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Background: There is growing evidence that essential tremor (ET) patients are at high risk of cognitive impairment. Predictors of cognitive impairment have not been studied extensively. There is evidence from cross-sectional studies that sleep dysregulation is associated with cognitive dysfunction in ET, but longitudinal studies of the impact of sleep disruption on cognitive change have not been conducted. We investigated the extent to which sleep problems predict cognitive change in patients with ET., Methods: ET cases enrolled in a prospective, longitudinal study of cognitive performance. Sleep quality was assessed using the Pittsburg Sleep Quality Index (PSQI). Cognitive abilities across five domains (memory, executive function, attention, language, and visuospatial ability), and a global cognitive score (mean of the domains) were extracted from an extensive neuropsychological assessment. Generalized estimated equations were used to examine the association between baseline sleep problems and cognitive changes over three follow-up assessments each spaced 18 months apart., Results: The 188 non-demented ET cases had a mean age of 77.7 ± 9.5 years. Longer sleep latency was associated with longitudinal decline in executive function (p = 0.038), and marginally with longitudinal decline in global cognitive performance (p = 0.075). After excluding 29 cases with mild cognitive impairment, results were similar., Conclusion: Cognitively healthy people with ET who have longer sleep latency had greater declines in executive function during prospective follow-up. Early detection of, and possibly intervention for, abnormal sleep latency may protect against certain aspects of cognitive decline in ET patients., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Background: Previous studies have demonstrated the importance of the locus coeruleus (LC) in sleep-wake regulation. Both essential tremor (ET) and Parkinson's disease (PD) share common sleep disorders, such as poor quality of sleep (QoS). LC pathology is a feature of both diseases. A question arises regarding the contribution of LC degeneration to the occurrence of poor QoS., Objective: To evaluate the association between LC impairment and sleep disorders in ET and PD patients., Methods: A total of 83 patients with ET, 124 with PD, and 83 healthy individuals were recruited and divided into ET/PD with/without poor QoS (Sle/NorET and Sle/NorPD) subgroups according to individual Pittsburgh Sleep Quality Index (PSQI) score. Neuromelanin-sensitive magnetic resonance imaging (NM-MRI) and free-water imaging derived from diffusion MRI were performed. Subsequently, we evaluated the association between contrast-to-noise ratio of LC (CNRLC) and free-water value of LC (FWLC) with PSQI scores in ET and PD groups., Results: CNRLC was significantly lower in ET (p = 0.047) and PD (p = 0.018) than in healthy individuals, whereas no significant difference was found in FWLC among the groups. No significant differences were observed in CNR/FWLC between patients with/without sleep disorders after multiple comparison correction. No correlation was identified between CNR/FWLC and PSQI in ET and PD patients., Conclusions: LC degeneration was observed in both ET and PD patients, implicating its involvement in the pathophysiology of both diseases. Additionally, no significant association was observed between LC integrity and PSQI, suggesting that LC impairment might not directly relate to overall QoS.

