Respiratory Peridocity and Cognitive Decline in Elders

实验室和临床研究结果表明，大脑低氧状态与老年人的认知能力下降和痴呆症有关。睡眠是发生低氧事件的高危时期；低呼吸周期可能是识别睡眠期间脑氧合低者的一个重要指标。我们以前的研究表明，呼吸周期低的老年人睡眠更零碎，低幅度增量睡眠更多，睡眠期间大脑氧合下降更大。这项纵向观察性研究的目的是(1)检查呼吸周期、睡眠结构和睡眠期间脑氧合的测量之间的关系；(2)检查睡眠中呼吸周期或脑氧合是否单独或联合预测24个月后认知能力下降；以及(3)探索呼吸周期和脑氧合变化在24个月内如何变化。将在基线以及12个月和24个月时对106名70岁的社区居住老年人进行评估。呼吸周期将从呼吸感应体积图波形中测量，包括呼吸周期持续时间(SdIBI)、频率(SdIBF)和幅度(SdAMP)变异性的平均5分钟测量。标准的多导睡眠图方法将被用来测量睡眠结构，包括睡眠状态的比例，以及睡眠纺锤体、睡眠-觉醒转换、觉醒和K-复合体之间的平均间隔。将使用双(右-左)脑血氧饱和度测量仪来测量从静息清醒基线开始的平均5分钟左右脑氧合血红蛋白饱和度的最大变化。对次级记忆、工作记忆和注意力的标准化测试将与睡眠研究同时进行，以描述认知功能的变化，并检查呼吸周期或脑氧合是否单独或联合预测24个月后认知能力的下降。此外，我们还将探讨呼吸周期和脑氧合如何随时间变化和相互作用。睡眠质量、脑血管风险因素、体力活动和抑郁症状的数据将每6个月测量一次，因为这些测量方法变化迅速，可能会影响关键的结果测量方法。除了作为对照组，来自没有表现出认知能力下降的受试者的数据将被用于探索性分析，以确定性别和种族相关的呼吸周期和大脑氧合的差异。由于使用脑氧仪对老年人的呼吸周期或脑氧合作用知之甚少，这项前瞻性研究将为确定这些变量的变化提供重要数据，并可能用于预测经过仔细筛选的老年人样本的认知能力下降。

Laboratory and clinical findings suggest that states of low cerebral oxygenation are associated with cognitive decline and dementia in older adults. Sleep is a period of increased risk for hypoxic events; and low respiratory periodicity may be an important indicator for identifying individuals with low cerebral oxygenation during sleep. Our previous studies suggest that older adults with low respiratory periodicity have more fragmented sleep, more low amplitude delta sleep and greater declines in cerebral oxygenation during sleep. The aims of this longitudinal observational study are (1) to examine the relationship between measures of respiratory periodicity, sleep structure and cerebral oxygenation during sleep; (2) to examine whether respiratory periodicity or cerebral oxygenation during sleep, alone or in combination, predict cognitive decline over 24 months; and (3) to explore how changes in respiratory periodicity and cerebral oxygenation change over 24 months. One hundred and six community dwelling older adults, age 70+ years, will be evaluated at baseline and at 12-and 24-months. Respiratory periodicity will be measured from the respiratory inductance plethysmograph waveform and include the average 5- minute measures of the variability in the duration (sdIBI), frequency (sdIBF) and amplitude (sdAMP) of breathing cycles. Standard polysomnographic methods will be used to measure sleep structure, which include the proportion of sleep states, as well as the mean interval between sleep spindles, sleep-wake transitions, arousals, and K-complexes. Dual (right- left) cerebral oximetry will be used to measure maximum change in the average 5-minute right and left cerebral oxyhemoglobin saturation from resting awake baseline. Standardized tests of secondary memory, working memory, and attention will be measured at the same time as the sleep studies in order to describe changes in cognitive function and to examine whether respiratory periodicity or cerebral oxygenation alone or in combination predict cognitive decline over 24 months. In addition, we will explore how respiratory periodicity and cerebral oxygenation change and interact over time. Data on sleep quality, cerebrovascular risk factors, physical activity and depressive symptoms will be measured every 6 months because these measures can change rapidly and may affect the key outcome measures. In addition to serving as a comparison group, data from subjects who do not exhibit cognitive decline will be used in exploratory analyses to determine gender and race-associated differences in respiratory periodicity and cerebral oxygenation. Since little is known about respiratory periodicity or cerebral oxygenation using cerebral oximetry in older adults, this prospective study will provide important data for determining how these variables vary and may be used to predict cognitive decline in a carefully screened sample of older adults.