How Sleep Works – Sleep Phases and Stages
During REM sleep, your eyes twitch and your brain is active. Brain activity measured during REM sleep is similar to your brain’s activity during waking hours. Dreaming usually happens during REM sleep. Your muscles normally become limp to prevent you from acting out your dreams. You usually have more REM sleep later in the night, but you do not have as much REM sleep in colder temperatures. This is because, during REM sleep, your body does not regulate its temperature properly.
How do our patterns of sleep change as we age?
The patterns and types of sleep change as people mature. For example, newborns spend more time in REM sleep. The amount of slow-wave sleep peaks in early childhood and then drops sharply in the teenage years. Slow-wave sleep continues to decrease through adulthood, and older people may not have any slow-wave sleep at all.
NHLBI research on sleep
Sleep is one of the four primary areas of NHLBI research. Learn more about the ways the NHLBI is advancing understanding of sleep and sleep disorders. Research on this topic is part of the NHLBI’s broader commitment to advancing scientific discovery for sleep science.
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