It’s probably more than you realise.
Before dealing with this question, let’s talk about how sleep cycles work.
The normal human brain goes through a very systematic process every night during sleep. The brain undergoes four stages of non-dream sleep, and reaches dream sleep (also known as Rapid Eye Movement or REM sleep) in a cyclical fashion. The brain follows some “rules”:
- The time taken to fall asleep (also referred to as sleep latency) varies from a few minutes to half an hour.
- The time taken to have the first dream (dream sleep latency) varies from 60 to 90 minutes.
- The amount of dream sleep a person clocks varies with age – babies and children can dream about 50% of the night, while adults dream only 25% to 30% of the night.
- Most of a person’s dream sleep is clustered in the later half of the night.
One sleep cycle lasts for about 90 to 120 minutes and consists of four stages. In an average sleep period, a person will experience four to five complete sleep cycles.
The sleep cycle begins from stage I and systematically progresses to stage IV, with four cycles of slow-wave sleep. Note that after the fourth sleep cycle completes, the fifth sleep cycle does not immediately begin. Instead, it is followed by a REM (Rapid Eye Movement) period. The first REM period will occur roughly 60 to 90 minutes after falling asleep and the first REM period will last only about 10 to 15 minutes.
The length of the stages is not fixed. However, as the night proceeds, the length of stage III and IV sleep (also known as delta or deep sleep) begins to wane, and the length of REM sleep increases up to about one hour in length after a few cycles. Therefore, as the night goes on, one tends to dream for longer periods of time. Dream sleep is the most important element in the sleep process, for well-being, memory re-building, rejuvenation and mental alertness.
So, how much sleep does a person really need?
There is no real rule as to how much sleep one must have in a day, but there are general guidelines and needs depending on the age of the person:
A newborn may sleep up to 18 hours.
Babies aged between 1 and 12 months may need 14 to 18 hours of sleep.
Toddlers aged between 1 and 3 years may need 12 to 15 hours of sleep.
Children aged between 3 and 5 years may need 11 to 13 hours of sleep.
Children aged between 5 and 12 years may need 9 to 11 hours of sleep.
Adolescents aged between 10 and 19 may need 9 to 10 hours of sleep.
Adults, including elderly, may need 7 to 8-plus hours of sleep.
Pregnant women may need 8 or more hours of sleep.
And, in case you’re wondering if you could “train” your body to sleep less, research shows that restricting people to only 4 to 5 hours of sleep for several weeks makes them perform tasks at a slower pace, impairs their judgment, increases irritability, and puts them in a poorer mood. Give your brain and body the time it needs – you’ll be surprised at how much happens when you sleep.
Feeling tired despite clocking long hours of sleep? Find out if allergies may be affecting your sleep quality.