD groups. The correlations between several sleep and apathy values were significantly stronger in the PD group than MC. When accounting for anxiety and depression most differences were no longer significant, only the PROMIS-SRI was significantly predictive of the behavioral apathy sub score.

Discussion

Evidence supports an association between sleep disturbances and apathy in individuals with PD. Specifically, insomnia severity, poor sleep quality, and daytime sleepiness were uniquely associated with apathy in this group. We did not find these associations in the matched control group. Anxiety and depression are likely involved in the association between sleep and apathy in PD. Experimental studies that manipulate or improve sleep may further elucidate the mechanisms underlying the association between sleep disturbance and apathy in PD.

Sleep disturbances, cognitive decline, and AD biomarkers alterations in early Parkinson's disease

OBJECTIVE

We aimed to investigate whether each type of sleep disturbances (i.e., pRBD, EDS, and insomnia) is specifically associated with faster decline in global cognition and different cognitive domains among de novo PD patients. We also assessed the influence of sleep disturbances on core AD CSF biomarkers alterations and conversion to dementia.

METHODS

Prospectively longitudinal data were obtained from the PPMI cohort. Sleep disturbances and cognition ability were assessed by questionnaires at baseline and follow-up visits. Generalized linear mixed models were utilized to assess the effect of sleep disturbances on cognitive decline and core AD CSF biomarkers change. The associations between sleep disturbances and conversion to dementia were analyzed using Cox regression analysis.

RESULTS

Baseline pRBD was associated with faster decline in global cognition and all cognitive domains, including verbal episodic memory, visuospatial ability, executive function, language, and processing speed. EDS was associated with faster decline in three cognitive domains, including verbal episodic memory, executive function/working memory, and processing speed. Insomnia was associated with faster decline in global cognition and verbal episodic memory. Meanwhile, pRBD and EDS were associated with longitudinal decrease of CSF Aβ42. Baseline pRBD increased the risk of conversion to dementia. The risk of dementia in PD patients with multiple sleep disturbances also increased compared with those without sleep disturbance.

INTERPRETATION

Sleep disturbances (i.e., pRBD, EDS, and insomnia) were associated with cognitive decline in early PD. EDS and pRBD were associated with decrease of CSF Aβ42. Moreover, pRBD was associated with conversion to dementia.

Targeting sleep and the circadian system as a novel treatment strategy for Parkinson's disease

There is a growing appreciation of the wide range of sleep-wake disturbances that occur frequently in Parkinson's disease. These are known to be associated with a range of motor and non-motor symptoms and significantly impact not only on the quality of life of the patient, but also on their bed partner. The underlying causes for fragmented sleep and daytime somnolence are no doubt multifactorial but there is clear evidence for circadian disruption in Parkinson's disease. This appears to be occurring not only as a result of the neuropathological changes that occur across a distributed neural network, but even down to the cellular level. Such observations indicate that circadian changes may in fact be a driver of neurodegeneration, as well as a cause for some of the sleep-wake symptoms observed in Parkinson's disease. Thus, efforts are now required to evaluate approaches including the prescription of precision medicine to modulate photoreceptor activation ratios that reflect daylight inputs to the circadian pacemaker, the use of small molecules to target clock genes, the manipulation of orexin pathways that could help restore the circadian system, to offer novel symptomatic and novel disease modifying strategies.

Correlation and underlying brain mechanisms between rapid eye movement sleep behavior disorder and executive functions in Parkinson's disease: an fNIRS study

Purpose

Rapid eye movement sleep behavior disorder (RBD) affects 30%-40% of patients with Parkinson's disease (PD) and has been linked to a higher risk of cognitive impairment, especially executive dysfunction. The aim of this study was to investigate the brain activation patterns in PD patients with RBD (PD-RBD+) compared to those without RBD (PD-RBD-) and healthy controls (HCs), and to analyze the correlation between changes in cerebral cortex activity and the severity of RBD.

Methods

We recruited 50 PD patients, including 30 PD-RBD+, 20 PD-RBD-, and 20 HCs. We used functional near infrared spectroscopy during a verbal fluency task (VFT-fNIRS) and clinical neuropsychological assessment to explore the correlation between PD-RBD+ and executive function and changes in neural activity.

Results

The VFT-fNIRS analysis revealed a significant reduction in activation among PD-RBD+ patients across multiple channels when compared to both the PD-RBD- and HC groups. Specifically, PD-RBD+ patients exhibited diminished activation in the bilateral dorsolateral prefrontal cortex (DLPFC) and the right ventrolateral prefrontal cortex (VLPFC) relative to their PD-RBD- counterparts. Furthermore, compared to the HC group, PD-RBD+ patients displayed reduced activation specifically in the right DLPFC. Significantly, a noteworthy negative correlation was identified between the average change in oxygenated hemoglobin concentration (ΔHbO2) in the right DLPFC of PD-RBD+ patients and the severity of their RBD.

Conclusion

Our study offers compelling evidence that RBD exacerbates cognitive impairment in PD, manifested as executive dysfunction, primarily attributed to reduced prefrontal activation. These aberrations in brain activation may potentially correlate with the severity of RBD.

