Irregular sleep-wake rhythm disorder and non-24-hour sleep-wake disorder are typically the rarest forms of all circadian rhythm disorders.
Around 50% of people around the world experience a form of sleep issues at some point in their lives. While all of them carry certain levels of discomfort, some of them are very dangerous and seriously compromise the health of an individual, and others are merely changes to a person’s sleep pattern. The most common problems include teeth grinding (bruxism), insomnia, certain parasomnias and catathrenia (producing a groan-like sound while exhaling during sleep, as opposed to snoring). Some of these target very specific parts of the population, some are more equally prevalent in all groups, and some are so rare they are barely known outside of the sleep community. It is the case with the family of circadian rhythm disorders, although with the exception of the delayed sleep-wake phase disorder, which rates much higher on the common sleep disorder list.
What each one out of this family has in common, as the name suggests, is some form of abnormality of the circadian rhythm. A normal human circadian rhythm is a process that oscillates and re-occurs every 24 hours, regulated by the circadian clock. These rhythms control our core body temperature, hormone secretion, alertness levels, and regulate the sleep pattern in response to our exposure to light. The purpose of this is to make sure we do the right things at the right times: we fall asleep when it’s dark outside and wake up in the morning.
Abnormalities of this rhythm have a few variations: our sleep onset can be delayed or advanced; our sleep nonrestorative, stuck by jet-lag or shift-jobs, scattered throughout the day, or sometimes “run free” of the standard 24-hour rhythm. The last two disorders are often grouped into a subcategory called the “sleep-wake rhythm disorders.”
The two disorders that fall under this category are irregular sleep-wake rhythm disorder and non-24-hour sleep-wake disorder. These two neurological disorders are typically the rarest forms of all circadian rhythm disorders; their prevalence is practically unknown in otherwise healthy people, without the presence of another condition. However, the incidence rate among blind individuals, the elderly and people who have Alzheimer’s is significantly higher between these disorders.
The main characteristic of the irregular sleep-wake rhythm disorder is its unpredictable sleep pattern, with sleep periods occurring randomly throughout the 24-hour cycle. People who have this condition sleep a few times a day for shorter periods that can last anywhere from one to four hours, but their daily sleep sums up to eight or nine hours overall. They take multiple naps over the day but usually sleep the longest at nighttime.
While this disorder doesn’t impair the length of sleep an individual gets per day, the uncontrollable, scattered manner of it results in struggles with handling daily responsibilities; shifts at work and tasks requiring attentiveness can be compromised by an unpredictable, spontaneous sleep urge in the middle of the day. It can quickly put you and the people around you in danger. Besides that, if continued over a longer timespan, irregular sleep-wake rhythm disorder can lead to sleep deprivation, risking other potential complications for your health.
The exact cause of the irregular sleep-wake rhythm disorder is unknown, but infrequent light exposure and unpredictable mealtimes are the two factors believed to contribute to its development. Since these stimuli have a direct impact on the circadian rhythm, their infrequency lessens its ability to time sleep properly. Such a situation may happen when the patient lives in a nursing home, hospital, or has some debilitating condition that deters them from going outside and getting enough sunlight on a steadier, more regular basis.
Another possible factor could be age. Our body gradually stops producing certain circadian rhythm regulating hormones as we get older, making it harder for our brains to differentiate sleep time from wake time. Aside from that, Alzheimer’s disease and dementia are believed to be related to the irregular sleep-wake rhythm disorder; it is much more prevalent in patients who have one of these neurological conditions than in otherwise healthy people. In people under the age of 60 who don’t have another medical condition, the incidence rate is estimated to be under 1%, making this sleep disorder very rare.
Diagnosis and treatment
In order to diagnose irregular sleep-wake rhythm disorder, a doctor will start by taking your medical history and asking to hear your subjective impressions about the problem you came to address. A sleep diary is something you can start even before you go to your first appointment. Simply record everything you notice about your sleep pattern for a few weeks. How often you sleep, for how long, at which times of day, whether you are sleepy during daytime or not – all of these can be useful for a specialist to narrow down your symptoms much faster. Although used as a subjective overview, the information provided in a sleep log is often much more detailed and precise because it was fresh when you recorded it.
To rule out some other sleep disorders, the doctor might order polysomnography. This test is performed during the night, or during the patient’s usual sleep time; it tracks all the major bodily processes that occur during sleep, monitored by a sleep specialist. It could help determine whether or not you have the irregular sleep-wake rhythm disorder by tracking the circadian rhythm markers in the body – melatonin production and core body temperature oscillations.
The treatment of irregular sleep-wake rhythm disorder usually consists of a combination of behavioral therapy, phototherapy and melatonin supplementation.
The other neurological sleep-wake condition is known for causing the usually 24-hour long circadian rhythm to stretch beyond that time frame, moving the person’s sleep time later and later, seemingly at free will. This time frame gets progressively longer over time and causes fatigue and excessive sleepiness.
Non-24-hour sleep-wake disorder is caused by anomalies in the suprachiasmatic nucleus, the area of our brain that maintains the circadian clock. As mentioned above, this clock normally responds to light and synchronizes the body with external light-dark times of the day. Occasional disturbances in this cycle may happen prompted by travel, shift work, illness and so forth, usually when our light exposure changes, but then fall back in place after a bit of adjustment. However, in people with the non-24-hour sleep-wake disorder, this function is impaired, for two possible reasons:
The non-24-hour sleep-wake disorder is highly prevalent in blind individuals; up to 70% of them also have this disorder. The exact incidence rate of this disorder among sighted people is unknown, but those with current issues or a history of delayed sleep-wake phase disorder are prone to developing the non-24-hour sleep-wake disorder as well, pushing their already late bedtime even later. If this keeps going on for long enough, the person will get stuck, going back and forth between night owl and early bird sleep schedule, forming full circles before starting new rounds. This wheel results in excessive sleepiness and exhaustion, making any social life or work shift impossible to maintain for longer than a day.
Sleep scientists have recently begun researching the possibility of a genetic predisposition towards developing the non-24-hour sleep-wake disorder, but no significant evidence has yet linked the two.
Diagnosis and treatment
As with irregular sleep-wake rhythm disorder, after questionnaires, a physical exam and a thorough medical history, your doctor might suggest using a sleep tracking tool. Actigraphy is a device worn around the wrist to record your sleep-wake cycles – this method is used when polysomnography isn’t available or necessary.
As far as the treatment goes, a combination of melatonin supplements and light therapy is frequently used for patients with the non-24-hour sleep-wake disorder. The procedure is standard – melatonin is used in the evening to help with sleep onset, and light therapy is used in the morning, to alert the body and keep it awake until bedtime. However, unlike the other circadian rhythm disorders, non-24-hour sleep-wake disorder has to be treated even after optimal results have been achieved; that is, even when the circadian rhythm gains its usual functionality back. If the treatment stops abruptly and the new, balanced sleep hygiene isn’t properly maintained, the non-24-hour sleep-wake disorder often recurs. For blind people with this disorder, carefully timed and dosed melatonin is the most effective and frequently used method of therapy. Maintaining the normal circadian rhythm is especially difficult for them as well; regular medical help is often needed.
In addition to virtually all methods used for treating sleep disorders, some behavioral changes are a safe bet to keep your sleep in check and make sure past issues don’t return in the future. Try to follow these guidelines: