Associations among plasma markers for N-methyl-d-aspartate receptor hypofunction, redox dysregulation, and insufficient myelination in patients with schizophrenia.

Background: Several hypotheses regarding the pathomechanisms of schizophrenia have been proposed. If schizophrenia is a unitary disease, then these pathological processes must be linked; however, if such links do not exist, schizophrenia may best be considered a group of disorders. Only a few studies have examined the relationships among these pathomechanisms. Herein, we examined the relationships among deficient myelination, NMDA receptor hypofunction, and metabolic dysregulation by measuring various plasma markers and examining their correlations. Methods: Plasma samples were collected from 90 patients with schizophrenia and 68 healthy controls. Concentrations of nardilysin (N-arginine dibasic convertase, NRDC), a positive regulator of myelination, the NMDA receptor co-agonist d-serine and glycine, various additional amino acids related to NMDA receptor transmission (glutamate, glutamine, and l-serine), and homocysteine (Hcy), were measured. Concentrations were compared using independent samples t-test or logistic regression, and associations were evaluated using Pearson's correlation coefficients. Results: Plasma glycine (t = 2.05, p = 0.042), l-serine (t = 2.25, p = 0.027), and homocysteine (t = 3.71, p < 0.001) concentrations were significantly higher in patients with schizophrenia compared to those in healthy controls. Logistic regression models using age, sex, smoking status, glutamine, glutamate, glycine, l-serine, d-serine, homocysteine, and NRDC as independent variables revealed significantly lower plasma d-serine (p = 0.024) and NRDC (p = 0.028), but significantly higher l-serine (p = 0.024) and homocysteine (p = 0.001) in patients with schizophrenia. Several unique correlations were found between NMDA receptor-related amino acids and NRDC in patients with schizophrenia compared to those in healthy controls, while no correlations were found between plasma homocysteine and other markers. No associations were found between plasma marker concentrations and disease status or cognitive function in patients with schizophrenia, except for a significant correlation between plasma glycine and full intelligence quotient. Conclusion: Reduced myelination and NMDA receptor hypofunction may be related to pathological mechanisms in schizophrenia, while homocysteine dysregulation appears to be an independent pathological process. These results suggest that schizophrenia may be a group of disorders with unique or partially overlapping etiologies.

Case report: Impact of hyperthyroidism on psychotic symptoms in schizophrenia comorbid with Graves' disease.

Introduction: Auditory hallucinations are the most common type of hallucinations observed in schizophrenia; however, visual hallucinations are not uncommon. In Graves' disease, depression, hypomania, and psychosis can occur. While the association between Graves' disease and psychosis has been explored, understanding of the specific impact of thyroid dysfunction severity on psychiatric symptom severity is limited. Here, we present a case report of a patient with schizophrenia comorbid with Graves' disease whose psychotic symptoms were impacted by hyperthyroidism. Case: The patient was a 32-year-old Japanese woman who presented with auditory and visual hallucinations, agitation, and pressured speech. The patient was diagnosed with schizophrenia comorbid with Graves' disease and thyroid storm. The patient's psychotic symptoms were found to be associated with fluctuations in thyroid hormone levels, and visual hallucinations were observed only during thyroid storms. Treatment involved dexamethasone, potassium iodide, bisoprolol fumarate, and methimazole for thyrotoxicosis, and a blonanserin transdermal patch, paliperidone, and paliperidone palmitate for psychotic symptoms. The patient's auditory and visual hallucinations improved with antipsychotic treatment and decreased thyroid hormone levels. Conclusion: This case highlights the importance of monitoring thyroid function in patients with schizophrenia, particularly those with comorbid Graves' disease. The correlation between psychiatric symptoms and thyroid hormone levels was demonstrated on an individual level over time, with symptoms worsening as thyroid hormone levels increased. Additionally, our case suggests that abnormally high thyroid hormone levels may trigger visual hallucinations in individuals with schizophrenia. Further studies are needed to elucidate the underlying mechanisms and potential treatment implications of this association.

Limited social support is associated with depression, anxiety, and insomnia in a Japanese working population.

