What comes to mind when you hear the word “sleep”? You may think of it as an activity in which we close our eyes and is conducted during nighttime when we feel tired after completing our daily activities during the day. You may also think of it as a necessity for every human being after dealing with exhaustion from daily tasks or simply interacting with other people. Guess what? You are absolutely not wrong! However, the word “sleep” holds a meaning beyond simply closing our eyes. Let us dive deeper into the broader meaning of sleep.
Sleep in Scientific Terms
Some experts describe sleep as a natural phenomenon observed in most mammals. It is also considered as a near-universal feature in most creatures within kingdom Animalia that possess a brain and an interconnected nervous system, including humans. Furthermore, sleep is considered as a complex process that plays an important role in regulating various biological activities in the human body. These statements emphasize that sleep activity is an inseparable part of daily human life and is essential to support human well-being.
Sleep is scientifically defined as a state which meets several criteria, such as immobility of the body, rapidly reversible quiescence, increased arousal thresholds, and homeostatic regulation.
- Immobility
Although it serves as an iconic characteristic of the state of sleep, it is not always associated with sleep, as most people tend to twitch or involuntarily move parts of their bodies during sleeping, such as during non rapid eye movement (NREM) sleep.
- Rapidly Reversible Quiescence
This criterion is important for distinguishing sleep from other states, such as coma, unconsciousness under anesthesia, torpor, and hibernation. This is because sleep is a physiological condition in which the body enters a resting state and can revert back to its conscious state when stimulated by sufficient stimulation, unlike the aforementioned states, in which the body may be under the influence of drugs or experience damage to a specific part of brain responsible for wakefulness.
- Increased Arousal Threshold
It means that increased respiratory effort or simply stronger stimulus is required to trigger arousal from the state of sleep. This distinguishes sleep from quiet wakefulness, as it takes a stronger stimulus to wake someone from sleep than to stimulate someone who is in a condition of quiet wakefulness.
- Homeostatic Regulation
It means that sleep is regulated according to the body’s physiological need for rest. Consequently, lack of sleep is expected to be followed by a rebound of increased sleep amount or depth or both, as the body requires sleep physiologically.
Since sleep is a physiological activity that the body requires to maintain homeostasis or balance, it plays a more important role than simply allowing the body to rest after exposure to exhaustion or any external stressors. It serves a restorative function in our body, as it promotes biological processes essential in physical recovery such as protein synthesis, DNA repair, and autophagy, a process where the body removes damaged cellular components. In addition, because the state of sleep does not require a high energy input as a result of decrease in heart rate, blood pressure and core body temperature, it may help conserve the energy required for optimal daytime functioning.
Furthermore, sleep plays a crucial role in maintaining brain health by facilitating clearance of metabolic wastes or toxins from the brain and strengthening synaptic networks that are essential for learning and memory consolidation. Without these functions, our body may not be able to function effectively. Thus, sleep is not just an act of putting the body at rest. It is an act of maintaining the body’s health and sustainability.
Stages of Sleep
You may think that when you close your eyes you just go into a state of sleep. There is a lot more to it than that. Once you fall asleep, your body goes through two types of sleep. These are called non-rapid eye movement (NREM) and rapid eye movement (REM) sleep. Every night your body goes through a cycle where it moves back and forth between NREM sleep and REM sleep. This cycle happens about 4 to 5 times each night until you wake up in the morning.
When you close your eyes, you start to enter NREM sleep. This is the first stage of sleep that every person experiences. This stage has three parts called N1, N2 and N3. The first two parts, N1 and N2 are known as shallow sleep. This is the time when you move from being awake to being unconscious. The last part, N3 is called a slow-wave sleep. During this time your body starts to get rest. Your heart rate, breathing and blood pressure all go down during this stage. This stage is important because it helps your body repair itself. It also helps in making tissues and releasing growth hormones. These hormones are very important for how your body grows and repairs itself, especially in children. This is why if children do not get enough sleep, they may not grow properly. Another important job of this stage is to help your brain lock in memory, as it helps your brain process and store information.
After 90 to 110 minutes of NREM sleep your body moves into REM sleep. This stage is shorter than NREM sleep. During REM sleep your brain becomes very active like when you are awake. This activity causes your eyes to move behind your eyelids. At the same time, your muscles become very relaxed. This is why your body often feels temporarily paralyzed during this time. You also tend to have vivid dreams during this stage. This stage is very important for learning and memory consolidation processes. It helps you keep the information you learn at school or during work meetings. In other words, this stage helps you do well in school or, at work.
Determinant Factors of Sleep Quality
Do you ever feel like falling asleep at night and once you fall asleep you do not get woken up easily by even a strong stimulus, such as loud noise coming from your neighbor, the sound of your cat running around your bedroom, or just simply by having nightmare then you wake up the next morning feeling relieved from tiredness? If you do, congratulations! You have just had a good quality sleep!
Quality of sleep is scientifically referred to as a compilation of some sleep components, including latency, duration, continuity, and depth of sleep. Sleep latency is portrayed as the ability of our body to fall asleep immediately without delay whenever needed, for example, during the night after a day from work or after coming home from outside activity. Sleep duration pictures how long the time spent asleep with the range of sleep time between 7-9 hours daily. Sleep continuity refers to the ability of our body to stay asleep without interruption throughout the night. Lastly, sleep depth, which involves the feeling of restfulness and rejuvenation after waking up.
