Circadian Rhythm Sleep Disorders Fast Facts

Circadian rhythm sleep disorders (CRSDs) are conditions in which a person’s internal sleep-regulating body clock is out of sync with their daily schedule.

CRSDs cause problems with falling asleep, staying asleep, or waking at the proper time in the morning.

CRSDs are often caused by disruptions in sleep schedules due to work shifts, travel, or poor sleep habits.

Advanced age, inadequate exposure to sunlight, blindness, and certain medications are other possible causes of CRSDs.

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CRSDs are often caused by disruptions in sleep schedules due to work shifts, travel, or poor sleep habits.

What are Circadian Rhythm Sleep Disorders?

A circadian rhythm sleep disorder (CRSD) is a condition in which a person has trouble falling asleep at bedtime, has trouble staying asleep once they fall asleep, or is unable to wake at the desired time in the morning. CRSDs are often caused by short- or long-term disruption of regular sleep schedules, but they can also be caused by aging, illnesses or medical conditions, or reactions to certain medications.

Symptoms of CRSDs

Common symptoms of circadian rhythm sleep disorders include:

  • Difficulty falling asleep at bedtime
  • Falling asleep too early
  • Waking up during the night
  • Waking up in the morning before you want to or later than you need to
  • Daytime sleepiness
  • Irritability
  • Anxiety
  • Depression
  • Mental fogginess or confusion
  • Memory difficulties or problems with concentration

Types of CRSDs

Circadian rhythm sleep disorders are divided into categories according to the type of sleep disruption involved.

Altered sleep phase types. In these disorders, a person may be able to sleep normally for an adequate length of time, but their sleep schedule is out of sync with their daily schedule.

  • In delayed sleep phase disorder, the person goes to sleep and wakes later than the desired time.
  • In advanced sleep phase disorder, sleep and wake times are earlier than desired.
  • Non-24-hour sleep-wake disorder causes a person’s sleep-wake schedule to get progressively later during each 24-hour period. This disorder is most common among people with total blindness.
  • In irregular sleep-wake rhythm disorder, a person does not have a consistent sleep-wake cycle. It is most common in people with neurological disorders such as Parkinson’s disease or Alzheimer’s disease.

Jet lag is a disrupted sleep schedule caused by travel across two or more time zones.

Shift work disorder is a CRSD caused by frequent changes in work shifts across a 24-hour day.

What Causes Circadian Rhythm Sleep Disorders?

CRSDs can be caused by many medical problems, stressors, mental health-related issues, medication side effects, and lifestyle habits. Common causes include:

  • Schedule disruptions (due to work, travel, etc.)
  • Poor sleep habits
  • Medications, including antidepressants, high blood pressure medications, asthma medications, and over-the-counter stimulants
  • Degenerative neurological disorders such as Alzheimer’s or Parkinson’s disease
  • Brain damage from injuries, stroke, or conditions such as encephalitis

Are Circadian Rhythm Sleep Disorders Hereditary?

Most of the time, CRSDs are caused by external factors, medical disorders, or other underlying conditions other than genetics. However, studies have suggested that some people have a genetic predisposition to sleep disorders, and that predisposition may be inherited.

How Are Circadian Rhythm Sleep Disorders Detected?

More than half of adults experience occasional trouble sleeping, but sleep difficulties causing anxiety, leaving you feeling tired and unwell during the day, or lasting for a prolonged period could be a reason to consult a doctor. In addition, sleep disruptions that last for a long time and do not respond to lifestyle changes can be a cause for concern.

How Are Circadian Rhythm Sleep Disorders Diagnosed?

Doctors may take several different diagnostic steps when a patient is experiencing chronic sleep difficulties.