Clinical characteristics in early Parkinson's disease with excessive daytime sleepiness: A cross-sectional and longitudinal study

We aimed to explore excessive daytime sleepiness (EDS) and correlates of clinical characteristics by using cross-sectional and longitudinal analyses from the Parkinson's Progression Markers Initiative database. Four hundred twenty-three patients with Parkinson's disease (PD; EDS: non-EDS = 357:66) and 195 healthy controls (HCs; EDS: nEDS = 171:24) were enrolled in our study at baseline. Multiple linear and linear mixed-effects models were used to research the relationships between EDS/daytime sleepiness severity and clinical characteristics. Relationships between the change rates of clinical characteristics and daytime sleepiness severity were further investigated through multiple linear regression models. Mediating effect analysis was used to determine whether autonomic dysfunction was the mediator between cognition assessments and daytime sleepiness severity. Patients with PD with EDS and greater daytime sleepiness severity presented faster cognitive decline, high possibility for rapid eye movement sleep behavior disorder, autonomic dysfunction, depression, and anxiety from cross-sectional and longitudinal analyses. Furthermore, HC individuals with EDS showed a higher striatal binding ratio of the right putamen, right striatum, and mean striatum. Autonomic dysfunction may act as a mediator between PD and cognitive decline. In early PD, EDS and daytime sleepiness severity were related to several clinical variables, suggesting that EDS might play an essential role in regulating PD progression.

Neurological Insights into Sleep Disorders in Parkinson's Disease

Parkinson's disease (PD) is a common multidimensional neurological disorder characterized by motor and non-motor features and is more prevalent in the elderly. Sleep disorders and cognitive disturbances are also significant characteristics of PD. Sleep is an important physiological process for normal human cognition and physical functioning. Sleep deprivation negatively impacts human physical, mental, and behavioral functions. Sleep disturbances include problems falling asleep, disturbances occurring during sleep, abnormal movements during sleep, insufficient sleep, and excessive sleep. The most recognizable and known sleep disorders, such as rapid-eye-movement behavior disorder (RBD), insomnia, excessive daytime sleepiness (EDS), restless legs syndrome (RLS), sleep-related breathing disorders (SRBDs), and circadian-rhythm-related sleep-wake disorders (CRSWDs), have been associated with PD. RBD and associated emotional disorders are common non-motor symptoms of PD. In individuals, sleep disorders and cognitive impairment are important prognostic factors for predicting progressing neurodegeneration and developing dementia conditions in PD. Studies have focused on RBD and its associated neurological changes and functional deficits in PD patients. Other risks, such as cognitive decline, anxiety, and depression, are related to RBD. Sleep-disorder diagnosis is challenging, especially in identifying the essential factors that disturb the sleep-wake cycle and the co-existence of other concomitant sleep issues, motor symptoms, and breathing disorders. Focusing on sleep patterns and their disturbances, including genetic and other neurochemical changes, helps us to better understand the central causes of sleep alterations and cognitive functions in PD patients. Relations between α-synuclein aggregation in the brain and gender differences in sleep disorders have been reported. The existing correlation between sleep disorders and levels of α-synuclein in the cerebrospinal fluid indicates the risk of progression of synucleinopathies. Multidirectional approaches are required to correlate sleep disorders and neuropsychiatric symptoms and diagnose sensitive biomarkers for neurodegeneration. The evaluation of sleep pattern disturbances and cognitive impairment may aid in the development of novel and effective treatments for PD.

Narcolepsy genetic marker HLA DQB1*06:02 and excessive daytime sleepiness in Parkinson disease patients treated with dopaminergic agents

OBJECTIVE

To determine whether narcolepsy Human Leukocyte Antigen (HLA) risk allele DQB1*0602 is associated with excessive daytime sleepiness (EDS) and inappropriate sleep in patients with Parkinson disease (PD).

BACKGROUND

EDS is a common and disabling non-motor manifestation of PD, affecting quality of life and driving performance. DQB1*0602 is an HLA risk allele for narcolepsy. It is present in 12-30% of the general population. We hypothesize that DQB1*0602 is associated with an increased risk of EDS and inappropriate sleep in PD patients.

METHODS

This was a cross-sectional observational study of 150 PD individuals on dopaminergic agents. Main outcome measures were DQB1*0602 status and the modified Epworth Sleepiness Scale. Individuals with dementia, loss of independence, narcolepsy and untreated sleep apnea were excluded. Confounding variables for EDS were assessed using Parkinson Disease Sleep Scale, Mayo Sleep Questionnaire, Unified PD Rating Scale, Hoehn and Yahr scale.

RESULTS

DQB1*06:02 positive PD patients were approximately three times more likely to experience EDS and fall asleep inappropriately during activities that required sustained alertness (e.g. driving, eating, attending work etc.). Exploratory post hoc analysis showed a dopaminergic drug dose- and type- dependent effect on daytime sleepiness in DQB1*06:02 positive individuals. No significant differences were found in confounding variables.

CONCLUSION

PD individuals are more likely to experience EDS and fall asleep inappropriately during activities if DQB1*0602 positive. Genetic vulnerability may explain EDS risk in PD.

Locus Coeruleus Pathology Indicates a Continuum of Lewy Body Dementia

BACKGROUND

Lewy body dementia (LBD) has two main phenotypes of LBD, Parkinson's disease dementia (PDD) and dementia with Lewy bodies (DLB), separated by the 'one-year-rule'. They also show different symptom profiles: core DLB features include fluctuating cognition, REM-sleep behaviur disorder, and visual hallucinations. These symptoms are sometimes present in PDD, representing an intermediate 'PDD-DLB' phenotype.

OBJECTIVE

DLB-like features may reflect deficits in the functions of the noradrenergic nucleus locus coeruleus (LC). Therefore, we compared the LC in the LBD phenotypes, PD, and controls.

METHODS

38 PD, 56 PDD, 22 DLB, and 11 age-matched control cases from the Parkinson's UK tissue bank were included. LC tissue sections were immunostained for tyrosine-hydroxylase (TH), α-synuclein, tau, and amyloid-β. TH-neurons were quantified and pathologic burden calculated by %-coverage method.

RESULTS

The LC shows a stepwise reduction in neuron count from controls, PD, PDD, to DLB. PDD-DLB cases showed an intermediate clinical phenotype that was reflected pathologically. Cell counts were significantly reduced in DLB compared to PDD after correction for demographic factors. LC degeneration contributed significantly to the onset of all DLB symptoms. While α-synuclein was not significantly different between PDD and DLB cases, DLB exhibited significantly less tau pathology.