Background: Lack of social support is associated with depression, anxiety, and insomnia. This study aimed to determine the source of support related to depression, anxiety, and insomnia among Japanese workers. Methods: As part of a cohort study, we conducted a questionnaire survey among city government employees in Koka City, Shiga Prefecture, Japan, from September 2021 to March 2022. We used the Patient Health Questionnaire-9 (PHQ-9), Generalized Anxiety Disorder-7 (GAD-7), and Insomnia Severity Index (ISI) to assess depressive symptoms, anxiety symptoms, and insomnia, respectively. We used the Brief Job Stress Questionnaire (BJSQ) to assess job stressors and social support (from supervisors, colleagues, and family). Results: A total of 1,852 Japanese employees (38.4% male, 45.9 ± 12.9 years) participated in the survey, with 15.5, 10.8, and 8.2% of the participants having depressive symptoms (PHQ-9 ≥ 10), anxiety symptoms (GAD-7 ≥ 10), and insomnia (ISI ≥ 15), respectively. The logistic regression analysis suggested that job stressors were associated with depressive symptoms (p < 0.001), anxiety symptoms (p < 0.001), and insomnia (p = 0.009). In contrast, support from co-workers (p = 0.016) and family members (p = 0.001) was associated with decreased depressive symptoms. Support from family members was associated with decreased insomnia (p = 0.005). Conclusion: Social support from co-workers and family may be associated with reduced depressive symptoms, and family support may be associated with reduced insomnia in the Japanese working population. Clinical trial registration: https://clinicaltrials.gov/ct2/show/NCT03276585.

Idiopathic rapid eye movement sleep behavior disorder in Japan: An observational study.

INTRODUCTION: Idiopathic rapid eye movement sleep behavior disorder (iRBD) is one of the most specific prodromal symptoms of synucleinopathies, including Parkinson's disease (PD) and multiple system atrophy. The Japan Parkinson's Progression Markers Initiative (J-PPMI) was a prospective cohort study conducted in Japanese patients with iRBD to investigate biomarkers for prodromal synucleinopathies. We carried out an initial assessment of the J-PPMI study to reveal the factors correlated with dopamine transporter single-photon emission computed tomography (DaT) and 123I-meta-iodobenzylguanidine (MIBG) myocardial scintigraphy. METHODS: This cross-sectional study was conducted in 108 patients with iRBD, selected from the J-PPMI study. We divided the patients into four groups based on the MIBG and DaT results. We also recorded the patients' demographics and clinical data. Following PD probability calculation, we examined the biomarkers associated with DaT and MIBG. RESULTS: Ninety-five of the enrolled patients (88%) met the diagnostic criteria for prodromal PD based on the probability score. Only five patients had normal MIBG and DaT. We identified 29 cases with decreased DaT and MIBG, all of whom met the above diagnostic criteria. Both DaT and MIBG were significantly correlated with the Japanese version of the Montreal Cognitive Assessment (MoCA-J) score. CONCLUSION: Both DaT and MIBG are important biomarkers for confirming synucleinopathies and/or staging disease progression. Although 95% of iRBD patients were consistent with the body-first subtype concept, alpha-synuclein pathologies of iRBD might have widespread systemic involvement rather than being confined to the lower brainstem, particularly in patients with reduced MoCA-J scores.

The prevalence of depression in isolated/idiopathic rapid eye movement sleep behavior disorder: A systematic review and meta-analysis.

This systematic review and meta-analysis aimed to investigate depression prevalence and depression-related symptoms among patients with isolated/idiopathic rapid eye movement sleep behavior disorder (iRBD). We systematically searched online databases (PubMed and Scopus), performed meta-analyses of psychiatric symptoms prevalence using a random-effects model, and calculated 95% prediction intervals (PIs) and I2 values to evaluate the degree of heterogeneity. We conducted a meta-regression analysis to assess the relationship between psychiatric symptom severity, age at diagnosis, and disease duration from onset of iRBD. We analyzed 31 studies which included 3,576 patients (2,871 men, 80.3%; mean age, 66.6 ± 8.6 years). The pooled depression prevalence was 28.8% (95% CI 23.1-35.2, 95% PI 8.1-65.1, and I2 = 83.9%). We found a significantly negative correlation between depression-scale scores and disease duration in iRBD (p = 0.012, ß = -0.36, R2 analog = 0.33). Pooled prevalence of apathy and anxiety was 38.4% (95% CI 27.7-50.4, 95% PI 0.02-99.9, and I2 = 57.8%) and 21.3% (95% CI 15.5-28.5, 95% PI 4.2-62.6, and I2 = 47.1%), respectively. Few articles on alexithymia were available for meta-analysis. This study confirmed high prevalence of depression, apathy, and anxiety in patients with iRBD.

