Poor sleep quality may be associated with impaired memory and decreased functional abilities in multiple sclerosis (MS) patients, according to the study “Impact of Sleep Quality on Cognitive and Physical Function in Individuals with Multiple Sclerosis.” The study was presented during the Whitaker Research Track Session II at the June 1 – 4 Consortium of Multiple Sclerosis Centers (CMSC) 2016 Annual Meeting, in National Harbor, Md.
More than half of the MS population experience sleep disturbances. Although poor sleep quality has been associated with increased depression and anxiety, and decreased quality of life in MS patients, little is known about its effects on cognitive and physical function.
Researchers at the University of Kansas Medical Center examined the effects of sleep quality on physical and cognitive functions in MS patients. The study included 40 patients with relapsing-remitting or secondary progressive MS, who had been recruited to participate in an exercise intervention study.
Sleep quality was measured through the Pittsburgh Sleep Quality Index (PSQI) test, and further examined through a battery of cognitive tests, including a test for visuospatial memory (Brief Visuospatial Memory Test, BVMT), verbal memory (Hopkins Verbal Learning Test, HVLT), information processing (Paced Auditory Serial Addition Test, PASAT), and executive function (Stroop).
Functional abilities were also assessed through the six-minute walk test (6MWT), which determines walking ability, the Physical Performance Test (PPT), used to evaluate performance of daily activities, and the Functional Status Questionnaire (FSQ), that assesses self-reported functional ability.
Study results demonstrated that 67.5% of the patients reported poor sleep quality. But, patients who had good sleep quality performed significantly better on the BVMT and FSQ tests, suggesting that MS patients with better sleep quality have increased visuospatial memory and higher self-reported functional ability than patients with poor sleep quality. No significant differences were found on the remaining tests between both groups.
Given that sleep is known to consolidate memories, the investigators believe that poor sleep may influence visuospatial memory without affecting the other cognitive parameters. Additionally, although the 6MWT and PPT tests results did not show any association with quality of sleep, patients with good sleep quality reported higher functional ability, suggesting that patients with poor sleep quality underestimate their own functional abilities.