The Biological Clock - Circadian Rhythm and Health

“Circadian Rhythm” is likely to make you think about your sleep cycle– you go to bed when it is dark, and you wake up when it is light. If you have ever pulled an all nighter, or even just had a bad night of sleep, you will likely have noticed an increase in energy the next morning even though you are not well rested. This burst of energy can be attributed to your Circadian Rhythm. Your Circadian Rhythm extends far beyond just your sleep and is impacted by the foods you consume, stress, physical activity, temperature, and even your social environment. In this article, an overview of the body’s biological clock, the Circadian Rhythm, will be detailed.

The Circadian Rhythm, according to the National Institute of General Medical Sciences, is  “the physical, mental, and behavioral changes an organism experiences over a 24-hour cycle.” While influenced by lifestyle factors, as mentioned previously, in addition to genetics, the Circadian Rhythm influences hormone release, appetite and digestion, temperature, and most notably and well known, sleep patterns. One of the best ways to view the effect, and modulation, of the Circadian Rhythm is through the paradigm of Melatonin. Commonly used as a sleep aid (and rarely taken in proper doses) Melatonin is a hormone that is naturally produced by the body and is released at night in order to prompt sleep. While generally released at the same time every night, Melatonin release can be inhibited by light. This is the reason that it is recommended to keep a low light environment prior to bedtime and also to avoid electronic devices before bed. 

• Melatonin release is controlled by the suprachiasmatic nucleus (SCN), a large cluster of nerve cells. Based upon the amount of light that the brain receives, the SCN releases varying levels of Melatonin. In lower light environments, more melatonin is released leading to feelings of sleepiness.

In 2017, the Nobel Prize was won by researchers of the Circadian Rhythm Jeffery Hall, Michael Rosbash, and Michael Young. In their work, a protein present in fruit flies, PER, was observed to break down during the daytime but not during the nighttime. At night, another protein, TIM, binded to PER and prevented breakdown of the molecule. The PER-TIM complex then entered the nucleus, the command center of the cell, and no more PER was produced until daybreak when the PER-TIM complex broke down and the cycle repeated. Through this feedback loop, PER is in a way able to regulate its own synthesis.

If your Circadian Rhythm is out of sync, you are likely to experience sleepiness in the daytime, decreased alertness, and even problems with memory and decision making. If you have ever traveled across multiple time zones before, you will likely have felt some of these symptoms as your body has not yet adjusted the circadian rhythm to fit the light content of your new time zone environment. Disruption to an individual's Circadian Rhythm is not just problematic in that an individual will feel tired; sleep is extremely important for brain performance, mood, and health. The natural sleep cycle that accommodates the circadian rhythm is primarily where recovery, physical and mental, occurs, and is also when learning happens. Lack of sleep has been noted to increase the risk of many diseases and disorders ranging from physical ailments like heart disease and obesity to mental ailments like depression and anxiety.

From complex processes like the PER protein and light impacting the release of hormones in the body to the importance of sleep, the presence and importance of the Circadian Rhythm in every individual's day to day life can not be understated. Impacts of disruption of the Circadian Rhythm on sleep and mental land physical illnesses further underscore the importance of maintaining an environment that is conducive to maintaining your Circadian Rhythm.

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