The clock that makes us tick

One of the wonders of the human physiology is the circadian rythm. Often described as an internal clock which regulates our sleep and wake cycle, the circadian rhythm is in-fact the mechanism which keeps us moving.

The circadian rhythm is based on the day- night principle and governed by light and darkness. There are two types of clocks that our systems use , the biological clocks and the master clock1. Our body has a number of biological clocks located in the different cells and tissues these are responsible for regulating the circadian rythm. The master clock is the "main clock" located in the brain it controls all the biological clocks in the system.

The circadian rhythm is responsible for a number of body and system functions. It is responsible for sleep/ wake patterns, regulating hormone production and release, mantainance of metabolic processes like digestion, body temperature among many others 2. such disorders affecting the circadian rhythm. Research has found relationships between disruptions of the circadian rhythm' and glucose metabolism3.

Psychological impacts of circadian dysfunction include, mental disorders particularly neurodevelopmental, cognitive , mood, and aging-related mental disorders4. Interesting to note disruption of circadian rhythm patterns in pregnancy have been proven to impact the development of the progeny5. This highlights the importance of studying the circadian rhythm and how best it can be mantained. Research has proven that disturbance can result in mood disorders such as depression, anxiety, bipolar , and seasonal affective disorder6.

A number of factors affect the circadian rhythm. First and foremost is light. The circadian rhythm is regulated by the light- darkness cycle. It works based on the natural light system 7. Light activates certain receptors in the body and creates alertness . As such during the day the circadian rhythm signals for the body to be awake and to work. When it becomes dark the body is prepared for rest or sleep through the secretion of melatonin a sleep hormone.

Exposure to artificial light impacts the rhythm negatively as does exposure to light at least 2hours before sleep time. Melatonin production is increased when it is dark, as such when there is light the brain is confused as to what time of the day it is. Increased screen time at night also affects the sleep-wake cycle (this will be discussed in depth in a follow up article on sleep disorders).This results in sleep disturbances.

Jet lag and shift work is also a factor that affects the internal clock. Jet lag refers to migration to a different time zone or oversleeping and overworking which is referred to as social jet lag. This also confuses the brain and alters the central clock or main clock . When individuals move to a different time zone the circadian rhythm has to adjust to the new schedule. Similarly for individuals who have shifts , tbe circardian rhythm struggles to maintain a schedule.

Symptoms of circadian rhythm sleep disorders are not limited to the ones listed ,Insomnia (difficulty falling asleep or staying asleep),excessive daytime sleepiness,difficulty waking up in the morning,sleep loss,depression,stress in relationships,poor work/school performance , irritability, mood swings and inability to meet social obligations.

The importance of maintaining the circadian rhythm in good health cannot be over emphasized. Its impact on physical, social and mental health cannot be underestimated. As such regularity in sleep, eating among many other behaviors is key in maintaining good sleep-wake cycle. One of my favorite authors says: "If the youth would form habits of regularity and order, they would improve in health, in spirits, in memory, and in disposition." Ellen G White, Book Child Guidance page 112

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1. https://nigms.nih.gov/education/fact-sheets/Pages/circadian-rhythms.aspx

2. https://www.ncbi.nlm.nih.gov/books/NBK519507/

3. https://www.levelshealth.com/blog/how-circadian-rhythm-impacts-metabolic-health

4. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9283542/

5. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7156466/

6. https://www.health.harvard.edu/blog/why-your-sleep-and-wake-cycles-affect-your-mood-2020051319792

7. https://www.cdc.gov/niosh/emres/longhourstraining/light.html