Sleep Disorders

Shift work and circadian rhythm disorders

Shift work sleep disorder

A circadian sleep disorder in which a person experiences a constant or recurrent pattern of sleep interruption due to shift work schedule, resulting in difficulties initiating and maintaining sleep and/or excessive sleepiness when awake.

Shift work sleep disorder

Delayed sleep phase syndrome

A disorder in which the timing of sleep and the peak period of alertness are delayed several hours relative to societal clock.

Delayed sleep phase syndrome

Circadian rhythm disorders

A family of sleep disorders affecting the timing of sleep; people with circadian rhythm sleep disorders are unable to sleep and wake at the times required for normal work, school, and social needs.

Circadian rhythm disorders

Advanced sleep phase syndrome

A disorder in which the timing of sleep and the peak period of alertness are advanced several hours relative to societal clock.

Advanced sleep phase syndrome

Shift work sleep disorder

Shift work sleep disorder is a circadian sleep disorder in which a person experiences a constant or recurrent pattern of sleep interruption due to shift work schedule, resulting in difficulties initiating and maintaining sleep and/or excessive sleepiness when awake. Other symptoms of shift work sleep disorderinclude difficulty concentrating, headaches, and low energy. Non-traditional shifts, particularly rotating shifts, force people to place their sleep window at a time that is not congruent with their underlying circadian clock. Rotating shifts also weaken the signals from the internal clock leading to greater difficulties with sleep and sleepiness. As a result, people with shift work sleep disorder may have trouble staying alert at their work shift and feel their sleep is unrefreshing.

Learn more about circadian sleep disorders.

Managing shift work sleep disorderis inherently difficult. Research is showing that some shift work schedules are better than others, but shift workers do not always have a choice. Improving the sleep of a shift worker with sleep difficulties requires understanding how the circadian clock works and finding pragmatic solutions to help people keep as strong of a circadian rhythm as is feasible under these unnatural work conditions. Adjusting the internal clock to adapt to a night-time may include properly timed bright and dim light exposures relative to the timing of the sleep window. For example, an individual whose shift ends in the morning who intends to go home and sleep should minimize exposure to light between the end of work and bedtime (e.g., wear sunshade, have blackout shades).

Shift work is often combined with a longer than 8 hour work schedule. As a result, shift workers tend to sleep less than day workers and become more sleep-deprived over several days and therefore need to be cautious when driving and when in environments in which dozing off is dangerous. Sleep specialists can often help shift workers maintain alertness by offering alerting medication or counter fatigue behavioral recommendations. Workers with irregular or rotating shifts are at particularly high risk for accidents and their sleep problem is harder to manage. Young adults and people who describe themselves as "night owls" appear to find it easier to adjust to night and non-traditional work shifts.

Delayed sleep phase syndrome

Delayed sleep phase syndrome (DSPS) is a disorder in which a person’s sleep is delayed by two hours or more beyond what is considered an acceptable or conventional bedtime. The delayed sleep then causes difficulty in being able to wake up at the desired time.

For example, a person with DSPS may fall asleep after midnight instead of at 10 p.m. and then will have difficulty getting up in the morning for school or work.  

People with delayed sleep phase syndrome generally have difficulty:

  • Falling asleep, unless they go to bed very late (usually some hours after midnight) because their internal clock is sending alerting signals until late into the night
  • Waking up at a "normal" time in the morning, because their internal clock is not yet producing strong alerting signals

Unless you have other sleep disorders, such a sleep apnea or insomnia, you may actually sleep well with DSPS, in terms of duration and quality of sleep. The problem is that the delay makes it difficult to wake up in time for a typical school or work day.

You may have DSPS if the sleep disorder is also causing impairment in social, occupational or other areas of your life. The prevalence of DSPS among adolescents and young adults is approximately seven to 16 percent.

DSPS may develop in early childhood but most commonly it emerges or worsens during adolescence. Some adolescents delay their sleep schedules for social reasons and may not have underlying abnormalities in their circadian rhythm (the internal body clock). For those, sleep schedules normalize in early adulthood. Learn more about circadian sleep disorders.

If you have been unsuccessful in changing your sleeping pattern on your own, it may be time to seek the help of sleep disorder specialists. Our sleep specialists use two treatment methods to treat DSPS:

  • Bright light therapy: We use light to gradually shift your sleeping pattern to a more conventional schedule. Learn more about bright light therapy
  • Chronotherapy: This technique aims to reset your circadian clock by slowly delaying your bedtime (and your sleep period) by about two hours every few days. We use this strategy less frequently than the light therapy method. The disadvantage is that it disrupts your normal schedule of activity during the shift, when day and night are reversed.

