By Siha Hoque
A relatively large segment of medical problems are caused by unnatural changes to the environmental pattern our bodies have evolved to exist in harmony with - a key example of which is our optimum levels of sleep being incompatible with our daily routines. This results in somewhat harmful alterations stemming from our lifestyles and regular activities that can cause negative long term impacts on our health, which we may view as mere minor discomforts in our lives.
Sleep is something that is difficult for many of us in our society. Some of us get too little, others too much and there are a myriad of more specific issues one may face when sleeping. This can be caused by careers, school, living conditions or inherited disorders.
Our bodies, and those of other animals, plants and even microbes, are controlled by biological rhythms - which we normally refer to in our lives as our ‘bodies’ clocks’. These usually are twenty-four hour long patterns of physical and behavioural adjustments guiding the specific cycles in the body, and the study of these rhythms are called chronobiology. Biological rhythms correlate with our environment and have evolved in response to it - they are managed by our biological clocks, which are made up of protein molecules that interact with each other throughout the body, in almost every cell or tissue. They offer a series of timings for processes our body naturally abides to. The majority of these are kept in sync by a group of nerve cells in the brain, known as the suprachiasmatic nucleus (SCN) or ‘master clock’.
An example of one of the most significant biological rhythms in our bodies include the sleep/wake cycle - or circadian rhythm. ‘Circadian’ stems from the Latin for ‘around’ - ‘circa’ - and the word for ‘day’ - ‘diem. ’ This cycle influences factors such as the different hormones being released, our digestive system’s daily progress, our overall body temperature and the times we sleep and wake.
Almost all of one’s individual biological rhythms develop when they are a newborn - before birth there are barely any of the necessary external factors a being needs to be exposed to for this to occur. At only a few months of age, hormones such as melatonin (in control of drowsiness) and cortisol (responsible for stress) start to be produced in humans and one of the first features of a circadian rhythm to develop is a series of mild body temperature peaks and dips throughout sleep. Prehistoric creatures developed biological rhythms simultaneously to the Earth geologically evolving; adapting to the external stimuli they were surrounded by so they could grow to predict the events of the next few hours and have their bodies be best suited for those moments too. They also provided longer term benefits, such as being able to anticipate changes in radiation levels and food availability. For instance nocturnal animals of prey started being more relaxed and restful in the day, yet more vigilant at night.
Fruit flies also have a circadian rhythm, their body’s clock governed by a specific gene - the period gene - which was identified by researchers Jeffrey C. Hall, Michael Rosbash, and Michael W. Young, for which they won the 2017 Nobel Prize in Physiology and Medicine. They studied fruit flies and their discoveries show that this gene produces a protein which accumulates in cells during the night and degrades in the daytime. This applies to humans as well, and this gene and its process has an effect on when someone sleeps as well as their cognitive abilities.
The circadian rhythm is specific to our alertness in the day and tiredness at night. This cycle is most responsive to light, and even specific types of it. The SCN, in the brain, is located above the optic nerves (nerves carrying visual messages from the eyes to the brain), and can regulate the levels of melatonin produced. When you see low levels of light intensity for prolonged amounts of time, the SCN recognises these signals from the optic nerves, and sends on signals to increase the levels of melatonin being produced, therefore making you sleepier.
See above: Stages of the sleep cycle.
The sleep/wake cycle regulates our rest and periods of activity throughout a 24 hour period. However, sleep itself is split into separate stages, each with their own traits that help refresh and develop the mind and body. When the average person sleeps for approximately ninety minutes, they complete four stages that form one cycle of sleep. These four stages are: N1, N2, N3 and REM. N1 is also known as the first non-rapid eye movement sleep stage, usually lasting a maximum of ten minutes. It typically involves the body slowly falling into a very light sleep, and the brain’s activity slightly slows down.
