Sleep and fatigue in multiple sclerosis

Fatigue is common in multiple sclerosis (MS) and is an important cause of disability. However, the cause of fatigue is poorly understood. This study aimed to describe the frequency and pattern of sleep disturbance in a group of outpatients with MS, and to investigate the relationship between sleep disturbance and fatigue. Sixty outpatients with MS completed the Fatigue Severity Scale (FSS) and the Epworth Sleepiness Scale and kept a sleep diary for seven days. Fatigue and excessive daytime sleepiness were common in this group of patients (64 and 32%). Sleep problems on at least two nights per week occurred frequently, including initial insomnia in 42%, middle insomnia in 53% and terminal insomnia in 58%. The reasons cited for different types of insomnia varied, with anxiety and pain/discomfort being the commonest causes of initial insomnia and nocturia the commonest cause of middle insomnia. Middle insomnia was significantly correlated with daytime fatigue, a relationship that remained after controlling for disability. Sleep disturbance is common in MS and is associated with treatable symptoms, including pain and nocturia. Sleep disturbance may be an important factor contributing to fatigue in patients with MS.