Beyond Sleep: How the Circadian Rhythm Influences Health and Disease

One of the most underestimated and overlooked components of health is sleep. Many people think that sleep is just a time for their bodies to rest, heal, and detoxify. While this is true, sleep also orchestrates a multitude of critical physiological processes that extend far beyond mere rest. Sleep can not only play a role in disease development and progression but it can also be harnessed in surprisingly impactful ways for health and healing. The key to understanding these effects lies in the circadian rhythm.

What is the Circadian Rhythm?

Have you ever wondered why you naturally feel sleepy at night and wake up refreshed in the morning? The answer lies in an instinctive cycle called the circadian rhythm. The circadian rhythm is an internal biological clock that regulates the timing of our sleep, as well as nearly all of our body’s physiological processes. In addition to regulating when we go to sleep and wake up, the circadian rhythm also coordinates the timing of hormone releases, body temperature, digestion, and other crucial functions to ensure our bodies operate at their full potential.

Here’s a general overview of how the circadian rhythm coordinates these functions throughout the day:

• In the morning—melatonin decreases, cortisol rises, and body temperature rises to kickstart metabolism and promote alertness.
• In the afternoon—energy levels peak, coordination improves, and cognitive function and physical performance are optimized.
• In the evening—melatonin rises, heart rate and body temperature lower to promote relaxation and prepare for sleep.

The circadian rhythm can be viewed as the conductor of an orchestra. Just as a conductor ensures that each musician plays their part at precisely the right moment to create harmonious music, the circadian rhythm coordinates the timing of the bodily functions, synchronizing them to work together seamlessly. Without this coordination, it’s like having an orchestra where each musician plays at their own pace, resulting in chaos instead of a symphony.

If our hormones were not released according to a rhythm, our bodies would release hormones randomly and haphazardly. One day, our brain might release melatonin at 11 AM, making us sleepy and unable to work, while the next day, it might release melatonin at 6 AM, right when we’re trying to wake up. This lack of synchronization would not only be uncomfortable but would significantly disrupt our daily activities.

Our bodies are attuned to a 24-hour cycle, influenced by the Earth’s rotation and the alternating periods of light and darkness. On average, humans need about 7 hours of sleep per night (1) . But this varies widely depending on factors like sex, age, and genetics. For example, women generally need more sleep than men, and teenagers need more sleep than adults (2, 3) . In addition, scientists have found a gene mutation called DEC2 that allows some individuals to function well on just 4 to 6 hours of sleep per night (4) . So, if you find that you need more or less sleep than others, don’t worry—it’s just how you’re wired. However, don’t mistake this natural wiring for an excuse to develop bad sleep habits, as we will discuss below.

What Disrupts the Circadian Rhythm?

Since we have evolved in sync with the Earth’s natural light-dark cycle, our eyes are highly responsive to light. Indeed, the eyes have sensors specifically designed to detect light and dark. When exposed to light (especially blue light), these sensors send signals to the brain that it’s daytime, which delays the production of melatonin. This is precisely why screen time before bed confuses the brain, subsequently disrupting the overall circadian rhythm.

However, screen time is not the only contributing factor to circadian rhythm disruption. Other factors include:

• Shift work: Working night shifts or irregular hours can confuse your internal clock, making it difficult to maintain a consistent sleep schedule. The constant switching between day and night shifts disrupts the natural circadian rhythm and can lead to sleep disorders and chronic fatigue.
• Jetlag: Traveling across time zones can throw off your circadian rhythm. Your body is still aligned with your home time zone, making it difficult to adjust to the new time zone. This misalignment can result in insomnia, daytime fatigue, and general malaise until your body adjusts.
• Caffeine: Consuming caffeine, especially later in the day, can interfere with your sleep. Caffeine blocks adenosine receptors in the brain, which helps keep you awake and alert. This can delay sleep onset and reduce sleep quality if consumed too close to bedtime.
• Sleep disorders: Conditions such as insomnia, sleep apnea, and restless leg; syndrome can disrupt your circadian rhythm by preventing you from maintaining a regular sleep schedule. These disorders often lead to fragmented sleep, reducing the overall quality and restorative power of your rest.

Circadian rhythm dysfunction is truly a modern-day phenomenon. In the past, humans went to bed when the sun went down and awoke when the sun rose. Without electricity, phones, or TVs, there were no artificial lights to keep them up late or distractions to interfere with their sleep patterns. Air travel didn’t exist, so jet lag wasn’t an issue either. The number of night shift jobs also became a more common phenomenon as technology continued to evolve, particularly following the Industrial Revolution. Unfortunately, now that circadian disruption is a normal part of our lives, we’re seeing a cascade of downstream health effects.

What are the Downstream Effects of Circadian Disruption?

When we sleep, our bodies carry out vital maintenance and repair processes, including repairing DNA damage that naturally occurs in our cells throughout the day. When our sleep is disrupted, our DNA repair is also disrupted (5). This makes our cells more susceptible to DNA damage, and the subsequent accumulation of damage can increase the risk of cells turning cancerous.

In addition, our immune system is highly in tune with our circadian rhythm. Our immune system is strongest during the day and weakest at night—our bodies are tuned this way because the majority of pathogens we’re exposed to are through food, and since we don’t eat at night, we theoretically need less protection at that time (6). Unfortunately, this means that when our circadian rhythm is disrupted, so is our immune system. Individuals who work the night shift, for example, have dramatically lower levels of Natural Killer (NK) cells compared to those who work in the day (NK cells are critical immune cells that target and kill cancer cells and other pathogens)(7). As another example, people with insomnia have measurably lower levels of key white blood cells compared to good sleepers (8).

