This is a seemingly inane question. Everyone sleeps. All living beings on this planet have some form of sleep schedule and what we call a circadian (sir-KAY-dee-un) rhythm. Therefore, how we sleep, is not a mystery. We go to bed and fall asleep, and we hopefully feel refreshed in the morning. A circadian rhythm is our body’s internal clock that allows the processes to happen promptly. Every organ system follows its circadian rhythm, and this is how our body knows how to run properly. Imagine this as a master clock in our brains that is always running in the background. Also known as a diurnal rhythm, the word circadian comes from the Latin phrase “circa diem” meaning “around a day”, signifying the 24-hour cycle. The most obvious form of the circadian rhythm is the sleep-wake cycle through which our bodies’ sleep is regulated through a series of brain processes connected to melatonin. Have you ever heard of melatonin? It’s a very popular sleeping aid that people use to fall asleep at night. It is naturally produced in our pineal glands, and it’s very tightly regulated. Taking melatonin on your own, without an explicit medical prescription can lead to throwing off our cycle and deepen insomnia. Therefore, only take melatonin as prescribed.
The circadian rhythm explains why we sleep though – but not exactly how we sleep. The circadian rhythm is dependent on sunlight, hours without sleep, and the time of day, and sleep descends on us when the adenosine and melatonin levels in our brains are high. They tie to specific parts of the brain known as receptors that make us sleepy. How sleepy we depend on the above-mentioned factors, and when we decide to close our eyes sleep descends on us – and we (or rather our brains) start moving throughout specific stages. At first, we enter the shallow sleep stage or the first NREM (non-REM) phase of sleep. REM stands for rapid eye movement, which happens in later stages. This first NREM phase allows our bodies to relax and start resting. After a certain time, depending on multiple factors – we enter our first REM stage (Rapid Eye Movement). The REM stages are incredibly important for the brain and allow our short-term memory to turn into long-term or erase from our hippocampi (the part of the brain responsible for memory and concentration) and help us focus when we are awake. The fascinating aspect of the REM phase is the fact we have the clearest dreams during this time of night, and to prevent our bodies to reenact these dreams, our brain keeps our bodies paralyzed. In this stage, only our closed eyes move rapidly from side to side – ergo the reason why this phase of sleep got its name. The more we sleep, the more time goes into different NREM and REM phases, and it is the second and third change of phases that are the deepest sleep that brings the most benefits. Without REM phases, our immune systems, hormones, skin, memory, focus, and overall well-being would completely fall apart. In rare instances, especially seen in teenagers and children – the mechanism with which the brain keeps our bodies paralyzed during REM fails – and in those cases, we have a condition known as sleep walking. This condition usually resolves after adolescence. If you happen to wake up in the middle of a REM phase – you usually wake up tired and irritated. Without being able to predict the phase, it is important to sleep at least 7-9 hours for the age group of adults, and 8-9 hours in the case of teenagers – to allow our brain to move between at least three REM phases during sleep. And that is how we sleep and why the process of sleeping is life-changing and life-sustaining for all human beings on our planet.
Goran Stevanovski MD, MA
