In healthy adults, about 70% of sleep is deep sleep and around 25% of your sleeping time is your deepest sleep. So, if you sleep for 7–8 hours, the time spent in your deepest sleep should be around 105–120 minutes or one and three quarters to 2 hours.
However, as you get older, you’ll need less of this very deep sleep and spend more time in N2. During the deepest sleep, a variety of functions take place, including:
- relaxation of muscle
- increase in blood supply to the muscles
- slowing of heart rate and breathing
- tissue growth and repair
- release of essential hormones
Without deep sleep, these functions cannot take place and you may start to experience the symptoms of sleep deprivation.
How much REM sleep do you need?
There’s no official agreement on how much REM sleep you need, but this stage is important for dreaming, and experts believe dreaming helps you process emotions.
For most adults, REM takes up about 25% of sleep, which seems to be healthy during average sleep cycles.
How much light sleep do you need?
There is no minimum requirement for light sleep. It is nearly impossible to avoid light sleep if you want to sleep.
How much deep and light sleep do children need?
Babies and children need more sleep than adults. Newborns need the most, around 14–17 hours in every 24 hours.
This includes:
- quiet sleep, which is similar to NREM sleep
- active sleep, similar to REM sleep
- indeterminate sleep
They go through only one or two cycles in every period of sleep.
As children grow older, the amount of total sleep they need decreases.
Here are the recommendations for sleep in children:
| Age | Sleep requirements per 24 hours |
| 0–3 months | 14–17 hours, with the longest episode lasting |
| 4–12 months | 12–16 hours, with naps |
| 1–2 years | 11–14 hours, with naps |
| 3–5 years | 10–13 hours, with naps |
| 6–12 years | 9-12 hours |
| 13–18 years | 8–10 hours |
Signs that children are having sleep problems include:
- irritability
- learning and memory problems
- frequent illness
