Deterioration of executive dysfunction in elderly with REM sleep behavior disorder (RBD)

Minimal effect of long-term clonazepam on cognitive function in patients with isolated rapid eye movement sleep behavior disorder

STUDY OBJECTIVES

Despite its widespread use in patients with isolated rapid eye movement sleep behavior disorder (iRBD), the cognitive effect of clonazepam is uncertain. This study aimed to investigate the effect of cumulative clonazepam on cognitive function in patients with iRBD.

METHODS

Demographic characteristics, baseline cognitive test, and most recent cognitive test information were collected retrospectively. Based on cumulative clonazepam doses, patients were classified into 4 subgroups: group 1, < 365 mg (1 mg × 1 year); group 2, 365 mg to < 1,095 mg (1 mg × 3 years); group 3, 1,095 mg to < 2,190 mg (1 mg × 6 years); and group 4, 2,190 mg or more. Cognitive test scores were calculated as z scores adjusted for age, education, and sex.

RESULTS

This study included 101 patients with iRBD (63 males). Groups 1, 2, 3, and 4 had 14, 20, 32, and 35 patients, respectively. In within-group comparisons, follow-up Digit Span Backward test and the Trail Making Test A scores decreased in group 3, and follow-up Trail Making Test A and the Trail Making Test B scores decreased significantly in group 4. In the multiple regression analysis to determine influential factors on cognitive decline, cumulative clonazepam dose did not show a significant correlation with any cognitive domain. Follow-up cognitive function showed significant correlation only with baseline cognitive function.

CONCLUSIONS

Memory and executive functions tended to decline in patients with iRBD. However, there was no significant effect of cumulative clonazepam. There was no evidence that long-term use of clonazepam was related to cognitive decline in patients with iRBD.

CITATION

Lee M, Kim TK, Hong JK, Yoon I-Y. Minimal effect of long-term clonazepam on cognitive function in patients with isolated rapid eye movement sleep behavior disorder. J Clin Sleep Med. 2024;20(7):1173-1182.

Sex differences in rapid eye movement sleep behavior disorder: A systematic review and meta-analysis

Although rapid eye movement (REM) sleep behavior disorder (RBD) has been widely considered as a male-predominant parasomnia, the existing evidence for the sex difference in the risk of RBD in the general population was conflicting. The present study conducted a systematic review to explore the sex differences in the prevalence, comorbidities, clinical characteristics, and phenoconversion of RBD. One hundred thirty-five eligible studies were identified for the systematic review, and 133 were finally included in the meta-analysis. Males in the general population showed a trend for a higher risk of probable/possible RBD (pRBD), especially among the male older adults (aged ≥60). In the clinical populations, males showed a significantly higher risk of confirmed RBD, but not of pRBD. Among idiopathic RBD (iRBD) patients, males had a significantly earlier age onset of RBD compared with females. Male patients with Parkinson's disease (PD) had a higher risk of comorbid RBD. There was no significant sex difference in the risk of developing neurodegenerative diseases in iRBD patients. Large scale and prospective studies utilizing stringent diagnostic criteria for RBD are recommended to further verify the sex differences in RBD and to investigate the mechanism underlying the sex difference.

Association of sleep disorders with clinical symptoms and age in Chinese older adult patients with and without cognitive decline

Objective

To investigate correlation between cognitive function, age, and sleep disturbances.

Methods

This retrospective clinical study enrolled 78 patients with sleep disorders who were divided into three groups: a group of 24 patients with sleep disorders accompanied by cognitive decline (SD-CD); 54 patients with sleep disorders and no cognitive decline (SD-nCD) was divided into two groups, one of 30 patients aged between 60 and 70 years and another of 24 patients aged >70 years. Polysomnography was used to record patients' sleep indicators throughout night; these included total sleep duration, sleep efficiency (SE), sleep latency, sleep structure and percentage of N1, N2, and N3 stages, rapid eye movement (REM) stage, as well as apnea hypopnea index (AHI), and oxygen saturation (OS). Analysis of variance (ANOVA) for continuous variables and chi-square test for categorical variables were used to analyze variables between different groups. Pearson's correlation was used to analyze correlation between sleep parameters and mini-mental state examination (MMSE). Blood samples were used to determine their Aβ, Aβ40, Aβ42, total tau, phosphorylated tau protein (ptau), ptau181, ptau217, the inflammatory factor IL-1β, vitamin B12 (VB12), and melatonin levels.