Objective: Our study aimed to explore the associative relationship between neurodegenerative diseases and sleep disorders., Patients: This 15-year retrospective longitudinal nationwide population-based matched case-control study used data extracted from the National Health Insurance Research Database. We evaluated 25,589 patients diagnosed with neurodegenerative diseases between 2000 and 2015 and a matched control of 102,356 patients without neurodegenerative diseases., Results: Sleep disorders were an independent risk factor for the development of neurodegenerative diseases (adjusted odds ratio (OR): 1.794, 95% confidence interval (CI): 1.235-2.268, P < 0.001), with a positive dose-effect relationship (adjusted OR (95% CI): <1 year: 1.638 (1.093-2.872), P < 0.001; 1-5 years: 1.897 (1.260-3.135), P < 0.001; >5 years: 2.381 (1.467-3.681), P < 0.001. Moreover, patients with sleep disorder and comorbid depression had a significantly higher risk of neurodegenerative disorders (adjusted OR: 5.874). Subgroup analysis showed that insomnia was associated with Alzheimer's disease, Pick's disease and essential tremor (adjusted OR (95% CI): 1.555 (1.069-1.965), 1.934 (1.331-2.445) and 2.089 (1.439-2.648), respectively). Obstructive sleep apnea was associated with Parkinson's disease, essential tremor, and primary dystonia (adjusted OR (95% CI): 1.801 (1.239-2.275), 5.523 (3.802-6.977), and 4.892 (3.365-6.178), respectively). Other specific sleep disorders were associated with Pick's disease, Parkinson's disease, essential tremor, and primary dystonia (adjusted OR (95% CI): 8.901 (6.101-11.010), 1.549 (1.075-1.986), 2.791 (1.924-3.531), and 9.114 (6.283-10.506), respectively)., Conclusion: Sleep disorders are associated with the subsequent development of neurodegenerative disorders. Moreover, sleep disorder patients with comorbid depression have a higher risk of neurodegenerative diseases., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Purpose of the Review: Patients diagnosed with essential tremor (ET) report frequent sleep complaints. This review focuses on the main findings of studies addressing sleep features in patients diagnosed with ET, updating previously reported information. Bad quality of sleep and excessive daytime somnolence are very frequent in patients with ET, although the effects of the drugs used for the therapy of ET could contribute to these complaints. REM sleep behavior disorder, restless legs, insomnia, and nocturia are frequent complaints as well. There is a lack of studies addressing polysomnographic features of ET.

Sleep disorders are frequent in patients diagnosed with essential tremor (ET). The present review focuses on sleep disorders and the results of polysomnographic studies performed in patients with ET. For this purpose we performed a systematic review crossing the search term "essential tremor" with "sleep," "sleep disorders," "sleep disturbances" and "polysomnography," and with specific sleep disorders, according to the International Classification of the Sleep Disorders-Third Edition, using the PubMed, EMBASE, MEDLINE, and Web of Science Databases. The most frequent sleep problems reported by patients with ET were the bad quality of sleep and excessive daytime somnolence (the latter could be related to drugs commonly used for the treatment of ET). Probable rapid eye movement sleep behavior disorder, coexistent restless legs syndrome, insomnia, and nocturia were not infrequent complaints, while the presence of other sleep disorders in patients with ET was restricted to anecdotal reports or not described. Meta-analyses of previous reports showed that patients with ET (according to the PRISMA and MOOSE guidelines) showed higher scores in the Pittsburgh Sleep Quality Index and the Epworth Sleepiness Scale than controls and lower scores than those of patients diagnosed with Parkinson's disease. Studies using polysomnography in patients with ET are scarce and do not permit to establish valid conclusions regarding polysomnographic features in this disorder., (© Sleep Research Society 2020. Published by Oxford University Press on behalf of the Sleep Research Society. All rights reserved. For permissions, please e-mail journals.permissions@oup.com.)

Essential Tremor (ET) is one of the most common neurological diseases, with an estimated 7 million affected individuals in the US; the pathophysiology of the disorder is poorly understood. Recently, we identified a mutation (KCNS2 (Kv9.2), c.1137 T > A, p.(D379E) in an electrically silent voltage-gated K + channel α-subunit, Kv9.2, in a family with ET, that modulates the activity of Kv2 channels. We have produced transgenic Drosophila lines that express either the human wild type Kv9.2 (hKv9.2) or the ET causing mutant Kv9.2 (hKv9.2-D379E) subunit in all neurons. We show that the hKv9.2 subunit modulates activity of endogenous Drosophila K + channel Shab. The mutant hKv9.2-D379E subunit showed significantly higher levels of Shab inactivation and a higher frequency of spontaneous firing rate consistent with neuronal hyperexcitibility. We also observed behavioral manifestations of nervous system dysfunction including effects on night time activity and sleep. This functional data further supports the pathogenicity of the KCNS2 (p.D379E) mutation, consistent with our prior observations including co-segregation with ET in a family, a likely pathogenic change in the channel pore domain and absence from population databases. The Drosophila hKv9.2 transgenic model recapitulates several features of ET and may be employed to advance our understanding of ET disease pathogenesis.