CONCLUSION

DLB and DLB-like symptoms represent noradrenergic deficits resulting from neuronal loss in the LC. PDD and DLB are likely to represent a clinical continuum based on the presence or absence of DLB-like symptoms mirrored by a pathological continuum in the LC.

Association between sleep disorders and cognitive dysfunctions in non-demented patients with advanced Parkinson's disease

Background

Parkinson’s disease (PD) is increasingly recognized as a multidimensional disorder, characterized by several non-motor symptoms, including disturbances of sleep and cognition. Current studies on the relationship between sleep problems and neuropsychological functions, mainly conducted in early to moderate PD patients, outline mixed results. In this study, we analysed the relationship between subjectively reported sleep alterations and cognitive functions in a large cohort of 181 advanced PD patients.

Methods

All consecutive, non-demented, advanced PD patients candidates for device-aided therapy completed two self-administered sleep questionnaires—the Parkinson’s Disease Sleep Scale (PDSS-2) and the Epworth Sleepiness Scale (ESS)—and underwent a comprehensive battery of neuropsychological tests encompassing five cognitive domains (reasoning, memory, attention, frontal executive functions, and language).

Results

Patients showed mild to moderate sleep problems (PDSS-2 score: 23.4 ± 1.2) and mild daytime sleepiness (ESS 8.6 ± 5.1). A significant correlation was found between PDSS-2 total score and non-verbal reasoning, as well as attentive skills, executive functions, and language abilities. No correlations were found between sleep measures and memory tests scores. Patients with clinically relevant sleep disturbances performed worse on attention, executive functions, and language. No significant correlations were found between daytime sleepiness and any neuropsychological test.

Conclusions

In advanced PD patients, sleep disturbances selectively correlate with specific neuropsychological functions and not with short-term memory and consolidation. Even if confirmations by means of longitudinal studies are needed, our observations suggest the importance of considering treatment of sleep disturbances to minimize their potential impact on cognition.

Exploring Nonmotor Neuropsychiatric Manifestations of Parkinson Disease in a Comprehensive Care Setting

Parkinson disease (PD) is a debilitating neurological condition that includes both motor symptoms and nonmotor symptoms (NMS). Psychiatric complaints comprise NMS and are collectively referred to as neuropsychiatric manifestations. Common findings include atypical depressive symptoms, anxiety, psychosis, impulse control disorder, deterioration of cognition, and sleep disturbances. Quality of life (QoL) of patients suffering from NMS is greatly impacted and many times can be more debilitating than motor symptoms of PD. We expand on knowledge gained from treatment models within a comprehensive care model that incorporates multidisciplinary specialists working alongside psychiatrists to treat PD. Insight into background, clinical presentations, and treatment options for patients suffering from neuropsychiatric manifestations of PD are discussed. Identifying symptoms early can help improve QoL, provide early symptom relief, and can assist tailoring treatment plans that limit neuropsychiatric manifestations.

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.

Excessive daytime sleepiness in Parkinson's disease: A systematic review and meta-analysis

OBJECTIVE

To provide a robust estimate of the prevalence of excessive daytime sleepiness (EDS) and its clinical correlates in patients with Parkinson's disease (PD).

METHOD

We searched the PubMed and Embase databases for studies investigating the prevalence and clinical correlates of EDS from inception to March 01, 2020. Quality assessment was performed using the Newcastle-Ottawa quality assessment scale. Random-effects models were set to pool the risk estimates. Sensitivity analyses were performed to evaluate the stability of the outcomes.

RESULTS

After screening 1367 titles and abstracts, 59 studies involving 12,439 participants were included in the systematic review and meta-analysis. The pooled prevalence of EDS in PD was 35.1%, which was higher in South America, North America, Europe, and Australia than that in Asia. Compared to patients without EDS, patients with EDS had higher effect size on disease duration (0.76 years; 95% CI: 0.16-1.37, I² = 68.8%), Hoehn and Yahr (HY) stage (0.23 grade; 95% CI: 0.11-0.34, I² = 69.1%), Unified PD Rating Scale (UPDRS)-III (3.02 points; 95% CI: 1.53-4.51, I²: 61.2%), levodopa equivalent daily dose (LEDD) (141.46 mg; 95% CI: 64.17-218.77, I² = 86.1%), depression symptoms (Hedges' g = 0.35; 95% CI: 0.15-0.55, I² = 72.0%) and male sex (OR = 1.50; 95% CI: 1.30-1.72, I² = 0).

CONCLUSION

Our results showed that approximately one-third of patients with PD had EDS, which may be associated with the severity of the disease, depression, and male sex, or a combination of neurodegeneration and medication.

Association Between REM Sleep Behavior Disorder and Cognitive Dysfunctions in Parkinson's Disease: A Systematic Review and Meta-Analysis of Observational Studies