  • Physical exam. A basic physical exam will screen for indications of medical conditions that could be causing sleep problems.
  • Blood tests. The doctor may order laboratory blood tests to rule out conditions that may be causing sleep disruptions.
  • Other tests. Measurements of body temperature, daily activity levels, and melatonin levels may help your doctor understand why you are having trouble sleeping.
  • Sleep diary. Your doctor may ask you to keep a log of your sleep over two weeks or so to look for patterns in your sleep behavior. You may also be asked to track other habits that could impact your sleep, such as caffeine use.
  • Sleep study. A study of your sleep patterns, which may be conducted at a sleep center, may be recommended if your doctor suspects that a condition such as sleep apnea could be the cause of your sleep difficulties.


How Are Circadian Rhythm Sleep Disorders Treated?

Treatment for a CRSD varies according to its underlying cause. In many cases, sleep disruptions resolve with the treatment of an underlying medical condition or the removal of a stressor causing the sleep difficulty.

Common treatment approaches include:

  • Medications. Prescription medications such as benzodiazepines, zolpidem, modafinil, or armodafinil may help control the symptoms of CRSDs. Your doctor will determine the best medication based on your symptoms and other overall health considerations.
  • The supplement melatonin may help some people establish a more healthy sleep schedule.
  • Light therapy. Carefully controlled exposure to artificial light can help some people adjust their sleep schedule.

You should always follow your doctor’s guidance for any treatment program and consult your doctor before using any over-the-counter sleep aid.

How Do Circadian Rhythm Sleep Disorders Progress?

Untreated CRSDs can lead to a wide variety of medical problems, quality-of-life complications, and mental health-related issues, including:

  • Problems at work or school
  • Relationship difficulties
  • Accidents caused by fatigue or mental fogginess
  • Anxiety or depression
  • Substance abuse
  • Weight gain
  • Diabetes
  • High blood pressure
  • Heart disease

How Are Circadian Rhythm Sleep Disorders Prevented?

Good sleep habits and a healthy lifestyle can help prevent CRSDs. Steps you can take to ensure better sleep include:

  • Stick to a regular sleep schedule (even on weekends)
  • Don’t eat or drink close to bedtime
  • Avoid stimulating activities (e.g., watching TV, using electronics) 30 minutes before bedtime
  • Use your bedroom only for sleep
  • Keep your bedroom dark and cool
  • Get plenty of exercise
  • Limit consumption of caffeine and alcohol
  • Quit smoking
  • Don’t take naps

Circadian Rhythm Sleep Disorders Caregiver Tips

Some people with CRSDs also suffer from other brain and mental health-related issues, a condition called co-morbidity. Here are a few of the disorders commonly associated with CRSDs:

Circadian Rhythm Sleep Disorders Brain Science

A circadian rhythm is an internal cycle used by your body to control functions that vary throughout a 24-hour day. These rhythms regulate cyclical functions such as body temperature, hormone levels, hunger, and digestion. Most significantly for CRSDs, circadian rhythms also regulate the sleep-wake cycle, the schedule that tells your body when it’s time to go to sleep and wake up.

Circadian rhythms are controlled by a neurological mechanism in your brain called the circadian clock. Located in a part of the hypothalamus called the suprachiasmatic nucleus, the circadian clock sends signals to the rest of your body to trigger responses such as body temperature changes or sleepiness.

The circadian clock runs on an internal cycle that resets roughly every 24 hours, but external factors, including temperature and activity levels, also influence it. The most influential factor on the circadian clock is light, as the brain tries to use sunlight (or its absence) as a cue to know when it’s time for sleep. That’s why inconsistent exposure to sunlight, such as that caused by shift work, can be disruptive to sleep schedules.

Circadian Rhythm Sleep Disorders Research

Title: Facilitating Adjustment to Simulated Jet Lag

Stage: Recruiting

Principal investigator: Shawn Youngstedt, PhD

Arizona State University

Tucson, AZ

This study aims to compare 3 different treatments for circadian adjustment to a laboratory protocol that will mimic westward air travel across 8 time zones. One treatment will involve simply following the new schedule for 3 days. Another treatment will also involve exposure to bright light for 1 hour per day. A third treatment will involve exposure to bright light plus exercise for 1 hour per day, plus consuming a melatonin tablet. Adjustment to the shifted schedule will be assessed by comparing measures of sleep, mood, mental performance, physical performance, and timing of melatonin across the 3 treatment conditions.


