Delayed Sleep-Wake Phase – Overview & Facts
Delayed sleep-wake 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.
Someone with DSP may:
- Have a delay in their sleep pattern in relation to their desired sleep and wake times
- Have trouble falling asleep at the desired time of night
- Be unable to awaken at the desired or socially acceptable time
- Have a normal duration and quality of sleep when left to their own sleep schedule, but this sleep occurs in a stable, but delayed time period in relation to what is desired or socially acceptable
- Have this kind of stable but delayed sleep time for at least seven days
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
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.