The Circadian Rhythm: An Anticipatory System Essential to Health
“As a shift worker, I aim for this blog to be an absolute “light bulb” moment for you. I want this to help you understand more why shift work impacts our health in such a drastic way and as you read through it you identify areas that you can improve in your own life to support your biological health.
This is a really important topic to understand properly.”– Roger Sutherland, A Healthy Shift
Understanding the intricate mechanisms of the human body is essential for optimising health and wellbeing, particularly for those navigating the challenges of shift work. One such fundamental mechanism is the circadian rhythm. Contrary to popular belief, the circadian rhythm is not merely a reactive system that responds to environmental cues. Instead, it is an anticipatory system, finely tuned to predict and prepare the body for regular changes in the environment. Recognising and maintaining the synchronisation of this internal clock is paramount for overall health, especially for shift workers whose schedules often clash with natural rhythms.
The Nature of Circadian Rhythms
Circadian rhythms are roughly 24-hour cycles in the biochemical, physiological, and behavioural processes of all living organisms. They are driven by an internal time-keeping system known as the circadian clock, which is located in the suprachiasmatic nucleus (SCN) of the hypothalamus in the brain. This master clock coordinates with peripheral clocks in various organs and tissues, ensuring that the body's functions are harmonised. Imagine the conductor conducting an orchestra if you would. The conductor unifies all the performers by listening to the orchestra and setting the tempo and beat. So does your biological master clock, doing its best to keep all the peripheral clocks in beat with each other.
The term "circadian" derives from the Latin words "circa" (around) and "diem" (day), reflecting the near-24-hour cycle of these rhythms. What sets circadian rhythms apart from simple reactive systems is their predictive nature. They anticipate environmental changes—such as light and dark cycles—and prepare the body for upcoming events rather than merely responding to them after they occur.
The Anticipatory Role of the Circadian Rhythm
1. Hormonal Regulation:
Hormone secretion is a prime example of the circadian rhythm's anticipatory role. Cortisol, often referred to as the "stress hormone," peaks in the early morning to prepare the body for the day ahead, enhancing alertness and energy levels. Conversely, melatonin, the "sleep hormone," begins to rise in the evening, signaling the body to wind down and prepare for sleep.
2. Metabolic Processes:
The circadian rhythm regulates metabolism by anticipating feeding times. For instance, insulin sensitivity is higher during the the earlier part of the day when food intake is expected, optimising glucose metabolism. Disruptions to this rhythm, such as irregular meal times, can lead to metabolic disorders like obesity and diabetes.
3. Body Temperature:
Core body temperature follows a circadian pattern, peaking during the day to support physical and mental activity and dropping at night to facilitate restful sleep. This temperature regulation is not a response to environmental temperature but rather a preparation for the body's needs.
The Importance of Synchronisation
Maintaining a synchronised circadian rhythm is crucial for health and well-being. Desynchronisation, often experienced by shift workers, can lead to a host of health issues, including sleep disorders, cardiovascular diseases, impaired cognitive function and even cancers. Here’s why keeping the circadian rhythm synchronised matters:
1. Sleep Quality and Mental Health
A well-synchronised circadian rhythm ensures high-quality sleep by aligning the sleep-wake cycle with the body's natural melatonin production. This alignment is critical for mental health, as inadequate or poor-quality sleep can lead to mood disorders, anxiety, and depression.
2. Physical Health
Circadian synchronisation plays a vital role in maintaining cardiovascular health. Research has shown that disruptions to the circadian rhythm can lead to increased blood pressure, inflammation, and a higher risk of heart disease. Keeping the internal clock aligned with environmental cues helps regulate blood pressure and reduce the risk of cardiovascular issues.
3. Metabolic Health
Synchronising meal times with the circadian rhythm enhances metabolic efficiency. Eating at irregular times can disrupt insulin sensitivity and glucose metabolism, leading to metabolic syndrome, obesity, and type 2 diabetes. Consistent eating patterns aligned with the body's anticipatory mechanisms support better metabolic health.
4. Cognitive Function
Cognitive performance is closely tied to the circadian rhythm. Tasks requiring attention, memory, and executive function are performed best when the circadian rhythm is aligned with natural light-dark cycles. Shift workers often experience a decline in cognitive performance due to desynchronisation, impacting their productivity and safety.
Strategies for Maintaining Synchronisation
For shift workers and others with irregular schedules, maintaining circadian synchronisation can be challenging but is not impossible. Here are some strategies to support a well-synchronised circadian rhythm:
1. Light Exposure:
Exposure to natural light during the day and minimising exposure to artificial light at night helps regulate the circadian rhythm. Using blue light filters on devices and maintaining a dark sleep environment can enhance melatonin production and improve sleep quality.
2. Consistent Sleep Schedule:
Attempt to keep a regular sleep schedule, even on days off. Consistency in sleep timing helps stabilise the circadian rhythm and improves overall sleep quality.
3. Timed Meals:
Aligning meal times with natural circadian cues supports metabolic health. Avoid eating large meals late at night and try to have regular meal times throughout the day.
4. Physical Activity:
Regular physical activity, especially when performed in daylight, can reinforce circadian rhythms. Exercise can help regulate sleep patterns and improve overall health.
5. Relaxation Techniques:
Stress management through relaxation techniques such as mindfulness, meditation, and deep breathing can reduce the negative impact of circadian disruption. Lower stress levels support better sleep and overall circadian alignment.
Morning Larks and Night Owls
We refer to the people who go to bed early and rise early, bright-eyed and ready to go, as “morning larks.” Conversely, we assign people who go to sleep and rise later as night owls.
There is an argument in science emerging, that perhaps night owls are just more sensitive to light. Could this be the case? What we do know is that night owls are more prone to obesity.
Research conducted [1] on a group of healthy individuals with no sleep disorders or regular sleep timing were taken on a camping expedition in the mountains with no artificial light exposure at all.
It was noted that all participants fell asleep and woke within 30 minutes of each other.
We are ignoring the biological impact of light pollution these days and artificial light, particularly blue rich light, is ruining our biological clocks and impacting on our metabolic health in a much more drastic way than we realise.
We also now know that light cues are the predominant driver of circadian mechanisms, so much so that when we do not sleep in accordance to the anticipated circadian clock and we don’t embrace light cues in accordance to human physiology, we increase the risks for metabolic diseases like cancer.
Conclusion
Understanding the anticipatory nature of the circadian rhythm and its importance for health is crucial, particularly for shift workers who face unique challenges in maintaining synchronisation. By recognising the predictive role of this internal clock and adopting strategies to keep it aligned with environmental cues, individuals can enhance their sleep quality, mental and physical health, and overall well-being. Embracing the power of the circadian rhythm is not just about surviving shift work but thriving in all aspects of life.
About Roger Sutherland
As a coach and advocate for shift workers, my goal is to provide practical, evidence-based strategies that empower individuals to thrive in their roles. By understanding and addressing the challenges of shift work sleep disorder, shift workers can achieve better health outcomes and lead more fulfilling lives both on and off the job.
Note:
I also run Nutrition, Health & Wellbeing Seminars for shift working environments.
REFERENCE:
1. Stothard, Ellen R et al. “Circadian Entrainment to the Natural Light-Dark Cycle across Seasons and the Weekend.” Current biology : CB vol. 27,4 (2017): 508-513. doi:10.1016/j.cub.2016.12.041