Circadian rhythm disorders

A circadian rhythm disorder occurs when the internal clock regulating sleep and wakefulness is weakened or when it is misaligned with a person's desired sleep period. Sleep specialists use a diagnostic system called the International Classification of Sleep Disorders (ICSD). The diagnostic category is established by a panel of experts who take into account available research and clinical experience.

The current version of the diagnostic system include nine different circadian rhythm disorders, the most common of which are delayed sleep phase, advanced sleep phase, and shift work disorder.

Advanced sleep phase syndrome

Advanced sleep phase syndrome is a disorder in which the timing of sleep and the peak period of alertness are advanced several hours relative to societal clock. People with advanced sleep phase syndrome generally have difficulty staying awake unless they go to bed very early because their internal clock is already at a relatively quiet state, and wake up very early, at what is considered a "normal" time in the morning, unable to fall back asleep, because their internal clock is already producing strong alerting signals.

Unless other sleep disorders, such a sleep apnea or insomnia, are present, an individual with advanced sleep phase syndrome sleeps well (in terms of duration and quality) when going to bed and waking up early but the syndrome makes it difficult to stay awake in the evening and be engaged in social activities. Sleep quality is not impaired by the syndrome but afflicted individuals may have short sleep duration if they delay their bedtime. Nonetheless people with advanced sleep phase syndrome do not report that the syndrome affects their daytime work or school activities. Their most common complaint is that their evening activities are cut short by the need to sleep much earlier than what is considered the norm. This can affect family and social relationships. Individuals with Advanced Sleep Phase Syndrome should be cautious about driving in the late afternoon and evening, because they may be too drowsy. They also do not adjust well to evening or night shifts.

The prevalence of advanced sleep phase syndrome in the general population is unknown although it is most prevalent among older adults. Advanced sleep phase syndrome has the same prevalence among men and women. Researchers have also found a strong genetic link: 40%-50% of people suffering from advanced sleep phase syndrome are related to someone who has the syndrome.

Learn more about circadian sleep disorders.

Most people don't seek treatment unless it starts to significantly impact their social life. Sleep specialists treat advanced sleep phase syndrome with evening bright light exposure.

Bright light therapy is used to manage circadian rhythm disorders such as delayed sleep phase syndrome (DSPS), a condition which shifts the normal sleeping pattern outside what is considered the social norm. People who have DSPS generally don't fall asleep until several hours after midnight and have trouble waking up in the morning, making adhering to a normal work or school schedule difficult. However, if allowed to follow their own schedules, their quality of sleep is otherwise normal.

Bright light therapy is used to gradually shift sleeping patterns to what we consider normal. For treatment, the timing of light exposure is critical. For DSPS, the light must be delivered to the retina as soon after spontaneous awakening as possible to achieve the desired effect. People have also reported success with lights that turn on shortly before awakening, to simulate dawn. Morning use may also be effective for non-24-hour sleep-wake syndrome, while evening use is recommended for advanced sleep phase syndrome. There is less data about the effectiveness of light therapy for advanced sleep phase syndrome than there is for morning light exposure in delayed sleep phase syndrome.

This technique—also called phototherapy—uses appropriately timed exposure to light to help delay the patients biological clock. The source of light could be artificial, such as a full spectrum lamp at 10,000 lux or portable visor at lower light intensity or, when reliably available at the right time, natural outdoor light. Longer properly timed light exposure is better, with recommended exposure duration of 30-90 minutes. The ideal timing of the light exposure depends on the best approximation available of the persons circadian clock.

The sleep specialists works with the patient to decide on the timing of the light exposure based on patients symptoms and life circumstances. The specialist may start by recommending light exposure take place shortly before the patients usual time of spontaneous awakening.

The specialist helps the patient slowly shift the sleep period to an earlier time. After the desired sleep schedule is attained patients should maintain a fixed rise time (even on weekends and vacations) and ideally continue to use morning light exposure on most mornings, though the duration of light exposure can be shorter. Specialists often recommend using dim lights in the evening in conjunction with bright light exposure in the morning during the advancement of the sleep schedule.

For maintenance, some patients continue the treatment indefinitely, while some reduce their daily treatment to 15 minutes. Others may use the lamp a few days a week or even every other or third week. The degree of success is different for each patient. Light therapy generally adds a little extra time to the morning routine. If you have a family history of macular degeneration, you should consult with an eye doctor prior to starting bright light therapy.

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