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Delayed Sleep Phase

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What is it?

Delayed sleep phase disorder (DSP) is a circadian rhythm disorder. It consists of a typical sleep pattern that is "delayed" by two or more hours. This delay occurs when one’s internal sleep clock (circadian rhythm) is shifted later at night and later in the morning. Once sleep occurs, the sleep is generally normal. But the delay leads to a pattern of sleep that is later than what is desired or what is considered socially acceptable. This pattern can be a problem when it interferes with work or social demands.

A person with DSP is likely to prefer late bedtimes and late wake-up times. When left to his or her own schedule, a person with DSP is likely to have a normal amount and quality of sleep. It simply occurs at a delayed time. One sign of this disorder is difficulty falling asleep until late at night. Another sign is having a hard time getting out of bed in the morning for work or school. These signs can make DSP look like insomnia. Daytime functioning can be severely impaired by DSP. It can lead to excessive sleepiness and fatigue. When able to sleep on their own schedules, people with DSP often stay up until they get tired and then sleep until they awaken late in the morning. In this case, they tend to have no complaint of difficulty falling to sleep or feeling poorly during the day.


Who gets it?

The exact rate of DSP is unknown in the general population. It is much more common in teens and young adults. From 7% to 16% of them may have it. DSP is likely to be found in 10% of people with a complaint of chronic insomnia. People who tend to be "evening types" or "night owls" are likely to develop DSP.

There is likely to be some genetic component. Some environmental factors may also be involved. A lack of exposure to morning sunlight may make it worse. Too much exposure to bright evening sunlight may also increase symptoms of DSP. A family history of DSP is common in about 40% of people with the disorder.


How do I know if I have it?

  1. Is there a delay in your sleep pattern in relation to your desired sleep and wake times? Do you have trouble falling asleep at the desired time of night? Are you then unable to awaken at the desired or socially acceptable time?
  2. When left to your own sleep schedule, do you have a normal duration and quality of sleep? Does this sleep occur in a stable, but delayed time period in relation to what is desired or socially acceptable?
  3. Have you had this kind of stable but delayed sleep time for at least seven days?

If you answered “yes” to these questions, then you may have delayed sleep phase disorder.

It is also important to know if there is something else that is causing your sleep problems. They may be a result of one of the following:

  • Another sleep disorder
  • A medical condition
  • Medication use
  • A mental health disorder
  • Substance abuse

Do I need to see a sleep specialist?

Yes. It is easy to confuse DSP with normal variations of sleep and other types of insomnia. Consulting with a sleep specialist is your best bet to help clarify current sleep problems. He or she will also be able to help you develop a plan to correct these problems. A specialist can assess the factors that cause and make this problem worse. These include both social and behavioral factors.


What will the doctor need to know?

The sleep doctor will do a thorough physical exam. He or she will also discuss with you the history of these sleep problems. It would be helpful to keep a sleep diary prior to seeing a sleep doctor. Bring this information with you to the appointment. A sleep diary is a systematic way to track your sleep pattern. You record the time you get into bed, the time required to fall asleep, and the time you wake up in the morning. Sleep diaries often show a regular pattern of difficulty falling to sleep. They often show few or no awakenings once asleep. They also tend to show a sleep duration that is reduced during the work week and lengthy on the weekend.


Will I need to take any tests?

An overnight sleep study is not normally needed for someone who suffers from DSP. Your doctor may have you do an overnight sleep study if your problem is severely disturbing your sleep. This study is called a polysomnogram. It charts your brain waves, heart rate, and breathing as you sleep. It also records how your arms and legs move. This study will help determine if there are any objective sleep disorders related to your sleep problem.


How is it treated?

The most accepted treatment for DSP is what is called chronotherapy. This is a method of behavioral treatment. Your bedtime is delayed by about three hours per day for five or six consecutive days. Once the desired bedtime is reached the schedule is frozen. This schedule needs to be maintained rigidly at this point.

Bright light therapy is another proven technique for changing one’s internal circadian rhythms. But its specific use for DSP has not been well validated. In theory, exposure to bright light should occur shortly after waking up at the desired time in the morning. Then bright outdoor light in the evening hours should be avoided.

By Donald R. Townsend, PhD
Updated on October 21, 2005

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