Kristin was running late again. Could she possibly make it to school on time? Her school has a very strict morning start time and she had often missed it. If she is late, not only will she be locked out of her first period class, but she could be suspended this time. She's already had several warnings and fears this could be her last. Why had she stayed up so late last night texting her friends?

Kristin has been having a hard time getting to school on time because she doesn't go to bed until 3 a.m. This is not because she has a hard time falling asleep once she gets in bed. She does not have insomnia. She only has trouble falling asleep if she goes to bed before 3 a.m. At 3 a.m. she is able to easily fall asleep. She does not find it easy, however, to get up at 6:30 a.m., which is the last possible time she can get up and still make it to school on time. In fact, her mother and father practically have to pull her out of bed to get her up. When she does make it to school on time, she often falls asleep during her morning classes. By the time of her afternoon classes, she finally seems to wake up. She is tired all the time and can be irritable. Her grades have suffered as well. On the weekends she still goes to bed around 3 a.m. but sleeps until 1 or 2 p.m. The weekends are the only time she feels rested. She dreads Sunday night knowing what will happen Monday morning.

The sleep problem Kristin is having is one of the circadian rhythm sleep disorders and one that is very common among young people. Circadian rhythm sleep disorders often lead to poor sleep among teens, as I discussed in a previous blog. The primary feature of the Circadian Rhythm Sleep Disorder, Delayed Sleep Phase Type (Delayed Sleep Phase Disorder) is that the major sleep episode is delayed as compared to the desired clock time. That is, the bedtime is at a notably later time than the "normal" time to retire. Instead of sleeping from, say, 10:30 p.m. to 6:30 a.m., the person with delayed sleep phase may sleep, as in Kristin's case, from 3:00 a.m. until whenever she is forced to get up. This can lead to problems such as difficulty falling asleep if trying to go to bed at an earlier time; insufficient sleep if having to get up earlier than the delayed morning rise time; and extreme difficulty waking up when necessary due to social demands such as school or work.

With a Delayed Sleep Phase Disorder, the person's bed time is usually delayed until after 2 a.m. and may be as late as 6 a.m. Adequate functioning is very difficult during the day if the person has to get up at regular times for work or school. Often there is heavy use of alcohol or sleeping medication in an effort to initiate sleep at an earlier time. The sleep architecture is generally normal if the person is allowed to keep an uninterrupted sleep schedule. This means that the stages of sleep are about the same as someone sleeping on a "normal" schedule, just at a different time of the day.

This disorder often starts gradually and leads to a "resetting" of the circadian (24 hour) biological "clock." It often develops as the person stays up later working on a computer, texting friends who also have sleep problems, playing video games or watching TV. Not only do these activities keep the person up but they expose the eye to a significant amount of light later and later in the day. The circadian clock is most strongly set or "entrained" by light. The presence of bright light is a signal for humans to be awake, just as it is in other diurnal animals. For us, darkness is the signal to sleep. Historically there was not much light after the sun went down and sleep generally came easy. Today we can have very bright light sources impinging on our retinas at any time of the day and this can easily, to our detriment, shift the circadian clock.

While the prevalence of delayed sleep phase disorder is currently unknown, it is clearly more common among adolescents and young adults. Among these young people, the prevalence is reported to be 7% to 16%. About 10% of patients that present to sleep disorders clinics with a complaint of chronic insomnia have a Delayed Seep Phase Disorder.

In the next blog I will discuss what Kristin did to treat her Delayed Sleep Phase Disorder and to stop being- sleepless in America.


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