Background: Rapid eye movement sleep behavior disorder (RBD) is thought to be a prodromal symptom of Parkinson's disease (PD). RBD is also thought to be involved in cognitive decline and dementia in PD. In PD, although the relationship between RBD and cognitive dysfunctions was confirmed by considerable studies, whether RBD was associated with distinct types of cognitive defects is worth of study. Objectives: This systematic review summarizes the evidence relating to cognitive dysfunction in PD patients with RBD (PD-RBD) and those without and explores their specificity to cognitive domains. Methods: A meta-analysis using a random-effects model was performed for 16 different cognitive domains, including global cognitive function, memory (long-term verbal recall, long-term verbal recognition, long-term visual recall, short-term spatial recall, and short-term verbal recall), executive function (general, fluid reasoning, generativity, shifting, inhibition, and updating), language, processing speed/complex attention/working memory, visuospatial/constructional ability, and psychomotor ability. The cognitive difference between the groups of patients was measured as a standardized mean difference (SMD, Cohen's d). PD-RBD patients were classified into Confirmed-RBD (definite diagnosis with polysomnography, PSG) and Probable-RBD (without PSG re-confirmation). In some domains, RBD patients could not be analyzed separately due to the exiguity of primary studies; this analysis refers to such RBD patients as "Mixed-RBD." Results: Thirty-nine studies with 6,695 PD subjects were finally included. Confirmed-RBD patients showed worse performance than those without in global cognitive function, long-term verbal recall, long-term verbal recognition, generativity, inhibition, shifting, language, and visuospatial/constructional ability; Probable-RBD, in global cognitive function and shifting; and Mixed-RBD, in long-term visual recall, short-term spatial recall, general executive function, and processing speed/complex attention/working memory. Conclusion: This meta-analysis strongly suggests a relationship between RBD, Confirmed-RBD in particular, and cognitive dysfunctions in PD patients. Early and routine screening by sensitive and targeted cognitive tasks is necessary for all PD-RBD patients because it may offer the therapeutic time window before they evolve to irreversible dementia.

Cognitive deficits in Parkinson's disease with excessive daytime sleepiness: a systematic review

Objectives: This systematic review synthesizes the most recent literature on neuropsychological deficits in adults with Parkinson's disease who experience excessive daytime sleepiness (EDS). Confounds and methodological limitations are explored. A framework entitled the Cascade Model of Excessive Daytime Sleepiness (CMEDS) is proposed to explain the role of EDS in contributing to cognitive impairment for patients with Parkinson's disease.Method: Systematic search through PubMed, PsychInfo and citation records. In total, 175 articles were screened for possible inclusion. Eight studies were included, encompassing 1373 patients with Parkinson's disease - 442 of whom had Parkinson's disease with EDS.Results: For Parkinson's disease patients with EDS, global deficits, executive dysfunction and deficits in processing speed were found beyond the typical cognitive phenotype of patients without EDS. Language skills, memory and visuospatial skills appeared to be similar between those with and without EDS. In untreated, de novo, patients, there were no cognitive differences between the EDS groups.Conclusion: This review suggests that Parkinson's disease patients suffering from EDS may have additional cognitive deficits globally, in executive control, and in processing speed. As suggested by the CMEDS framework, the impact of EDS on cognition may be related to Parkinson's disease pathology, comorbidities and medication use.

Temporal Associations between Sleep and Daytime Functioning in Parkinson's Disease: A Smartphone-Based Ecological Momentary Assessment

OBJECTIVES/BACKGROUND

Disruptions to mood, cognition, and other daytime functioning are common and debilitating symptoms of Parkinson's disease (PD), and there is evidence that sleep problems contribute to these symptoms. However, previous studies are limited by reliance on self-reported sleep and cross-sectional designs. With the aim of assessing sleep as a possible treatment target for improving daytime functioning in PD, we used smartphone-based ecological momentary assessment (EMA) and actigraphy to investigate temporal associations between sleep (objective and subjective) and daytime functioning.

PARTICIPANTS/METHODS

Twenty participants with mild-moderate PD wore actigraphs and completed sleep diaries for 14-15 days. They reported daytime functioning (anxiety, positive affect, cognitive function, fatigue, and social function) twice daily via smartphone-administered questionnaires. Multilevel modeling examined whether sleep quantity/quality predicted next-day functioning, and whether current mood (anxiety, positive affect) predicted later sleep.

RESULTS

Average completion rates for sleep diaries and daytime questionnaires were 94% and 91%, respectively. Subjective sleep quality predicted next-day anxiety (B = -.75, SE = .25, p= .003), but objective sleep did not predict any daytime functioning variables (p's>.112). Positive affect predicted later subjective sleep quality (B = 0.03, SE = .01, p = .003) but not objective sleep quantity/quality (p's>.107).

CONCLUSIONS

We demonstrated the feasibility of using EMA in PD. On a daily timescale, subjective sleep quality was bidirectionally associated with mood, whereas objective sleep was not associated with any daytime functioning. This discrepancy suggests that perception of sleep is important for mood in PD, which could provide targets for non-pharmacological interventions.

Sleep cardiac dysautonomia and EEG oscillations in amyotrophic lateral sclerosis

Study Objectives

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease due to loss of motor neurons. However, the autonomic nervous system (ANS) can also be involved. The aim of this research was to assess the sleep macro- and microstructure, the cardiac ANS during sleep, and the relationships between sleep, autonomic features, and clinical parameters in a cohort of ALS patients.

Methods

Forty-two consecutive ALS patients underwent clinical evaluation and full-night video-polysomnography. Only 31 patients met inclusion criteria (absence of comorbidities, intake of cardioactive drugs, or recording artifacts) and were selected for assessment of sleep parameters, including cyclic alternating pattern (CAP) and heart rate variability (HRV). Subjective sleep quality and daytime vigilance were also assessed using specific questionnaires.

Results

Although sleep was subjectively perceived as satisfactory, compared with age- and sex-matched healthy controls, ALS patients showed significant sleep alteration: decreased total sleep time and sleep efficiency, increased nocturnal awakenings, inverted stage 1 (N1)/stage 3 (N3) ratio, reduced REM sleep, and decreased CAP rate, the latter supported by lower amounts of A phases with an inverted A1/A3 ratio. Moreover, a significant reduction in HRV parameters was observed during all sleep stages, indicative of impaired autonomic oscillations.

Conclusion

Our results indicate that sleep is significantly disrupted in ALS patients despite its subjective perception. Moreover, electroencephalogram activity and autonomic functions are less reactive, as shown by a decreased CAP rate and a reduction in HRV features, reflecting an unbalanced autonomic modulation.