Results

In the SD-CD group, there was a significant decrease in SE and an increase in N1 stage sleep in older patients and a significant increase in AHI, REM stage AHI, and non-REM stage AHI. In patients with SD-nCD, the minimum OS, minimum OS in the REM period, and minimum OS in the non-REM period were significantly reduced. OS was significantly correlated with cognitive level, as evaluated by the MMSE. The addition of sleep parameters can significantly improve the accuracy of dementia diagnosis. Dementia biomarkers of Aβ and tau proteins in blood showed cognition-related differences, while ptau181 was associated with both cognition and age-related differences. Regression models revealed that age was related to higher levels of cognitive decline before (β = -0.43, P < 0.001) and after (β = -0.38, P < 0.001) adjustment of gender, BMI, and education level. There was a significant mediation effect of relationship between aging and cognitive function by sleep efficiency and N1 stage sleep.

Conclusion

Sleep disorders and low OS are associated with a higher incidence of cognitive decline and dementia.

Predictors of RBD progression and conversion to synucleinopathies

Purpose of review

Rapid eye movement (REM) sleep behaviour disorder (RBD) is considered the expression of the initial neurodegenerative process underlying synucleinopathies and constitutes the most important marker of their prodromal phase. This article reviews recent research from longitudinal research studies in isolated RBD (iRBD) aiming to describe the most promising progression biomarkers of iRBD and to delineate the current knowledge on the level of prediction of future outcome in iRBD patients at diagnosis.

Recent findings

Longitudinal studies revealed the potential value of a variety of biomarkers, including clinical markers of motor, autonomic, cognitive, and olfactory symptoms, neurophysiological markers such as REM sleep without atonia and electroencephalography, genetic and epigenetic markers, cerebrospinal fluid and serum markers, and neuroimaging markers to track the progression and predict phenoconversion. To-date the most promising neuroimaging biomarker in iRBD to aid the prediction of phenoconversion is striatal presynaptic striatal dopaminergic dysfunction.

Summary

There is a variety of potential biomarkers for monitoring disease progression and predicting iRBD conversion into synucleinopathies. A combined multimodal biomarker model could offer a more sensitive and specific tool. Further longitudinal studies are warranted to iRBD as a high-risk population for early neuroprotective interventions and disease-modifying therapies.

The epidemiology of cognitive function in Parkinson's disease

Epidemiology is the study of the distribution of disease in human populations, which is important in evaluating burden of illness, identifying modifiable risk factors, and planning for current and projected needs of the health care system. Parkinson's disease (PD) is the second most common serious neurodegenerative illness and is expected to further increase in prevalence. Cognitive changes are increasingly viewed as an integral non-motor feature in PD, emerging even in the prodromal phase of the disease. The prevalence of PD-MCI ranges from 20% to 40% depending on the population studied. The incidence of PD-dementia increases with duration of disease, with estimates growing from 3% to 30% of individuals followed for 5 years or less to over 80% after 20 years. There are several challenges in estimating the frequency of cognitive change, including only recently standardized diagnostic criteria, variation depending on exact neuropsychological evaluations performed, and differences in population sampling. Clinical features associated with cognitive decline include older age, increased disease duration and severity, early gait dysfunction, dysautonomia, hallucinations and other neuropsychiatric features, the presence of REM behavior disorder, and posterior predominant dysfunction on neuropsychological testing. There is increasing evidence that genetic risk factors, in particular GBA and MAPT mutations, contribute to cognitive change. Possible protective factors include higher cognitive reserve and regular exercise. Important sequelae of cognitive decline in PD include higher caregiver burden, decreased functional status, and increased risk of institutionalization and mortality. Many remaining uncertainties regarding the epidemiology of cognitive change in PD require future research, with improved biomarkers and more sensitive and convenient outcome measures.

Prodromal Cognitive Deficits and the Risk of Subsequent Parkinson’s Disease

Background: There is growing interest in identifying individuals who are in the prodromal phase of Parkinson’s disease (PD), as these individuals are potentially suitable for inclusion in intervention trials to prevent clinically manifest PD. However, it is less clear whether—and to what extent—cognitive deficits are present in prodromal PD. Methods: A systematic query was conducted through PubMed and Embase for prospective observational cohort studies that (a) assessed cognitive performance in individuals free of manifest PD at baseline and (b) subsequently followed up participants for incident PD. We grouped the results by cognitive domain, and for domains that had been reported in at least three separate studies, we performed random-effects, inverse variance meta-analyses based on summary statistics. Results: We identified nine articles suitable for inclusion, with a total of 215 patients with phenoconversion and 13,524 individuals remaining disease-free at follow-up. The studies were highly heterogeneous in study design, study population, and cognitive test batteries. Studies that included only cognitive screening measures such as MMSE or MoCA reported no association between worse cognitive performance and onset of manifest PD (combined odds ratio 1.08; 95% confidence interval 0.66–1.77). By contrast, studies that used extensive cognitive testing batteries found that global cognitive deficits were associated with an increased risk of manifest PD. In domain-specific analyses, there was evidence for an association between worse executive functioning (OR 1.45; 95% CI 1.10–1.92), but not memory (OR 1.20; 95% CI 0.85–1.70) or attention (OR 0.98; 95% CI 0.23–4.26), and clinically manifest PD. Conclusion: Although some caution due to high heterogeneity among published studies is warranted, the available evidence suggests that global and executive cognitive deficits are prodromal features of PD. Collaborative prospective studies with extensive cognitive test batteries are required to shed light on domain-specific deficits, temporal relations, and subgroup differences in prodromal cognitive deficits in PD.

