Why We Sleep

Sleep is one of the most basic needs of the human body, yet one of the most underestimated. In today's world, where the emphasis is on constant productivity, many see sleep as a luxury they cannot afford. Matthew Walker, renowned neuroscientist and sleep expert, reveals in his book "Why We Sleep" the crucial role sleep plays in our physical health, mental well-being and overall performance. The book combines scientific facts, personal stories and practical advice to show how quality sleep can transform our lives. Walker doesn't just offer theory-he provides concrete evidence of how sleep deprivation affects every part of our being, from the risk of chronic disease to our ability to learn and manage stress. "Why We Sleep" is not only a challenge to value sleep, but also a guide to how to improve it. Readers will learn about the fascinating mechanisms that take place during sleep and understand why sleep should be considered an integral part of a healthy life, much like diet or exercise.

Sleep is not just a time of inactivity when the body rests, but an active process that is essential for survival and proper functioning of the body. Since childhood, we have been told that "good sleep is the foundation of health," but few of us realise the profound importance of this biological process. During sleep, a complex symphony of regeneration, repair and learning takes place in the body and brain, without which we would not be able to face the challenges of the next day. Imagine an athlete training for the Olympics. His body needs rest to repair muscle fibers and restore energy. In the same way, our brain, after a day full of stimuli, needs to process and organize information. Without enough sleep, this process fails - much like a computer that never shuts down, and becomes sluggish and inefficient. In the 1950s, for example, experiments by psychologists showed that sleep deprivation not only leads to impaired concentration, but also to an inability to cope with simple tasks such as solving mathematical examples. Modern studies show that sleep is also essential for our physical health. During deep sleep, the production of growth hormone increases, which helps regenerate cells. In addition, the immune system is stabilized, which is why you feel weak and susceptible to illness when you don't get enough sleep. Evidence comes from 2016 research that confirmed that people who sleep less than six hours a day are up to 70% more likely to develop cardiovascular disease. Sleep neglect also has a direct impact on the risk of chronic diseases such as diabetes and obesity. When sleep patterns are disrupted, the levels of hormones responsible for hunger and satiety are thrown into chaos. You may have noticed yourself having a constant craving for sweet and fatty foods after a sleepless night. This biological imbalance, caused by lack of sleep, leads to unhealthy eating habits and long-term weight gain. In today's fast-paced world, where productivity is often placed above all else, sleep has become a luxury many can't "afford." However, ignoring this basic need can have serious consequences not only on our health, but also on our ability to be productive and creative. Just look at cases where sleep deprivation has led to tragedies such as the Chernobyl nuclear accident or the Challenger space shuttle crash - both incidents where human failure played a role in sleep deprivation. The crucial importance of sleep is not just a theory. It is a reality that we need to recognise. Investing in quality sleep is an investment in long-term health, vitality and mental well-being. Perhaps it's time to stop seeing sleep as a waste of time and start seeing it as the key to a fulfilling life.

Sleep is one of the most important tools for keeping our minds sharp and performance ready. Without it, the brain resembles a library where books are scattered about without any order. It is during sleep, however, that these "books" - that is, information and experiences - are systematically stored, allowing our memory to function optimally and creativity to flourish. When we are awake, the brain is exposed to a continuous flow of stimuli. Throughout the day, we absorb new information, learn new skills, and solve problems. However, this process is not complete without the subsequent sleep. Case in point, a 2007 study showed that students who slept well before exams remembered up to 40% more information compared to those who studied late into the night at the expense of sleep. In the REM stage of sleep, areas of the brain responsible for creative thinking and problem-solving skills are activated. You may have experienced a situation yourself where you couldn't concentrate on even simple tasks after a sleepless night, but after a good night's sleep, everything suddenly seemed clearer. Interesting is the story of the chemist Dmitri Mendeleev who, after years of trying to create the periodic table of elements, claimed that he "saw it in a dream." This phenomenon is not accidental - the brain can connect information in innovative ways during sleep. In addition to memory and creativity, sleep also affects decision-making ability. Sleep deprivation weakens the frontal lobe of the brain, which is responsible for logical and analytical thinking. Instead, the emotional centers begin to dominate, leading to impulsive decisions. This can have serious consequences, especially in professions where it is critical to react quickly and correctly, such as pilots, doctors or drivers. The importance of sleep for cognitive function is not only manifested in the short term. Chronic sleep deprivation can have long-term consequences, including an increased risk of neurodegenerative diseases such as Alzheimer's disease. Scientists have found that during sleep the brain is "cleansed" - the lymphatic system removes toxins and waste products that might otherwise interfere with neural connections. It's not necessary to make big changes to improve our cognitive function. The key is a regular sleep schedule, ideally 7-9 hours a day. It is also important to create an environment that promotes quality sleep - a quiet, dark and cool place free of distractions. If you want to strengthen your mind, the best investment you can make is to give it time to regenerate during the night. Your brain will pay you back in the form of better memory, sharper thinking and greater resilience to everyday challenges.

