(A) High REM # SLEEP PATTERN WITH AGE: Changes in sleep with age. NOTE: Time (in minutes) for sleep latency, amount of time spent awake after initially falling asleep (WASO), rapid eye movement (REM), non-rapid eye movement (NREM), stages 1, 2, and slow-wave sleep (SWS).> Sleep patterns change as people age.> As shown in the two graphs above, infants spend more time sleeping and spend a greater percentage of sleep in REM sleep compared with the times of older children & adults,> For example, newborn babies sleep about 16 hours per day and spend about 50% of that time in REM sleep.> Older people (50-85 years old) sleep only 5.75-6 hours per day and spend 13.8-15% of that time in REM sleep.> As you might expect, as children grow, they spend less time sleeping during the day.> Graph illustrates how nighttime and daytime sleep time changes with age.> Sleep architecture continues to change with age across adulthood.> Two major attributes of age-related sleep changes are earlier wake time and reduced sleep consolidation.> A hallmark change with age is a tendency toward earlier bedtimes and wake times.> Older adults (approximately ages 65 to 75) typically awaken 1.33 hours earlier, and go to bed 1.07 hours earlier, than younger adults (approximately ages 20 to 30). There are no conclusive studies that demonstrate why older adults experience earlier wake times, despite decreased sleep efficiency, but one hypothesis may be an advanced circadian pacemaker that accompanies age.> It is unclear if this is due to older adults experiencing an increased sensitivity to light.> Consequences of an advanced circadian rhythm are a 1-hour advance in body temperature increase in the early morning and misaligned melatonin and cortisol secretion rhythms with the circadian clock.> Younger adults may experience brief awakenings, but they are usually minor and occur close to an REM sleep transition; thus, sleep remains relatively consolidated. Arousal occurring mostly from REM sleep in young adults suggests that there is a protective mechanism to keep from awakening during NREM sleep; however, this protective effect appears to also decline with age.> As an individual ages (between the ages of 20 to 60), SWS declines at a rate of about 2 percent per decade.> Because arousal thresholds are typically highest during SWS, and because SWS declines with age, older adults experience more frequent awakenings during a sleep episode.> Another important variable may be an age-related reduction both in homeostatic sleep pressure and circadian pacemaker effectiveness during the night.