Global cognitive performance is associated with sleep efficiency measured by polysomnography in patients with Parkinson's disease

AIM

Sleep disorders can be associated with an increased risk for cognitive decline in patients with Parkinson's disease (PD). The aim of this study was to examine the association between cognitive status and presence of sleep symptoms and sleep disorders in PD patients.

METHODS

We evaluated excessive sleepiness, other sleep symptoms, and performed polysomnography and neuropsychological evaluation in 79 patients. They were classified as having normal cognition (PDNC), mild cognitive impairment (PDMCI), or dementia (PDD).

RESULTS

There were 29 PDNC, 39 PDMCI, and 11 PDD patients. PDD patients were older, had higher scores on the Unified Parkinson's Disease Rating Scale, and lower Schwab and England Activities of Daily Living scores than PDNC patients. After analysis of the polysomnographic variables, it was also found that PDD patients had a lower sleep efficiency, lower total sleep time, and lower number of sleep state changes than PDNC patients. In a stepwise analysis, defining Mattis Dementia Rating Scale scores as the dependent variable, the results were a model that selected three variables that accounted for 59% of the variation in the Mattis Dementia Rating Scale score: wake time after sleep onset, number of state changes, and schooling.

CONCLUSION

We found a significant association between global cognitive performance and wake time after sleep onset and the number of state changes during sleep measured in the polysomnography of PD patients. However, we did not find any other association between sleep disorders or symptoms and cognitive status or cognitive performance of PD patients.

Pedestrian safety in patients with Parkinson's disease: A case-control study

BACKGROUND

Patients with Parkinson's disease experience debilitating motor symptoms as well as nonmotor symptoms, such as cognitive dysfunction and sleep disorders. This constellation of symptoms has the potential to negatively influence pedestrian safety. The objective of this study was to investigate the association of motor symptoms, daytime sleepiness, impaired vigilance, and cognitive dysfunction with pedestrian behavior in patients with Parkinson's disease and healthy older adults.

METHODS

Fifty Parkinson's disease and 25 control participants were evaluated within a virtual reality pedestrian environment and completed assessments of motor performance, daytime sleepiness (Epworth Sleepiness Scale), vigilance (psychomotor vigilance task), and visual processing speed (Useful Field of View) outside the virtual reality environment. The primary outcome measure was time to contact, defined as the time remaining until a participant would have been hit by an approaching vehicle while crossing the virtual street.

RESULTS

The virtual reality pedestrian environment was feasible in all participants. Patients with Parkinson's disease demonstrated riskier pedestrian behavior compared with controls. Among Parkinson's disease participants, walking speed, objective measures of vigilance, and visual processing speed were correlated with pedestrian behavior, with walking speed the strongest predictor of time to contact, explaining 48% of the variance. Vigilance explained an additional 8% of the variance. In controls, vigilance was also important for street-crossing safety, but older age was the most robust predictor of pedestrian safety.

CONCLUSIONS

Walking speed is associated with unsafe pedestrian behavior in patients with Parkinson's disease. In contrast, age was the strongest predictor of pedestrian safety in healthy older adults. © 2017 International Parkinson and Movement Disorder Society.

Sleep Disturbance May Alter White Matter and Resting State Functional Connectivities in Parkinson's Disease

Study Objectives

To clarify whether sleep disturbance would alter the patterns of structural and functional networks underlying cognitive dysfunction in patients with Parkinson's disease (PD).

Methods

Among the 180 patients with nondemented PD in our cohort, 45 patients were classified as the group with sleep disturbance according to the 5-item scales for outcomes in Parkinson's disease nighttime scale. Based on propensity scores, another 45 PD patients without sleep disturbance were matched to this group. We performed a comparative analysis of cortical thickness, diffusion tensor imaging-based white matter integrity, resting-state functional connectivity, and cognitive performance between PD patients with and without sleep disturbance.

Results

PD patients with sleep disturbance showed poorer performance in attention and working memory and a tendency toward a lower score in frontal executive function relative to those without sleep disturbance. The PD with sleep disturbance group exhibited widespread white matter disintegration compared to the PD without sleep disturbance group, although there were no significant differences in cortical thickness between the PD subgroups. On functional network analysis, PD patients with sleep disturbance exhibited less severely decreased cortical functional connectivity within the default mode network, central executive network, and dorsal attention network when compared to those without sleep disturbance.

Conclusions

The present study suggests that sleep disturbance in PD patients could be associated with white matter and functional network alterations in conjunction with cognitive impairment.

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.

Mood and neural correlates of excessive daytime sleepiness in Parkinson's disease

For patients with Parkinson's disease (PD), excessive daytime sleepiness (PD-EDS) is a debilitating non-motor symptom and may be affected by mood symptoms, especially depression and anxiety. Few neuroimaging works have attempted to identify the neural features of PD-EDS, but various findings were reported. The purpose of this study was to systematically review the literature on mood and neuroimaging correlates of PD-EDS. A MEDLINE, PubMed, EMBASE, and PsycInfo search for peer-reviewed original research articles on depression, anxiety, and neuroimaging in PD-EDS identified 26 studies on depression, nine on anxiety, and eight on neuroimaging. Half of the studies reported greater depression in PD-EDS-positive patients compared with PD-EDS-negative patients. There was a significantly positive correlation between depression and PD-EDS. Limited studies on anxiety in PD-EDS suggested a weak correlation between anxiety and EDS. For depression and anxiety, the effect sizes were medium when EDS was subjectively measured, but became small when EDS was objective measured. Current neuroimaging studies generally suggested diminished neural structural and functional features (eg, brain volume, white matter integrity as indicated by fractional anisotropy, and cerebral metabolism) in patients with PD-EDS. Future studies should apply objective and subjective measures of mood symptoms and EDS and improve the neuroimaging methodology via using multimodal techniques and whole-brain analysis to provide new clues on the mood and neural correlates of PD-EDS.