Emotions are like a river - sometimes calm, other times turbulent. Sleep acts like a dam to help control their flow, preventing emotional swings and protecting us from being overwhelmed by negative feelings. Without quality sleep, however, this dam weakens, which can lead to increased irritability, anxiety, and problems in interpersonal relationships. One of the most remarkable mechanisms of sleep is its ability to "reset" the emotional state of the brain. During the REM phase, when dreams take place, the areas of the brain responsible for processing emotions are activated, especially the amygdala - the centre of fear and anger. A 2007 study led by neuroscientist Matthew Walker found that people who got enough REM sleep were better able to cope with stressful situations and respond with greater calm. Conversely, those who were deprived of this stage of sleep showed higher levels of emotional reactivity. Imagine having a difficult day full of conflicts. Quality sleep can help you "process" these experiences and lessen their emotional intensity. This is why it is said that "the morning is wiser by the evening." This natural process allows the brain to cope with negative experiences and prepare for new challenges. However, long-term sleep deprivation has the opposite effect. Chronic fatigue reduces the ability of the brain's frontal lobe to control the amygdala, which means emotions take over. The result is more impulsive behavior, outbursts of anger, and difficulty resolving conflicts. In extreme cases, sleep deprivation can contribute to the development of mental illnesses such as depression and post-traumatic stress disorder (PTSD). Practical evidence for this theory comes from 2013 research that followed a group of parents of young children. Those who were able to get at least 7 hours of sleep on a regular basis rated their emotional well-being significantly higher than those who neglected sleep. In addition, they were better able to cope with the challenges of parenting, including child care and dealing with unforeseen situations. Sleep is also a powerful tool for reinforcing positive emotions. During the night, memory traces are reorganized, with negative experiences losing intensity while positive ones are reinforced. This explains why we often feel more optimistic and motivated after a good night's sleep after a hard day. Improving emotional regulation through sleep is simple but requires discipline. Following a regular routine, limiting caffeine and electronics before bed, and creating a peaceful sleep environment can significantly impact your emotional stability. So if you want to be more resilient to stress and handle daily challenges with ease, remember: sleep is not a luxury, but a necessity.

Sleep is not a monolithic process, but a fascinating interplay of different phases that together form a cycle of regeneration. Each has a unique function and is essential for our physical and mental health. Understanding these phases can help us better understand why sleep is so crucial to our lives. The sleep cycle consists of four basic phases that repeat approximately every 90 minutes. The first phase is called light sleep, which is the transition between wakefulness and sleep. Your body begins to relax, your heart rate and breathing slow down. This stage serves as preparation for deeper levels of sleep. This is followed by deep sleep, also known as the NREM (non-REM) phase, which is the most restorative part of the sleep cycle. During this period, cell repair, immune system strengthening and growth hormone release occur. Imagine that your body is like a factory, working at full capacity during the day and needing to repair and prepare for the next day at night. Without sufficient deep sleep, this "maintenance" could not take place, leading to physical fatigue and weakened immunity. The most interesting stage, however, is REM sleep, named after the rapid eye movements, that characterize it. It is in this stage that dreams take place, with the brain processing emotional experiences and connecting new information with pre-existing knowledge. REM sleep is crucial for creative thinking and emotional balance. A 2010 study showed that REM sleep helps people solve complex problems more effectively, suggesting that dreams may be more than just random images - they can be a tool to a deeper understanding of reality. Interestingly, the proportion of each phase varies throughout the night. In the beginning, deep sleep predominates, while towards morning the time spent in the REM phase increases. This explains why we sometimes wake up in the middle of a vivid dream - our brain is just in REM sleep when the cycle is complete. If we interrupt sleep or don't give the body enough time to complete all the cycles, we disrupt the natural harmony of these phases. For example, in chronic sleep deprivation, deep and REM sleep in particular suffers, leading to physical exhaustion and emotional instability. Understanding the sleep phases is not just a theory, but a practical tool for improving life. If you create a healthy sleep routine and ensure that you allow your body to complete all phases of the sleep cycle, you can gain more energy, better memory, and a more balanced psyche. Sleep is like an orchestral concert - each phase has its own meaning and together they create a harmony that keeps our body and mind in perfect rhythm.

