Stages of REM sleep (solid bars), the four stages of NREM sleep, and wakefulness over the course of the entire night for representative young and older adult men. Characteristic features of sleep in older people include reduction of slow-wave sleep, frequent spontaneous awakenings, early sleep onset, and early morning awakening. (From the Division of Sleep Medicine, Brigham and Women's Hospital.) | Chapter 028. Sleep Disorders Part 2 Stages of REM sleep solid bars the four stages of NREM sleep and wakefulness over the course of the entire night for representative young and older adult men. Characteristic features of sleep in older people include reduction of slow-wave sleep frequent spontaneous awakenings early sleep onset and early morning awakening. From the Division of Sleep Medicine Brigham and Women s Hospital. The first REM sleep episode usually occurs in the second hour of sleep. More rapid onset of REM sleep in a young adult particularly if 30 min may suggest pathology such as endogenous depression narcolepsy circadian rhythm disorders or drug withdrawal. NREM and REM alternate through the night with an average period of 90-110 min the ultradian sleep cycle . Overall REM sleep constitutes 20-25 of total sleep and NREM stages 1 and 2 are 50-60 . Age has a profound impact on sleep state organization Fig. 28-1 . Slow-wave sleep is most intense and prominent during childhood decreasing sharply at puberty and across the second and third decades of life. After age 30 there is a progressive decline in the amount of slow-wave sleep and the amplitude of delta EEG activity comprising slow-wave sleep is profoundly reduced. The depth of slow-wave sleep as measured by the arousal threshold to auditory stimulation also decreases with age. In the otherwise healthy older person slow-wave sleep may be completely absent particularly in males. A different age profile exists for REM sleep than for slow-wave sleep. In infancy REM sleep may comprise 50 of total sleep time and the percentage is inversely proportional to developmental age. The amount of REM sleep falls off sharply over the first postnatal year as a mature REM-NREM cycle develops thereafter REM sleep occupies a relatively constant percentage of total sleep time. Neuroanatomy of Sleep Experimental studies in animals have variously implicated the medullary reticular formation the thalamus and the basal .
