Circadian rhythm sleep disorder
Circadian rhythm sleep disorders (CRSDs) are neurological disorders where an individual’s sleep-wake cycle is out of sync with the day-night cycle. Circadian is from the Latin roots circa, “about”, and diem, “day” and refers to the 24-hour rotation of the earth, and its internally produced effect on living things.
CRSDs refer to the disruption of these cycles and resultant irregularities. The most common CRSDs include delayed sleep phase disorder, non-24-hour sleep-wake disorder, advanced sleep phase disorder, irregular sleep-wake rhythm disorder, and shift work sleep disorder.
Definition & Facts
Typically, circadian rhythms allow living organisms to anticipate regular physical events based on the daily revolution of the earth around the sun, and adjust their physical and behavioral processes in accordance with this internalized “body clock”. The most notable feature of a reliable circadian rhythm is the “sleep-wake” cycle—most organisms operate on either a primarily diurnal (daylight) or nocturnal (nighttime) circadian rhythm, where sleep and activity are dictated by the presence or absence of sunlight.
Other circadian rhythms are also controlled by this schedule, including biological functions that reoccur daily. These include the cycle of body temperature, alertness, appetite, alertness and productivity, hormone secretion, and the timing of the sleep cycle. The internalized circadian clock prevents people from continuous sleepiness throughout the day. The desire (and ability) to fall asleep is in part dependent on the length of time that has passed since the person’s last sleep interval, as determined by the healthy circadian rhythm.
Among those with a healthy circadian rhythm function, there exists a spectrum of types—from the “morning person”, who generally sleeps earlier and wakes earlier, to the “night owls”, who prefer a later bedtime and rise later in the day. CRSDs address the people who fall outside of this normal spectrum of circadian rhythm and body clocks: those who, for reasons either biological or situational, have suffered a disruption to their circadian cycles that prevents the normal execution of body processes dictated by the cycle.
Symptoms & Complaints
The symptoms of delayed sleep phase disorder (or syndrome, DSPD/DSPS) include a markedly later onset and offset of sleep cycles and a period of peak alertness in the middle of the night. Non-24-hour sleep-wake disorder affects a person’s ability to fall asleep on a reliable schedule; here, the onset of sleep occurs later and later, continuously moving around a person’s body clock.
Irregular sleep-wake rhythm type CRSD (ISWD) is recognized by the irregularity of sleeping times, including frequent waking throughout the night and napping throughout the day, in a sleep cycle atypical of the person’s age.
Extrinsic CRSDs are easier to recognize and correct, generally falling into two basic categories: Shift work sleep disorder, which is characterized by graveyard shifts, rotating shifts, or work schedules which affect a person’s normal circadian rhythm, or jet lag type CRSD, which presents as a disrupted circadian rhythm due to a change in time zone, thus affecting the sleep-wake cycle.
CRSDs can be chronic, (biological or neurological) in origin, or temporary with social, behavioral, or environmental causes. Chronic CRSDs—such as advanced sleep phase disorder (ASPD), delayed sleep phase disorder (DSPD/DSPS), non-24-hour sleep-wake disorder (Non-24), and irregular sleep-wake rhythm (ISWD)—are all caused from within the body.
Pregnancy, medications, mental disorders, and medical problems such as cancer, Alzheimer's disease, or Parkinson disease, can all cause chronic CRSDs. Temporary CRSDs are caused by controllable, easily remedied factors: shift work, changes in time zone, and changes in routine are the most common causes of temporary CRSDs.
Diagnosis & Tests
The first step to a correct diagnosis is for a patient to schedule a physical examination with his or her health care provider, where he or she will review symptoms and complete a medical history to identify and isolate any potential intrinsic causes. Health providers may ask patients to fill out an Epworth Sleepiness Scale questionnaire, which employs a 0-3 “sleepiness scale” rating to 8 situations, which can identify the category of CRSD.
It may be necessary to follow up an initial visit to the doctor with additional tests. These may include sleep logs, where detailed sleep diaries are maintained, providing a description of each night’s sleep. Actigraphy, which includes wearing a motion-sensor to measure sleep-wake cycles, may be employed as a precursor to participation in sleep studies, usually performed in a sleep lab, which monitor a person’s sleep and collect vital statistics on oxygen levels, snoring, or sleep apnea.
In more persistent cases of CRSDs, imaging studies, such as CT scans or MRIs may be employed to check for sinus infections, airway blockages, or neurological diseases which may be interrupting the circadian rhythm. Once a person is diagnosed with a CRSD, the doctor will be able to review the treatment options available to help him or her decide on a course of action.
Treatment & Therapy
Though many chronic CRSDs are caused by internal factors, many respond to non-medicinal treatments, an option that many patients prefer over drug therapy. Behavior therapy and sleep hygiene counseling are the most common starting points for treating CRSDs: here, patients are advised to avoid napping throughout the day, and to avoid ingesting caffeine or other stimulants where possible.
Additionally, sleep hygiene includes creating an environment that is conducive to sleep by only using your bed for sleeping or sex, eschewing distractions such as the television, music, or unnecessary lighting in the bedroom. Dark therapy is another treatment for common CRSDs, employing blue-blocking goggles, blocks the light of blue and bluegreen wavelengths from reaching the eye during evening hours, so that the production of melatonin is not diminished or compromised.
Bright light therapy approaches the issue from the opposite direction: here, sleep is advanced or delayed, depending on the needs of the patient, through exposure to high-intensity light from the sun, a light box, or a wearable light therapy device. This therapy is performed for between 30-60 minutes daily depending on the needs of the patient.
Medication is another alternative to relieve the effects of CRSDs. Melatonin is an over-the-counter drug that provides relief, as well as a variety of other short term sleep aids or OTC remedies promoting wakefulness. For more stubborn CRSDs, prescription medications, such as modafinil (Provigil ®/Nuvigil®), may be prescribed. Recently, melatonin agonist tasimelteon, (Hetlioz®), was approved exclusively to treat non-24 CRSD.
Prevention & Prophylaxis