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Odessa Chan

What if you just don’t Sleep? Sleep and the Circadian Rhythm

Sleep is a fundamental biological process that is essential for our well-being. It allows our bodies to rest, repair, and rejuvenate, ensuring optimal functioning. The circadian rhythm, our internal biological clock, plays a critical role in regulating our sleep-wake cycles. But what happens if we deliberately or inadvertently deprive ourselves of sleep? Let's delve into the fascinating world of sleep deprivation and its profound impact on our biology.


The Circadian Rhythm


The circadian rhythm, derived from the Latin words "circa" and "diem" meaning "around" and "day," respectively, follows a rough 24-hour cycle. It is governed by a complex interplay of biological processes and external cues, primarily the light-dark cycle. The suprachiasmatic nucleus (SCN), a cluster of cells in the hypothalamus, acts as the master regulator of this rhythm.


The Importance of Sleep



The circadian rhythm may be used to define when the best times to sleep and wake up are throughout each day. At around 9pm, the brain starts to secrete melatonin into the body. The melatonin hormone signals to the body that it is time to sleep and helps promote the onset of sleep. The melatonin secretion stops at 7:30am, signalling to the body that it is time to wake up and start the day.

However, whether we intentionally or unintentionally disrupt our sleep patterns, we ultimately disrupt the delicate balance of our circadian rhythm at least every now and then. The consequences are far-reaching, affecting various aspects of our biology.


One of the most notable effects of sleep deprivation is its impact on cognitive function. Sleep plays a crucial role in memory consolidation and learning. Without adequate sleep, our ability to focus, concentrate, and retain information is compromised. We become more forgetful and find it challenging to solve problems and think critically. Even simple tasks can become arduous and mentally draining.


Sleep deprivation also takes a toll on our emotional well-being. It disrupts the brain's emotional regulation centres, leading to mood swings, irritability, and increased susceptibility to stress, anxiety, and depression. The world can feel overwhelming, and our ability to cope with daily challenges diminishes.


From a biological perspective, sleep deprivation affects our immune system. During sleep, the body produces and releases cytokines, proteins that help combat infection and inflammation. Lack of sleep weakens the immune response, making us more vulnerable to illnesses and infections. Chronic sleep deprivation has been linked to an increased risk of conditions such as obesity, diabetes, and cardiovascular diseases.


Furthermore, sleep deprivation interferes with the regulation of hormones that control appetite and metabolism. It increases the production of ghrelin, a hormone that stimulates hunger, while suppressing leptin, a hormone that signals satiety. Consequently, sleep-deprived individuals are more prone to overeating and weight gain, which can lead to further health complications.


In addition to these biological effects, sleep deprivation impairs physical performance and coordination. Reaction times are delayed, motor skills are compromised, and accidents become more likely. The risk of workplace incidents or automobile accidents significantly increases when individuals are sleep-deprived.


Recognizing the detrimental effects of sleep deprivation underscores the importance of prioritising healthy sleep habits and respecting our circadian rhythm. Establishing a consistent sleep schedule, creating a conducive sleep environment, and practising good sleep hygiene are crucial steps towards ensuring adequate rest.


Improving our Circadian Rhythm

To optimise our circadian rhythm, exposure to natural light during the day and reduced exposure to bright lights, particularly blue light, in the evening are recommended. Blue light emitted by electronic devices can disrupt the production of melatonin, a hormone that helps regulate sleep. Establishing wind-down routines that promote relaxation before bedtime can also aid in preparing the body for a restful sleep.


In conclusion, sleep deprivation disrupts the delicate balance of our circadian rhythm with profound consequences on our biology. From impaired cognition and emotional well-being to compromised immune function and increased risk of chronic diseases, the effects of sleep deprivation are far-reaching. Understanding the importance of sleep and respecting our biological need for rest can lead to improved overall health and well-being. So, it is important for all to remember to prioritise sleep, nurture one’s circadian rhythm, and give one’s body the rest it deserves.


Works Cited

Epstein, L. and MD, H. (2020). Why your sleep and wake cycles affect your mood - 

Harvard Health. [online] Harvard Health. Available at: https://www.health.harvard.edu/blog/why-your-sleep-and-wake-cycles-affect-your-mood-2020051319792 [Accessed 8 Jan. 2024].


Hope, P. (2020). What is Circadian Rhythm? - Disorders, Symptoms, Health 

Effects. [online] Prescription Hope. Available at: 


Reddy, S., Reddy, V. and Sharma, S. (2023). Physiology, Circadian Rhythm. [online] 

Nih.gov. Available at: 

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