Which parts of sleep were linked to sleep quality and performance?

Details

Sleep and its sub-states are thought to matter for brain function throughout life, but their relationships with specific aspects of cognition, mood and self-reported sleep quality have not been established in detail. Researchers measured sleep using polysomnography, quantitative electroencephalogram (EEG) analysis and self-report in 206 healthy men and women aged 20–84 who had no sleep complaints. Five assessments scheduled across the day measured waking brain function: objective performance across domains including sustained attention and arousal, decision and response time, motor and sequence control, working memory and executive function, as well as self-reported alertness, mood and affect.

After controlling for age and sex, better self-reported sleep quality was associated with fewer awakenings and longer rapid eye movement (REM) sleep, but not significantly associated with slow-wave sleep (SWS) measures. When controlling only for age, associations between objective and subjective sleep quality were much stronger in women than in men. An analysis of 51 performance measures found that, after controlling for age and sex, fewer awakenings and more REM sleep were significantly associated with better performance on the Goal Neglect task, a test of executive function.

Factor analysis of individual performance measures identified four latent variables: Mood/Arousal, Response Time, Accuracy and Visual Perceptual Sensitivity. Mood/Arousal improved with age and Response Times became slower, while Accuracy and Visual Perceptual Sensitivity changed little with age. After controlling for sex and age, nominally significant associations with sleep showed faster Response Times with more SWS and reduced Accuracy among people who woke more often or had less REM sleep. The researchers interpreted the data as indicating a positive contribution of SWS to processing speed and highlighting sleep continuity and REM sleep for subjective sleep quality and performance accuracy across the adult lifespan. They called for further investigation of the contribution of sleep continuity and REM sleep to brain function.