The relationship between objective parameters of sleep and measures of fatigue, depression, and cognition in multiple sclerosis

BACKGROUND People with multiple sclerosis (MS) often report poor sleep, fatigue, sleepiness, depression and cognitive dysfunction. Interrelationships between symptoms and sleep are poorly understood. OBJECTIVES To document objective parameters of sleep measured by polysomnography (PSG) and multi-sleep latency tests (MSLTs) in patients experiencing fatigue or sleepiness and to determine whether they correlate with symptoms. METHODS Thirty-two MS patients, not on therapy, with fatigue or sleepiness completed the Modified Fatigue Impact Scale, Fatigue Severity Scale, Epworth Sleepiness Scale, Beck Depression Index and NeuroTrax cognitive tests and underwent PSG and MSLTs. RESULTS Sleep efficiency (SE) averaged 75.1%. wake after sleep onset (WASO), sleep onset latency and multi-sleep latency were 66.2, 43.4 and 10.43 min, respectively. Stage N3 and rapid eye movement sleep were absent in 10 and four patients, respectively. Increased limb movements were observed in eight patients. Obstructive sleep apnea was observed in 12 patients. Neither SE nor WASO correlated with fatigue or sleepiness. SE correlated with the global cognitive score and with executive function and information processing subscales. CONCLUSIONS Overall, 30/32 MS patients reporting fatigue or sleepiness had evidence of one or more sleep disturbances. PSG should be considered in MS patients reporting fatigue or sleepiness in order to rule out treatable disturbances.