Sleep disorders occur in some people with cancer and may be caused by physical illness, pain, treatment drugs, being in the hospital, and emotional stress. Sleep has two phases: rapid eye movement (REM) and non-REM (NREM). REM sleep, also known as "dream sleep," is the phase of sleep in which the brain is active. NREM is the quiet or restful phase of sleep. The stages of sleep occur in a repeated pattern of NREM followed by REM. Each sleep cycle lasts about 90 minutes and is repeated 4 to 6 times during a 7- to 8-hour sleep period. The four major categories of sleep disorders that interfere with normal sleep patterns include:

• The inability to fall asleep and stay asleep (insomnia).
• Disorders of the sleep-wake cycle.
• Disorders associated with sleep stages, or partial waking (parasomnia).
• Excessive sleepiness.

Glossary Terms

A term for diseases in which abnormal cells divide without control. Cancer cells can invade nearby tissues and can spread to other parts of the body through the blood and lymph systems. There are several main types of cancer. Carcinoma is cancer that begins in the skin or in tissues that line or cover internal organs. Sarcoma is cancer that begins in bone, cartilage, fat, muscle, blood vessels, or other connective or supportive tissue. Leukemia is cancer that starts in blood-forming tissue such as the bone marrow, and causes large numbers of abnormal blood cells to be produced and enter the blood. Lymphoma and multiple myeloma are cancers that begin in the cells of the immune system. Central nervous system cancers are cancers that begin in the tissues of the brain and spinal cord.

In medicine, a disturbance of normal functioning of the mind or body. Disorders may be caused by genetic factors, disease, or trauma.

Any substance, other than food, that is used to prevent, diagnose, treat or relieve symptoms of a disease or abnormal condition. Also refers to a substance that alters mood or body function, or that can be habit-forming or addictive, especially a narcotic.

Difficulty in going to sleep or getting enough sleep.