Irregular sleep–wake rhythm
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Irregular sleep–wake rhythm (ISWD) is a rare form of
circadian rhythm sleep disorder Circadian rhythm sleep disorders (CRSD), also known as circadian rhythm sleep-wake disorders (CRSWD), are a family of sleep disorders which affect the timing of sleep. CRSDs arise from a persistent pattern of sleep/wake disturbances that can be ...
. It is characterized by numerous naps throughout the 24-hour period, no main nighttime sleep episode, and irregularity from day to day. Affected individuals have no pattern of when they are awake or asleep, may have poor quality sleep, and often may be very sleepy while they are awake. The total time asleep per 24 hours is normal for the person's age. The disorder is serious—an
invisible disability Invisible disabilities, also known as hidden disabilities or non-visible disabilities (NVD), are disabilities that are not immediately apparent, are typically chronic illnesses and conditions that significantly impair normal activities of dail ...
. It can create social, familial, and work problems, making it hard for a person to maintain relationships and responsibilities, and may make a person home-bound and isolated.


Causes

ISWD has various causes, including neurological disorders such as dementia (particularly Alzheimer's Disease), brain damage, or intellectual disabilities. It is thought that those affected have a weak
circadian clock A circadian clock, or circadian oscillator, is a biochemical oscillator that cycles with a stable phase (waves), phase and is synchronized with solar time. Such a clock's ''in vivo'' period is necessarily almost exactly 24 hours (the earth's curre ...
. The risk for the disorder increases with age, but only due to increased prevalence of co-morbid medical disorders.


Diagnosis

A
sleep diary A sleep diary is a record of an individual's sleeping and waking times with related information, usually over a period of several weeks. It is self-reported or can be recorded by a care-giver. The sleep diary, or sleep log, is a tool used by docto ...
should be kept to aid in diagnosis and for chronicling the sleep schedule during treatment. Other ways to monitor the sleep schedule are
actigraphy Actigraphy is a non-invasive method of monitoring human rest/activity cycles. A small actigraph unit, also called an actimetry sensor, is worn for a week or more to measure gross motor activity. The unit is usually in a wristwatch-like package wo ...
or use of a
Continuous Positive Airway Pressure Continuous positive airway pressure (CPAP) is a form of positive airway pressure (PAP) ventilation in which a constant level of pressure greater than atmospheric pressure is continuously applied to the upper respiratory tract of a person. The ap ...
(CPAP) machine that can log sleeping times The following are possible warning signs: * 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, and * excessive daytime sleepiness. Because of the changes in sleep/wake time, and because this is a rare disorder, initially it can seem like another circadian rhythm sleep disorder such as
non-24-hour sleep–wake disorder Non-24-hour sleep–wake disorder (non-24 or N24SWD) is one of several chronic circadian rhythm sleep disorders (CRSDs). It is defined as a "chronic steady pattern comprising ..daily delays in sleep onset and wake times in an individual livin ...
or like insomnia.


Initial visit with sleep physician

A physician specializing in
sleep medicine Sleep medicine is a medical specialty or subspecialty devoted to the diagnosis and therapy of sleep disturbances and sleep disorder, disorders. From the middle of the 20th century, research has provided increasing knowledge and answered many ...
may ask patients about their medical history; for example: neurological problems, prescription or non-prescription medications taken, alcohol use, family history, and any 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 The Epworth Sleepiness Scale (ESS) is a scale intended to measure daytime sleepiness that is measured by use of a very short questionnaire. This can be helpful in diagnosing sleep disorders. It was introduced in 1991 by Dr Murray Johns of Epwort ...
may be used.


Medical testing

A neurological condition or another medical problem may be suspected, in which case, blood tests, a CT scan or an MRI may be used. An overnight sleep study 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. The overnight sleep study is called
polysomnography Polysomnography (PSG), a type of sleep study, is a multi-parameter study of sleep and a diagnostic tool in sleep medicine. The test result is called a polysomnogram, also abbreviated PSG. The name is derived from Greek and Latin roots: the Gree ...
. It charts brain waves, heart beat, muscle activity, and breathing during sleep. It also records arm and leg movement. It will show if there are other sleep disorders that are causing or increasing the problems with ISWD.


Management

Treatment for irregular sleep–wake rhythm tries to enable the body clock in the brain, such that a normal long sleep period at night can be achieved. Education about
sleep hygiene Sleep hygiene is a behavioral and environmental practice developed in the late 1970s as a method to help people with mild to moderate insomnia. Clinicians assess the sleep hygiene of people with insomnia and other conditions, such as depression, ...
is important, and counseling can be helpful.
Melatonin Melatonin is a natural product found in plants and animals. It is primarily known in animals as a hormone released by the pineal gland in the brain at night, and has long been associated with control of the sleep–wake cycle. In vertebrates ...
, vitamin B12,
sleep aids Insomnia, also known as sleeplessness, is a sleep disorder in which people have trouble sleeping. They may have difficulty falling asleep, or staying asleep as long as desired. Insomnia is typically followed by daytime sleepiness, low energy, ...
, wake aids, and other medications may also be used. Exposure to light during the daytime and activities occurring at regular times each day may help to restore a normal rhythm. The management of this disorder may vary for different subgroups of patients. Affected individuals with dementia should not be prescribed sleep-promoting medications (sedatives) for ISWD due to the increased prevalence of adverse effects in this group outweighing the possible benefits.


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. An example is the program with
Harvard Medical School Harvard Medical School (HMS) is the graduate medical school of Harvard University and is located in the Longwood Medical Area of Boston, Massachusetts. Founded in 1782, HMS is one of the oldest medical schools in the United States and is consi ...
and
Brigham and Women's Hospital Brigham and Women's Hospital (BWH) is the second largest teaching hospital of Harvard Medical School and the largest hospital in the Longwood Medical and Academic Area, Longwood Medical Area in Boston, Massachusetts. Along with Massachusetts Gener ...
. This research includes programs that are staffed by researchers from various departments at the university, including psychiatry, neurology, chemistry, biology. Other major sleep research centers are in Tel Aviv in Israel, Munich in Germany and in Japan. A wide variety of sleep disorders are actively being researched. Measuring body temperature or melatonin levels may be used. Some hospitals do blood tests for melatonin levels. Saliva tests for melatonin are now available for online purchase; 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 Advanced Sleep Phase Disorder (ASPD), also known as the advanced sleep-phase type (ASPT) of circadian rhythm sleep disorder, is a condition that is characterized by a recurrent pattern of early evening (e.g. 7-9 PM) sleepiness and very early mor ...
*
Chronobiology Chronobiology is a field of biology that examines timing processes, including periodic (cyclic) phenomena in living organisms, such as their adaptation to solar- and lunar-related rhythms. These cycles are known as biological rhythms. Chronobi ...
*
Circadian rhythm A circadian rhythm (), or circadian cycle, is a natural, internal process that regulates the sleep–wake cycle and repeats roughly every 24 hours. It can refer to any process that originates within an organism (i.e., Endogeny (biology), endogeno ...
*
Delayed sleep phase disorder Delayed sleep phase disorder (DSPD), more often known as delayed sleep phase syndrome and also as delayed sleep–wake phase disorder, is a delaying of a person's circadian rhythm (biological clock) compared to those of societal norms. The diso ...


References


External links

{{DEFAULTSORT:Irregular Sleep-Wake Rhythm Circadian rhythm Sleep disorders Syndromes Congenital disorders of nervous system