Advanced sleep phase disorder

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 early morning awakening. This sleep phase advancement can interfere with daily social and work schedules, and results in shortened sleep duration and excessive daytime sleepiness. The timing of sleep and melatonin levels are regulated by the body's central circadian clock, which is located in the suprachiasmatic nucleus in the hypothalamus. Individuals with ASPD report being unable to stay awake until conventional bedtime, falling asleep early in the evening, and being unable to stay asleep until their desired waking time, suffering early morning insomnia. When someone has advanced sleep phase disorder their melatonin levels and core body temperature cycle hours earlier than an average person. These symptoms must be present and stable for a substantial period of time to be correctly diagnosed. Individuals expressing the above symptoms may be diagnosed with ASPD using a variety of methods and tests. Sleep specialists measure the patient’s sleep onset and offset, dim light melatonin onset, and evaluate Horne-Ostberg morningness-eveningness questionnaire results. Sleep specialists may also conduct a polysomnography test to rule out other sleep disorders like narcolepsy. Age and family history of the patient is also taken into consideration. Once diagnosed, ASPD may be treated with bright light therapy in the evenings, or behaviorally with chronotherapy, in order to delay sleep onset and offset. The use of pharmacological approaches to treatment are less successful due to the risks of administering sleep-promoting agents early in the morning. Additional methods of treatment, like timed melatonin administration or hypnotics have been proposed, but determining their safety and efficacy will require further research. Unlike other sleep disorders, ASPD does not necessarily disrupt normal functioning at work during the day and some patients may not complain of excessive daytime sleepiness. Social obligations may cause an individual to stay up later than their circadian rhythm requires, however, they will still wake up very early. If this cycle continues, it can lead to chronic sleep deprivation and other sleep disorders. ASPD is more common among middle and older adults. The estimated prevalence of ASPD is about 1% in middle-age adults, and is believed to affect men and women equally.  The disorder has a strong familial tendency, with 40-50% of affected individuals having relatives with ASPD. A genetic basis has been demonstrated in one form of ASPD, familial advanced sleep phase disorder (FASPS), which implicates missense mutations in genes hPER2 and CKIdelta in producing the advanced sleep phase phenotype. The identification of two different genetic mutations suggests that there is heterogeneity of this disorder.   While advanced sleep and wake times are relatively common, especially among older adults, the extreme phase advance characteristic of familial advanced sleep phase syndrome (also known as familial advanced sleep phase disorder) is rare. Individuals with FASPS fall asleep and wake up 4–6 hours earlier than the average population, generally sleeping from 7:30pm to 4:30am. They also have a free running circadian period of 22 hours, which is significantly shorter than the average human period of slightly over 24 hours. The shortened period associated with FASPS results in a shortened period of activity, causing earlier sleep onset and offset. This means that individuals with FASPS must delay their sleep onset and offset each day in order to entrain to the 24-hour day. On holidays and weekends, when the average person’s sleep phase is delayed relative to their workday sleep phase, individuals with FASPS experience further advance in their sleep phase. Aside from the unusual timing of sleep, FASPS patients experience normal quality and quantity of sleep. Like general ASPD, this syndrome does not inherently cause negative impacts, however, sleep deprivation may be imposed by social norms causing individuals to delay sleep until a more socially acceptable time, causing them to losing sleep due to earlier-than-usual wakeup time. Another factor that distinguishes FASPS from other advanced sleep phase disorders is its strong familial tendency and life-long expression. Studies of affected lineages have found that approximately 50% of directly-related family members experience the symptoms of FASPS, which is an autosomal dominant trait. Diagnosis of FASPS can be confirmed through genetic sequencing analysis by locating genetic mutations known to cause the disorder. Treatment with sleep and wake scheduling and bright light therapy can be used to try to delay sleep phase to a more conventional time frame, however treatment of FASPS has proven largely unsuccessful. Bright light exposure in the evening (between 7:00 and 9:00), during the delay zone as indicated by the phase response curve to light, has been shown to delay circadian rhythms, resulting in later sleep onset and offset in patients with FASPS or other advanced sleep phase disorders.