Irregular sleep–wake rhythm

ISWD has various causes, including neurological disorders such as dementia (particularly Alzheimer's Disease), brain damage, or intellectual disabilities.[6] It is thought that sufferers have a weak circadian clock.[4][5] The risk for the disorder increases with age, but only due to increased prevalence of co-morbid medical disorders.[6]

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

A sleep diary should be kept to aid in diagnosis and for chronicling the sleep schedule during treatment. Other ways to monitor the sleep schedule are actigraphy[4][5] or use of a Continuous Positive Airway Pressure (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.[4][5]

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 or like insomnia.

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 is important, and counseling can be helpful. Melatonin, vitamin B₁₂, sleep aids, wake aids, and other medications may also be used.[4][5] Light during the daytime, and activities occurring at regular times each day, may help to restore a normal rhythm.[4][5]

Because there are different systems in the body that help establish regulation, it's helpful to employ a multi-modal approach. A 2008 review states that "...each clock is differentially sensitive to zeitgebers. The suprachiasmatic nucleus (SCN) is very responsive to light, the clock in the liver is very sensitive to food, and clocks in muscle are sensitive to exercise."[7]

Circadian rhythm labeled

The following approaches are recommended by one source:[8]

1. Spend <7–8 hours in bed.
2. Add environmental cues such as light and social interactions, regular meal times, and regular sleep–wake times.
3. Morning and eve light at 3000 lux for 2 hours have been shown to improve nocturnal sleep in institutionalized patients and reduce agitation in patients with dementia.
4. Melatonin at desired sleep time.

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 and Brigham and Women's Hospital.[9] 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.[4][5]

The current formally correct name of the disorder is Circadian Rhythm Sleep Disorder: Irregular Sleep Wake Rhythm Type.[10] This disorder has been referred to by many other terms, including: Irregular Sleep Wake Pattern,[11] irregular sleep wake syndrome,[6] Irregular Sleep Wake Rhythm (ISWRD),[12] Irregular Sleep Wake Cycle,[13] Irregular Sleep Wake Schedule[14] and Irregular Sleep Wake Disorder (ISWD).[5] 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.

• Advanced sleep phase syndrome
• Chronobiology
• Circadian rhythm
• Delayed sleep phase disorder