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。老年受试者的睡眠效率降低，觉醒和觉醒次数增加，睡眠碎片化，这可能在老年人白天嗜睡和与年龄相关的神经认知功能下降中起关键作用。该应用程序开发并测试了一个综合假设，该假设将觉醒与指示阈下觉醒和睡眠巩固的瞬态EEG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）白人和非洲裔美国男性和女性，我们期望对老年人睡眠碎片的原因产生新的见解。初步结果表明，C3 A2脑电信号的样本熵随睡眠状态系统地变化，在清醒时最高，在3-4阶段最低，并且这种变化是年龄依赖性的。因此，睡眠状态内的睡眠深度的时间波动的概念模型和一种新的测量睡眠深度，EEG熵（不规则性的措施），提出。该模型的核心原则是睡眠深度是连续分级的。本文将检验三个假设：（1）在给定的睡眠状态下，脑电熵是波动的，当熵瞬时增加时，觉醒更容易发生;（2）在给定的睡眠状态下，脑电熵随时间的波动，（反映EEG中的短暂事件，如微觉醒和δ波的爆发）并不完全随机;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）老年人中过去睡眠干扰事件的影响的衰减时间过程比中年人慢;该因素通过延长对随后的睡眠障碍的敏感性增加的时间段而导致老年人觉醒次数的增加。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（可获得超过6400名受试者的多导睡眠图）。 公共卫生相关性：我们希望，拟议的研究将开发和验证一个新的框架，了解随时间变化的关系，瞬态脑电图事件觉醒和他们的增加与老化。此外，EEG信号的样本熵可以用作评估治疗效果的睡眠深度的测量。这项研究的目的是了解为什么老年人比年轻人在夜间醒来更频繁。为了实现这一目标，我们将分析从中年和老年受试者获得的脑电图（EEG）记录，而他们是睡着了，以提高我们的理解，发生在这些EEG的变化之前，立即受试者醒来。

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.