How Much Sleep Do You Need?

Your need for sleep and your sleep patterns change as you age, but this varies significantly across individuals of the same age.  There is no magic “number of sleep hours” that works for everybody of the same age.  Babies initially sleep as much as 16 to 18 hours per day, which may boost growth and development (especially of the brain).  School-age children and teens on average need about 9.5 hours of sleep per night.  Most adults need 7-9 hours of sleep a night, but after age 60, nighttime sleep tends to be shorter, lighter, and interrupted by multiple awakenings.  Elderly people are also more likely to take medications that interfere with sleep. 

In general, people are getting less sleep than they need due to longer work hours and the availability of round-the-clock entertainment and other activities. 

Many people feel they can "catch up" on missed sleep during the weekend but, depending on how sleep-deprived they are, sleeping longer on the weekends may not be adequate. 

top

Dreaming

Everyone dreams.  You spend about 2 hours each night dreaming but may not remember most of your dreams.  Its exact purpose isn’t known, but dreaming may help you process your emotions.  Events from the day often invade your thoughts during sleep, and people suffering from stress or anxiety are more likely to have frightening dreams.  Dreams can be experienced in all stages of sleep but usually are most vivid in REM sleep.  Some people dream in color, while others only recall dreams in black and white.

top

The Role of Genes and Neurotransmitters

Chemical signals to sleep      

Clusters of sleep-promoting neurons in many parts of the brain become more active as we get ready for bed.  Nerve-signaling chemicals called neurotransmitters can “switch off” or dampen the activity of cells that signal arousal or relaxation.  GABA is associated with sleep, muscle relaxation, and sedation.  Norepinephrine and orexin (also called hypocretin) keep some parts of the brain active while we are awake.  Other neurotransmitters that shape sleep and wakefulness include acetylcholine, histamine, adrenaline, cortisol, and serotonin.

Genes and sleep

Genes may play a significant role in how much sleep we need.  Scientists have identified several genes involved with sleep and sleep disorders, including genes that control the excitability of neurons, and "clock" genes such as Per, tim, and Cry that influence our circadian rhythms and the timing of sleep.  Genome-wide association studies have identified sites on various chromosomes that increase our susceptibility to sleep disorders.  Also, different genes have been identified with such sleep disorders as familial advanced sleep-phase disorder, narcolepsy, and restless legs syndrome.  Some of the genes expressed in the cerebral cortex and other brain areas change their level of expression between sleep and wake.  Several genetic models–including the worm, fruit fly, and zebrafish–are helping scientists to identify molecular mechanisms and genetic variants involved in normal sleep and sleep disorders.  Additional research will provide better understand of inherited sleep patterns and risks of circadian and sleep disorders. 

Sleep studies

Your health care provider may recommend a polysomnogram or other test to diagnose a sleep disorder.  A polysomnogram typically involves spending the night at a sleep lab or sleep center.  It records your breathing, oxygen levels, eye and limb movements, heart rate, and brain waves throughout the night.  Your sleep is also video and audio recorded.  The data can help a sleep specialist determine if you are reaching and proceeding properly through the various sleep stages.  Results may be used to develop a treatment plan or determine if further tests are needed. 

top

Tracking Sleep Through Smart Technology

Millions of people are using smartphone apps, bedside monitors, and wearable items (including bracelets, smart watches, and headbands) to informally collect and analyze data about their sleep.  Smart technology can record sounds and movement during sleep, journal hours slept, and monitor heart beat and respiration.  Using a companion app, data from some devices can be synced to a smartphone or tablet, or uploaded to a PC.  Other apps and devices make white noise, produce light that stimulates melatonin production, and use gentle vibrations to help us sleep and wake.

top