REM sleep behavior disorder, as assessed by questionnaire, in G2019S LRRK2 mutation PD and carriers

BACKGROUND

Rapid eye movement sleep behavior disorder occurs with idiopathic Parkinson's disease (PD) and often precedes PD. Its frequency in LRRK2-PD and utility as a preclinical marker has not been established.

METHODS

One hundred forty-four idiopathic PD, 142 LRRK2 G2019S mutation PD, 117 non-manifesting carriers, 93 related noncarriers, and 40 healthy controls completed the Rapid eye movement sleep Behavior Disorder Screening Questionnaire.

RESULTS

Cut scores were met by 30.6% idiopathic PD, 19.7% LRRK2-PD, 6% nonmanifesting carriers, 20.4% related noncarriers, and 15% controls. The likelihood of abnormal scores was decreased in LRRK2-PD versus idiopathic PD (odds ratio = 0.55, P = 0.03), nonmanifesting carriers versus related noncarriers (OR = 0.25, P < 0.01), and PD of less than 3 years' duration, 1 of 19 LRRK2-PD versus 14 of 41 idiopathic PD (P < 0.05).

CONCLUSIONS

A lower frequency of abnormal questionnaire scores is seen in LRRK2-PD, especially in early LRRK2-PD, and in nonmanifesting carriers. Therefore, the Rapid eye movement sleep Behavior Disorder Questionnaire is unlikely to serve as a preclinical marker for phenoconversion to PD.

The Interaction between Obstructive Sleep Apnea and Parkinson's Disease: Possible Mechanisms and Implications for Cognitive Function

Parkinson's disease (PD) is a relentlessly progressive neurodegenerative disorder associated with hallmark motor and nonmotor symptoms (NMS) such as sleep disturbances and cognitive dysfunction. While dopaminergic treatments have improved the motor aspects of PD, progression remains inevitable. Research has recently increasingly focused on strategies to modify disease progression and on nonmotor manifestations of PD, given their impact on patients' quality of life. Obstructive sleep apnea (OSA) is a treatable sleep disorder, common in the general population, associated with excessive daytime sleepiness and neurocognitive deficits. Neuroimaging has demonstrated structural and functional changes in OSA patients; in animal models, OSA causes brain inflammation and oxidative injury, including in key areas involved in PD pathophysiology such as locus coeruleus. The prevalence of OSA in PD has been variable in studies to date, and potential consequences and interrelationship between the two disorders have not been well studied. There is however emerging evidence that OSA is associated with increased NMS in PD, particularly cognitive dysfunction. This review focuses on the possible interrelationship between OSA and PD. Mechanisms promoting OSA in PD will be reviewed, as well as mechanisms whereby OSA can affect the neurodegenerative process in PD.

Sleep disorders and respiratory function in amyotrophic lateral sclerosis

Sleep disorders in amyotrophic lateral sclerosis (ALS) present a significant challenge to the management of patients. Issues include the maintenance of adequate ventilatory status through techniques such as non-invasive ventilation, which has the ability to modulate survival and improve patient quality of life. Here, a multidisciplinary approach to the management of these disorders is reviewed, from concepts about the underlying neurobiological basis, through to current management approaches and future directions for research.

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.

Relationships among cognitive impairment, sleep, and fatigue in Parkinson's disease using the MDS-UPDRS

BACKGROUND

Non-motor complications of Parkinson's disease (PD), specifically cognitive impairment, sleep disturbances, and fatigue, are recognized as important contributors to poor patient outcomes and quality of life. How sleep problems and fatigue interrelate and impact cognitive function, however, has not systematically been investigated across the stages of PD. The aim of our study was to investigate the relationships among cognitive impairment, night-time sleep problems, daytime sleepiness, and fatigue across all severities of PD.

METHODS

We examined these non-motor problems using the Movement Disorder Society-Sponsored Revision of the Unified Parkinson's Disease Rating Scale (MDS-UPDRS) in a study of 1319 PD patients drawn from three large cohort studies: the Parkinson's Progressive Markers Initiative, the Rush University PD Cognitive-Behavioral-Imaging study, and the Movement Disorder Society-Unified Parkinson's Disease Rating Scale Clinimetric testing program study, which spanned the gamut of disease, from early to advanced PD. Generalized linear mixed models with logit linking functions and covariates including study cohort, age, PD duration, and presence/absence of PD medications were used to examine relationships between these three non-motor symptoms and cognitive impairment.

RESULTS

Of these three frequent, and often inter-twined, non-motor complications, greater daytime sleepiness and fatigue were associated with worse cognitive impairment across the full spectrum of PD (F[16,1158] = 2.40 and F[16,1158] = 3.45 respectively, p's < 0.0005), but an association with night-time sleep was not detected (p = 0.83).

CONCLUSIONS

Given this association of daytime sleepiness and fatigue with cognitive impairment, clinical monitoring for these problems should be considered across all points in the PD spectrum, from early to more advanced disease.

The Relationships Between Poor Sleep Efficiency and Mild Cognitive Impairment in Parkinson Disease

BACKGROUND

Mild cognitive impairment (MCI) and sleep disturbances are common features in Parkinson disease (PD). This study sought to investigate whether patients with MCI in PD (PD-MCI) have more pronounced sleep disturbance compared to those without PD-MCI and whether phenotypic presentations differ according to the PD-MCI subtypes.

METHODS

A total of 95 patients with idiopathic PD (53 meeting criteria for PD-MCI and 42 who were not cognitively impaired) and 22 controls underwent neurological and neuropsychological examination. They wore actigraphy watches for 2 weeks, from which measures of nocturnal sleep efficiency were calculated.

RESULTS

Patients with PD-MCI has significantly poorer sleep efficiency compared to those without PD-MCI. This effect was particularly apparent in those with multiple-domain PD-MCI, compared to those with single-domain PD-MCI. Furthermore, patients in the PD-MCI group had significantly more nontremor features.