R-R interval-based sleep apnea screening by a recurrent neural network in a large clinical polysomnography dataset.

OBJECTIVE: Easily detecting patients with undiagnosed sleep apnea syndrome (SAS) requires a home-use SAS screening system. In this study, we validate a previously developed SAS screening methodology using a large clinical polysomnography (PSG) dataset (N = 938). METHODS: We combined R-R interval (RRI) and long short-term memory (LSTM), a type of recurrent neural networks, and created a model to discriminate respiratory conditions using the training dataset (N = 468). Its performance was validated using the validation dataset (N = 470). RESULTS: Our method screened patients with severe SAS (apnea hypopnea index; AHI ≥ 30) with an area under the curve (AUC) of 0.92, a sensitivity of 0.80, and a specificity of 0.84. In addition, the model screened patients with moderate/severe SAS (AHI ≥ 15) with an AUC of 0.89, a sensitivity of 0.75, and a specificity of 0.87. CONCLUSIONS: Our method achieved high screening performance when applied to a large clinical dataset. SIGNIFICANCE: Our method can help realize an easy-to-use SAS screening system because RRI data can be easily measured with a wearable heart rate sensor. It has been validated on a large dataset including subjects with various backgrounds and is expected to perform well in real-world clinical practice.

Obstructive Sleep Apnoea Severity Is Negatively Associated with Depressive Symptoms: A Cross-Sectional Survey of Outpatients with Suspected Obstructive Sleep Apnoea in Japan.

Background: Multiple clinical departments are involved in the provision of obstructive sleep apnoea (OSA) therapy in Japan. Inconsistent results regarding the association between depression and OSA have been reported. Methods: This cross-sectional survey compared newly diagnosed OSA patients at two outpatient sleep apnoea units in Shiga Prefecture, Japan: one associated with the psychiatry department (n = 583), and the other with the otolaryngology department (n = 450). Results: The unit associated with the psychiatry department had more patients referred by psychiatrists than that with the otolaryngology department (11% vs. 3% p < 0.05). Sleepiness, insomnia, and depression were assessed using the Epworth Sleepiness Scale (ESS), Athens Insomnia Scale (AIS), and Patient Health Questionnaire-9 (PHQ-9), respectively. The ESS, AIS, and PHQ-9 scores were higher in the sleep unit in the psychiatry department (p < 0.001 each). Snoring and moderate to severe OSA were more prevalent in the unit attached to the otolaryngology department (p < 0.001 each). Patients with moderate to severe OSA had lower PHQ-9 scores than those with no to mild OSA (OR: 0.96, 95% CI: 0.92−1.00, p = 0.042). Conclusion: Patients with sleepiness, insomnia, and depressive symptoms were more likely to attend a sleep outpatient unit associated with a psychiatry department, whereas those with snoring and sleep apnoea attended that associated with an otolaryngology department. OSA severity was negatively associated with depressive symptoms.

[Sleep Disorders and Autonomic Nervous System Dysfunction].

Parasympathetic nervous system activity dominates during non-rapid eye movement (REM) sleep, whereas the sympathetic nervous system is dominant during REM sleep. The balance between the sympathetic and parasympathetic nervous systems reduces the heart rate and blood pressure during non-REM sleep and increases these parameters during REM sleep and wakefulness. Heart rate variability analysis, a non-invasive method of autonomic nervous system analysis, may be useful in screening for obstructive sleep apnea and also to predict orthostatic hypotension secondary to autonomic disturbances in patients with REM sleep behavior disorder.

Prolonged Sleep Latency and Reduced REM Latency Are Associated with Depressive Symptoms in a Japanese Working Population.

