Sleep Disorders

There are more than 80 different sleep disorders. The most common include apnea, insomnia, narcolepsy, periodic limb movements and restless leg syndrome. UCSF's Sleep Disorders Center is a specialized diagnostic clinic designed to evaluate patients with a wide range of sleep-related problems.

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During sleep, we usually pass through five phases and complete several full cycles of these phases each night:

  • Stage 1 is light sleep, where we drift in and out of sleep. We can be awakened easily. Our eyes may move very slowly and we may experience sudden muscle contractions called hypnic myoclonia.
  • During stage 2, our eye movements stop and our brain waves become slower.
  • Stage 3 and 4 are called deep sleep, when it's extremely difficult to wake someone and there's no eye or muscle activity. In stage 3, extremely slow brain waves called delta waves appear, interspersed with small, faster waves. The brain produces delta waves almost exclusively in stage 4.
  • When we enter the fifth stage or rapid eye movement (REM) sleep, our breathing becomes more rapid, irregular and shallow. Our eyes jerk rapidly, our heart rate increases, our blood pressure rises and our limb muscles become temporarily paralyzed. Males may develop penile erections.

The first REM sleep usually occurs about an hour to an hour-and-a-half after we fall asleep. As adults, we spend almost 50 percent of our total sleep in stage 2 sleep, about 20 percent in REM sleep and the remaining 30 percent in the other stages.

When our sleep cycles are disrupted due to disease, medication, stress or physical problems, sleep deprivation can result. Sleep deprivation can interfere with work, driving and even social activities.

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Related Information

UCSF Clinics & Centers


Sleep Disorders Center
2330 Post St., Suite 420
San Francisco, CA 94115
Phone: (415) 885-7886
Fax: (415) 885-3650
Appointment information

Snoring and Sleep Apnea Surgery
2380 Sutter St., Third Floor
San Francisco, CA 94115
Phone: (415) 353–2757
Fax: (415) 353–2603
Appointment information

Visit UCSF Benioff Children's Hospital