Impact of sleep deprivation on health

Sleep is divided into two main, cyclically repeating phases: NREM (Non-Rapid Eye Movement) and REM (Rapid Eye Movement). Each has its own characteristic features and plays an important role in the body’s recovery.

It is divided into 3 stages:

1 – transitional phase (drowsiness)
The first stage of falling asleep, lasting a few minutes, is characterised by a slowing down of brain waves (Alpha and Theta waves are present in the EEG). It is easy to wake up from and may be accompanied by a feeling of ‘falling’ caused by involuntary muscle movements (myoclonus).

2 – light sleep
Lasts for about 50% of all sleep, sleep spindles and K complexes appear in the EEG. Sleep spindles are associated with memory consolidation, while K complexes protect against awakening. During this stage, the heart rate slows down and our body temperature decreases.

 3 – deep sleep
This is the time when our body regenerates intensively. Delta waves of extremely low frequency are present in the EEG. During this phase, it is most difficult to wake up. However, episodes of somnambulism known more widely as sleepwalking or sleepwalking may occur.

It first appears about 90 minutes after falling asleep and is very important for memory consolidation and emotional processing. It is characterised by increased brain activity, intense daydreaming and rapid eye movements. The muscles of the body, on the other hand, are relaxed.

The average sleep cycle (NREM + REM) lasts approximately 90 minutes. During the night we experience 4-6 such cycles. At the beginning, deep sleep dominates and in the second half of the night the REM phase.

The role of sleep in everyone’s life is invaluable. When we sleep, the brain organises information, the immune system is strengthened and the body’s cells repair themselves and begin to function properly. Lack of sleep can lead to cognitive impairment, obesity and even type 2 diabetes. To avoid developing the disease, it is a good idea to follow the principles of sleep hygiene and get a minimum of 7-9 hours of sleep per night.

• Brain
  Sleep supports the ability to learn, remember, make rational decisions and make logical choices. In the NREM phase, also known as slow-wave sleep, the brain “recreates” newly learned information and consolidates traces of it. In the REM phase – it integrates information, gives it meaning and supports creative connections. During sleep, irrelevant or infrequently used neural connections are removed, improving the clarity and efficiency of memory and protecting the brain from information overload. During sleep, the brain also gets rid of toxins, such as β-amyloid protein, which is a major neuropathological feature of Alzheimer’s disease.
• Mental health
  During the REM phase, the brain “reworks” difficult and intense experiences. This helps to reduce their emotional charge and lower over-reactivity during the day. Brain imaging studies show that healthy, regular REM sleep helps maintain a balance between the amygdala and prefrontal cortex – centres very important for controlling emotions and anxiety. When we sleep, levels of norepinephrine – a neurotransmitter associated with the “fight or flight” response – fall. This allows the brain to process emotionally charged memories in a “sedated” nervous system.
• Immune system
  Sleep strengthens the immune system, helps fight cancer cells, prevents infections and the development of a number of diseases. During sleep, especially during the deep sleep phase, the production of cytokines – proteins that help the body fight inflammation and infection – increases. T lymphocytes – cells that recognise and destroy antigens – are also activated, and levels of interleukin-1 and gamma interferon, key to fighting viruses and bacteria, increase.
• Metabolism
  A good night’s sleep influences appetite regulation, metabolism and weight maintenance. It has an important influence on the hormones responsible for the sensations of hunger and satiety, mainly ghrelin and leptin. Insufficient sleep impairs the prefrontal cortex, responsible for making rational decisions, and increases activity in the limbic system, which controls feelings of pleasure and regulates mood. Sleep-deprived people are more likely to reach for high-calorie, sugary or fatty foods, making them more prone to developing compulsive overeating.
• Gut health
  An adequate amount of sleep per day helps maintain a healthy gut microbiome. Disrupted sleep patterns (shift work, falling asleep at different times, travelling to different time zones) can disrupt it, increasing the number of pathogenic bacterial strains. Studies have shown that after just two nights with sleep restricted to four hours, the composition of the microbiome begins to resemble that observed in obese people.
• Circulatory system
  Sleep affects the regulation of blood pressure through the secretion of melatonin and cortisol. When sleep is too short, intermittent or of poor quality, blood pressure can become elevated, increasing the risk of hypertension and cardiovascular disease.
• Endocrine system
  Hormone management has a huge impact on the quality of our sleep. Lack of sleep causes endocrine disruption, which results from changes in levels of cortisol, insulin, testosterone and oestrogen, among others. The list of potential health burdens resulting from insomnia is very long, and treatment methods are chosen depending on the cause and the individual needs of the patient.

Too little sleep worsens quality of life and can be the cause of many health complaints. The problem has assumed such serious proportions that the World Health Organisation (WHO) has declared an epidemic of sleep deprivation in industrialised countries. Where average sleep duration has decreased dramatically over the last century, such as in a number of Western European countries, the United States, Japan and South Korea, it is no coincidence that the greatest increases in mental illness and disorders are also being observed.

This is why it is so important to take care of the length and quality of sleep on a daily basis. The practice of Yoga Nidra can also be helpful. This ancient relaxation technique, also known as “yogic sleep”, involves achieving a state between sleep and wakefulness, where the body is fully relaxed and the mind remains active and focused. It is assumed that an hour’s practice of Yoga Nidra is equivalent to four hours of sleep, allowing for a deep regeneration of the body and mind.

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