Caffeine and alcohol are a normal part of our lives, we often think of them as helpers in coping with stress or fatigue. However, their impact on sleep is more insidious than we might think. Both substances have a profound effect on the quality and structure of sleep, robbing us of its most important restorative phases. Caffeine, found not only in coffee but also in tea, chocolate and energy drinks, acts as a stimulant. Its main role is to block adenosine, a substance that signals fatigue in the brain. The result is a feeling of alertness and energy. The problem arises, however, when we have a cup of coffee late in the day. Caffeine has a half-life of about 5-7 hours, which means that if you have an espresso at 5pm, half the amount of caffeine is left in your body by 10pm. This effect can severely impair the ability to fall asleep and shorten deep sleep, which is crucial for recovery. The consequences of regularly consuming caffeine before bed can manifest not only as difficulty falling asleep, but also as general fatigue and irritability. Interestingly, many people become so accustomed to caffeine that they stop noticing its effects on sleep - but their body still suffers. A 2013 study showed that even coffee consumed 6 hours before bedtime can reduce total sleep time by more than an hour. Alcohol, on the other hand, may act as a "friend" to help you fall asleep, but its effects are paradoxical. Although alcohol initially induces drowsiness and helps you fall asleep faster, it disrupts the structure of sleep, especially the REM phase. The latter is responsible for processing emotions and strengthening memory. Without it, we wake up feeling mentally 'foggy' and emotionally unstable. In addition, alcohol affects breathing during sleep, increasing the risk of sleep apnoea - a disorder in which breathing temporarily stops. The result is interrupted sleep and lack of recovery. Studies show that people who regularly consume alcohol before bed are more prone to chronic fatigue and lower productivity. An interesting example is the story of the famous inventor Thomas Edison, who was known for his love of coffee and frequent bedtime drinking. Although his work ethic was admirable, many experts now believe that his constant fatigue and health problems were the result of excessive caffeine consumption and sleep neglect. To improve the quality of your sleep, start by limiting caffeine to the morning hours and avoid alcohol for at least 3-4 hours before bedtime. These simple changes can have a major impact on how you feel when you wake up - more energy, a better mood, and a sharper mind are benefits that are definitely worth it. Sleep is a precious source of restoration that deserves respect, which is why it's important to be wary of substances that can subtly disrupt it.

As we age, sleep changes - in quality, length and texture. This natural process is the result of the biological and neurological changes that accompany ageing. Although we may assume that older people need less sleep, the reality is different. The need for sleep remains the same, but the ability to achieve deep and uninterrupted sleep gradually decreases. One of the most noticeable changes is the decline in deep sleep (NREM phase), which is responsible for the recovery of the body and brain. In young adults, deep sleep accounts for about 20% of total sleep time, but in people over the age of 70, this proportion may fall to less than 5%. This decline has a significant impact on muscle recovery, immune system strengthening and overall vitality. Another sign of ageing is a reduction in the production of melatonin, the hormone that regulates our circadian rhythm and promotes feelings of sleepiness. The consequence is more frequent awakenings during the night and difficulty falling asleep. For example, research from 2015 showed that up to 50% of seniors suffer from insomnia or other sleep disorders. This fragmentation of sleep can lead to feelings of fatigue, even if the total time spent in bed remains the same. Sleep changes are also related to diseases that are common in the elderly. Disorders such as sleep apnoea or restless legs syndrome can further impair sleep quality. These problems are often underestimated but can have serious consequences, such as increased risk of heart disease or depression. In addition to the physical aspects, ageing also affects the psychological side of sleep. Older people are more likely to suffer from loneliness or loss of loved ones, which can contribute to increased anxiety and sleep problems. Additionally, changes in daily routines after retirement can disrupt natural routines, further complicating falling asleep. On the other hand, not all news about sleep and aging is negative. Researchers agree that simple changes can help maintain quality sleep well into older age. A regular routine, plenty of daylight, and physical activity are key. For example, moderate exercise during the day can not only improve mood but also promote deeper sleep at night. The story of British spinster Edith Murway-Traina, who at the age of 100 became the oldest female competitor in a power triathlon, illustrates that good quality sleep and an active lifestyle can make a significant contribution to vitality in old age. Although her body is subject to the laws of biology, a regular regimen and sleep care help her overcome physical limitations. Sleep is an essential pillar of health at any age, but its role becomes even more significant in old age. If we pay attention to it and promote its quality, it can help us face the challenges of aging with greater energy and resilience. Regardless of age, sleep is the best investment in a healthy and fulfilling life.