CONCLUSIONS

These data suggest that PD-MCI is associated with greater sleep disturbance and nontremor features of PD. This is further evidence for the potential role that sleep disturbance plays in the heterogeneity of PD.

Investigating rapid eye movement sleep without atonia in Parkinson's disease using the rapid eye movement sleep behavior disorder screening questionnaire

Rapid eye movement (REM) sleep behavior disorder (RBD) is frequently observed in patients with Parkinson's disease (PD). Accurate diagnosis is essential for managing this condition. Furthermore, the emergence of idiopathic RBD in later life can represent a premotor feature, heralding the development of PD. Reliable, accurate methods for identifying RBD may offer a window for early intervention. This study sought to identify whether the RBD screening questionnaire (RBDSQ) and three questionnaires focused on dream enactment were able to correctly identify patients with REM without atonia (RWA), the neurophysiological hallmark of RBD. Forty-six patients with PD underwent neurological and sleep assessment in addition to completing the RBDSQ, the RBD single question (RBD1Q), and the Mayo Sleep Questionnaire (MSQ). The REM atonia index was derived for all participants as an objective measure of RWA. Patients identified to be RBD positive on the RBDSQ did not show increased RWA on polysomnography (80% sensitivity and 55% specificity). However, patients positive for RBD on questionnaires specific to dream enactment correctly identified higher degrees of RWA and improved the diagnostic accuracy of these questionnaires. This study suggests that the RBDSQ does not accurately identify RWA, essential for diagnosing RBD in PD. Furthermore, the results suggest that self-report measures of RBD need to focus questions on dream enactment behavior to better identify RWA and RBD. Further studies are needed to develop accurate determination and quantification of RWA in RBD to improve management of patients with PD in the future.

Objective measurement of daytime napping, cognitive dysfunction and subjective sleepiness in Parkinson's disease

Introduction

Sleep-wake disturbances and concomitant cognitive dysfunction in Parkinson’s disease (PD) contribute significantly to morbidity in patients and their carers. Subjectively reported daytime sleep disturbance is observed in over half of all patients with PD and has been linked to executive cognitive dysfunction. The current study used daytime actigraphy, a novel objective measure of napping and related this to neuropsychological performance in a sample of PD patients and healthy, age and gender-matched controls. Furthermore this study aimed to identify patients with PD who may benefit from pharmacologic and behavioural intervention to improve these symptoms.

Methods

Eighty-five PD patients and 21 healthy, age-matched controls completed 14 days of wrist actigraphy within two weeks of neuropsychological testing. Objective napping measures were derived from actigraphy using a standardised protocol and subjective daytime sleepiness was recorded by the previously validated Epworth Sleepiness Scale.

Results

Patients with PD had a 225% increase in the mean nap time per day (minutes) as recorded by actigraphy compared to age matched controls (39.2 ± 35.2 vs. 11.5 ± 11.0 minutes respectively, p < 0.001). Significantly, differences in napping duration between patients, as recorded by actigraphy were not distinguished by their ratings on the subjective measurement of excessive daytime sleepiness. Finally, those patients with excessive daytime napping showed greater cognitive deficits in the domains of attention, semantic verbal fluency and processing speed.

Conclusion

This study confirms increased levels of napping in PD, a finding that is concordant with subjective reports. However, subjective self-report measures of excessive daytime sleepiness do not robustly identify excessive napping in PD. Fronto-subcortical cognitive dysfunction was observed in those patients who napped excessively. Furthermore, this study suggests that daytime actigraphy, a non-invasive and inexpensive objective measure of daytime sleep, can identify patients with PD who may benefit from pharmacologic and behavioural interventions to improve these symptoms.

Dissociations among daytime sleepiness, nighttime sleep, and cognitive status in Parkinson's disease

BACKGROUND

Daytime and nighttime sleep disturbances and cognitive impairment occur frequently in Parkinson's disease (PD), but little is known about the interdependence of these non-motor complications. Thus, we examined the relationships among excessive daytime sleepiness, nighttime sleep quality and cognitive impairment in PD, including severity and specific cognitive deficits.

METHODS

Ninety-three PD patients underwent clinical and neuropsychological evaluations including the Epworth Sleepiness Scale (ESS) and Pittsburgh Sleep Quality Index (PSQI). Patients were classified as having normal cognition (PD-NC), mild cognitive impairment (PD-MCI), or dementia (PDD) using recently proposed Movement Disorder Society PD-MCI and PDD criteria. Relationships between the sleep and cognitive measures and PD cognitive groups were examined.

RESULTS

The PD cohort included PD-NC (n = 28), PD-MCI (n = 40), and PDD (n = 25) patients. ESS scores, as a measure of daytime sleepiness, were significantly worse (p = 0.005) in cognitively impaired PD patients, particularly PDD patients. ESS scores correlated significantly with Mini-Mental State Examination scores and also with cognitive domain scores for attention/working memory, executive function, memory, and visuospatial function. In contrast, PSQI scores, as a measure of nighttime sleep quality, neither differed among cognitive groups nor correlated with any cognitive measures.

CONCLUSIONS

Daytime sleepiness in PD, but not nighttime sleep problems, is associated with cognitive impairment in PD, especially in the setting of dementia, and attention/working memory, executive function, memory, and visuospatial deficits. The presence of nighttime sleep problems is pervasive across the PD cognitive spectrum, from normal cognition to dementia, and is not independently associated with cognitive impairment or deficits in cognitive domains.

