Dynamics of Sleep Fragmentation in the Elderly

描述（由申请人提供）：衰老与睡眠结构和质量的重大变化有关。老年人的睡眠效率下降，觉醒和觉醒次数增加，睡眠碎片化，这可能是老年人白天嗜睡和与年龄相关的神经认知功能下降的关键因素。本应用程序开发并测试了一个综合假设，该假设将唤醒与指示阈下唤醒和睡眠巩固的瞬态脑电图事件的发生联系起来。通过将这一综合框架应用于中年（40-49岁）和老年（70-79岁）白人和非裔美国男性和女性，我们希望对老年人睡眠断裂的原因产生新的见解。初步结果表明，C3A2脑电信号的样本熵随睡眠状态有系统的变化，醒时最高，3-4期最低，且该变化具有年龄依赖性。因此，提出了睡眠状态下睡眠深度时间波动的概念模型和一种新的睡眠深度测量方法——脑电图熵（一种不规则性测量方法）。该模型的一个核心原则是睡眠深度是连续分级的。本文将检验由该模型导出的三个假设：(1)EEG熵在给定的睡眠状态下波动，当熵瞬态增加时更有可能唤醒；(2)在给定的睡眠状态下，脑电图熵随时间的波动（反映脑电图中的短时间事件，如微觉醒和δ波爆发）并非完全随机；相反，它们也反映了干扰睡眠深度的先前事件的影响的缓慢衰减；(3)过去的睡眠干扰事件的影响在老年人中的消退时间比中年人慢；这一因素通过延长对随后的睡眠障碍的易感性而增加老年人的觉醒次数。这项小型研究资助将利用nhlbi支持的睡眠心脏健康研究的现有数据（可获得来自bbbb6400名受试者的多导睡眠图）。公共卫生相关性：我们期望提出的研究将发展和验证一个新的框架，以理解瞬态脑电图事件与觉醒的时变关系，以及它们随着年龄的增长而增加。此外，脑电图信号的样本熵可以作为评估治疗效果的睡眠深度的度量。这项研究的目的是了解为什么老年人比年轻人更频繁地在夜间醒来。为了实现这一目标，我们将分析从中老年受试者睡眠时获得的脑电图（EEG）记录，以增强我们对受试者醒来前脑电图变化的理解。

DESCRIPTION (provided by applicant): Aging is associated with major changes in the structure and quality of sleep. Older subjects experience decreased sleep efficiency, increased numbers of arousals and awakenings, and sleep fragmentation, which may well play a pivotal role in both the daytime sleepiness and the age-associated decline in neurocognitive function in the elderly. This application develops and tests an integrative hypothesis that relates arousals to the occurrence of transient EEG events indicative of subthreshold arousals and sleep consolidations. By applying this integrative framework to both middle-aged (40-49 yrs) and elderly (70-79 yrs) Caucasian and African-American men and women, we expect to generate novel insights into the causes of sleep fragmentation in the elderly. Preliminary results show that Sample Entropy of the C3A2 EEG signal varies systematically with sleep state, being highest in Wake and lowest in stage 3-4, and that this variation is age-dependent. Thus, a conceptual model of temporal fluctuations of depth of sleep within a sleep state and a novel measure of depth of sleep, EEG entropy (a measure of irregularity), are proposed. A core principle of the model is that depth of sleep is continuously graded. Three hypotheses derived from this model will be tested: (1) EEG entropy fluctuates in a given sleep state and arousals are more likely when entropy transiently increases; (2) in a given sleep state, fluctuations of EEG entropy with time (which reflect short-lived events in the EEG such as microarousals and bursts of delta waves) are not entirely random; rather, they also reflect the slow decay of the effects of prior events that perturbed the depth of sleep; and, (3) the time course of decay of the effects of past sleep-disturbing events is slower in elderly than in middle- aged subjects; this factor contributes to the increased number of arousals in the elderly by prolonging the period of increased susceptibility to a subsequent sleep disturbance. This Small Research Grant will utilize existing data from the NHLBI-supported Sleep Heart Health Study (polysomnograms from >6400 subjects are available). PUBLIC HEALTH RELEVANCE: We expect that the proposed studies will develop and validate a novel framework for understanding the time-varying relationship of transient EEG events to arousals and their increase with aging. Additionally, Sample Entropy of EEG signals may find utility as a measure of depth of sleep for evaluating the effects of therapies. The goal of this study is to understand why the elderly awaken more frequently at night than younger individuals. To accomplish this objective, we will analyze electroencephalogram (EEG) recordings obtained from middle-aged and elderly subjects while they are asleep to enhance our understanding of the changes that occur in these EEGs immediately before subjects wake up.