A circadian rhythm sleep disorder occurs when a person’s internal sleep-wake cycle is out of sync with their external environment. A person with this disorder may have difficulty sleeping or staying asleep.

Everyone has a natural, internal process that regulates their sleep-wake cycle in a 24-hour interval. This is called the circadian rhythm.

The body naturally picks up external signals — such as day, nighttime, and physical activities — to align a person’s sleep-wake cycle with their environment. This ensures that a person is awake during the day and asleep at night.

For people with a circadian rhythm sleep disorder, their internal sleep-wake rhythm and the external light-darkness cycle are out of sync.

As the body attempts to restore order to the sleep-wake cycle, a person may develop symptoms, including insomnia, difficulty staying asleep during the night, and daytime sleepiness.

This article explores circadian rhythm sleep disorder. It also looks at the various types, effects, diagnoses, and treatment options.

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The circadian clock is the body’s 24-hour internal clock that controls a person’s sleep-wake cycle. It lies in the brain’s control center, called the suprachiasmatic nucleus.

The suprachiasmatic nucleus (SCN) acts as the pacemaker of the circadian timing system. It regulates the body’s circadian rhythm by staying sensitive to light and dark signals.

As rays from sunlight enter the eyes during the day, the optic nerve transmits signals to the SCN to produce cortisol. This helps a person stay alert and awake during the day.

The longer a person stays awake, the more their body senses the need to sleep.

At night, the absence of light activates the SCN to send signals to the pineal gland. The pineal gland triggers the release of melatonin to make a person fall asleep.

According to the Centers for Disease Control and Prevention (CDC), the circadian clock controls other internal processes, including:

  • eating and digesting
  • body temperature
  • hormonal activity

Disruption to a person’s circadian clock can adversely affect their pattern of sleep and wakefulness. Poor sleep habits, working patterns, and travel may cause an acute, temporary disruption. Aging, genetics, and underlying health conditions may cause chronic disruptions.

Below are the various types of circadian rhythm sleep disorders.

Delayed sleep phase disorder (DSPD)

If a person’s bedtime and wake time are more than 2 hours later than conventional times, they may have DSPD, according to 2018 research. People with DSPD typically stay awake until the early hours of the morning and wake up in the late morning or afternoon.

DSPD is more common among adolescents and young adults, with a reported prevalence of 7–16%. Research estimates that 10% of people with chronic insomnia in sleep clinics have DSPD. Also, approximately 40% of individuals with DSPD may have a family history of the condition.

Advanced sleep phase disorder (ASPD)

People with ASPD fall asleep and wake up several hours earlier than most. For example, a person with this condition may fall asleep between 6 p.m. and 9 p.m. and wake up between 2 a.m. and 5 a.m. ASP affects approximately 1% of middle-aged and older adults and increases with age.

Some people can align their jobs and lifestyle to suit their ASPD sleep pattern, but for others, it can cause significant issues. Feeling very tired in the evening can get in the way of social plans and may mean a person misses out on activities. It can also be difficult to wake up early while others are asleep.

Jet lag disorder

If a person travels through two or more time zones from their usual home, they may experience jet lag disorder.

In this condition, a person’s sleep-wake internal clock has not adjusted to the new local time. They may feel sleepy during the day and alert at night.

The National Heart, Lung and Blood Institute (NHLBI) notes that jet lag disorder is often more severe when a person travels east than when they travel west. This condition is usually temporary and resolves with time.

While jet lag disorder affects all age groups, younger adults recover faster than older adults.

Find 10 tips for getting over jet lag.

Shift work disorder

This type of circadian rhythm sleep disorder is most common among people who do night, early morning, or rotating shifts. These work schedules affect the body’s natural circadian rhythm, making it difficult to sleep during regular hours.

Symptoms may include severe tiredness, waking up feeling unrefreshed, and low mood.

Shift work disorder may lead to:

  • accidents at work, at home, or while driving
  • a person needing to take sick leave
  • substance misuse

Learn about how to cope with night shifts.

Irregular sleep-wake rhythm disorder (ISWRD)

ISWRD is rare. It happens when a person’s sleep-wake cycle is undefined. People with this disorder have at least three periods of sleep in 24 hours. They may seem very sleepy during the day and unable to sleep at night. People may also not have a main sleep at a regular time.

