Sleep Disorders and Cognition in Older Men

Bill Yates
Brain Posts

Nov 21 / 2011

Sleep contributes to brain function through a variety of mechanisms.  Sleep functions change over the life cycle with older adults showing a greater amount of time in light sleep phases (stage 1 and stage 2 sleep).  Less time is typically spent among older adults in restorative or deep sleep (slow-wave sleep)  and rapid age movement sleep.

Since dementia risk increases with age, it is natural to wonder how age-related sleep changes might interact with cognitive function.

One method of examining the sleep-cognition relationship is to perform sleep studies and neuropsychological testing in a cohort of individuals.  Large samples of elderly subjects with such association studies are limited.

Sleep Stage Architecture Figure with REM Sleep in Red

A recent study of a large correlational study of sleep and cognition has been recently published in the Journal of the American Geriatrics Society.  This data set analysis is a secondary study as the data was collected originally for the Osteoporotic Fractures in Men Study (MrOS).  Nearly 6,000 men aged 65 and older from six centers in the U.S.  Subjects needed to be ambulatory not had have had bilateral hip replacement. The sleep and cognitive function variables collected in the study included:

Sleep parameters (from ambulatory polysomnography testing): sleep stages duration (Rapid eye movement sleep, i.e. dreaming sleep--REM, Stages 1-4, Non-rapid eye movement sleep--NonREM),  arousal index (number of EEG arousals per hour of sleep), apnea-hypopnea index (measure of sleep-disordered breathing) and arterial oxygen saturation.

Cognitive function testing: Trail Making Test Part B (measure of psychomotor speed and visuospatial functioning, modified Mini-Mental State Exam (screening test of orientation, memory, comprehension, speech), Digital Vigilance Test (testing of attention and memory).

Spending more time during sleep in light sleep (stage 1) and spending less time in REM sleep correlated with decreased cognitive function.  Surprisingly, sleep apnea measures did not associate many of the cognitive function variables tested in this population.  Severe levels of sleep hypoxia were related to decreased vigilance scores but no change was found on other cognitive function variables.

Reduced REM sleep time was linked to a variety of clinical characteristics including: hypertension, history of stroke or transient ischemic attack (TIA), coronary artery disease, current antidepressant use, higher current Geriatric Depression Scale score, less education, lower physical activity and lower self-rated health.

The authors note that a primary weakness of their study is the correlational analysis--direction of effect is unknown.  From this study it is impossible to know if having a sleep problems contributes to risk or vice versa--cognitive decline may produce sleep changes.  It is also possible a third unknown pathway may be in operation.

This study is not sufficient to change clinical practice.  However, it seems prudent to monitor cognitive function in older adults and consider the potential for sleep problems (and sleep disorders) to contribute to process of mental decline in the elderly.

Sleep architecture from Wikipedia Commons file authored by Petitemontagnedujura

Blackwell, T., Yaffe, K., Ancoli-Israel, S., Redline, S., Ensrud, K., Stefanick, M., Laffan, A., Stone, K., & , . (2011). Associations Between Sleep Architecture and Sleep-Disordered Breathing and Cognition in Older Community-Dwelling Men: The Osteoporotic Fractures in Men Sleep Study Journal of the American Geriatrics Society DOI: 10.1111/j.1532-5415.2011.03731.x

See the original article:

Sleep Disorders and Cognition in Older Men

in

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