There have, however, been several studies of sighted people with the syndrome. McArthur et al reported treating a sighted patient who "appeared to be subsensitive to bright light. In other words, the brain does not react normally to light (people with the disorder may or may not, however, be unusually subjectively sensitive to light; one study found that they were more sensitive than the control group). In 2002 Uchiyama et al examined five sighted Non-24 patients who showed, during the study, a sleep-wake cycle averaging 25.12 hours. That is appreciably longer than the 24.02 h average shown by the control subjects in that study, which was near the average innate cycle for healthy adults, younger and older, of 24.18 hours. The literature usually refers to a "one to two hour" delay per twenty four hour day (i.e. a 25-26 hour cycle).
Uchiyama et al had earlier determined that sighted Non-24 patients' minimum core body temperature occurs much earlier in the sleep episode than the normal two hours before awakening. They suggest that the long interval between the temperature trough and awakening, makes illumination upon awakening virtually ineffective. (See Phase response curve)
In their Clinical Review in 2007, Okawa and Uchiyama reported that people with Non-24 have a mean habitual sleep duration of nine to ten hours and that their circadian periods average 24.8 hours.
People with the disorder may have an especially hard time adjusting to changes in "regular" sleep-wake cycles, such as vacations, stress, evening activities, time changes like daylight saving time, travel to different time zones, illness, medications (especially stimulants or sedatives), changes in daylight hours in different seasons, and growth spurts, which are typically known to cause fatigue. They also show lower sleep propensity after total sleep deprivation.
Most people with this disorder find that it severely impairs their ability to function socially and occupationally. Typically, they are "partially or totally unable to function in scheduled social activities on a daily basis, and most are unable to work at conventional jobs. Attempts to keep conventional hours by people with the disorder generally result in insomnia (which is not a normal feature of the disorder itself) and excessive sleepiness, to the point of falling into microsleeps, as well as myriad effects associated with acute and chronic sleep deprivation.
Bright light therapy combined with the use of melatonin as a chronobiotic (see phase response curve, PRC) may be the most effective treatment. However the timing of both is tricky and a lot of determination and experimentation is usually necessary.
A good night's sleep and morning exercise may protect against dementia: changes in the sleep-wake cycle interfere with brain function.(MIND & MEMORY)
Feb 01, 2012; If you tend to wake up early and get in some physical activity during the morning hours, you may be doing much more than getting...