Alerting network alteration in isolated rapid eye movement sleep behavior disorder patients with mild cognitive impairment

OBJECTIVE

Mild cognitive impairment (MCI) was found in 30-50% of the isolated REM sleep behavior disorder (iRBD) patients. Furthermore, it is known that patients with Parkinson's disease have attention network defects. Given that iRBD is known to be the prodromal disease of α-synucleinopathies, our aim was to investigate whether there are attention network dysfunctions in iRBD patients following the presence of MCI.

METHODS

14 healthy controls, 48 iRBD patients, 24 with MCI and 24 without MCI, were included in this study. Attention network task (ANT) was used to assess alerting, orienting, and executive control networks. Event-related potentials (ERPs) and behavioral performances were recorded during the ANT. Parietal N1 and P3 components were analyzed to find effects of the three attention networks.

RESULTS

IRBD patients without MCI showed neuropsychological, behavioral, and ERP results similar to those of healthy controls. On the other hand, iRBD patients with MCI showed a general decline in cognitive domains with no alerting effect (controls, p = 0.043; iRBD-noMCI, p = 0.014; iRBD-MCI, p = 0.130) while preserving orienting and executive control effect. Furthermore, iRBD patients with MCI had impairments in executive function and verbal memory domains, compared to iRBD patients without MCI.

CONCLUSIONS

Our findings indicate that when cognition is reduced to MCI levels in iRBD patients, the attention network, especially the alerting component, is impaired. The attention network and cognition, on the other hand, can be preserved in iRBD patients due to the compensatory mechanism.

Mild cognitive impairment and abnormal brain metabolic expression in idiopathic REM sleep behavior disorder

BACKGROUND

Mild cognitive impairment (MCI) is a common feature of isolated rapid-eye-movement sleep behavior disorder (iRBD). Here, we assessed cognitive functions and MCI in a prospective iRBD cohort and investigated their association with disease-specific brain metabolic patterns.

METHODS

Forty-four patients with polysomnography-confirmed iRBD performed a standardized battery of neuropsychological examinations every two years. We used previously established spatial covariance patterns from de novo drug-naïve Parkinson's disease with concomitant RBD (_denovoPDRBD-RP) and iRBD (iRBD-RP) using ¹⁸F-fluorodeoxyglucose PET scan. We compared those expressions between iRBD with normal cognition (iRBD-NC) and with mild cognitive impairment (iRBD-MCI), and evaluated whether they predict progressive cognitive deterioration.

RESULTS

Twenty iRBD patients (45 %) had MCI at baseline and 12 patients (27 %, about 7 % per year) had clinically significant cognitive deterioration after 4 years. The iRBD-MCI and iRBD-NC groups showed similar rates of cognitive change, but iRBD-MCI consistently performed worse in the domains of verbal memory and executive function. Elevated _denovoPDRBD-RP expression predicted cognitive deterioration (hazard ratio = 5.98 [1.70-21.06]), whereas iRBD-RP did not.

CONCLUSIONS

Increased disease-specific brain metabolic patterns are associated with iRBD-MCI and impending cognitive deterioration with the risk of progression to Lewy body dementia.

