What Happens When You Sleep?

When you sleep well, you wake up feeling refreshed and alert for your daily activities. Sleep affects how you look, feel and act on every basis, and can have a major impact on your overall quality of life.

To get the most out of your sleep, both quantity and quality are important. Teens need at least 8½ hours—and on average 9¼ hours—a night of uninterrupted sleep to leave their bodies and minds rejuvenated for the next day, while adults need 7-9 hours. If your sleep is cut short, your body doesn’t have time to complete all of the phases needed for muscle repair, memory consolidation and release of hormones regulating growth and appetite. Then you wake up less prepared to concentrate, make decisions, or engage fully in school, work and social activities.

The one-third of our lives that’s spent sleeping, far from being “unproductive,” plays a direct role in how full, energetic and successful the other two-thirds of our lives can be.

How Much Sleep do you Really Need?
AgeSleep Needs
Newborns (0-2 months) 12-18 hours
Infants (3-11 months) 14-15 hours
Toddlers (1-3 years) 12-14 hours
Preschoolers (3-5 years) 11-13 hours
School-age children (5-10 years) 10-11 hours
Teans (10-17 years) 8.5-9.25 hours
Adults 7-9 hours

What are the stages of sleep, and what role do they play?
Sleep architecture follows a pattern of alternating REM (rapid eye movement) and NREM (non-rapid eye movement) sleep throughout a typical night in a cycle that repeats itself about every 90 minutes.

NREM (75% of night): As you begin to fall asleep, you enter the first of four stages of NREM sleep.

Stage 1

  • Between being awake and falling asleep
  • Light sleep

Stage 2

  • Onset of sleep
  • Becoming disengaged from surroundings
  • Breathing and heart rate are regular
  • Body temperature drops (so sleeping in a cool room is helpful)

Stages 3 and 4

  • Deepest and most restorative sleep
  • Blood pressure drops
  • Breathing becomes slower
  • Muscles are relaxed
  • Blood supply to muscles increases
  • Tissue growth and repair occurs
  • Energy is restored
  • Hormones are released, such as: Growth hormone, essential for growth and development, including muscle development

REM (25% of night):

  • First occurs about 90 minutes after falling asleep and recurs about every 90 minutes, getting longer later in the night
  • Provides energy to brain and body
  • Supports daytime performance
  • Brain is active and dreams occur
  • Eyes dart back and forth
  • Body becomes immobile and relaxed, as muscles are turned off
SOURCE: National Sleep Foundation, Accessed August 11, 2011. Available at: http://www.sleepfoundation.org/