Individuals with mild MS with poor sleep quality have impaired visuospatial memory and lower perceived functional abilities.

BACKGROUND: Sleep disturbances are common in individuals with Multiple Sclerosis (MS), but the impact of poor sleep quality on cognitive and physical function in individuals with MS is less clear. OBJECTIVE/HYPOTHESIS: The purpose of this study was to examine the relationship between sleep quality and cognitive and physical function in individuals with mild MS. METHODS: Forty individuals with relapsing-remitting or secondary-progressive MS (50.3 ± 11.6 years of age) participated. The Pittsburgh Sleep Quality Index (PSQI) was used to index sleep quality. A PSQI of ≤5 was considered good sleep quality and >5 was considered poor sleep quality. Cognitive function was assessed using a battery of cognitive tests, and physical function was assessed using 2 objective measures and a self-report measure. RESULTS: Thirteen individuals (32.5%) indicated good sleep quality and 27 (67.5%) of the participants reported poor sleep quality. Those with good sleep quality performed significantly better on a visuospatial memory test (p = 0.025) and reported higher functional abilities (p < 0.001) compared to those with poor sleep quality. There was no difference in performance on the cognitive tests of verbal memory, information processing, or executive function, or the objective function measures. Individuals with poor sleep quality had higher levels of fatigue, depression, and anxiety, and lower quality of life. CONCLUSIONS: Visuospatial memory appears to be the memory domain particularly associated with poor sleep quality in people with mild MS. Also, individuals with mild MS with poor sleep quality may underestimate their functional abilities.