Cancer-related fatigue and sleep disorders

Sleep disorders, such as difficulty falling asleep, problems maintaining sleep, poor sleep efficiency, early awakening, and excessive daytime sleepiness, are prevalent in patients with cancer. Such problems can become chronic in some patients, persisting for many months or years after completion of cancer therapy. For patients with cancer, sleep is potentially affected by a variety of factors, including the biochemical changes associated with the process of neoplastic growth and anticancer treatments, and symptoms that frequently accompany cancer, such as pain, fatigue, and depression. Fatigue is highly prevalent and persistent in patients with cancer and cancer survivors. Although cancer-related fatigue and cancer-related sleep disorders are distinct, a strong interrelationship exists between these symptoms, and a strong possibility exists that they may be reciprocally related. The majority of studies that have assessed both sleep and fatigue in patients with cancer provide evidence supporting a strong correlation between cancer-related fatigue and various sleep parameters, including poor sleep quality, disrupted initiation and maintenance of sleep, nighttime awakening, restless sleep, and excessive daytime sleepiness. This paper reviews the data from these studies with a view toward suggesting further research that could advance our scientific understanding both of potential interrelationships between sleep disturbance and cancer-related fatigue and of clinical interventions to help with both fatigue and sleep disturbance.