Why Do We Need Sleep?
There are many reasons to mention for why sleep is needed. To keep it short, below you will see a detailed overview on how much sleep any persons needs, but first read about some of the reasons on why we need sleep with a scientific back-up to make you realise why sleep is so important to your body.
Sleep stages are divided in two stages. Non-rapid eye movement (No-REM) and rapid eye movement (REM).
NREM sleep (No-REM)
No-rapid eye movement (NREM) sleep has 3 stages:
- The first stage occurs right after you fall asleep and is very short, less than 10 minutes. It involves light sleep from which you can wake up easily.
- The second stage lasts between 30 to 60 minutes. During this stage your muscles become more relaxed and you may begin to have Slow Wave Brain Activity, also called Delta brain activity. It is not easy to wake someone up in this stage of sleep.
- The third stage is deep sleep and takes around 20 to 40 minutes. During this stage, delta brain activity increases and you might experience body movements. It´s very hard to wake up in this stage of sleep.
R sleep (REM)
Rapid eye movement sleep is deeper than non-REM sleep. During REM sleep:
- The eyes and eyelids move.
- You start breathing irregular. During REM sleep it´s normal to have short periods of not breathing, also called Apnea.
You do most of your dreaming during REM sleep. But your brain paralyzes your muscles so you do not act out the dreams.
During sleep, a person usually progresses through the 3 stages of non-REM sleep before entering REM sleep. This takes about 1 to 2 hours after falling asleep. The cycle is repeated three to four times each night. And adult spends more time in NREM sleep than in REM sleep. An infant or child usually spends about half of the sleeping time in NREM and half in REM stages.
How Much Sleep Do You Need?
Our internal biological clock, which regulates the cycling of many functions including the sleep/wake cycle, can vary slightly from individual to individual. Although our internal clock is set to approximately 24 hours, if your clock runs faster than 24 hours, you tend to be a “lark” and wake up early; if your clock runs more slowly, you tend to be an “owl” and go to bed later.
The majority of healthy adults require between 7.5 to 8.5 hours per 24-hour period. This is true from young adulthood through late in life, though many older people have difficulty sleeping in a single block of time each night. Generally, sleep needs during a 24-hour period follow this pattern:
- Newborns (1 to 2 months) – 10.5 to 18 hours
- Infants (3 to 11 months) – 10 to 14 hours
- Toddlers (1 to 3 years) – 12 to 14 hours
- Preschoolers (3 to 5 years) – 11 to 13 hours
- School-aged children (5 to 12 years) – 10 to 11 hours
- Adolescents (12 to 18 years) – 8.5 to 9.5 hours
- Adults (18 years to the end of life) – 7.5 to 8.5 hours