Sleep disturbances occur in about 12% to 25% of the general population [1] and are often associated with situational stress, illness, aging, and drug treatment.[2,3] It is estimated that 45% of people with cancer experience sleep disturbance.[4] Physical illness, pain, hospitalization, drugs and other treatments for cancer, and the psychological impact of a malignant disease may disrupt the sleeping patterns of persons with cancer. Poor sleep adversely affects daytime mood and performance. In the general population, persistent insomnia has been associated with a higher risk of developing clinical anxiety or depression. Sleep disturbances and, ultimately, sleep-wake cycle reversals can be early signs of a developing delirium. (Refer to the PDQ summary on Cognitive Disorders and Delirium ¹ for more information.) Adequate sleep may increase the cancer patient's pain tolerance.

Sleep consists of two phases: rapid eye movement (REM) sleep and non-REM (NREM) sleep.[5] REM sleep, also known as dream sleep, is the active or paradoxic phase of sleep in which the brain is active. NREM sleep is the quiet or restful phase of sleep. NREM, also referred to as slow wave sleep, is divided into four stages of progressively deepening sleep based on electroencephalogram findings.[2,6]

The stages of sleep occur in a repeated pattern or cycle of NREM followed by REM, with each cycle lasting approximately 90 minutes. The sleep cycle is repeated four to six times during a 7- to 8-hour sleep period.[6] The sleep-wake cycle is dictated by an inherent biological clock or circadian rhythm. Disruptions in individual sleep patterns can disrupt the circadian rhythm and impair the sleep cycle.[7]

Four major categories of sleep disorders have been defined by the Sleep Disorders Classification Committee of the American Academy of Sleep Medicine:

1. Disorders of initiating and maintaining sleep (insomnias).
2. Disorders of the sleep-wake cycle.
3. Dysfunctions associated with sleep, sleep stages, or partial arousals (parasomnias).
4. Disorders of excessive somnolence.

References

1. Walsleben J: Sleep disorders. Am J Nurs 82 (6): 936-40, 1982.  [PUBMED Abstract]
   
   
2. Anderson P, Grant M: Comfort: Sleep. In: Johnson BL, Gross J, eds.: Handbook of Oncology Nursing. 3rd ed. Boston, Mass: Jones & Bartlett Publishers, 1998, pp 337-59. 
   
   
3. Savard J, Morin CM: Insomnia in the context of cancer: a review of a neglected problem. J Clin Oncol 19 (3): 895-908, 2001.  [PUBMED Abstract]
   
   
4. Beszterczey A, Lipowski ZJ: Insomnia in cancer patients. Can Med Assoc J 116 (4): 355, 1977.  [PUBMED Abstract]
   
   
5. Guyton AC: Textbook of Medical Physiology. 7th ed. Philadelphia, Pa : WB Saunders, 1986. 
   
   
6. Feirerman JR: Disordered sleep. Emerg Med 2: 160-71, 1985. 
   
   
7. Taub JM, Berger RJ: The effects of changing the phase and duration of sleep. J Exp Psychol Hum Percept Perform 2 (1): 30-41, 1976.  [PUBMED Abstract]