Title: Validation of Circadian Biomarkers in Patients With Sleep Disorders

Stage: Recruiting

Principal investigator: Emmanuel Mignot, MD, PhD

Brigham and Women’s Hospital

Boston, MA

Current methods for assessing circadian timing require sampling over hours (or even up to a day) while the patient is in controlled conditions. The investigators aim to develop a method that can estimate individual circadian time with a single blood sample taken at any time of the day or night. To do this, the investigators will use two state-of-the-art methods, a plasma proteomics-based method to identify a panel of rhythmic proteins (extending our preliminary data) and a whole blood-derived monocyte-based method using a panel of 15 transcripts (to validate and extend a recent study).

Researchers will test both methods in a series of patients with circadian rhythm sleep disorders. They will validate separately the proteomics-based biomarker and the monocyte-based transcript biomarker, and also explore whether combining them can improve the accuracy of our timing estimates. In all cases, circadian phase estimates from the biomarker panels will be compared with those derived from plasma or saliva melatonin (the current “gold-standard” circadian phase marker).

Adults who meet ICSD-3 criteria for Advanced Sleep-Wake Phase Disorder or Delayed Sleep-Wake Phase Disorder will be studied at Brigham and Women’s Hospital and Stanford University.

The outpatient protocol will consist of two segments: clinic visit and in-home saliva sample collection. For the first segment, the patient participant will be scheduled for a daytime visit to the sleep clinic, where they will have blood drawn for protein and monocyte analysis after having kept a sleep diary and worn a wrist activity monitor for at least 1 week. The patient participant will be provided with an at-home saliva sampling kit and instructed in its use, particularly how to maintain appropriate dim light conditions. For the second segment, the patient will be instructed to collect the series of saliva samples on that same evening, collecting a saliva sample each hour beginning 7 hours before their usual bedtime and ending one hour after their usual bedtime. As each sample is collected, the patient participant will document the tube number and clock time on a log that the investigators provide them. The patient participant will store each sample in a zip lock bag in their home freezer until the next day. After waking the next day, the patient will pack their samples in the insulated shipping box they were provided, along with their sample collection log and freezer packs they were provided. Then they call a courier to pick up the box, which is sent directly to the assay facility.

Alternatively, patients may be given the opportunity to come for a single extended visit at the laboratory or clinic. This visit will include the blood sampling for protein and monocyte analysis, followed by 8 hours in which they remain in dim lighting conditions in the lab or clinic and provide a saliva sample each hour. The saliva sampling segment will begin 7 hours before their usual bedtime and end one hour after their regular bedtime. After the final saliva sample, the study will be over, and the patient will be allowed to go home.


Title: Experimental Manipulation of Sleep and Circadian Rhythms and the Role Played on Reward Function in Teens (CARRS-P2)

Stage: Recruiting

Contact: Ronette G. Blake, MS

Western Psychiatric Hospital

Pittsburgh, PA

Adolescence is a time of heightened reward sensitivity and greater impulsivity. On top of this, many teenagers experience chronic sleep deprivation and misalignment of their circadian rhythms due to biological shifts in their sleep/wake patterns paired with early school start times. Many studies find that this increases the risk of substance use (SU). However, what impact circadian rhythm and sleep disruption either together or independently have on the neuronal circuitry that controls reward and cognition, or if there are interventions that might help to modify these disruptions is unknown. Project 2 (P2) of the CARRS center will test an innovative and mechanistic model of brain circuitry that uses multi-method approaches, takes a developmental perspective, and incorporates key sleep and reward constructs.

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