As previously discussed, the circadian rhythm plays a crucial role in regulating our hormones. When this coordination is disrupted, it can lead to significant imbalances. Here are some of the hormones affected by circadian rhythm disturbances:

• Stress hormones: Cortisol, the “fight-or-flight” hormone, is an example of a stress hormone that is increased with circadian disruption. Higher levels of this hormone can suppress the immune system, increase blood sugar, and lead to weight gain.
• Insulin: Circadian disruption increases insulin levels, which contributes to insulin resistance, metabolic syndrome, and obesity (9).
• Growth hormone: Most growth hormone secretion occurs during deep sleep, and there is some evidence that circadian disruption decreases the levels of this critical hormone. In turn, this can interfere with growth and cell-repair processes (10).
• Leptin and Ghrelin: Leptin signals to the brain that you’re full, while ghrelin stimulates hunger. Sleep deprivation can reduce leptin levels and raise ghrelin levels, leading to increased hunger and potential weight gain (11).
• Melatonin: Light exposure at night suppresses melatonin production. This negatively impacts the body because, in addition to helping us fall asleep, melatonin also has antioxidant properties and helps protect DNA from damage.
• Cytokines: Inflammatory markers like TNF-α, interleukins, and C-reactive protein are significantly elevated in those with circadian imbalances, which subsequently contributes to chronic inflammation (12).

Proper sleep plays a critical role in the automatic daily detoxification routines of our bodies and minds. The extracellular matrix (ECM), the structural support that surrounds our cells, tissues, and organs, shuttles nutrients and removes waste products from them in a coordinated fashion in alignment with the circadian rhythm. While we sleep, the ECM releases all the accumulated cellular waste, ensuring their elimination. Chronic lack of sleep means that toxins progressively accumulate in our ECM spaces, increasing oxidative stress and affecting all physiological processes. It also affects the glymphatic system, the waste-clearing system in the brain and central nervous system, as well as disrupts the blood-brain barrier, allowing toxins and inflammatory molecules to enter the brain more easily, affecting both physical and mental health (13, 14).

As you can see, maintaining a consistent and healthy sleep pattern isn’t merely about waking up feeling refreshed; it holds significant importance in protecting our bodies from cancer and other chronic diseases. Misalignments in our circadian rhythm can lead to increased DNA damage, weakened immune responses, hormonal imbalances, and chronic inflammation—the list goes on and on. By acknowledging the profound influence of good sleep on our overall health, we can better appreciate the need to prioritize quality sleep, thereby contributing to a robust defense against the development of cancer and other chronic diseases.

How Can the Circadian Rhythm Be Harnessed for Health?

Aside from the value we get from a good night’s sleep, the circadian rhythm can actually be harnessed in unique ways to improve treatment outcomes. This was first discovered in the 1970s when researchers realized that people and animals responded differently to treatment depending on what time of day a specific therapy was administered (15). Subsequent research has seen the same phenomenon for all sorts of medications, treatments, and even surgeries.

These discoveries gave rise to chronotherapy—a treatment approach that optimizes the timing of medical interventions to align with an individual’s circadian rhythm. Chronotherapy is showing promising results for cancer in particular. In one study of advanced colorectal cancer patients, those who were administered chemotherapy in sync with their circadian rhythms saw a 50% increase in survival compared to standard administrations (16). The benefits extend beyond survival, too; in an analysis of 18 studies of chronotherapy, the majority of patients who received circadian-timed treatments experienced a decrease in drug toxicity (17).

Chronotherapy utilizes the tools we already have at our disposal but with a deeper understanding of when they can be most effective and least harmful. This approach underscores the core philosophy of integrative medicine—emphasizing personalized treatments that work in harmony with the body’s natural rhythms.

One of the most simple ways to harness the circadian rhythm is to ensure you get enough high-quality sleep. Here are some strategies to help achieve this:

• Maintain a Regular Sleep Schedule: Go to bed and wake up at the same time every day, even on weekends. This helps regulate and maintain the circadian rhythm.
• Limit Exposure to Blue Light Before Bed: Reduce screen time from devices like phones, tablets, and computers at least an hour before bedtime. Many devices have settings that reduce blue light emission, often called “night mode” or “blue light filter,” which can help mitigate this effect.
• Create a Restful Environment: Make your bedroom dark, quiet, and cool. Consider using earplugs or an eye mask, or play gentle, healing music. Additionally, some people prefer to sleep with their phones outside the room and turn off Wi-Fi and other electronics to decrease EMF exposure.
• Practice Relaxation Techniques: Engage in calming activities before bed, such as reading, taking a warm bath, meditating, praying, or practicing deep breathing exercises.
• Exercise Regularly: Regular physical activity can help you fall asleep faster and enjoy deeper sleep. However, avoid vigorous exercise close to bedtime.

By implementing these practices, you can better align your sleep patterns with your circadian rhythm, which is essential for optimizing the body’s healing processes and improving treatment outcomes. Ultimately, this contributes to a balanced treatment plan that not only targets the disease but also strengthens the body’s innate ability to heal, leading to better patient outcomes and an improved quality of life.

References-

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