Slow wave sleep, also called deep sleep, is an important stage in the sleep cycle that enables proper brain function and memory. While most adults are aware that they should aim for 7-9 hours of sleep each night, the science of sleep is quite complex.
The two main categories of sleep are called rapid eye movement (REM) sleep and non-REM sleep, and each has important stages. Humans go through these stages in a somewhat regular pattern while they sleep, and a full night’s rest means going through these stages a few times before waking up.
There may be a few ways to sleep better and sleep more soundly each night, allowing a person to wake up feeling more rested and rested.
The first stage of the sleep cycle is a transitional period during which the body and brain change from a waking state to a dream state. This period is relatively short, lasts only a few minutes, and sleep is quite light. People can wake up from this stage of sleep more easily than from other stages.
During stage one, the body begins to slow down. The heart rate and breathing rate decrease, and the eyes begin to relax. The muscles also relax, but they can occasionally contract.
The brain unwinds along with the body. Brain waves begin to decrease as brain activity and sensory stimulation decrease.
The second stage of non-REM sleep is another lighter stage of sleep that occurs when the body begins to shift into deeper sleep. As noted by the National Institute of Neurological Disorders and Stroke, humans spend most of their time during the sleep cycle in this stage of sleep.
In the body, the heart rate and respiratory rate decrease even more. The muscles relax more and eye movements stop. Body temperature also drops. Although brain waves slow down even further, this stage also includes small bursts of electrical signals in the brain.
Deep sleep or slow wave sleep is the third stage of non-REM sleep. Although the body completes a few cycles throughout the night, the third stage occurs in longer periods during the first part of the night.
In the body, heart rate and respiratory rate are lowest during this part of the sleep cycle. The muscles and eyes are also very relaxed, and the brain waves become even slower. It can be very difficult to wake someone up from this stage of sleep, which is when sleep disorders such as sleepwalking occur.
REM sleep is the fourth and final stage of the sleep cycle. The body first enters REM sleep about 90 minutes after falling asleep. During this stage of sleep, the eyes dart from side to side behind closed eyelids. This state is closer to the waking state than the other stages of sleep.
In REM sleep, brain waves begin to resemble waking brain waves. The heart rate and breathing rate accelerate. The REM stage is also when most dreams occur. The brain temporarily paralyzes the arms and legs to prevent the body from realizing these dreams.
Deep sleep requirements
While a person needs all stages of sleep, deep sleep is especially important for brain health and function. Deep sleep helps the brain create and store new memories and improves its ability to collect and retrieve information. This stage of sleep also helps the brain rest and recover from one day of thinking, allowing it to replenish energy in the form of glucose for the next day.
Deep sleep also plays a role in keeping hormones balanced. The pituitary gland secretes human growth hormone during this stage, which helps the body’s tissues to grow and regenerate cells.
It is important that a person has to get enough sleep for these functions to take place. The amount of deep sleep a person has will be related to the overall amount of sleep they get. Getting 7-9 hours of sleep is the recommendation for most adults, which will generally give the body plenty of time in the deepest states of sleep.
How to get a deeper sleep
There may be a few ways to increase the amount of deep sleep a person receives each night. As the Sleep Association points out, the most important thing a person can do to increase the amount of deep sleep they get each night is to set aside more time for sleep. By doing so, the body goes through more sleep cycles, making deeper sleep possible.
Other practices can help promote deep sleep and good sleep in general, such as:
- Get vigorous exercise, such as swimming, jogging, or running, earlier in the day rather than before bed.
- Make dietary changes that include eating fewer carbohydrates and healthier fats.
- Warm up the body in a hot spa or sauna.
Also, some antidepressants can help people sleep more soundly, although this is not the case for everyone.
Pink noise can also increase the effectiveness of a person’s deep sleep. Pink noise is random noise with more low-frequency components than white noise. A study in the journal Frontiers in Human Neuroscience looked at the effects of using sound stimulation, such as pink noise, in deep sleep. The results indicated that listening to these sounds could improve a person’s deep sleep state, leading to better memory function when they wake up.
Some general healthy sleep habits can also help promote better overall sleep, such as:
- Avoid blue lights, such as smartphones or computers near bedtime.
- Keep the room as dark as possible by closing windows and turning off the lights on alarm clocks.
- Avoid caffeine at the end of the day.
- Avoid large meals before bedtime.
- Reduce stress.
- Set a sleep schedule and try to fall asleep at the same time each night.