Impaired cerebral microcirculation in isolated REM sleep behaviour disorder

During the prodromal period of Parkinson's disease and other α-synucleinopathy-related parkinsonisms, neurodegeneration is thought to progressively affect deep brain nuclei, such as the locus coeruleus, caudal raphe nucleus, substantia nigra, and the forebrain nucleus basalis of Meynert. Besides their involvement in the regulation of mood, sleep, behaviour, and memory functions, these nuclei also innervate parenchymal arterioles and capillaries throughout the cortex, possibly to ensure that oxygen supplies are adjusted according to the needs of neural activity. The aim of this study was to examine whether patients with isolated REM sleep behaviour disorder, a parasomnia considered to be a prodromal phenotype of α-synucleinopathies, reveal microvascular flow disturbances consistent with disrupted central blood flow control. We applied dynamic susceptibility contrast MRI to characterize the microscopic distribution of cerebral blood flow in the cortex of 20 polysomnographic-confirmed patients with isolated REM sleep behaviour disorder (17 males, age range: 54-77 years) and 25 healthy matched controls (25 males, age range: 58-76 years). Patients and controls were cognitively tested by Montreal Cognitive Assessment and Mini Mental State Examination. Results revealed profound hypoperfusion and microvascular flow disturbances throughout the cortex in patients compared to controls. In patients, the microvascular flow disturbances were seen in cortical areas associated with language comprehension, visual processing and recognition and were associated with impaired cognitive performance. We conclude that cortical blood flow abnormalities, possibly related to impaired neurogenic control, are present in patients with isolated REM sleep behaviour disorder and associated with cognitive dysfunction. We hypothesize that pharmacological restoration of perivascular neurotransmitter levels could help maintain cognitive function in patients with this prodromal phenotype of parkinsonism.

Clinical features of multiple system atrophy with or without rapid eye movement behavior disorder: a cross-sectional study in southwest China

OBJECTIVE

The aim of this study was to investigate the prevalence of rapid eye movement behavior disorder (RBD) in Chinese patients with multiple system atrophy (MSA) and to compare motor and non-motor symptoms and sleep disturbance of MSA patients with and without RBD.

METHODS

A total of 55 patients who were consecutively admitted to West China Hospital of Sichuan University from 2016 to 2019 and subsequently diagnosed with probable MSA were enrolled in this cross-sectional study. The diagnosis of RBD was based on the results of video polysomnography (PSG) and a history of abnormal sleep-related behaviors. The patients were divided into two groups: those with RBD and those without. These two groups were then compared in terms of severity of motor symptoms (Unified Multiple System Arophy Rating Scale) and non-motor symptoms (Non-Motor Symptoms Scale, Mini-Mental State Examination score, Epworth Sleepiness Scale, Fatigue Severity Scale, Pittsburgh Sleep Quality Index, REM Sleep Behavior Disorder Screening Questionnaire, Hamilton Depression Rating Scale, Hamilton Anxiety Rating Scale) and sleep parameters as recorded on PSG.

RESULTS

Of the 55 patients (35 males), 18 (33%, 13 males) were diagnosed with RBD. Patients with or without RBD did not differ in demographic characteristics, clinical features, or sleep parameters based on PSG.

CONCLUSION

There was no difference in motor and non-motor symptoms between MSA patients with or without RBD, indicating that the presence of RBD may not be significantly associated with the severity of motor or non-motor dysfunction in MSA.

Assessment of cognitive profile as a prodromal marker of the evolution of rapid eye movement sleep behavior disorder

Study Objectives

To search for a specific neuropsychological profile in idiopathic REM sleep behavior disorder (iRBD), able to predict the onset of neurodegenerative disorders.

Methods

In a longitudinal follow-up study of 63 consecutive iRBD patients (follow-up duration 6.7 ± 3.8 years), the baseline cognitive profile of converters to neurodegenerative disease was compared with that of the nonconverters. Five cognitive domains were assessed: memory, attention-working memory, executive functions, visuospatial abilities, language. Mild cognitive impairment (MCI) was diagnosed according to the Movement Disorder Society’s diagnostic criteria for Parkinson’s disease.

Results

30 subjects (47.6%) developed a neurodegenerative disease (latency to conversion 60.33 ± 44.81 months). MCI was found in 50% of the converters and 12% of the nonconverters (p = .001), and its presence conferred a neurodegenerative disease risk of 10% at 3 years, 36% at 5 years, and 73% at 10 years (p = .002). Pathological equivalent scores on at least one neuropsychological test were detected in 46.7% of the converters versus 21.2% of the nonconverters in the memory domain (p = .032), in 40.0% versus 6.1% in that of executive functions (p = .002), and in 20.0% versus 3% in the visuospatial abilities domain (p = .047). On multivariate analysis, impaired executive functions significantly correlated with phenoconversion (p = .018). Lower Mini Mental State Examination (MMSE) scores (p = .004) and memory deficits (p = .031) were found in patients who developed dementia first.

Conclusions

Cognitive profile is useful for stratifying risk of phenoconversion in patients with iRBD. The presence of MCI and impaired executive functions, memory, and visuospatial abilities discriminated the converters. Lower MMSE scores and memory deficits may characterize those subjects who first develop dementia.