Masahiro Matsuo

Association of sleep-disordered breathing with decreased cognitive function among patients with dementia.

Sleep is known to be essential for proper cognitive functioning. Sleep disturbance, especially respiratory disturbance during sleep, is a risk factor for the development of dementia. However, it is not known whether hypopnoea during sleep is related to severity of cognitive function in patients already diagnosed with dementia. Considering the high prevalence of sleep problems in aged people, it is important to determine if hypopnoea during sleep contributes to dementia. In addition, it would be desirable to develop a feasible method for objectively evaluating sleep in patients with dementia. For this purpose, a simple sleep recorder that employs single or dual bioparameter recording, which is defined as a type‐4 portable monitor, is suitable. In this study, a type‐4 sleep recorder was used to evaluate respiratory function during sleep in 111 patients with dementia, and data suggesting a possible relationship with cognitive function levels were examined. Multivariate logistic regression was used to investigate the association of severity of dementia with sleep‐disordered breathing, age, diabetes, dyslipidaemia and hypertension. It was found that the respiratory disturbance index was associated with severity of cognitive dysfunction in our subjects. Furthermore, patients younger than 80 years were more susceptible to lower cognitive function associated with sleep‐disordered breathing than patients 80 years old or over, because an increase in the respiratory disturbance index was associated with deteriorated cognitive function only in the former age group. These results suggest that proper treatment of sleep apnea is important for the preservation of cognitive function, especially in patients with early‐stage dementia.

Comparisons of Portable Sleep Monitors of Different Modalities: Potential as Naturalistic Sleep Recorders

Background Humans spend more than one-fourth of their life sleeping, and sleep quality has been significantly linked to health. However, the objective examination of ambulatory sleep quality remains a challenge, since sleep is a state of unconsciousness, which limits the reliability of self-reports. Therefore, a non-invasive, continuous, and objective method for the recording and analysis of naturalistic sleep is required. Objective Portable sleep recording devices provide a suitable solution for the ambulatory analysis of sleep quality. In this study, the performance of two activity-based sleep monitors (Actiwatch and MTN-210) and a single-channel electroencephalography (EEG)-based sleep monitor (SleepScope) were compared in order to examine their reliability for the assessment of sleep quality. Methods Twenty healthy adults were recruited for this study. First, data from daily activity recorded by Actiwatch and MTN-210 were compared to determine whether MTN-210, a more affordable device, could yield data similar to Actiwatch, the de facto standard. In addition, sleep detection ability was examined using data obtained by polysomnography as reference. One simple analysis included comparing the sleep/wake detection ability of Actiwatch, MTN-210, and SleepScope. Furthermore, the fidelity of sleep stage determination was examined using SleepScope in finer time resolution. Results The results indicate that MTN-210 demonstrates an activity pattern comparable to that of Actiwatch, although their sensitivity preferences were not identical. Moreover, MTN-210 provides assessment of sleep duration comparable to that of the wrist-worn Actiwatch when MTN-210 was attached to the body. SleepScope featured superior overall sleep detection performance among the three methods tested. Furthermore, SleepScope was able to provide information regarding sleep architecture, although systemic bias was found. Conclusion The present results suggest that single-channel EEG-based sleep monitors are the superior option for the examination of naturalistic sleep. The current results pave a possible future use for reliable portable sleep assessment methods in an ambulatory rather than a laboratory setting.

Development of sleep apnea syndrome screening algorithm by using heart rate variability analysis and support vector machine

Although sleep apnea syndrome (SAS) is a common sleep disorder, most patients with sleep apnea are undiagnosed and untreated because it is difficult for patients themselves to notice SAS in daily living. Polysomnography (PSG) is a gold standard test for sleep disorder diagnosis, however PSG cannot be performed in many hospitals. This fact motivates us to develop an SAS screening system that can be used easily at home. The autonomic nervous function of a patient changes during apnea. Since changes in the autonomic nervous function affect fluctuation of the R-R interval (RRI) of an electrocardiogram (ECG), called heart rate variability (HRV), SAS can be detected through monitoring HRV. The present work proposes a new HRV-based SAS screening algorithm by utilizing support vector machine (SVM), which is a well-known pattern recognition method. In the proposed algorithm, various HRV features are derived from RRI data in both apnea and normal respiration periods of patients and healthy people, and an apnea/normal respiration (A/N) discriminant model is built from the derived HRV features by SVM. The result of applying the proposed SAS screening algorithm to clinical data demonstrates that it can discriminate patients with sleep apnea and healthy people appropriately. The sensitivity and the specificity of the proposed algorithm were 100% and 86%, respectively.

Association of different neural processes during different emotional perceptions of white noise and pure tone auditory stimuli

Sound is a sensory stimulant ubiquitously found throughout our environment. Humans have evolved a system that effectively and automatically converts sound sensory inputs into emotions. Although different emotional responses to sounds with different frequency characteristics are empirically recognized, there is a paucity of studies addressing different emotional responses to these sounds and the underlying neural mechanisms. In this study, we examined effects of pure tone (PT) and white noise (WN) inputs at ordinary loudness levels on emotional responses. We found that WN stimuli produced more aversive responses than PT stimuli. This difference was endorsed by larger late posterior positivity (LPP). In a source localization study, we found increased neural activity in the parietal lobe prior to LPP. These findings show that WN stimuli produce aversive perceptions compared with PT stimuli, at typical loudness levels. In addition, different emotional responses were processed in a similar manner as visual stimulations, as reflected by increased LPP activation. Various emotional effects of WN and PT stimuli, at ordinary loudness levels, could expand our understanding of adverse effects of noise as well as favorable effects associated with music.