Objective: Sleep problems are a common non-motor complication of Parkinson disease (PD), and patients with essential tremor (ET) share a number of motor and non-motor features of PD. To clarify the relationship between these disorders, we evaluated the sleep problems in patients with ET and PD using assessment scales and objective polysomnographic (PSG) testing., Method: Twenty-one consecutive patients with PD, 16 with ET, and 14 healthy subjects participated in this study and were compared in terms of sleep related complaints, final sleep related diagnosis, and polysomnographic features., Results: The results of our study have shown that patients with PD were more likely than were those with ET to have a history of REM sleep behavior disorders (RBD) (p = 0.001) and excessive daytime sleepiness (p ≤ 0.05). Additionally, PSG data revealed that ET patients had lower mean SpO2 values (p ≤ 0.05) and REM without atonia (RWA) (p = 0.032) than did patients with PD., Conclusion: This is the first study to use PSG to evaluate sleep problems both in ET and PD patients. The results point out different sleep problems in these two common movement disorders which should be investigated in further studies., (© 2015 American Academy of Sleep Medicine.)

There is a growing evidence to suggest that apart from motor features, patients with Essential Tremor (ET) may have significant non-motor features. This review critically analyzes the available evidence of the various non-motor symptoms in patients with ET. Apart from tremor, patients with ET have been reported to have: (i) cognitive abnormalities characterized by mild frontal dysfunction that may have a functional impact, (ii) an association with dementia (both prevalent and incident) among those with late onset of tremor (>65 years), (iii) a higher prevalence of anxiety and an anxious and worrisome personality type, (iv) depressive symptomatology and may even have depression as a premotor symptom, (v) poor sleep quality and (vi) subjective hearing impairment. It is controversial whether olfactory dysfunction occurs in ET and its utility as a diagnostic aid. The biological basis for each of these observations requires further clarification and some findings need confirmation in population-based studies. However the available evidence is sufficient to support the notion that ET can no longer be considered as a pure motor disorder and further studies of these non-motor aspects will go a long way in understanding and comprehensively treating ET., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Background: Recent studies have shed light on non-motor features of ET, such as depressive symptoms and cognitive changes, which might be attributed to pathophysiological changes in the brains of ET patients. Given these brain changes, we explored sleep abnormalities in ET patients., Methods: Sleep was assessed using the Epworth Sleepiness Scale (ESS) and the Pittsburgh Sleep Quality Index (PSQI) in 120 ET cases, 120 normal controls, and 40 PD cases., Results: The mean±SD (median) ESS score increased from normal controls (5.7±3.7 (5.0)), to ET cases (6.8±4.6 (6.0)), to PD cases (7.8±4.9 (7.0)), test for trend p=0.03. An ESS score >10 (an indicator of greater than normal levels of daytime sleepiness) was observed in 11 (9.2%) normal controls, compared to 27 (22.5%) ET cases and 10 (25.0%) PD cases (p=0.008 when comparing all three groups, and p=0.005 when comparing ET to normal controls). The global PSQI score was 7.8±2.8 (7.5) in controls, 8.0±3.3 (8.0) in ET cases, and 9.9±3.9 (10.0) in PD cases. The ET case-control difference was not significant (p=0.8), yet in a test for trend, PD cases had the highest PSQI score (most daytime sleepiness), followed by ET (intermediate), and lowest scores in controls (p=0.02)., Conclusions: Some sleep scores in ET were intermediate between those of PD cases and normal controls, suggesting that a mild form of sleep dysregulation could be present in ET., (Copyright © 2011 Elsevier Ltd. All rights reserved.)