BACKGROUND: Examining the relationship between sleep and depression may be important for understanding the aetiology of affective disorders. Most studies that use electroencephalography (EEG) to objectively assess sleep have been conducted using polysomnography in the laboratory. Impaired sleep continuity, including prolonged sleep latency and changes in rapid eye movement (REM) sleep, have been reported to be associated with depression in clinical settings. Here, we aimed to use home EEG to analyse the association between sleep and depressive symptoms. METHODS: We performed a cross-sectional epidemiological study in a large Japanese working population to identify the EEG parameters associated with depressive symptoms based on the results of a questionnaire survey and home EEG measurements using 1-channel (1-Ch) EEG. RESULTS: The study included 650 Japanese patients (41.2% male, 44.7 ± 11.5 years) who underwent home EEG monitoring along with the Patient Health Questionnaire-9 (PHQ-9) to assess depressive symptoms. Logistic regression analysis revealed that depressive symptoms (PHQ-9 ≥ 10) were associated with sleep latency (odds ratio (OR) 1.02; 95% confidence interval (CI): 1.00-1.04) and REM latency (OR, 0.99; 95% CI: 0.99-1.00). CONCLUSIONS: Our results suggest that depressive symptoms are associated with prolonged sleep latency and reduced REM latency in a Japanese working population. The 1-Ch EEG may be a useful tool to monitor sleep and screen depression/depressive symptoms in non-clinical settings.

Minor hallucinations in isolated rapid eye movement sleep behavior disorder indicative of early phenoconversion: A preliminary study.

OBJECTIVES: Minor hallucinations (MH) are psychotic symptoms that can occur anywhere between prodromal to early Parkinson's disease and after onset of motor problems. MH include visual illusions, presence hallucinations, and passage hallucinations. Isolated rapid eye movement sleep behavior disorder (RBD) is a harbinger of neurodegenerative diseases. We conducted a retrospective cohort study to investigate the clinical characteristics of isolated RBD with MH and the risk of phenoconversion. MATERIALS AND METHODS: We retrospectively analyzed the data of 36 patients with isolated RBD (four females; median age, 75.0 years). We defined cases reporting at least one minor hallucination as RBD with MH. Demographic data and cognitive function were compared between patients with and without MH, and Cox proportional hazards models estimated the risk of phenoconversion. RESULTS: We included 10 (27.8%) patients with MH and 26 (72.2%) without MH. Patients with MH were older, had less dopamine transporter accumulation, more severe autonomic dysfunction, more depressive symptoms, and lower verbal fluency and symbol coding test scores than patients without MH. After follow-up (median, 2.50 years), 13.9% (5/36) of all patients developed phenoconversion (Parkinson's disease, two patients; dementia with Lewy bodies, three patients). The rate of phenoconversion was significantly higher in patients with MH (40.0% vs. 3.8%, p = .005). The Cox proportional hazards model adjusted for age, sex, and disease duration revealed that MH was a significant risk factor for phenoconversion (hazard ratio, 14.72; 95% confidence interval, 1.35-160.5). CONCLUSIONS: Minor hallucinations may be utilized as early clinical markers for prodromal estimation of neurodegenerative diseases.

Explosive sound without external stimuli following electroencephalography kappa rhythm fluctuation: A case report.

BACKGROUND: The pathology underlying exploding head syndrome, a parasomnia causing a loud sound/sense of explosion, is not well understood. Kappa rhythm is a type of electroencephalogram alpha band activity with maximum potential between contralateral temporal electrodes We report a case of preceding kappa activity before exploding head syndrome attacks. CASE REPORT: A 57-year-old woman complained of explosive sounds for 2 months; a loud sound would transpire every day before sleep onset. She was diagnosed with exploding head syndrome. During polysomnography and the multiple sleep latency test, the exploding head syndrome attacks occurred six times. A kappa wave with activity disappearing a few seconds before most exploding head syndrome attacks was observed. The alpha band power in T3-T4 derivation gradually waxed followed by termination around the attacks. CONCLUSION: This case demonstrated that the dynamics of kappa activity precede exploding head syndrome attacks. Finding ways to modulate electroencephalogram oscillation could elucidate their causality and lead to therapeutic intervention.

