Advanced sleep phase syndrome (ASPS) is a condition in which patients feel very sleepy early in the evening and wake up very early in the night. The disorder is more likely to appear in the elderly. ASPS may be corrected through exposure to bright light for two hours during the evening, which may shift the body's circadian timing mechanism and delay the onset of sleep until a typical bedtime. The exact cause of ASPS is not known, but the disorder is related to circadian rhythms, which regulate the internal biological clock and influence functions such as sleep-wake patterns. It has been postulated that ASPS is a circadian rhythm disorder in which the phase of the circadian rhythm of sleep and wake is advanced in relation to the "normal timing," which is synchronized, to the external environment.

Advanced sleep phase syndrome isfrequently encountered in the elderly and in post-menopausal women. There may be more than one cause of a sleep disorder, and they may be difficult to identify. Advanced sleep phase syndrome is characterized by the inability to fall asleep before early morning and difficulty waking in the morning. This disorder is also known as the advanced sleep phase type(ASPT). If a person tries to force the body into a particular phase, symptoms such as excessive daytime sleepiness, fatigue, and altered eating habits might develop. Drug therapy (such as melatonin) may be helpful for a short time, but behavioral modifications in tandem with helpful drugs can be even more effective.

Advanced sleep phase syndrome is mediated with chronotherapy or bright light therapy. Chronotherapy would affect a efficient advancement of bedtime until the desired bedtime is achieved. Bright light therapy would involve inducing a phase delay and the light exposure must be in the early evening. There is not a lot of data about the effectiveness of light therapy for ASPS. People receiving treatment gradually adjust to an earlier bedtime with sleep therapy. This therapy usually combines proper sleep hygiene practice and external stimulus therapy such as bright light therapy and chronotherapy. Bright-light therapy is designed to reset a person’s circadian rhythm to a later hour. Patients can also be treated with one medicine that puts them to sleep earlier in the evening and another medicine that helps wake them up in the morning, but this form of treatment is usually used only in extreme cases.

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