What is it? This condition, in which the person's biological clock shifts to earlier hours—typically falling asleep before 9 p.m. and awakening between 3 and 5 a.m. and failing to return to sleep.
How common is it? This condition occurs most often in older people. In fact, some doctors believe it is more a normal consequence of aging than a disorder.
What's the treatment? Light therapy is effective in helping people to delay their sleep phase. The person is administered bright light (through special light boxes purchased through medical supply sources. They are similar to those used to treat seasonal affective disorder) for two hours before bedtime, which helps to delay sleep, and avoided at other times.