Dynamics of Sleep Fragmentation in the Elderly

描述(申请人提供)：衰老与睡眠结构和质量的重大变化有关。老年人的睡眠效率降低，唤醒和唤醒的次数增加，睡眠碎片化，这可能在老年人白天困倦和与年龄相关的神经认知功能下降中发挥关键作用。这项应用开发并测试了一个综合假设，该假说将觉醒与指示阈值下觉醒和睡眠整合的瞬时脑电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)高加索人和非裔美国人的男性和女性，我们希望对老年人睡眠碎片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的变化呈系统性变化，在觉醒时最高，在3-4期最低，且这种变化与年龄有关。因此，提出了一种睡眠状态下睡眠深度随时间变化的概念模型和一种新的睡眠深度度量方法--脑电熵(EEG)(一种不规则性度量)。该模型的一个核心原则是睡眠深度连续分级。由该模型得出的三个假说将被检验：(1)在给定的睡眠状态下，脑电的熵波动，并且当熵瞬时增加时，唤醒的可能性更大；(2)在给定的睡眠状态下，脑电的熵随时间的波动(反映脑电中的短暂事件，如微唤醒和三角波的爆发)不是完全随机的；相反，它们也反映了先前扰乱睡眠深度的先前事件的影响的缓慢衰减；以及，(3)过去睡眠干扰事件的影响的衰减过程在老年人中比在中年受试者中慢；这一因素延长了老年人对随后睡眠障碍的敏感期，从而导致了唤醒次数的增加。这一小额研究拨款将利用NHLBI支持的睡眠心脏健康研究的现有数据(可获得6400名受试者的多导睡眠图)。公共卫生相关性：我们预计拟议的研究将开发和验证一个新的框架，以了解瞬时脑电事件与觉醒的时变关系及其随着年龄的增加而增加。此外，脑电信号的样本熵可能会被用作评估治疗效果的睡眠深度的衡量标准。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，我们将分析中老年受试者在睡眠中获得的脑电(EEG)记录，以加强我们对受试者醒来前这些脑电记录的了解。

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.