Night Owl or Early Bird?: How to Work with Your Body's Natural Clock

If you’ve ever wondered why you feel more alive under the glow of the moon than the shine of the sun, I hate to break it to you, but your late-night tendencies could be linked to genetic mutations. Curious? Let’s dive into the science behind it.

What is the Circadian Rhythm?

Our bodies are tightly maintained by an internal timekeeper called the circadian rhythm, which regulates the physical, mental, and behavioral changes in an organism over a set timeframe, typically aligning with a 24-hour cycle. In mammals, including humans, this rhythm is controlled by the hypothalamic suprachiasmatic nucleus (SCN) and is heavily influenced by the surrounding light-dark environment. During daylight hours, the eyes process light and send signals to the brain to suppress melatonin production, helping you stay awake and alert. Conversely, as darkness falls, the absence of light cues the brain to release melatonin, promoting feelings of sleepiness (Fagiani et al., 2022).

Average teen circadian rhythm (NIGMS: 6611)

Molecular Regulations of the Circadian Rhythm

Other than external cues like light and darkness, the circadian rhythm is also heavily programmed by our genes. At the molecular level, the circadian clock is composed of multiple sets of transcription factors. Two key regulators of this system are the circadian locomotor output cycles kaput (CLOCK) and brain and muscle Arnt-like protein 1 (BMAL1). These transcription factors govern numerous downstream genes involved in intracellular processes, such as cell proliferation, DNA damage repair and response, angiogenesis, metabolic and redox balance, as well as inflammatory and immune responses. Notably, studies have shown that around 20% of the human genome is influenced by the circadian clock. Given its critical regulatory functions, disruptions in the circadian rhythm have been linked to the development of various diseases, including cancer, obesity, arthritis, and atherosclerosis (Fagiani et al., 2022; Ruan et al., 2021).

💡 Fun fact: as night shift work can disrupt the circadian rhythm, the International Agency for Research on Cancer (IARC) has classified night shift work as a “probable human carcinogen”.

The circadian rhythm is also influenced by additional mechanisms, such as membrane depolarization, intracellular calcium flux, and activation of cyclic AMP (cAMP) signaling (Fagiani et al., 2022)– though these will not be covered in detail here.

Circadian Rhythm in Sleep Disorders

The sleep-wake cycle within the circadian rhythm is regulated by genes encoding PERs (Period Circadian Regulator) and casein kinases which phosphorylate PER proteins. It was estimated that genetic differences account for 30% of sleep quality variance and 40% of sleep pattern variance (Liu et al., 2022). For instance, mutations in the PER2 and CSNK1D genes have been linked to familial advanced sleep phase disorder (ASPD), a condition characterized by early evening sleepiness (7-9 PM) and very early morning awakenings (2-4 AM). On the other hand, delayed sleep phase syndrome (DSPS), a condition where a person’s sleep schedule is delayed by two or more hours, has been associated with mutations in the PER3 gene, causing them to feel more alert late at night (Ruan et al., 2021).

Unfortunately, these mutations are not only associated with sleep disorders but are also linked to various diseases. Specifically, mutations in the PER1 gene have been shown to raise the risk of Alzheimer's and Parkinson's diseases, while mutations in PER3 have been connected to symptoms such as excitement, agitation, akathisia, dizziness, and tachycardia (Gršković & Korać, 2023).

What Can You Do?

Although gene mutations are permanent changes that can only be corrected through gene therapy, you can still improve your circadian rhythm health by adopting a healthy and active lifestyle. There are some things you may implement in your daily routine, such as:

• Set a consistent daily schedule. This includes going to bed and waking up at the same time every day, scheduling regular times for social activities and meals, and exercising around the same time each day.

• Get bright light exposure during the day, especially within the first two hours of waking to boost alertness and wakefulness of the body. It also helps to get direct sunlight or take a short walk shortly after waking up.

• Conversely, dim the lights and engage in more relaxing activities during the evening. This signals your body that it’s time to wind down and prepare to rest.

• Avoid light-emitting devices for at least one hour before bedtime. Exposure to light inhibits melatonin production, making it harder to feel sleepy (Yuan et al., 2020).

Understanding your circadian rhythm can make a big difference in how you feel and perform, whether you’re an early riser or a night owl. By aligning your lifestyle with your chronotype, you will sleep better, feel healthier, be more productive, and also minimize health risks. At the end of the day, it’s all about finding what works best for you and getting the most out of it.

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References

• Fagiani, F., Di Marino, D., Romagnoli, A., Travelli, C., Voltan, D., Di Cesare Mannelli, L., Racchi, M., Govoni, S., & Lanni, C. (2022). Molecular regulations of circadian rhythm and implications for physiology and diseases. Signal Transduction and Targeted Therapy, 7(1). https://doi.org/10.1038/s41392-022-00899-y

• Gršković, P., & Korać, P. (2023). Circadian gene variants in diseases. Genes, 14(9), 1703. https://doi.org/10.3390/genes14091703

• Liu, C., Tang, X., Gong, Z., Zeng, W., Hou, Q., & Lu, R. (2022). Circadian Rhythm Sleep Disorders: genetics, mechanisms, and Adverse Effects on health. Frontiers in Genetics, 13. https://doi.org/10.3389/fgene.2022.875342

• Ruan, W., Yuan, X., & Eltzschig, H. K. (2021). Circadian rhythm as a therapeutic target. Nature Reviews Drug Discovery, 20(4), 287–307. https://doi.org/10.1038/s41573-020-00109-w

• Yuan, R. K., Pardilla-Delgado, E., Zitting, K., & Duffy, J. F. (2020). Tips for circadian sleep health while working from home. PubMed. https://pubmed.ncbi.nlm.nih.gov/32341887/