Sleep in host defense.

Sleep remains an important enigma in neurobiology; it has a robust adaptive value yet its function remains elusive. Changes in sleep are hallmarks of the acute phase response to infectious challenge. The molecular regulation of these responses involves a cytokine cascade within brain, including interleukin-1 and tumor necrosis factor, and several other substances such as growth hormone releasing hormone, prolactin, nitric oxide and nuclear factor kappaB. These substances are also involved in the regulation of normal spontaneous sleep. Fatigue and sleep disturbances are common in cancer patients and in those receiving cytokine therapy. Regardless, the role of sleep in cancer is relatively uninvestigated.