Understanding Rem Sleep: Deep Sleep's Elusive Cousin

Sleep is divided into two categories: REM (rapid eye movement) sleep and non-REM sleep. Deep sleep, or slow-wave sleep, is the final stage of non-REM sleep. During this stage, the body repairs and regrows tissues, builds bone and muscle, and strengthens the immune system. Deep sleep is also when the pituitary gland secretes important hormones, like human growth hormone, leading to growth and development. While the amount of deep sleep needed varies by age, it is essential for health and well-being.

Deep sleep is the final stage of non-REM sleep

Sleep is divided into two categories: REM (rapid eye movement) and non-REM sleep. After falling asleep, we first enter non-REM sleep, followed by a brief period of REM sleep, and the cycle repeats throughout the night.

Non-REM sleep is further divided into three stages. Stage 1 is the lightest stage of sleep and lasts only a few minutes. During this stage, the body and brain activities start to slow down, and there are light changes in brain activity. It is easy to wake someone during this stage, but if uninterrupted, they quickly move into stage 2.

Stage 2 is a deeper sleep where the body temperature drops, muscles relax, and breathing and heart rate slow down. Brain activity also slows, but there are short bursts of activity that help resist being woken up. This stage accounts for about 50% of the total sleep cycle.

Stage 3 is deep sleep, the final stage of non-REM sleep, and it is harder to wake someone during this stage. Muscle tone, pulse, and breathing rate decrease further, and brain activity is characterised by delta waves. This stage is critical for restorative sleep, allowing bodily recovery, growth, and strengthening the immune system. It also contributes to insightful thinking, creativity, and memory.

Deep sleep typically lasts longer during the early sleep cycles, ranging from 20 to 40 minutes, and gets shorter as the night progresses, with more time spent in REM sleep. As people age, they spend less time in deep sleep and more time in stage 2 sleep.

During deep sleep, the body repairs and regrows tissues, builds bone and muscle, and strengthens the immune system

Sleep is divided into two categories: REM (rapid eye movement) and non-REM sleep. After initially falling asleep in the non-REM stage, you move into a brief period of REM sleep, and then the cycle starts over again. During REM sleep, your brain activity is similar to its activity when you're awake, and dreams typically occur. Non-REM sleep is further divided into four stages, with the final two being the deep sleep stages.

During the deep stages of non-REM sleep, the body repairs and regrows tissues, builds bone and muscle, and strengthens the immune system. Here's how:

Tissue Repair and Regrowth

Human growth hormone (HGH), which stimulates protein synthesis and repairs and builds new muscle tissue, is released during deep sleep. The more deep sleep you get, the more HGH your body produces. This process is crucial for muscle recovery and repair, helping to maintain muscle mass and prevent muscle breakdown.

Bone and Muscle Building

Deep sleep is when the pituitary gland releases important hormones, such as human growth hormone, that promote the growth and development of the body. Additionally, during this stage, your blood supply to your muscles increases, further aiding in muscle growth and repair.

Immune System Strengthening

During deep sleep, your body produces cytokines, proteins that target infection and inflammation, creating an immune response. Your body also produces T-cells, white blood cells that play a critical role in fighting infectious diseases. Getting a good night's sleep helps to keep your immune system strong and ensures your body can dedicate its resources to repairing muscles.

Deep sleep is also referred to as slow-wave sleep or delta sleep

Deep sleep, or slow-wave sleep (SWS), is the third stage of non-rapid eye movement sleep (NREM). During this stage, brain activity is characterised by slow delta waves, with a frequency range of 0.5-4.5 Hz and a relatively high amplitude power with peak-to-peak amplitude greater than 75 μV.

Slow-wave sleep is preceded by two other stages of NREM sleep. The first stage occurs when a person first falls asleep and normally lasts just one to seven minutes. During this stage, the body has not fully relaxed, but the body and brain activities start to slow, with periods of brief movements. In the second stage, the body enters a more subdued state, with a drop in temperature, relaxed muscles, and slowed breathing and heart rate. Eye movement also stops, and brain activity slows, but there are short bursts of activity.