The second stage - N2 - is a longer period of time, usually half one full cycle of sleep, ranging from ten to thirty minutes. If someone stays asleep for multiple sleep cycles, which most people normally do at night, this stage gets longer successively. The body relaxes and it is harder to wake someone from this stage due to lowering brain activity, albeit occasional spikes in which, that help the person sleep through external disturbances. Breathing and heart rate slow down, the overall body temperature drops and muscles significantly relax. It is an essential part of sleep as it can aid memory consolidation.
Deep sleep, or N3, is essentially a more intense version of the second stage; muscles, heart and breathing rate all decrease further. The brain in this stage of sleep maintains a pattern of delta waves, which are the slowest identified brain waves in human beings. However despite that, this stage of sleep has been seen to help people develop their skills for insightful thinking and creativity. Deep sleep additionally aids growth and repair, as well as strengthening the immune system. The duration of this stage decreases with each cycle in one night of sleep, but is typically twenty to forty minutes long.
The final stage of sleep, REM (rapid-eye movement) makes up about 25% of the total amount of sleep adults get on average, and it is required for healthy learning skills and creativity. The principal characteristics of this stage are a sharp increase in brain activity, resulting in realistic and vivid dreams which are most common here. Muscles are temporarily paralysed in a state known as atonia, excluding the eyes and those necessary for comfortable breathing. Although remaining closed, the eyes can often be seen to be moving a lot, giving this stage of sleep its name.
Circadian rhythm is often disrupted by light levels. The specific type of light has distinct effects on it, blue light during the night being the most harmful. Its brightness can send such strong signals to the suprachiasmatic nucleus that the production of melatonin is suppressed for long amounts of time, even for minutes after removing the source of blue light. On the other hand, dim red light has no effect on circadian rhythm, making it ideal for lamps. Naturally, during the day the sun maintains shorter wavelengths that gradually lengthen approaching sunset, and the colour blue has far shorter wavelengths than the colour red. Travelling to a place with a change in time zones can also cause difficulty maintaining an ideal energy level throughout the day with the body being used to releasing melatonin at a certain time each day, even if it is still bright outside. These are all experiences that many people, even teenagers and children, face often on a regular basis, essentially resulting in mild chaos within their systems.
See above: Wavelengths of blue visible light vs red visible light.
However, what may begin as a few nights of disrupted sleep can eventually result in circadian rhythm disorders. One of which is known as ‘Non-24-hour sleep-wake rhythm disorder’. The circadian rhythm here is delayed and doesn’t align with real time. It can result in interference with day to day activities, for example, feeling incredibly fatigued during the daytime in the middle of a regular activity due to untimely drowsiness. Additionally, it can also cause someone to struggle with going to sleep at night: insomnia. This in turn results in issues with memory and decision-making skills. Every few weeks, with Non-24-hour sleep-wake rhythm disorder, one may have significantly less symptoms due to eventually aligning with a natural healthy cycle - yet this does not last long as the delay continues.
Another serious circadian rhythm disorder is ‘Irregular sleep-wake rhythm disorder’. This involves sleeping in short bursts throughout a 24 hour period rather than one prolonged amount of time at night. This causes the SCN to lose its balanced timings of when to suppress and when to release melatonin, and also often prevents someone from achieving all four stages of a healthy sleep cycle, which is potentially very damaging for one's cardiac and cognitive health.
Shift Work Disorder is a more common circadian rhythm disruption amongst those who work at night, often healthcare staff or security guards. As stated earlier, in response to low light intensity levels, the SCN releases melatonin, which makes someone tired. Those suffering from Shift Work Disorder may experience extreme exhaustion during their work due to it being at night and when they do have the opportunity to sleep in the day, the overall quality of it is poorer due to higher light intensity and therefore lower levels of melatonin.
In conclusion, our bodies have evolved to work in parallel with our natural environment, and as technology and the need for night time jobs rise, so does one of the largest sources of our internal chaos: the disruption of Circadian rhythm - which is perhaps inevitable.
Add comment
Comments