Irregular sleep–wake rhythm

A sleep diary with nighttime in the middle and the weekend in the middle, to better notice trends

Circadian rhythm labeled

Irregular sleep-wake rhythm is a rare form of circadian rhythm sleep disorder characterized by numerous naps throughout the 24-hour period, no main nighttime sleep episode, and irregularity from day to day. People with this disorder have no pattern of when they are awake or asleep, may experience poor quality sleep, and often feel very sleepy while they are awake. The total time asleep per 24 hours is normal for the person's age. This disorder can create social, familial, and work problems, making it difficult for individuals to maintain relationships and responsibilities and may result in a person becoming home-bound and isolated.

Causes

Irregular sleep-wake rhythm disorder (ISWD) has various causes, including neurological disorders such as dementia (particularly Alzheimer's Disease), brain damage, or intellectual disabilities. It is thought that people with this disorder have a weak circadian clock. The risk for the disorder increases with age, but only due to increased prevalence of co-morbid medical disorders.

Diagnosis

To aid in the diagnosis and monitor the sleep schedule during treatment, a sleep diary should be kept. Other methods to monitor the sleep schedule include actigraphy or the use of a Continuous Positive Airway Pressure (CPAP) machine that can log sleeping times.

Possible warning signs include:

• Sleeping off and on in a series of naps during the day and at night, with no regular pattern but with normal total sleep time
• Difficulty getting restorative sleep
• Excessive daytime sleepiness

Initial evaluation by a sleep physician may include questions about the patient's medical history, neurological problems, medications, alcohol use, family history, and other sleep problems. A thorough medical and neurological exam is indicated. The patient will be asked to complete a sleep diary, recording natural sleep and wake-up times, over several weeks. Sleep rating with the Epworth Sleepiness Scale may be used.

Medical testing may involve blood tests, a CT scan, or an MRI if a neurological condition or another medical problem is suspected. An overnight sleep study (polysomnography) is usually not needed to detect this disorder, but may be indicated if other sleep disorders, such as sleep apnea and periodic limb movement disorder, seem likely.

Management

Treatment for irregular sleep-wake rhythm disorder aims to enable the body clock in the brain, such that a normal long sleep period at night can be achieved. Education about sleep hygiene is important, and counseling can be helpful. Melatonin, vitamin B12, sleep aids, wake aids, and other medications may also be used. Light during the daytime, and activities occurring at regular times each day, may help to restore a normal rhythm.

Research

There is currently a great deal of active research on various aspects of circadian rhythm. This often occurs at major universities in conjunction with sleep research clinics at major hospitals, such as the program with Harvard Medical School and Brigham and Women's Hospital. This research includes programs staffed by researchers from various departments at the university, including psychiatry, neurology, chemistry, and biology. Other major sleep research centers are located in Tel Aviv, Israel, Munich, Germany, and Japan.

A wide variety of sleep disorders are actively being researched. Measuring body temperature or melatonin levels may be used. Some hospitals conduct blood tests for melatonin levels. Saliva tests for melatonin are now available for online purchase, and its metabolites can also be tested in urine.

Nomenclature

The current formally correct name of the disorder is Circadian Rhythm Sleep Disorder: Irregular Sleep-Wake Rhythm Type. This disorder has been referred to by many other terms, including: Irregular Sleep-Wake Pattern, Irregular Sleep-Wake Syndrome, Irregular Sleep-Wake Rhythm (ISWRD), Irregular Sleep-Wake Cycle, Irregular Sleep-Wake Schedule, and Irregular Sleep-Wake Disorder (ISWD). Sometimes the words sleep and wake are hyphenated (sleep-wake), sometimes joined with an en dash (sleep–wake), and sometimes open (sleep wake). Sometimes the words are capitalized and sometimes they are not.

See Also

• Advanced Sleep Phase Syndrome
• Chronobiology
• Delayed Sleep Phase Disorder
• Circadian rhythm

Classification	ICD-10: G47.23 ICD-9-CM: 327.33 MeSH: D021081
External resources	MedlinePlus: 000806 eMedicine: neuro/655

Irregular sleep–wake rhythm Resources
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