Advanced Sleep Phase Syndrome. a circadian rhythm disorder in which sleep onset occurs in early evening and as a consequence, wakefulness occurs in early morning. This disorder is more common in the elderly.
advanced sleep phase syndrome. disorder in which the major sleep episode is advanced in relation to the desired clocktime, that results in symptoms of compelling evening sleepiness, an early sleep onset, and an awakening that is earlier than desired. This is classified as a circadian rhythm disorder. The sleep phase occurs well ahead of the conventional bedtime and the tendency is to wake up too early. The major complaint may concern either the inability to stay awake in the evening, or early morning awakening insomnia, or both.
Advanced Sleep Phase Syndrome. Advanced Sleep Phase Syndrome (ASPS) occurs when a person's "body clock" (i.e., circadian rhythm) is set to fall asleep very early in the afternoon. Individuals with ASPS wake up very early (or during the middle of the night) and are unable to fall back asleep.