Why is sleep important?

Specialist sleep nurse Beccy Mullins explains the benefits of sleep and how it works

Sleep is a fundamental biological need, essential for good physical, mental and emotional health. Lack of sleep can have serious consequences on health and wellbeing, in particular. According to the Division of Sleep Medicine at Harvard University, these are the benefits of sleep:

Learning and memory: Sleep helps the brain to process new information, increasing understanding and retention.
Metabolism and weight: Chronic sleep deprivation may cause weight gain by interrupting the balance of the hormones that regulate appetite. Not only does this create a desire to eat more but to eat food with a higher calorific value such as carbohydrates and fat. This hormone imbalance can also lead to poor insulin control and to increased risk of diabetes, and is particularly prevalent in those who have less than five hours sleep each night.
Safety: A poor night’s sleep contributes to a greater tendency to fall asleep during the daytime. These lapses may cause falls and mistakes such as medical errors, air traffic mishaps, and road accidents.
Mood: Sleep loss often results in irritability, impatience, inability to concentrate, and moodiness. Too little sleep can also leave you too tired to do the things you like to do. Chronic sleep loss can also lead to long-term conditions such as depression or anxiety.
Heart health: Serious sleep disorders have been linked to high blood pressure, increased stress hormone levels, and irregular heartbeat. Having sufficient sleep helps to reduce stress and inflammation levels that are linked to heart disease and strokes, and can also help to keep blood pressure and cholesterol levels in check.
Disease: Sleep deprivation alters immune function, including the activity of cells that carry disease, while good sleep, strengthens ability to fight infection and encourages body tissue repair.

The stages of sleep

Stage 1
This is the lightest stage of sleep, the transition phase, where you feel yourself drifting off. This stage typically lasts for five to 10 minutes, just enough to allow your body to slow down and your muscles to relax.

Stage 2
The second stage of sleep is still considered light sleep. Your brain activity starts to slow down, as well as your heart rate and breathing. Your body temperature falls a little and you're beginning to reach a state of total relaxation in preparation for the deeper sleep to come.

Stage 3
Stage 3 is the beginning of deep sleep. If you were to get awakened suddenly during this stage, you would be groggy and confused, and find it difficult to focus at first.

Stage 4
Of the five stages of sleep, this is the one when you experience your deepest sleep of the night. This is the time when the body undertakes most of its repair work and regeneration.

REM Sleep
REM sleep in adult humans typically occupies 20–25% of total sleep, about 90–120 minutes of a night's sleep. During a normal night of sleep, humans usually experience about four or five periods of REM sleep; they are quite short at the beginning of the night and longer toward the end.

During REM sleep, blood flow, breathing, and brain activity increases, and it is the stage of sleep when you dream. During the night, your sleep follows a pattern, moving back and forth between deep and lighter stages and REM sleep (dreaming). These form a sleep cycle, each cycle lasting approximately 90 minutes and repeating 5-6 times a night.

The time spent in each stage varies throughout the night, with the length of time in REM sleep becoming longer as the night goes on.

More information on sleep stages from the NHS

Beccy Mullins, RGN is the Business Manager for Patient Services at ResMed UK Ltd. She is a Registered Nurse and has specialised in sleep medicine for 15 years, previously working at the Oxford sleep unit with Professor John Stradling as a clinical nurse specialist.