Impact of Sleep Quality on Cognitive and Physical Function in Individuals with Multiple Sclerosis

Background: Over 50% of individuals with multiple sclerosis (MS) experience sleep disturbances. Poor sleep quality has been associated with decreased quality of life and increased depression and anxiety in individuals with MS. However, it is unknown how poor sleep quality impacts cognitive and physical function in individuals with MS.

Objectives: The purpose of this study was to examine the effect of sleep quality on cognitive and physical function in individuals with MS.

Methods: Forty individuals with relapsing-remitting or secondary-progressive MS (50.3 ±11.6 years of age) were recruited to participate in an exercise intervention study. Baseline assessment consisted of a battery of cognitive tests: the BVMT to assess visuospatial memory, the HVLT to assess verbal memory, the PASAT to assess information processing, and the Stroop to assess executive function. The 6MWT was used to assess walking ability, the PPT was used to evaluate performance of activities of daily living, and the FSQ was used to assess self-reported functional ability. The PSQI was used to assess sleep quality. Following baseline assessment, participants were divided into two groups based on their sleep quality. A PSQI of ≤5 was considered good sleep quality (n=13); > 5 was considered poor sleep quality (n=27). Mann-Whitney U tests were used to determine between group differences.

Results: 67.5% of the participants reported poor sleep quality. There was no difference between the groups for age or disease severity. Those with good sleep quality performed significantly better on the BVMT (p=0.025) and the FSQ (p<0.001) compared to those with poor sleep quality. However, there were no statistically significant differences between groups for the other outcomes.  

Conclusions: This study suggests that individuals with MS with good sleep quality have better visuospatial memory and higher self-report functional abilities compared to individuals with MS with poor sleep quality. Evidence demonstrates sleep consolidates memory. Therefore, poor sleep may selectively impair memory while not impacting the other cognitive domains. In addition, individuals with MS with poor sleep quality may underestimate their functional abilities compared to those with good sleep quality. Future research is needed to verify these contentions.