Treating the sleep disorder is critical, not only because people who sleep well feel better, have more energy, and are in a better mood, but sleep is critical to the body's recuperation, repair and healing, especially with chronic disease. Repair and some parts of the recuperation process occur only during sleep; for instance, 90% of Somatamedin C, a hormone that is critical in maintaining nerve and muscle health, is produced in deepest stages of sleep. If you don't make Somatamedin C, you are not going to repair tissues from normal wear and tear, which in turn causes more pain. It is a vicious circle. People in chronic pain don't get into these deep stages of sleep so essential to healing, and Somatomedin C is only one example of critical neuroendocrine products produced during sleep.

We treat sleep disorders very aggressively. and try to use agents that hit "2 or 3 birds with one stone." For example, some of the antidepressant drugs (such as nortriptaline or doxepine) are actually great analgesics. The brain stem (where you produce several critical neurochemicals such as serotonin and norepinephrine. coordinates pain, sleep, and mood. These "antidepresseant agents" modulate serotonin and norepinephrine, critically important for quality and quantity of sleep, normal mood and pain modulation.
Since you only have to take these agents once a day you can use them as anti-insomnia agents as well as analgesics to help initiate sleep, prolong it, improve the quality of sleep, and relieve the pain.

The Stages of Sleep
There are five stages of sleep that cycle over and over again during a single night: stages 1, 2, 3, 4 and REM (rapid eye movement).Stages 1 through 4 are also known as non-rapid eye movement sleep (NREM). Approximately 50% of our sleeping time is spent in stage 2 and 20% in REM. A complete sleep cycle, from the beginning of stage 1 to the end of REM, usually takes about 90 minutes. An adult normally sleeps more than 2 hours a night in REM.

Stage 2: brain activity slows down and eye movement stops.

Stages 3 and 4: deep sleep, during which all eye and muscle movement ceases. It can be difficult to wake a person during deep sleep. Stage 3 is characterized by very slow brain waves (delta waves), interspersed with small, quick waves. In stage 4, the brain waves are all delta waves.
REM: It is during REM sleep that people dream. The muscles of the body stiffen, the eyes move, the heart rate increases, breathing becomes more rapid and irregular, and the blood pressure rises. [www.neurologychannel.com/sleepdisorders/]

http://www.rsds.org/3/education/harden_sleep_disorder.htm