How Our Body's Internal Clock, or Circadian Rhythm, Affects Various Aspects of Health

How Our Body's Internal Clock, or Circadian Rhythm, Affects Various Aspects of Health

As the sun begins its descent, many of us find ourselves feeling weary, a subtle sign that our internal clocks are ticking in harmony with the natural world. This synchrony is orchestrated by our circadian rhythms, 24-hour cycles that govern essential bodily functions. While most of us associate circadian rhythms with the sleep-wake cycle, their influence extends far beyond, impacting our overall health and well-being. In this comprehensive guide, we delve into the intricate workings of circadian rhythms, exploring their role in sleep, health, and ways to maintain a healthy balance.

Understanding Circadian Rhythms:

Circadian rhythms, derived from the Latin phrase "circa diem" meaning "around a day," are the body's internal clockwork, orchestrating vital processes throughout a 24-hour cycle. A central player in this symphony is the sleep-wake cycle, finely tuned by environmental signals, primarily light. The suprachiasmatic nucleus (SCN) in the brain's hypothalamus acts as the conductor, sending signals to synchronise circadian rhythms in various bodily systems. When aligned, circadian rhythms promote restorative sleep, but disruptions can lead to sleep disorders and impact broader aspects of health.

The Intricacies of Circadian Rhythm:

Circadian rhythms extend beyond sleep, coordinating mental and physical systems throughout the body. From the digestive system producing proteins in sync with meal times to the endocrine system regulating hormones for energy expenditure, these rhythms play a vital role in overall health. Light, the most powerful external cue, influences the SCN, ensuring circadian rhythms align with the day-night cycle. The interconnectedness of these rhythms highlights their significance in maintaining holistic well-being.

Circadian Rhythm vs. Biological Clock:

While the terms circadian rhythm and biological clock are often used interchangeably, it's essential to recognise their nuanced relationship. Biological clocks regulate various bodily processes, with circadian rhythms being a specific manifestation. Not all biological clocks operate on a 24-hour cycle, as seen in plants adapting to changing seasons. Understanding this distinction provides insight into the diverse ways organisms synchronise with their environments.

The Sleep-Wake Cycle and Circadian Rhythm:

The discussion around circadian rhythm often revolves around its influence on sleep. The sleep-wake cycle stands out as a prominent and crucial manifestation of circadian rhythms' significance.

Throughout the day, exposure to light prompts the internal clock to send signals that foster alertness, aiding in maintaining wakefulness and activity. As evening approaches, the internal clock triggers the release of melatonin, a sleep-promoting hormone, and continues sending signals to facilitate a sustained and restful night's sleep.

In this manner, circadian rhythms synchronise sleep and wakefulness with the natural progression of day and night, establishing a consistent pattern of rejuvenating rest that supports increased daytime productivity.

Beyond Sleep- Circadian Rhythms and Health:

Beyond its impact on the sleep-wake cycle, circadian rhythm plays a pivotal role in nearly every facet of the body's functioning.

Ongoing research continues to unveil the intricate connections between circadian rhythms and various physiological processes. Evidence has established links between circadian rhythms and metabolic functions, influencing elements such as blood sugar regulation and cholesterol levels. Furthermore, circadian rhythms exert a notable influence on mental health, influencing the susceptibility to psychiatric conditions like depression and bipolar disorder and contributing to the potential development of neurodegenerative diseases like dementia.

Significant indications also suggest that circadian rhythms play a crucial role in shaping the immune system and processes related to DNA repair, crucial for preventing cancer. Early-stage research hints at the potential for circadian cycles to impact the efficacy of anti-cancer drugs, offering the possibility of more strategically employing new medications in cancer treatment.

Consequences of Circadian Rhythm Disruptions:

When the circadian rhythm is disrupted, the body's various systems experience suboptimal functioning. An unsettled sleep-wake circadian rhythm can lead to significant sleep-related issues. In the absence of proper signalling from the body's internal clock, individuals may struggle to initiate sleep, experience more frequent awakenings throughout the night, or find it challenging to sleep as late into the morning as desired. This disruption can result in a reduction in total sleep duration, and a disturbed circadian rhythm may contribute to sleep that is shallower, fragmented, and of lower quality.

Furthermore, research has suggested that disruptions in circadian rhythm may play a role in conditions such as obstructive sleep apnea (OSA), a sleep disorder characterised by repeated interruptions in breathing. OSA diminishes oxygen levels in the body and leads to numerous disturbances in sleep throughout the night.

Collectively, an out-of-sync circadian rhythm can adversely impact sleep in various ways, heightening the risk of conditions like insomnia and excessive daytime sleepiness. Considering the vital role of sleep in both productivity and overall health, the consequences of a misaligned circadian rhythm can be substantial.

Types of Circadian Rhythm Disorders:

Sometimes, our body's internal clock, known as the circadian rhythm, can get messed up in the short or long term. Experts have pinpointed various types of sleep-wake disorders linked to these disruptions.

1. Jet Lag Disorder

  • Occurs when travelling across many time zones quickly.
  • Results in sleeping problems and fatigue until adapting to the new day-night cycle.
2. Shift Work Sleep Disorder
  • Caused by working night shifts, conflicting with natural daylight hours.
  • Leads to disruptions in the circadian rhythm, causing sleep-related issues.
3. Advanced Sleep Phase Disorder
  • People feel tired early in the evening and wake up very early.
  • Difficulty staying up later at night due to the body's internal clock.
4. Delayed Sleep-Wake Phase Syndrome
  • Associated with staying up late and sleeping in.
  • Possible causes include genetics, physical conditions, or individual behaviour.
5. Non-24-Hour Sleep-Wake Disorder
  • Primarily affects blind individuals.
  • The body follows a 24-hour cycle, but sleeping hours constantly shift without light cues.
6. Irregular Sleep-Wake Rhythm Disorder
  • No consistent sleep pattern, often related to brain conditions.
  • Seen in conditions like dementia or traumatic brain injury.

Circadian disruptions can stem from external factors like travel or work, causing misalignments with normal daylight hours. Others result from an inability to receive or process environmental cues that regulate the biological clock. Genetic factors may also be involved, and in some cases, the cause remains unknown.

Maintaining a Healthy Circadian Rhythm:

While complete control over circadian rhythms may be elusive, adopting healthy sleep habits can enhance their stability. Seeking exposure to natural light, following a consistent sleep schedule, engaging in regular exercise, and avoiding stimulants like caffeine are crucial steps. Additionally, creating a conducive sleep environment and consulting with a healthcare professional for persistent sleep issues are integral components of circadian rhythm management.


As we unravel the mysteries of circadian rhythms, it becomes evident that these internal cycles are the orchestrators of our well-being. From sleep to overall health, their influence is profound and interconnected. By understanding the intricate dance of circadian rhythms and adopting healthy sleep habits, we empower ourselves to navigate the challenges of a modern, fast-paced world while prioritising the foundation of our vitality—restorative sleep and a harmonious circadian rhythm.

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