How Much Deep Sleep Do You Need?

How much sleep you need by age can range from 8 to 14 hours.
New research aims to identify not just how much total sleep you need — but also how much of each stage of sleep you need.

If you are getting the recommended amount of slumber — seven to nine hours a night — you spend about one-third of your life asleep.

Although that may seem like a lot of time, your mind and body are very busy during that time, so you can be productive, energetic, and healthy when you’re awake.

Five stages of sleep rotate between non-rapid eye movement (NREM) and rapid eye movement (REM) and include drowsiness, light sleep, moderate to deep sleep, deepest sleep, and dreaming.

The stages of sleep

Sleep stages 1, 2, and REM consist of light sleep, while 3 and 4 comprise deep sleep.

Stage 1

During stage 1, you drift from being awake to being asleep. This is a light, NREM sleep that doesn’t last very long. You may start to relax and dream, but may also twitch as you transition into stage 2.

Stage 2

Stage 2 of the sleep cycle is still a light sleep, but you are drifting into a steadier sleep. Your breathing and heartbeat slow down, and your muscles relax. Your body temperature decreases, and your brain waves are less active.

Stages 3 and 4

In stage 3, you enter deep sleep, and stage 4 is the deepest sleep stage. During deep sleep, your breathing, heartbeat, body temperature, and brain waves reach their lowest levels. Your muscles are extremely relaxed, and you are most difficult to rouse.

Stage 4 is known as the healing stage, when tissue growth and repair take place, important hormones are released to do their jobs, and cellular energy is restored.

REM sleep

Your first REM cycle of the night begins about 90 minutes after you fall asleep and recurs every 90 minutes. Your eyes move around quickly behind your eyelids and your brainwaves look similar to those of someone who is awake. Your breathing, heart rate, and blood pressure rise to near-waking levels.

REM sleep, often referred to as stage 5, is when you are most likely to dream.

Your arms and legs become temporarily paralyzed during this stage to prevent you from physically acting out your dreams.

How much deep sleep should you get?

In healthy adults, about 13 to 23 percent of your sleep is deep sleep. So if you sleep for 8 hours a night, that’s roughly 62 to 110 minutes.

However, as you get older you require less deep sleep.

During deep sleep, a variety of functions take place in the mind and body:

• memories are consolidated
• learning and emotions process
• physical recovery occurs
• blood sugar levels and metabolism balance out
• the immune system is energized
• the brain detoxifies

Without deep sleep, these functions cannot take place and the symptoms of sleep deprivation kick in.

On the other hand, there doesn’t seem to be any such thing as too much deep sleep.

How much REM sleep should you get

Although there’s no official consensus on how much REM sleep you should get, dreaming is most common during this stage. Experts believe that dreaming helps you process emotions and solidify certain memories.

For most adults, REM takes up about 20 to 25 percent of sleep, and this seems to be healthy during average sleep cycles. However, sleep research is raising some interesting questions. One recent study suggested that higher amounts of REM sleep may be associated with depression. But don’t go making sudden changes in your sleep habits — it is not clear which is the cause and which is the effect.

How much light sleep do you need?

Although sleep scientists believe that light sleep is good for you, there is no minimum to strive for. Light sleep is usually the default stage, one that is nearly impossible to avoid if you are asleep at all.

Too much overall sleep on a regular basis, however, is linked to obesity, depression, pain, heart disease, and even increased risk of death.

How much deep and light sleep do children need?

Babies and children need more sleep than adults. Babies need the most, spending about 16 of every 24 hours asleep. Approximately 50 percent of their slumber is spent in the REM stage, while the other 50 percent is divided between stages 1 through 4 and NREM sleep that cycles between light and deep.

As children grow older, the amount of sleep they need varies:

• toddlers: 11 to 14 hours
• preschoolers: 10 to 13 hours
• school-aged children: 9 to 12 hours
• teens: 8 to 10 hours

With enough sleep that appears to be restful, it’s likely that the light, deep, and REM ratio is exactly where it should be in young people.

If they’re having trouble with falling asleep, staying asleep, or sleeping well, or if they are sleeping way too much for their age, children may be irritable, could have learning and memory problems, or may be more susceptible to illness.

Takeaway

Scientists agree that sleep is essential to health, and while stages 1 to 4 and REM sleep are all important, deep sleep is the most essential of all for feeling rested and staying healthy.

The average healthy adult gets roughly 1 to 2 hours of deep sleep per 8 hours of nightly sleep. There are various ways to gauge whether you are, from personal trackers to a sleep study.

If you’re waking up tired on a regular basis, it’s a good idea to talk to a healthcare provider.