Why is sleep important?

About a third of the time we spend in the world, we spend sleeping. Few of you will have wondered why we sleep. After all, sleep is as essential to our daily routine as eating and drinking, and we know very well that we cannot live without sleep. It is less known that not just sleep itself, but also the quality of our sleep, is vital for our health and overall quality of life. In this article, we explain why people need good sleep.

The function of sleep

Sleep mainly affects brain activity. During the deep sleep phase, the brain cleanses itself of the by-products of our metabolism. The pituitary gland secretes the human growth hormone, which is responsible for the maintenance and repair of the body. So deep sleep is particularly important for physical rest and recovery: it restores body tissues, increases blood flow to the muscles, reduces blood pressure and replenishes the body’s energy levels.

The REM sleep phase is important for the development of the brain and the processing of information. This phase is necessary in order to fully recover physically and mentally.

Sleep is therefore important for the daily recovery of the body. Because a number of processes in the body are temporarily switched off, others can do their job. While we are awake, our brain cells use a lot of neurotransmitters. These are signal substances that ensure the transfer of information between our cells. These substances, and the receptors to which they bind, diminish over the course of the day and require restoration during sleep.

Why a good night’s rest is important

It goes without saying that we cannot go without any sleep for long. Fatigue is the first symptom that indicates that it is time for our daily rest. If we ignore that, it won’t be long before all aspects of our physical and mental functions start to deteriorate. The other consequences of insufficient, irregular or poor-quality sleep are less likely to show up and are typically not directly linked to the cause. We give an overview of the scientific insights into the influence of sleep quality on various functions of the body.

The importance of sleep for memory and performance

Research on the short-term and long-term health effects of sleep disruption has demonstrated a link between sleep and various brain functions, including memory and cognition. Sleep disturbance affects the way memories are processed and formed. During sleep, there seems to be a sort of reorganisation within the brain networks. The weaker links between brain cells vanish while the stronger ones get reinforced. This process leads to the storage of memories. As the brain does not have to process other stimuli while sleeping, it can assign a place for the information gathered throughout the day.

People’s performance at work, school, and other environments are affected by the quality of their sleep. This concerns focus, emotional reactivity, decision-making, risk behaviour and the ability to make judgements. That influence is already noticeable at an early age: a study published in 2015 in the Journal of Child Psychology and Psychiatry showed that children’s sleep patterns can have a direct impact on their behaviour and academic performance.

The importance of sleep for emotional and social intelligence

There is a link between sleep and social and emotional intelligence. Someone who doesn’t get enough sleep typically has more trouble recognising other people’s emotions and expressions. A 2022 study examined the relationship between sleep quality and sleep duration on the one hand and emotional intelligence on the other. Participants were asked to complete questionnaires about their sleep habits and emotional intelligence. Those who reported experiencing higher sleep quality scored best on emotional intelligence. They did well in social interactions, maintaining relationships, controlling impulses, and generally exhibited positive feelings.

The importance of sleep for preventing depression

The link between sleep and mental health has been a subject of scientific research for quite a while. A meta-analysis conducted in 2016 concluded that there might be a significant correlation between insomnia and an increased risk of depression. Sleep deprivation can lead to cognitive changes, such as impaired concentration or memory problems, which in turn lead to an increased risk of depression. Sleep disorders can also affect emotional stability and alter neural processes, which may consequently cause symptoms associated with depression. Qualitative sleep can therefore make an important contribution to preventing depression.

The importance of sleep for physical disorders

One of the risk factors for heart disease is high blood pressure. Getting enough sleep each night allows our blood pressure to regulate itself. A good night’s sleep can also reduce the chances of sleep-related disorders such as sleepwalking and bolster overall heart health.

There is also a link between getting enough sleep and reducing inflammation in the body. A 2019 study found a significant positive correlation between increased sleep inconsistency and elevated levels of inflammation, particularly in women. The study found that inconsistent sleep, where someone goes to sleep at irregular times or wakes up several times each night, can disrupt the body’s process of regulating inflammation.

Sleep helps the body recover and regenerate. The immune system is no exception to that relationship. Some studies suggest that deep sleep is essential for maintaining the immune system. Further scientific research is needed to fully understand the role of sleep in relation to its impact on the immune system.

The importance of sleep for body weight

Various studies have established a connection between overweight and poor sleep patterns. People who typically sleep less than seven hours per night are more prone to developing a higher BMI and even obesity compared to those who get more sleep. That’s because sleep deprivation is associated with higher levels of ghrelin (the hunger hormone), salt retention, and inflammatory markers. The effect can also be mental: reduced sleep leading to increased fatigue could hinder a person’s motivation or capability to maintain a healthy lifestyle.

There are also indications that a good night’s sleep can lead to the body consuming fewer calories. A clinical study conducted in 2022 found that overweight adults who extended their sleep duration had a lower calorie intake compared to the control group. Participants slept an average of 1.2 hours longer and ate about 270 fewer calories than the control group. The researchers concluded from this that improving sleep quality and maintaining a healthy sleep duration could help in losing weight and preventing obesity.

The importance of sleep for athletic performance

While adults typically require between 7 and 9 hours of sleep each night, recent research suggests that athletes may need more sleep than people who are less physically active. Getting enough sleep is important for athletes as it allows their bodies to recuperate from the physical demands of training or competitions.

Benefits of a good sleep quality for athletes:

• higher endurance
• more energy
• more accuracy
• shorter response time
• higher speed
• better mental functioning

How much sleep do we need?

The need for sleep varies from person to person, but is partly dependent on age. With age, the amount of sleep required to function at our best decreases. The general guideline according to age:

• newborn 0-3 months: 14-17 hours
• baby 4-11 months: 12-15 hours
• infant 1-2 years: 11-14 hours
• toddler 3-5 years: 10-13 hours
• school child 6-13 years: 9-11 hours
• adolescent 14-17 years: 8-10 hours
• adult 18-64 years: 7-9 hours
• senior 65 + years: 7-8 hours