Sleep and its associations with perceived and objective cognitive impairment in individuals with multiple sclerosis.

Problems with sleep and cognitive impairment are common among people with multiple sclerosis (MS). The present study examined the relationship between self-reported sleep and both objective and perceived cognitive impairment in MS. Data were obtained from the baseline assessment of a multi-centre intervention trial (NCT00841321). Participants were 121 individuals with MS. Nearly half (49%) of participants met the criteria for objective cognitive impairment; however, cognitively impaired and unimpaired participants did not differ on any self-reported sleep measures. Nearly two-thirds (65%) of participants met the criteria for 'poor' sleep, and poorer sleep was significantly associated with greater levels of perceived cognitive impairment. Moreover, the relationships between self-reported sleep and perceived cognitive impairment were significant beyond the influence of clinical and demographic factors known to influence sleep and cognitive functioning (e.g. age, sex, education level, disability severity, type of MS, disease duration, depression and fatigue). However, self-reported sleep was not associated with any measures of objective cognitive impairment. Among different types of perceived cognitive impairment, poor self-reported sleep was most commonly related to worse perceived executive function (e.g. planning/organization) and prospective memory. Results from the present study emphasize that self-reported sleep is significantly and independently related to perceived cognitive impairment in MS. In terms of clinical implications, interventions focused on improving sleep may help improve perceived cognitive function and quality of life in this population; however, the impact of improved sleep on objective cognitive function requires further investigation.