There are determinants of sleep quality depending on the demographic backgrounds of each individual. In elderly, as they age, they will undergo some neurological changes in their body. These changes cause degeneration of their nervous system, which consequently interferes with release of hormones or chemicals necessary for initiating sleep. Additionally, aging also promotes degeneration of sensory organs that will eventually lead to decrease in sensitivity to these organs. Consequently, this condition interrupts the maintenance of circadian rhythm, which depends a lot on sensory inputs from the surrounding environment.
In adolescents, since they are entering a period where brain development and maturation take place, and several biological changes occur, most of them will undergo delay in timing of sleep onset. Their urge to fall asleep thus decreases, for those during school years. They tend to be burdened with tasks and activities. This will eventually lead to decreased sleep duration and poor quality of sleep.
In adults, as they are burdened with an increase in work demands, they are more prone to stress, burnout, anxiety and depression. These conditions will interrupt production of hormones that are essential for maintaining circadian rhythm. Thus, sleep quality is sacrificed. Not to mention the increase of tendency towards caffeinated drinks or alcohol. These behaviors will furtherly worsen sleep quality.
Beside factors related to age mentioned above, some additional factors, such as environment and lifestyle factors, also contribute to sleep quality. Exposure to noise and light will slow down the production of melatonin, which is a hormone responsible for initiation of sleep. Additionally, regular exercise is also considered as a determinant factor in maintaining good sleep quality. It is proportional to increase in sleep quality, as it helps improve sleep depth.
Impact of Sleep Quality towards Various Life Aspects
- Health
Since sleep regulates some physiological and biological process in our body, it has a direct impact towards the health of our body. Thus, sleep deprivation may result in some health disturbances which potentially disrupt our well-being. Sleep deprivation is reported to be associated with obesity. This is because sleep deprivation causes disruption to the nocturnal pattern of our body, which is essential for glucose metabolism and hunger hormones regulation. This is why adolescents or adults who do not get enough sleep may be more prone to obesity than those that obtain sufficient sleep. The problem does not stop there, because once someone becomes obese, they are more likely to experience chronic illnesses, such as heart disease and cancer. Additionally, poor sleep quality is also associated with mental disorders, such as depression and mood disorders. These mental disorders may further urge people to engage in some health-risk behaviors, such as smoking, alcohol use, or violence.
- Personal Matters
Poor sleep quality is strongly associated with self-related problems, such as decrease in optimism and self-esteem. Some experts explain that people with poor sleep quality, such as people with insomnia, have both lower optimism and self-esteem than those who do not possess insomnia. Those self-related effects are also associated with other mental conditions caused by poor sleep quality, such as depression and mood disorders. Therefore, poor sleep quality can contribute to subsequent health and self-related issues.
- Social Relationships
When we experience low self-esteem as the consequence of poor sleep quality, it may inevitably affect our interaction with others. We may tend to avoid social interaction when we do not feel good about ourselves. This condition may eventually lead to social withdrawal and reduced participation in society.
- Education and Academic Performance
We now acknowledge that sleep is so powerful that it can affect many aspects of our lives, including academic performance. Certain phases of sleep are required for our brain to preserve memory and improve cognitive function. Therefore, sleep quality may influence academic performance. Students who experience sleep deprivation are at a risk of having a decrease of memory regarding information acquired from studying at school, as they do not get a positive impact of sleep. In contrast, some researchers reported that poor sleep quality does not always correlate with poor academic achievement. Yet, that does not mean that we should not worry about not getting enough sleep!
- Work Performance
The direct impact of sleep quality towards mental and cognitive function may also potentially affect work performance. Lack of focus due to lack of sleep may make workers more prone to mistakes and errors that lead to decreased work performance. Some detrimental health effects of poor sleep quality also affect productivity of workers. Workers who experience sleep deprivation tend to have a higher absence rate than those who obtain enough sleep.
How to Maintain a Good Sleep Quality?
We have discussed the powerful effects of sleep quality towards various aspects of our lives. Now, you may wonder how we can achieve good sleep quality in order to maintain a healthy lifestyle. Here are some tips that you can implement in your daily life:
- Limit caffeine intake acquired from caffeinated drinks such as coffee or tea, as caffeine is a stimulant that promotes wakefulness and alertness.
- Limit exposure to light during nighttime hours. In order to initiate sleep, our brain releases melatonin hormone that is sensitive to light. Therefore, prolonged exposure to light sources, such as gadgets or bright light, may disrupt the activation of this hormone, thus preventing the initiation of sleep.
- Do regular exercise. Staying active during the day through physical activities such as walking, cycling, or jogging may help improve sleep quality. Regular exercise can support the body’s natural sleep-wake cycle and contribute to more restorative sleep. However, exercising too close to bedtime may interfere with sleep for some individuals.
Conclusion
In conclusion, sleep is more than just a resting phase that we need after a long hours of working or doing daily activities. It influences various fundamental factors that determine cognitive and mental functions, which ultimately affects various aspects of our lives. It is really important to maintain a good quality of sleep. Because, a good quality of sleep means a better quality of life!
By: Naufal Issan Beryldivito Iskandar
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