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Circadian Rhythm and Body Clocks – How Do They Affect Sleep?
Linda May-Zhang, PhD


I pulled an all nighter a few nights ago and I can’t seem to catch up!

I am happy to be home but my brain is still on Italy time!

Taking three nightshifts in a row have really messed up my internal clock!

All these scenarios relate to circadian rhythm and often coincide with the concept of sleep patterns. Circadian rhythm encompasses a lot more than sleep – they encompass all physical, mental, and behavioral changes that follow a daily cycle. Most living things (animals, plants or even tiny microbes) have circadian rhythms, which follow both natural cues that the organism’s body makes and environmental cues, such as daylight and night cycles. In this article, we dive a bit deeper into understanding what exactly circadian rhythm is and how does it govern sleep.

Where do our natural circadian rhythms come from?

Clocks. Yes, that’s right. Every tissue and organ in our body have their own biological clocks. Clocks are innate timing devices that produce circadian rhythm. All clocks in our body are coordinated by the master clock located in the brain, which receives input from our eyes.

During the day, light causes the master clock to signal for alertness and wakefulness. At night, the master clock signals for the production of melatonin, a hormone that promotes sleep. The master clock works all night to keep us asleep.

Through environmental cues (light versus dark) and our body clocks, our circadian rhythm aligns our sleep and wakefulness with night and day. This creates a cycle of restorative rest that enables daytime activity. Any changes in light-dark cycles can change our biological clocks which in turn changes our circadian rhythm.

What happens when our circadian rhythm is off?

When circadian rhythm is thrown off, sleep is naturally thrown off. Without proper signaling from the body clocks, a person can struggle to fall asleep, wake up during the night or too early in the morning, or have decreased sleep quality. As a result, the person has excessive daytime sleepiness and exhaustion.

Because the clocks in every organ and tissue of your body are disrupted, those organ functions are also affected. Constant disruption of circadian rhythm results is linked to many chronic health conditions, including diabetes, depression, obesity, cancer, cardiovascular dysfunction, immune dysregulation, sleep disorders, bipolar disorder and reproductive problems.

How to maintain a healthy circadian rhythm

Here are some healthy sleep tips that can help train our bodies to adapt to a better cycle.

  • Follow a consistent sleep schedule. Set a consistent wake-up time and make sure to get enough sleep. Varying your bedtime or wake-up time can hinder your body’s ability to adopt a stable circadian rhythm.
  • Seek out natural sunlight, especially early in the day. Natural light helps reinforce the strongest circadian cue.
  • Avoid stimulants like caffeine, especially too late during the day. This can throw off the natural balance between sleep and wakefulness. The half-life of caffeine is 5 hours, which means it takes on average 5 hours for the caffeine levels in your body to drop by half.
  • Limit light exposure before bed. Artificial light, particularly blue light from computer or TV screens, can interfere with circadian rhythm.
  • Consider eating foods or taking a supplement containing Melatonin. Melatonin is a natural hormone produced by the pineal gland in the brain responsible for regulating sleep. Melatonin plays an important role in your circadian rhythm.

For more sleep tips, visit our other blog entry. These steps to improve sleep can be important for supporting a healthy circadian rhythm. If you have persistent sleeping problems, daytime drowsiness or a problematic sleep schedule, it is best to discuss with your doctor to figure out the cause and appropriate treatment regimen.

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