The importance of sleep is well established✓, regardless of age. Sleep is necessary for optimal health and well-being. Conversely, sleep deprivation and deficiency can lead to a host of physical and mental health problems, injuries and lack of productivity.
Sleep is divided into two components, namely rapid eye movement sleep (REM) and non-REM sleep. Non-REM sleep is then divided into three different stages.
The Stages Of Sleep
We cycle through all the stages of non-REM sleep and REM sleep several times during the night. Each phase serves a specific purpose✓ , and it's helpful to know the differences between them so that we understand why we need each one and how much time should be spent in each.
- Stage 1: this occurs right after you fall asleep - it is a brief light sleep when your breathing and heartbeat slow down.
- Stage 2: this is a period of light sleep before you enter deep sleep. Your heartbeat and breathing slow, muscles further relax, body temperature drops, and eye movements stop. Stage 2 sleep cycle lasts longer in each cycle throughout the night. You spend more of your sleep cycles in stage 2✓ than any other stage.
- Stage 3: this is the period of deep sleep that you need to feel refreshed in the morning - your heartbeat and breathing slow to their lowest levels, your muscles are completely relaxed, and brain waves are at their slowest.
- REM: during this period, your eyes move rapidly beneath your eyelids. Your breathing becomes faster and irregular, your heart rate and blood pressure increase, and your brain is similar to that of an awake person. It is believed that most of your dreaming occurs during REM sleep.
Did you know?
A complete sleep cycle takes 90-110 minutes - adults typically need 4-6 cycles each night/per 24 hour period✓.
What Is Deep Sleep?
Deep sleep occurs in the third stage of non-REM sleep and is known as slow-wave sleep. During this stage, EEG (electroencephalograph) recordings, which measure the brain's electrical activity, show slow waves with a high amplitude and slow frequency (0.5-4.5 Hz), known as delta waves✓.
Your breathing and heart rate are slow, and muscles relaxed during slow-wave deep sleep - a person is most difficult to wake up during this stage. People generally fall into a deep sleep within an hour of falling asleep and experience shorter periods of deep sleep as the night goes on.
The Benefits Of Deep Sleep
Whilst all stages of sleep are important deep, slow-wave sleep is believed to have a fundamental restorative and repairing function.
This stage of slow-wave sleep is essential for✓:
- The consolidation of memories - extensively studied✓
- Learning and optimal cognitive function
- A healthy immune system
- Heart health
- Tissue and muscle repair
- Hormone balance
How Much Deep Sleep Do We Need?
Adults are said to require a total of roughly 7-9 hours of sleep every night, and approximately 13-23% of our sleep time should be spent in deep sleep✓. Based on this, adults should have about 1 to 1.5 hours of deep sleep per night.
This, of course, may vary between individuals, as well as for individuals at different times. For example, if, for whatever reason, we have been sleep-deprived over several days, we may spend more time in deep sleep recovering from this time. Similarly, if we take regular naps, our time in deep sleep may be less✓.
Age✓ can also influence how much time we spend in deep sleep - older adults generally require less and infants and children more - most likely as it promotes growth and development.
What Happens When You Dont Get Enough Deep Sleep?
Just as the benefits of deep sleep are not limited to the brain, lack of deep sleep has consequences for the brain and the body.
Some of the potential dangers associated with insufficient slow-wave deep sleep include:
- Difficulty in the consolidation of memories✓
- Interference with our immune system✓
- Advancement of neurological disorders such as Alzheimer's✓ and Parkinson's✓ - through the inadequate clearing of waste from the brain
- Insulin resistance, type II diabetes, and cardiovascular risk factors✓
Did you know?
Sleepwalking✓ is one of the sleep disorders associated with deep sleep; specifically, partial arousal from deep sleep - some parts of the brain are awake whilst others are still asleep.
Tips For More Deep Sleep
Adopting a healthy sleep routine such as creating a sleep environment conducive to sleep, winding-down time, avoiding caffeine or alcohol close to bedtime will contribute to optimal restful sleep.
There are, however, a few additional steps listed below that may encourage more deep sleep.
- Allow yourself enough total sleep time.
- Exercise may increase deep sleep - recent research✓ shows vigorous exercise may improve the quality of deep sleep by increasing slow-wave stability.
- A warm bath an hour before bed - heating the body may promote deep sleep✓.
- Alter your diet - a diet low in fibre and high in saturated fat and sugar has been associated✓ with less deep sleep.
- Listen to 'binaural beats' - these beats are an 'illusion' created by the brain when you listen to two tones with slightly different frequencies. If specific frequencies are used, your brain waves can be induced to match that frequency. Some research✓ suggests that listening to delta wave 3-Hz binaural beats may help induce delta waves in the brain and, therefore, deep slow-wave sleep.
Deep or slow-wave sleep plays a crucial role in brain health and function. The amount of time spent in this sleep stage will differ between individuals and at different times; however, the average deep sleep time for adults is approximately 1-1.5 hours per night.
Exercise, a healthy diet and adequate total sleep are some methods that can potentially promote deep sleep.
Frequently Asked Questions
How much deep sleep do you need?
How much deep sleep you need will range between individuals and depend on different factors; however, 1-1.5 hours of deep sleep is generally required for the average adult.
How to get more deep sleep?
Some steps can be followed to encourage deep sleep, including allowing yourself adequate total sleep time and adopting a healthy diet and exercise regime.
What is deep sleep?
Deep sleep occurs in the third stage of non-REM sleep and is also known as slow-wave sleep. It is the period where your heart rate, breathing and brain waves slow to their lowest levels and your muscles are relaxed. It is the time when your brain can restore and repair itself and plays a vital role in overall health and wellbeing.