October 24, 2017
Study results suggest that interventions to improve patients’ sleep may improve cognitive performance in patients with Parkinson disease.
First author Amy W Amara, MD, University of Alabama (Birmingham, AL), said, “We found that sleep has a significant influence on cognitive performance in Parkinson's disease.” Dr Amara presented the team’s findings at the 2017 Annual Meeting of the American Neurological Association (Abstract S272).
According to Medscape, sleep dysfunction is a common consequence in those with Parkinson disease due to “multifactorial causes ranging from nocturnal motor symptoms of the disease to side effects from various drugs” (October 20, 2017).
Dr Amara and her colleagues decided to investigate the association between deep, or slow-wave, sleep—rapid eye movement (REM) stage 3 sleep—and cognitive performance in patients with Parkinson disease. Participants underwent polysomnography and then were evaluated for sleepiness and psychomotor skills.
Patients were categorized as experiencing either high slow-wave sleep—defined as more than 10% of the time in non-REM stage 3—or low slow-wave sleep—defined as 10% or less time in non-REM stage 3 sleep. Age, education, and disease severity did not differ between the two groups, but more women were in the high slow-wave sleep group than in the low slow-wave sleep group.
Despite the differences in time spent in deep sleep, no differences were seen between the two groups' subjective measures of daytime sleepiness, assessed on the Epworth Sleepiness Scale, or in their reports of sleep quality, assessed on the Pittsburgh Sleep Quality Index.
However, there were notable differences in neurocognitive measures. “Patients with high slow-wave sleep showed significantly faster reciprocal reaction time on the Psychomotor Vigilance Task (P = .04), and they performed significantly better on measures of global cognition, including the Montreal Cognitive Assessment (P = .04), attention/working memory (Stroop color naming: P = .0006; word naming: P = .0025; letter number sequencing: P = .031).”
Participants with higher slow-wave sleep also had higher scores in executive function (Trails B-A: P = .01; Stroop inhibition: P = .0052) and in one of the two measures of language (Controlled Oral Word Association: P = .021).
Authors said, “This study adds to our understanding of insomnia in Parkinson's by identifying a specific part of sleep, known as slow-wave-sleep, that seems to be specifically impacted in patients with Parkinson's disease,” but they noted that cognitive performance is extremely multifactorial, and researchers are only just beginning to understand all of the contributing factors of low cognitive status.
“Sleep is often implicated as one of those potential causes, and this study supports that idea. Further, it supports the idea that the connection between sleep and cognition is important to study in the future.”—Amanda Del Signore