Slow-wave sleep usually lasts between 70 and 90 minutes and typically occurs during the first hours of the night. It is characterised by moderate muscle tone, slow or absent eye movement, and a lack of genital activity. It is considered important for memory consolidation, declarative memory, and the recovery of the brain from daily activities.

During slow-wave sleep, the brain's glucose metabolism increases, supporting short-term and long-term memory and overall learning. The pituitary gland also secretes important hormones, such as the human growth hormone, leading to growth and development. Other benefits of slow-wave sleep include increasing blood supply to muscles, promoting growth and repair of tissues and bones, and strengthening the immune system.

Slow-wave sleep is also necessary for survival. Some animals, such as dolphins and birds, can sleep with only one hemisphere of the brain, leaving the other half awake to carry out essential functions and remain alert. This type of sleep is called unihemispheric slow-wave sleep and has also been observed in humans to some extent.

Deep sleep supports memory, growth, and cell regeneration

Sleep is divided into two categories: REM (rapid-eye movement) and non-REM sleep. Deep sleep, or slow-wave sleep, is a stage of non-REM sleep. During this stage, your body and brain waves slow down, and it is difficult to wake you up.

Memory

Deep sleep supports the formation of memories. Slow, synchronous electrical waves in the brain during this stage make the neocortex, the location of long-term memory, especially receptive to information. These waves strengthen the synaptic connections between neurons in the neocortex, enhancing their receptivity. As a result, the brain can more effectively transfer memories from short-term memory to long-term memory.

Growth

Deep sleep is when the pituitary gland secretes important hormones, such as the human growth hormone, which leads to growth and development. This growth hormone is responsible for growth during infancy and is crucial for continuous tissue restoration and repair.

Cell Regeneration

Deep sleep is believed to promote a suitable environment for stem cells to proliferate, migrate, and differentiate. Cell division and protein synthesis reach their highest levels during sleep and diminish throughout the day. The rate of healing of damaged tissues is also greater during sleep.

In summary, deep sleep is essential for memory consolidation, growth, and cell regeneration. Not getting enough deep sleep may contribute to health issues such as heart disease and Alzheimer's disease.

Deep sleep decreases with age

Sleep is a complex and mysterious process that plays a crucial role in our overall health and well-being. As we age, our sleep patterns undergo significant changes, and one of the most notable alterations is the decrease in deep sleep. Deep sleep, also known as slow-wave sleep, is essential for memory consolidation, growth, and cell regeneration. However, it becomes less prevalent as we grow older.

During deep sleep, our body and brain waves slow down, making it difficult to wake up. This stage of sleep is crucial for feeling refreshed and energised in the morning. Unfortunately, as we advance in age, the amount of deep sleep we experience diminishes. If you are under 30, you may enjoy up to two hours of deep sleep each night. In contrast, individuals over 65 might only get 30 minutes or even none at all.

This reduction in deep sleep is a natural part of the ageing process. It is associated with changes in our circadian rhythms and the sleep-wake cycle. Our internal body clock, governed by the suprachiasmatic nucleus (SCN) in the brain, undergoes modifications with age, disrupting our sleep patterns. Additionally, the production of hormones like melatonin and cortisol, which influence sleep, also declines with advancing age.

The decrease in deep sleep can have implications for overall health. Deep sleep supports memory, growth, and the repair of tissues and bones. A lack of deep sleep may be linked to health conditions such as heart disease and Alzheimer's disease. It is important to note that while deep sleep decreases, older adults still require the same amount of total sleep as younger individuals—typically seven to nine hours per night.

To summarise, deep sleep is an essential component of our nightly rest, and its reduction with age is a natural phenomenon. However, it is crucial to prioritise sleep hygiene and healthy habits to ensure adequate overall sleep, promoting well-being as we age.

Frequently asked questions