Large Questionnaire Survey on Sleep Duration and Insomnia Using the TV Hybridcast System by Japan Broadcasting Corporation (NHK).

BACKGROUND: Japanese people are known to have the shortest sleep duration in the world. To date, no study has assessed a large Japanese population for insomnia and sleep duration. METHODS: We performed an Ιnternet-based survey in association with a national television (TV) program. Questionnaire data were collected not only through personal computers, tablets, and smartphones, but also through the Hybridcast system, which combines broadcasts over airwaves with broadband data provided via the Internet using the TV remote controller. The Athens Insomnia Scale (AIS) was used to assess insomnia. RESULTS: A total of 301,241 subjects participated in the survey. Participants slept for an average of 5.96 ± 1.13 h; the average AIS score was 6.82 ± 3.69. A total of 26.1% of male and 27.1% of female participants had both insomnia (AIS ≥ 6) and short sleep duration (<6 h). Responses were recorded through the Hybridcast system for 76.4% of the elderly (age ≥ 65 years) subjects and through personal computers, tablets, or smartphones for 59.9-82.7% of the younger subjects (age ≤ 65 years). CONCLUSIONS: Almost a quarter of the Japanese participants presented short sleep duration and insomnia. Furthermore, the Hybridcast system may be useful for performing large internet-based surveys, especially for elderly individuals.

Work Habit-Related Sleep Debt; Insights From Factor Identification Analysis of Actigraphy Data.

The present study investigates the factors of "Weekday sleep debt (WSD)" by comparing activity data collected from persons with and without WSD. Since it has been reported that the amount of sleep debt as well the difference between the social clock and the biological clock is associated with WSD, specifying the factors of WSD other than chronotype may contribute to sleep debt prevention. We recruited 324 healthy male employees working at the same company and collected their 1-week wrist actigraphy data and answers to questionnaires. Because 106 participants were excluded due to measurement failure of the actigraphy data, the remaining 218 participants were included in the analysis. All participants were classified into WSD or non-WSD groups, in which persons had WDS if the difference between their weekend sleep duration and the mean weekday sleep duration was more than 120 min. We evaluated multiple measurements derived from the collected actigraphy data and trained a classifier that predicts the presence of WSD using these measurements. A support vector machine (SVM) was adopted as the classifier. In addition, to evaluate the contribution of each indicator to WSD, permutation feature importance was calculated based on the trained classifier. Our analysis results showed significant importance of the following three out of the tested 32 factors: (1) WSD was significantly related to persons with evening tendency. (2) Daily activity rhythms and sleep were less stable in the WSD group than in the non-WSD group. (3) A specific day of the week had the highest importance in our data, suggesting that work habit contributes to WSD. These findings indicate some WSD factors: evening chronotype, instability of the daily activity rhythm, and differences in work habits on the specific day of the week. Thus, it is necessary to evaluate the rhythms of diurnal activities as well as sleep conditions to identify the WSD factors. In particular, the diurnal activity rhythm influences WSD. It is suggested that proper management of activity rhythm may contribute to the prevention of sleep debt.

A model six-month workshop for developing systematic review protocols at teaching hospitals: action research and scholarly productivity.

BACKGROUND: Research engagement contributes to the improvement of patient care. A systematic review is a suitable first scholarly activity because it entails summarization of publicly available data and usually requires neither rigorous ethical review nor research funding. METHODS: This study aimed to develop a model workshop for healthcare staff to acquire skills in creating systematic review protocols based on their own clinical questions at teaching hospitals. We used an action research method to create a model workshop at four hospitals in Japan from April 2015 to March 2017. To improve the program, we solicited reflections using participant questionnaires for each lecture and examined the quality of homework submitted by participants after each lecture. We administered a revised final version of the workshop at five hospitals from April 2016 to March 2017. We evaluated the participants' scholarly productivity related to these workshops. The observation period was a minimum of 2 years following the workshops. RESULTS: Most participants had never developed a formal clinical research protocol and voluntarily participated in the workshop. The action research was developed and implemented at nine teaching hospitals in Japan, including one university hospital. The study developed a model nine-step workshop curriculum: 1) Research question development, 2) Search strategy development, 3) Search strategy brush-up, 4) Exclusion and inclusion criteria development, 5) Risk of bias assessment planning, 6) Meta-analysis planning, 7) Subgroup and sensitivity analysis planning, 8) Planning the presentation of results, and 9) Presentation protocols. A total of 233 participants, including medical doctors and other health professionals, produced 414 research questions. Seventy-nine participants (34%) completed the workshop, and 47 review teams accomplished systematic review protocols. The participants published 13 peer-reviewed articles as a result of the workshop. CONCLUSIONS: We developed a structured scholarly productive model workshop for healthcare staff working at hospitals. We found healthcare staff with clinical subspecialties were able to develop an unexpectedly high number of research questions through this workshop. Medical teachers at hospitals with prior systematic review experience could teach how to develop systematic review protocols using this model. Further research is needed to increase the academic productivity of such workshops. TRIAL REGISTRATION: UMIN (https://www.umin.ac.jp/ctr/), UMIN000017107 (4/15/2015), UMIN000025580 (1/10/2017).

