Currently, Non-24-Hour Sleep Wake Disorder (Non-24) is known to share symptoms that are similar to those found in other sleep disorders. Sleep patterns from previously recorded cases may give insight to certain signs to watch for. Although, recent work suggests that there is a large degree of variability of sleep complaints between individuals. Generally, the professional criteria suggest the presence of Non-24 if there is a complaint of cyclic insomnia and/or excessive daytime sleepiness, and that these abnormalities appear to be related to lack of synchronicity between the 24-hour day-night cycle and the internal body clock.
Non-24 patients sometimes complain of cyclic sleep problems; thus, individuals are able to enjoy episodes of good sleep. They can soon be followed, however, by episodes of poor sleep, then good sleep once again, and so on. The cyclic nature of Non-24 in some patients is one of the signs that separate Non-24 from other sleep disorders, although it is sometimes not easily recognized. Even total loss of vision does not necessarily eliminate the eye's ability to send day-night signals to the SCN. In the totally visually blind, however, Non-24 should be suspected with complaints of cyclic sleep difficulties due to its prevalence in this group of people.
It is important to seek a specialized health professional for diagnosis of Non-24, as it has been misdiagnosed for other sleep deprivation or non-related psychiatric disorders in the past. The sleep specialist will generally discuss patient history and any medical documentation of sleep complaints. If a problem with the internal body clock is suspected, the doctor will ask the patient to keep a sleep diary for a few weeks and possibly months. As many patients will have already researched circadian rhythm disorders, they may often come prepared with a sleep log during the consultation. In addition, sleep-wake patterns can be obtained by using actigraphy, a non-invasive method of monitoring human rest and activity cycles. Here, rest-activity patterns are recorded using a device worn like a wristwatch to track movement. Sometimes, the sleep doctor may order an overnight polysomnogram (sleep study) to rule out other sleep disorders.
Not all patients will exhibit a clearly changing sleep-wake pattern. Particularly in blind patients, and ideally all patients, blood, saliva, or urine should be collected over several weeks to look for circadian biochemical chemical rhythms that can determine for sure whether the clock is exhibiting a non-24-hour rhythm. The sleep diaries and test results together will aid a sleep specialist in looking for patterns that demonstrate sleep and wake times that delay or advance daily with a period other than 24 hours.