Symmetry of Parkinson's disease and REM sleep: One piece of the puzzle

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.

[Diagnostic of prodromal dementia with Levy bodies]

The issues of diagnosis of prodromal dementia with Lewy bodies are considered. Despite numerous studies using international diagnostic criteria, clinical and diagnosis are often inconsistent. Early and more accurate detection of dementia with Lewy bodies is needed for prognosis, optimal management and effective pharmacotherapy.

Prodromal dementia with Lewy bodies

Dementia with Lewy bodies (DLB) is the second most common neurodegenerative dementing disorder after Alzheimer's disease (AD), but there is limited information regarding the prodromal DLB state compared with that of AD. Parkinson's disease (PD) and DLB share common prodromal symptoms with Lewy body disease (LBD), allowing us to use a common strategy for identifying the individuals with an underlying pathophysiology of LBD. Dysautonomia, olfactory dysfunction, rapid eye movement sleep behavior disorder (RBD) and psychiatric symptoms antedate the onset of dementia by years or even decades in patients with DLB. Although RBD is the most potentially accurate prodromal predictor of DLB, disease progression before the onset of dementia could differ between the prodromal DLB state with and without RBD. Experts who specialize in idiopathic RBD and DLB might need communication in order to clarify the clinical relevance of RBD with the disease progression of DLB. The presence of prodromal LBD symptoms or findings of occipital hypoperfusion/hypometabolism helps us to predict the possible pathophysiological process of LBD in non-demented patients. This approach might provide the opportunity for additional neuroimaging, including cardiac (123) I-metaiodobenzylguanidine scintigraphy and dopamine transporter imaging. Although limited radiological findings in patients with prodromal DLB states have been reported, there is now a need for larger clinical multisite studies with pathological verification. The long prodromal phase of DLB provides a critical opportunity for potential intervention with disease-modifying therapy, but only if we are able to clearly identify the diversity in the clinical courses of DLB. In the present article, we reviewed the limited literature regarding the clinical profiles of prodromal DLB.

Surface EMG activity during REM sleep in Parkinson's disease correlates with disease severity

OBJECTIVES

Over 40% of individuals with Parkinson's disease (PD) have rapid eye movement sleep behavior disorder (RBD). This is associated with excessive sustained (tonic) or intermittent (phasic) muscle activity instead of the muscle atonia normally seen during REM sleep. We examined characteristics of manually-quantitated surface EMG activity in PD to ascertain whether the extent of muscle activity during REM sleep is associated with specific clinical features and measures of disease severity.

METHODS

In a convenience sample of outpatients with idiopathic PD, REM sleep behavior disorder was diagnosed based on clinical history and polysomnogram, and severity was measured using the RBD sleep questionnaire. Surface EMG activity in the mentalis, extensor muscle group of the forearms, and anterior tibialis was manually quantitated. Percentage of REM time with excessive tonic or phasic muscle activity was calculated and compared across PD and RBD characteristics.

RESULTS

Among 65 patients, 31 had confirmed RBD. In univariate analyses, higher amounts of surface EMG activity were associated with longer PD disease duration (srho = 0.34; p = 0.006) and greater disease severity (p < 0.001). In a multivariate regression model, surface EMG activity was significantly associated with RBD severity (p < 0.001) after adjustment for age, PD disease duration, PD severity and co-morbid sleep abnormalities.

CONCLUSION

Surface EMG activity during REM sleep was associated with severity of both PD and RBD. This measure may be useful as a PD biomarker and, if confirmed, may aid in determining which PD patients warrant treatment for their dream enactment to reduce risk of injury.

Primary visual cortical metabolism and rapid eye movement sleep behavior disorder in dementia with Lewy bodies

AIM

Significant glucose hypometabolism in the primary visual cortex (PVC) is considered to support a diagnosis of dementia with Lewy bodies (DLB), but its relationship to the clinical features remains unknown. The purpose of this study was to assess the association between the metabolic pattern and clinical variables in DLB.

METHODS

A total of 27 DLB patients who underwent [18F]fluoro-d-glucose (18F-FDG) positron emission tomography scans were examined. Demographics and clinical variables were compared between patients with and without glucose hypometabolism in the PVC. The correlations between the cerebral metabolic rate of glucose in the PVC and clinical variables were also investigated.

RESULTS

Only the onset age of probable rapid eye movement sleep behavior disorder (RBD) was significantly different between patients with and withoutglucose hypometabolism in the PVC, being younger in patients with the metabolic pattern; there were no other differences in clinical variables. The onset age of probable RBD was significantly correlated with the cerebral metabolic rate of glucose in the PVC.

CONCLUSIONS

Glucose hypometabolism in the PVC provides a potential mechanism for the link between antecedent RBD and the subsequent development of dementia in DLB patients. Glucose hypometabolism in the PVC may represent the effect of the pathophysiological process of DLB on RBD rather than a distinct condition in the disease progression. The physiological aspects of the link between this metabolic pattern and the onset of RBD remain unclear.

Probable rapid eye movement sleep behavior disorder, nocturnal disturbances and quality of life in patients with Parkinson's disease: a case-controlled study using the rapid eye movement sleep behavior disorder screening questionnaire

Background

Increasing evidence provides a clear association between rapid eye movement sleep behavior disorders (RBD) and Parkinson’s disease (PD), but the clinical features that determine the co-morbidity of RBD and PD are not yet fully understood.

Methods

We evaluated the characteristics of nocturnal disturbances and other motor and non-motor features related to RBD in patients with PD and the impact of RBD on their quality of life. Probable RBD (pRBD) was evaluated using the Japanese version of the RBD screening questionnaire (RBDSQ-J).

Results

A significantly higher frequency of pRBD was observed in PD patients than in the controls (RBDSQ-J ≥ 5 or ≥ 6: 29.0% vs. 8.6%; 17.2% vs. 2.2%, respectively). After excluding restless legs syndrome and snorers in the PD patients, the pRBD group (RBDSQ-J≥5) showed higher scores compared with the non-pRBD group on the Parkinson’s disease sleep scale-2 (PDSS-2) total and three-domain scores. Early morning dystonia was more frequent in the pRBD group. The Parkinson’s Disease Questionnaire (PDQ-39) domain scores for cognition and emotional well-being were higher in the patients with pRBD than in the patients without pRBD. There were no differences between these two groups with respect to the clinical subtype, disease severity or motor function. When using a cut-off of RBDSQ-J = 6, a similar trend was observed for the PDSS-2 and PDQ-39 scores. Patients with PD and pRBD had frequent sleep onset insomnia, distressing dreams and hallucinations. The stepwise linear regression analysis showed that the PDSS-2 domain “motor symptoms at night”, particularly the PDSS sub-item 6 “distressing dreams”, was the only predictor of RBDSQ-J in PD.

Conclusion

Our results indicate a significant impact of RBD co-morbidity on night-time disturbances and quality of life in PD, particularly on cognition and emotional well-being. RBDSQ may be a useful tool for not only screening RBD in PD patients but also predicting diffuse and complex clinical PD phenotypes associated with RBD, cognitive impairment and hallucinations.

Rapid eye movement sleep behavior disorder and subtypes of Parkinson's disease

Numerous studies have explored the potential relationship between rapid eye movement sleep behavior disorder (RBD) and manifestations of PD. Our aim was to perform an expanded extensive assessment of motor and nonmotor manifestations in PD to identify whether RBD was associated with differences in the nature and severity of these manifestations. PD patients underwent polysomnography (PSG) to diagnose the presence of RBD. Participants then underwent an extensive evaluation by a movement disorders specialist blinded to PSG results. Measures of disease severity, quantitative motor indices, motor subtypes, therapy complications, and autonomic, psychiatric, visual, and olfactory dysfunction were assessed and compared using regression analysis, adjusting for disease duration, age, and sex. Of 98 included patients, 54 had RBD and 44 did not. PD patients with RBD were older (P = 0.034) and were more likely to be male (P < 0.001). On regression analysis, the most consistent links between RBD and PD were a higher systolic blood pressure (BP) change while standing (-23.9 ± 13.9 versus -3.5 ± 10.9; P < 0.001), a higher orthostatic symptom score (0.89 ± 0.82 versus 0.44 ± 0.66; P = 0.003), and a higher frequency of freezing (43% versus 14%; P = 0.011). A systolic BP drop >10 could identify PD patients with RBD with 81% sensitivity and 86% specificity. In addition, there was a probable relationship between RBD and nontremor predominant subtype of PD (P = 0.04), increased frequency of falls (P = 0.009), and depression (P = 0.009). Our results support previous findings that RBD is a multifaceted phenomenon in PD. Patients with PD who have RBD tend to have specific motor and nonmotor manifestations, especially orthostatic hypotension.

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.