Screening of sleep apnea based on heart rate variability and long short-term memory.

PURPOSE: Sleep apnea syndrome (SAS) is a prevalent sleep disorder in which apnea and hypopnea occur frequently during sleep and result in increase of the risk of lifestyle-related disease development as well as daytime sleepiness. Although SAS is a common sleep disorder, most patients remain undiagnosed because the gold standard test polysomnography (PSG), is high-cost and unavailable in many hospitals. Thus, an SAS screening system that can be used easily at home is needed. METHODS: Apnea during sleep affects changes in the autonomic nervous function, which causes fluctuation of the heart rate. In this study, we propose a new SAS screening method that combines heart rate measurement and long short-term memory (LSTM) which is a type of recurrent neural network (RNN). We analyzed the data of intervals between adjacent R waves (R-R interval; RRI) on the electrocardiogram (ECG) records, and used an LSTM model whose inputs are the RRI data is trained to discriminate the respiratory condition during sleep. RESULTS: The application of the proposed method to clinical data showed that it distinguished between patients with moderate-to-severe SAS with a sensitivity of 100% and specificity of 100%, results which are superior to any other existing SAS screening methods. CONCLUSION: Since the RRI data can be easily measured by means of wearable heart rate sensors, our method may prove to be useful as an SAS screening system at home.

Self-Isolation Due to COVID-19 Is Linked to Small One-Year Changes in Depression, Sleepiness, and Insomnia: Results from a Clinic for Sleep Disorders in Shiga Prefecture, Japan.

We aimed to analyze (a) the changes in depression, sleepiness, insomnia, and sleep habits in relation to the degree of self-isolation and (b) the effects of changes in sleep habits and social interactions on depression, insomnia, and sleepiness during the coronavirus disease 2019 (COVID-19) pandemic. We enrolled 164 patients who visited the sleep outpatient clinic in Shiga University of Medical Science Hospital. We compared the sleep habits, depression (Patient Health Questionnaire-9: PHQ-9), insomnia (Athens Insomnia Scale: AIS), and sleepiness (Epworth Sleepiness Scale: ESS) of patients during the period from April to July 2019 vs. May 2020 (a period of self-isolation due to COVID-19). A Wilcoxon signed-rank test indicated no significant differences in PHQ-9, ESS, and AIS scores between 2019 and 2020 within both the strong self-isolation group and no/little self-isolation group. With respect to sleep habits, earlier bedtime (p = 0.006) and increased sleep duration (p = 0.014) were found in the strong self-isolation group. The former (p = 0.009) was also found in the no/little self-isolation group, but we found significant differences in sleep duration between the no/little self-isolation group and the strong self-isolation group (p = 0.047). Therefore, self-isolation due to COVID-19 had relatively small one-year effects on depression, sleepiness, and insomnia in a clinical population.

Resting Heart Rate Variability Is Associated With Subsequent Orthostatic Hypotension: Comparison Between Healthy Older People and Patients With Rapid Eye Movement Sleep Behavior Disorder.