Sleep hygiene is not about cleanliness, but about habits and environments that promote quality and uninterrupted sleep. In a modern world where we are constantly surrounded by technology and responsibilities, these principles become crucial to our physical and mental health. Proper sleep hygiene is like tending a garden - if you don't take care of it, the result is chaos. However, if you follow certain rules, your sleep can be exceptionally restorative. One of the most important steps is a regular sleep routine. Go to bed and get up at the same time every day, even on weekends. By doing this, you are helping your body set an internal clock, known as the circadian rhythm, which makes the process of falling asleep and waking up easier. If you wake up at different stages of the sleep cycle each night, you may feel tired even if you sleep long enough. Another crucial factor is creating a suitable sleep environment. Your bedroom should be dark, quiet and cool - ideally around 18°C. Eliminate distractions such as flickering lights or noise from outside by using curtains, earplugs or white noise. The quality of the mattress and pillow can also play an important role. If you spend a third of your life in bed, it's worth investing in a comfortable bed. Limiting exposure to blue light from electronic devices such as phones, tablets or TVs also has a big impact on sleep quality. Blue light suppresses the production of melatonin, the hormone responsible for sleepiness. If you can't give up screens before bed, consider using blue light filters or blue light-blocking glasses. Healthy sleep hygiene also includes maintaining good daytime habits. Avoid consuming caffeine in the afternoon and alcohol before bed, as they can disrupt the sleep cycle. Conversely, regular physical activity promotes deeper sleep if done at the right time - ideally at least three hours before bedtime to give the body time to cool down and prepare for rest. Bedtime rituals are another way to signal to the body that it's time to rest. These can be simple activities such as reading a book, taking a warm bath or meditating. These activities help to calm the mind and induce a state of calmness needed to fall asleep quickly and soundly. An example of good sleep hygiene is the famous American basketball player LeBron James, who puts a huge emphasis on his sleep regime. He regularly sleeps 8-10 hours a day, invests in a quality sleep environment, and strictly follows rituals that allow him to maximize recovery and performance on the court. Improving sleep hygiene is not difficult, but it does require discipline and conscious decisions. If you adopt these simple principles, you can look forward to better sleep, more energy, and greater resilience to everyday stresses. Sleep hygiene is the cornerstone of a healthy life - you just need to pay attention to it.

In his book "Why We Sleep", Matthew Walker reveals the importance of sleep in all its complexity - from its biological processes to its impact on everyday life. The reader will learn that sleep is not just rest, but an active process that supports our physical recovery, emotional stability, and mental acuity. Through scientific research and practical recommendations, Walker shows that quality sleep can be the key to a longer, healthier, and more productive life. The book delivers an important message: sleep is not a waste of time, but an investment in our future. We don't need to make dramatic changes for better health and higher performance - just focus on improving sleep hygiene, avoiding caffeine and alcohol before bed, or following a regular routine. Walker also warns of the consequences of sleep deprivation, which can have a devastating effect on our health and decision-making. "Why We Sleep" is a reminder that the key to long-term happiness and success may lie in a simple yet often neglected habit - quality sleep. Do you have feedback for us? We'd love it if you let us know your opinion on our content! Just send an email to feedback@rewio.app with the title of this book in the subject line and share your impressions!