How Much Sleep Do We Need

How much sleep do we need?


This is a common question many people ask me.

Before I answer this question let me briefly describe what sleep is.


Sleep is


Sleep is a highly complex and active process of

dynamic restoration, rejuvenation, recuperation and

reconsolidation, all of which are essential for health and wellbeing.

Sleep is a fundamental and highly complex biological

phenomenon. Neurotransmitters in the brain control our

sleeping patterns in interaction with neurons.

Neurotransmitters such as serotonin and norepinephrine keep

some parts of the brain active while we are awake. Other

neurons at the base of the brain begin to signal when we fall

asleep, “switching off” the signals that keep us awake.

Chemicals are central to sleep, particularly adenosine, which is

produced by our cells, accumulates in our blood and travels to

the brain while we are awake and causes what we experience as

sleepiness. This chemical gradually breaks down while we sleep

and allows us to wake. Yes, sleep has a complex biology.


The stages of sleep


Our nightly sleep is composed of a number of sleep cycles, each

of which is made up of different stages. There are two main

types of sleep – non-REM and REM sleep – and the differences

between them are almost as profound as the differences between

sleep and wakefulness. Scientists today use a variety of

technologies to understand the diverse aspects of sleep by

measuring the electrical activity of the brain, the muscles and

movement of the eye.

It is now understood that we pass through five stages of sleep as

we fall from wakefulness, with REM (rapid eye movement) sleep

the final of these stages. These stages progress in cycles, moving

through stage 1 to REM sleep and then back to stage 1. The

progress of each cycle lasts around 90 minutes in adults and 30–

40 minutes in children.

During the first stage, which lasts approximately 15 minutes, we

actually move back and forth between wakefulness and sleep.

Brain waves during this stage give way to alpha waves. In the

second stage, we enter what can be termed the first “real” sleep.

Here theta waves begin to appear as we enter a phase which

comprises 50% of our sleep time. During this stage, the body

prepares to enter deep sleep. Both stage one and two are

relatively light stages of sleep.

The third and fourth stages of sleep are termed “slow wave

sleep” and we spend approximately 20% of our total sleeping

time in these stages. Here we experience delta waves and a form

of deep sleep from which it is very hard to wake.

REM is the last stage of the sleep cycle. As rapid eye movement

begins, our skeletal muscles are virtually paralysed. The brain

wave pattern shows a blend of alpha and beta waves. During

this stage, our breathing becomes more rapid, irregular and

shallow, and our heart rate rises along with blood pressure. It is

at this stage that males develop penile erections. REM is the

stage during which we dream, often in a bizarre and illogical


The first period of REM usually has a duration of 10 minutes. Each

subsequent REM stage increases in duration, with the final one

lasting up to an hour.


Why we sleep?


It is still not understood why we evolved the need to sleep. What

is clear is that sleep, as with breathing, is a fundamental human

requirement and not somehow an optional add-on during life.

Studies into animals show that sleep is a prerequisite for

survival. Rats, for example, typically live for 2 to 3 years. Those

deprived of REM sleep survive only about 5 weeks on average

and rats deprived of all sleep stages live only 11–32 days.


Sleep-deprived rats develop a number of ailments: abnormally low

body temperature and sores on their tail and paws, to name two.

Some studies suggest that sleep deprivation affects the immune

system in detrimental ways. The sores developed by the sleep-deprived rats seem to be evidence of an immune system

imbalance caused by a lack of sleep. Sustained sleep deprivation

can lead to mental disturbance, anxiety, tiredness, fatigue and

even death if prolonged. There are reports of cases outside

scientific studies where people have died after periods of no

sleep at all. In such cases, people experience symptoms of

hallucinations, weight loss and finally dementia before their


Sleep is so important to well-being that scientists argue that

animals can survive for three times as long without food as

without sleep.


How much sleep do we need?


It is well known that people need approximately 8 hours of sleep

every night, but to be precise we need around 7.5 hours. As each

sleep cycle has a duration of about 90 minutes, and we need 5

such cycles, the total for recommended sleep is 7.5 hours.

Sleeping well depends not only on the number of hours, but on

the quality and consistency of sleep. Intuitively, we experience

this. One can spend 10 hours in bed and still feel tired in the


Sleep deprivation can be fatal.


Sleep calculator


To calculate in a meaningful way the sleep we require, and to

know when we should be going to bed, we need to work

backwards and define the time at which we need to get up. For

example, if we need to rise at 7 am, we need to, firstly, count

back 7.5 hours, which brings us to 11.30 pm. Yet getting to sleep

is a process and requires sleep onset latency, a period of time

required to fall asleep after lights have been turned off, which

lays the foundation for a solid night’s sleep. This period should

be about 10–20 minutes. Allowing, therefore, for 20 minutes of

sleep latency, 11.10 pm can be defined as the time to be getting

into bed to get enough hours of quality sleep, assuming a

reasonable quality of sleep ensues.

Interestingly, if you find yourself asleep as soon as you hit the

pillow, this may be an indicator of sleep deprivation. If the onset

of sleep takes longer than 20 minutes, this may be a symptom of


Find out more about sleep and how you can get a better quality sleep in my book:

book and meditation
Fix my sleep book and meditation


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