Background: Orthostatic hypotension (OH) caused by autonomic dysfunction is a common symptom in older people and patients with idiopathic rapid eye movement sleep behavior disorder (iRBD). The orthostatic challenge test is a standard autonomic function test that measures a decrease of blood pressure during a postural change from supine to standing positions. Although previous studies have reported that changes in heart rate variability (HRV) are associated with autonomic dysfunction, no study has investigated the relationship between HRV before standing and the occurrence of OH in an orthostatic challenge test. This study aims to examine the connection between HRV in the supine position and the occurrence of OH in an orthostatic challenge test. Methods: We measured the electrocardiograms of patients with iRBD and healthy older people during an orthostatic challenge test, in which the supine and standing positions were held for 15 min, respectively. The subjects were divided into three groups: healthy controls (HC), OH-negative iRBD [OH (-) iRBD], and OH-positive iRBD [OH (+) iRBD]. HRV measured in the supine position during the test were calculated by time-domain analysis and Poincaré plots to evaluate the autonomic dysfunction. Results: Forty-two HC, 12 OH (-) iRBD, and nine OH (+) iRBD subjects were included. HRV indices in the OH (-) and the OH (+) iRBD groups were significantly smaller than those in the HC group. The multivariate logistic regression analysis for OH identification for the iRBD groups showed the model whose inputs were the HRV indices, i.e., standard deviation 2 (SD2) and the percentage of adjacent intervals that varied by more than 50 ms (pNN50), had a receiver operating characteristic curve with area under the curve of 0.840, the sensitivity to OH (+) of 1.000, and the specificity to OH (-) of 0.583 (p = 0.023). Conclusions: This study showed the possibility that short-term HRV indices in the supine position would predict subsequent OH in iRBD patients. Our results are of clinical importance in terms of showing the possibility that OH can be predicted using only HRV in the supine position without an orthostatic challenge test, which would improve the efficiency and safety of testing.

Evaluation of Severity Levels of the Athens Insomnia Scale Based on the Criterion of Insomnia Severity Index.

The Athens Insomnia Scale (AIS) can be regarded as a highly useful instrument in both clinical and research settings, except for when assessing the severity level. This study aims to determine the severity criteria for AIS by using the Insomnia Severity Index (ISI). A total of 1666 government employees aged 20 years or older were evaluated using the AIS and ISI, the Patient Health Questionnaire for depressive symptoms, the Epworth Sleepiness Scale for daytime sleepiness, and the Short Form Health Survey of the Medical Outcomes Study for health-related quality of life (QoL). A significant positive correlation (r) was found between the AIS and the ISI (r = 0.80, p < 0.001). As a result of describing receiver-operator curves, the severity criteria of the AIS are capable of categorizing insomnia severity as follows: absence of insomnia (0-5), mild insomnia (6-9), moderate insomnia (10-15), and severe insomnia (16-24). In addition, compared to all scales across groups categorized by AIS or ISI, it was revealed that similar results could be obtained (all p < 0.05). Therefore, the identification of the severity of AIS in this study is important in linking the findings of epidemiological studies with those of clinical studies.

Sleep Spindle Detection Using RUSBoost and Synchrosqueezed Wavelet Transform.

Sleep spindles are important electroencephalographic (EEG) waveforms in sleep medicine; however, it is burdensome even for experts to detect spindles, so automatic spindle detection methodologies have been investigated. Conventional methods utilize waveforms template matching or machine learning for detecting spindles. In the former approach, it is necessary to tune thresholds for individual adaptation, while the latter approach has the problem of imbalanced data because the amount of sleep spindles is small compared with the entire EEG data. The present work proposes a sleep spindle detection method that combines wavelet synchrosqueezed transform (SST) and random under-sampling boosting (RUSBoost). SST is a time-frequency analysis method suitable for extracting features of spindle waveforms. RUSBoost is a framework for coping with the imbalanced data problem. The proposed SST-RUS can deal with the imbalanced data in spindle detection and does not require threshold tuning because RUSBoost uses majority voting of weak classifiers for discrimination. The performance of SST-RUS was validated using an open-access database called the Montreal archives of sleep studies cohort 1 (MASS-C1), which showed an F-measure of 0.70 with a sensitivity of 76.9% and a positive predictive value of 61.2%. The proposed method can reduce the burden of PSG scoring.