Cognitive dysfunction and REM sleep behavior disorder: key findings in the literature and preliminary longitudinal findings

A considerable proportion of subjects initially diagnosed with idiopathic REM sleep behavior disorder (iRBD) are reported to convert to a neurodegenerative disorder, mainly synucleinopathies. It is unclear whether cognitive deficits in iRBD represent an associated feature or a marker predictive of subsequent development of a synucleinopathy. Cross-sectional studies indicate that a proportion of iRBD patients show cognitive deficits similar to those typically found in patients with synucleinopathies. The available longitudinal data suggest that cognitive dysfunction in iRBD tends to progress over time, with this progression probably being underpinned by a neurodegenerative process. Furthermore, within the framework of Parkinson's disease, RBD has been shown to be a risk factor for progressive cognitive decline even advancing to dementia. This paper addresses the multifaceted issue of cognitive dysfunction in RBD. Taking into account some key literature findings and preliminary longitudinal observations of our own, it shows that cognitive deterioration, mainly involving visuospatial abilities (learning as a stable deficit and copying as an evolving deficit), non-verbal logic, attention and executive functions can be observed in iRBD follow-up, suggesting an underlying evolving degenerative process. Large cohort studies with more prolonged follow-ups and greater methodological uniformity are needed to provide more reliable and robust findings.

Manipulating the sleep-wake cycle and circadian rhythms to improve clinical management of major depression

BACKGROUND

Clinical psychiatry has always been limited by the lack of objective tests to substantiate diagnoses and a lack of specific treatments that target underlying pathophysiology. One area in which these twin failures has been most frustrating is major depression. Due to very considerable progress in the basic and clinical neurosciences of sleep-wake cycles and underlying circadian systems this situation is now rapidly changing.

DISCUSSION

The development of specific behavioral or pharmacological strategies that target these basic regulatory systems is driving renewed clinical interest. Here, we explore the extent to which objective tests of sleep-wake cycles and circadian function - namely, those that measure timing or synchrony of circadian-dependent physiology as well as daytime activity and nighttime sleep patterns - can be used to identify a sub-class of patients with major depression who have disturbed circadian profiles.

SUMMARY

Once this unique pathophysiology is characterized, a highly personalized treatment plan can be proposed and monitored. New treatments will now be designed and old treatments re-evaluated on the basis of their effects on objective measures of sleep-wake cycles, circadian rhythms and related metabolic systems.

The contribution of nocturnal sleep to the consolidation of motor skill learning in healthy ageing and Parkinson's disease

The benefits of sleep for the consolidation of procedural motor skills are less robust in older adults, although the precise reasons for this remain unclear. To date, even less is known about these processes in older adults with neurodegenerative diseases, particularly those which impact on motor functioning. While sleep disturbance and motor symptoms are frequent disabling features of Parkinson's disease, no known studies have directly probed sleep-dependent memory consolidation for motor skill learning in Parkinson's disease. Forty patients with idiopathic Parkinson's disease (age = 63.7 years ± 7.7; disease duration 4.1 years ± 4.4) completed a motor skill learning task pre- and post-sleep and were compared to 20 age- and sex-matched controls recruited from the community. Polysomnography was undertaken during the post-training night and measures of sleep architecture were derived. Parkinson's disease patients did not demonstrate any apparent deficits in within-session learning and overnight stabilization compared to controls, with both groups failing to demonstrate offline improvements in performance (i.e. memory consolidation). In controls, longer duration in slow wave sleep was associated with improved next-day session learning (P = 0.007). However, in Parkinson's disease, no relationships between sleep parameters and learning measures were found. Slow wave sleep microarchitecture and the use of dopaminergic medications may contribute to impaired sleep-dependent multi-session acquisition of motor skill learning in Parkinson's disease.

Cognition in rapid eye movement sleep behavior disorder

Rapid eye movement (REM) sleep behavior disorder (RBD) is a parasomnia characterized by excessive muscle activity and undesirable motor events during REM sleep. RBD occurs in approximately 0.5% of the general population, with a higher prevalence in older men. RBD is a frequent feature of dementia with Lewy bodies (DLB), but is only rarely reported in Alzheimer’s disease. RBD is also a risk factor for α-synuclein-related diseases, such as DLB, Parkinson’s disease (PD), and multiple system atrophy. Therefore, RBD has major implications for the diagnosis and treatment of neurodegenerative disorders and for understanding specific neurodegeneration patterns. Several markers of neurodegeneration have been identified in RBD, including cognitive impairments such as deficits in attention, executive functions, learning capacities, and visuospatial abilities. Approximately 50% of RBD patients present mild cognitive impairment. Moreover, RBD is also associated with cognitive decline in PD.

Rapid eye movement sleep behavior disorder and risk of dementia in Parkinson's disease: a prospective study

One of the most devastating nonmotor manifestations of PD is dementia. There are few established predictors of dementia in PD. In numerous cross-sectional studies, patients with rapid eye movement (REM) sleep behavior disorder (RBD) have increased cognitive impairment on neuropsychological testing, but no prospective studies have assessed whether RBD can predict Parkinson's dementia. PD patients who were free of dementia were enrolled in a prospective follow-up of a previously published cross-sectional study. All patients had a polysomnogram at baseline. Over a mean 4-year follow-up, the incidence of dementia was assessed in those with or without RBD at baseline using regression analysis, adjusting for age, sex, disease duration, and follow-up duration. Of 61 eligible patients, 45 (74%) were assessed and 42 were included in a full analysis. Twenty-seven patients had baseline RBD, and 15 did not. Four years after the initial evaluation, 48% with RBD developed dementia, compared to 0% of those without (P-adjusted = 0.014). All 13 patients who developed dementia had mild cognitive impairment on baseline examination. Baseline REM sleep atonia loss predicted development of dementia (% tonic REM = 73.2 ± 26.7 with dementia, 40.8 ± 34.5 without; P = 0.029). RBD at baseline also predicted the new development of hallucinations and cognitive fluctuations. In this prospective study, RBD was associated with increased risk of dementia. This indicates that RBD may be a marker of a relatively diffuse, complex subtype of PD.