Midpoint of Sleep Linked to Sleep Quality in Older Adults With Alzheimer Disease

Midpoint of sleep is associated with different measures of sleep quality and should be factored in when using sleep as a biomarker for Alzheimer disease (AD) risk, according to a study recently published in Sleep Advances.

Timing of sleep impacts sleep-wake cycles and has been linked to AD. However, little is known about the link between sleep disturbances and midpoint of sleep, specifically in older adults. The midpoint of sleep can be measured using sleep logs or questionnaires, and although it is a measure of sleep behavior rather the function of circadian rhythm, individuals with both early and late sleep midpoint are at risk of worse health outcomes, including dementia.

In this study, researchers analyzed 243 older adults who underwent standardized cognitive assessments, measurement of AD biomarkers, and at-home sleep monitoring. Sleep was recorded using longitudinal at-home tests for up to 6 consecutive nights using self-reported sleep logs, actigraphy (a commonly used sleep assessment tool), and an electroencephalogram device worn on participants’ foreheads.

Following analysis, the researchers concluded that later midpoint of sleep was associated with longer REM onset latency, decreased REM sleep time, and increased non-REM slow-wave activity. The researchers noted that sleep timing was also associated with multiple sleep measures. Moreover, the study found that Black people were more likely to have a later midpoint of sleep and greater night-to-night variability in the sleep midpoint.

“Noninvasive in vivo markers of brain function, such as sleep, are needed to track both future risk of cognitive impairment and response to interventions in older adults at risk for AD. Sleep timing is associated with multiple other sleep measures and may affect their utility as markers of AD. The midpoint of sleep may be changed through behavioral intervention and should be taken into account when using sleep as a marker for AD risk,” the researchers concluded.