People with certain neurological conditions may be at higher risk, including those with:

Non-24-hour sleep-wake rhythm disorder

This condition occurs due to an ever-changing sleep-wake cycle that shifts a little later every day. A person with this condition may have difficulty falling asleep or staying awake at the same time every day, according to the National Organization for Rare Disorders.

This is due to the brain’s inability to receive light cues from the surrounding environment. It is most common among blind people or those with neurological conditions.

A circadian rhythm sleep disorder may cause:

  • difficulty getting to sleep or staying asleep
  • daytime sleepiness or sleepiness during shift work
  • impaired judgment
  • low mood
  • impaired work performance
  • feeling less alert
  • memory issues
  • depression
  • difficulty concentrating
  • headache
  • low sex drive

Sleeping and waking at different times may also have serious long-term health effects. A 2020 study found that people with irregular sleep patterns were more likely than others to develop cardiovascular conditions.

Over the long term, poor sleep may lead to health conditions such as:

Learn more about why sleep is essential for health.

To diagnose a circadian rhythm sleep disorder, a doctor or a sleep specialist will take a person’s medical history and ask questions about their sleep patterns.

According to the NHLBI, they may also recommend the following tests:

  • Actigraph: For this test, a person will wear a small motion sensor for 3–14 days to measure their sleep-wake cycles.
  • Sleep studies: In this test, a health professional will observe a person’s sleep and monitor their heart rate, breathing, brain waves, and other functions.
  • Activity monitors: A person may wear an activity monitor for several days or weeks to help the doctor see how well and how much they sleep.

Learn more about sleep studies.

Treatment aims to reset a person’s sleep-wake rhythm to align with their environment. A person’s treatment plan will depend on the type and severity of their circadian rhythm disorder.

According to the NHLBI, to treat a circadian rhythm sleep disorder, a doctor may recommend:

  • Light therapy: Light therapy may help adjust how much melatonin the body makes to reset a person’s sleep-wake cycle. To conduct the therapy, a person will plan time each day to sit in front of a light box, which produces bright light similar to sunlight. This therapy is used during the time a person wants to be awake. In DSPD, light therapy is used in the morning. In ASPD, it is used in the evening.
  • Medications: Melatonin supplements or medications can help realign a person’s sleep-wake cycle with their environment. Doctors may also recommend the following:
    • Sleep-promoting medicines, such as benzodiazepines and zolpidem, can help a person fall asleep faster and stay asleep longer.
    • Wake-promoting medicines, such as modafinil and armodafinil, can help a person stay awake and alert during shift work.

Learn more about melatonin for sleep.

In addition to medications and light therapy, a doctor may recommend lifestyle adjustments to reset a person’s sleep-wake cycle, the NHLBI explains. These include:

  • keeping a regular eating schedule
  • sticking to a regular bedtime routine
  • avoiding daytime naps
  • avoiding light exposure at night
  • getting regular exercise
  • limiting caffeine, alcohol, nicotine, and some medications
  • sleeping in a quiet room

Learn more about good sleep hygiene.

A person should contact a doctor if they have any of the following symptoms:

  • difficulty falling asleep
  • waking up frequently during the night
  • waking up too early and being unable to go back to sleep
  • getting consistently poor quality sleep

A doctor will assess a person’s symptoms and recommend treatments. They may also make a referral to a sleep specialist for diagnosis and treatment.

Treatment can improve symptoms and help realign the circadian clock. Without treatment, a person with circadian rhythm disorder may be at high risk of:

A circadian rhythm sleep disorder occurs when a person’s 24-hour internal biological clock loses alignment with their environment. This may mean they have difficulty falling asleep, staying asleep, or waking up.

Shift work, travel, and neurological conditions can significantly affect a person’s circadian clock.

Poor sleep can lead to difficulty functioning at work and home. It can also lead to impaired judgment, making accidents more likely.

To treat circadian rhythm disorders, doctors may recommend medications, light therapy, and various lifestyle adjustments, such as getting more exercise and sunlight during the day.