Abstract

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 identify elders with low cerebral oxygenation during sleep. Our previous work suggests that elders with low respiratory periodicity have more fragmented sleep, more low amplitude delta sleep and greater declines in cerebral oxygenation during sleep. This longitudinal observational study will (1) examine the relationship between respiratory periodicity, sleep structure and cerebral oxygenation during sleep; (2) examine how respiratory periodicity and cerebral oxygenation during sleep predict cognitive decline over 24 months; and (3) explore how respiratory periodicity and cerebral oxygenation change over 24 months.

Measures of respiratory periodicity, cerebral oxygenation and sleep will be collected over two consecutive nights on 106 community dwelling adults, age 70+ years, at baseline and at 12-and 24-months. Respiratory periodicity will be measured with a respiratory inductance plethysmograph. Dual (right-left) cerebral oximetry will be used to measure changes in right and left cerebral oxyhemoglobin saturation from resting awake baseline. Standard polysomnographic methods will be used to measure sleep structure (the proportion of sleep states, as well as the mean interval between sleep spindles, sleep-wake transitions, arousals, and K-complexes). 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. 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 community-dwelling older adults.