Our body’s circadian rhythms help us transition throughout the day in a way that’s efficient and predictable.
They’re important but also easily disrupted. A number of factors can throw our circadian rhythms off, including the bright phone screens we often stare at while doomscrolling at night. And when that happens our sleep — and health — can suffer.
Let's get a better understanding of our circadian rhythms and what we can do to reset them when they're thrown out of alignment.
What Is a Circadian Rhythm?
Circadian rhythms are physical, mental, and behavioral changes that happen in a roughly 24-hour cycle.
Many, many years ago, humans evolved in alignment with the environment in order to survive. Our bodies began responding to things like the rising and setting of the sun in order to anticipate changes in food availability, radiation, and temperature.
As a result, our modern-day circadian rhythms still respond primarily to light and dark and continue to affect important functions like temperature, blood pressure, mental alertness, hormone levels, and sleep.
Circadian rhythms are created by specific molecules (proteins) interacting with cells throughout the body. Our genes make up the molecular components that create our biological clocks that dictate our circadian rhythms.
While we often refer to one, singular “circadian rhythm,” there are actually several circadian rhythms in the body, with the most noticeable being the sleep-wake cycle.
How Does a Circadian Rhythm Work?
The truth is: We’re sensitive creatures, and that’s a good thing!
Our circadian rhythms work by responding to slight changes in the environment and within ourselves. These changes can be so subtle that we're oblivious to them. But our internal operating system still processes the changes and alerts our cells to adjust accordingly.
You can think of your many circadian rhythms like gears that are all connected and causing each other to turn. Governing these gears is a master clock that keeps them running together.
This master clock — aka the suprachiasmatic nucleus, or SCN — is made up of 20,000 nerve cells. The SCN lives in the hypothalamus portion of our brain and receives input from our eyes — particularly light.
Internally, the two most important genes in guiding our circadian rhythms are the "period” and “cryptochrome” genes, which signal certain proteins to build up in the nuclei of our cells at night and lessen during the day. Externally, our circadian rhythms are also guided by natural light, temperature, air pressure, and other factors.
When our circadian rhythms are working properly, they help us achieve regular, restful nights of sleep. And when our circadian rhythms are out of whack, they can have a detrimental impact on how we feel and function. When that happens, these natural rhythms, which generally run smoothly and without any effort on our part, require a little help to get back on track.
How Does Circadian Rhythm Affect Sleep?
Our sleep-wake cycle is the most noticeable of our circadian rhythms.
Here’s how it works: When our SCN detects darkness, it tells the brain to produce more melatonin, which makes us sleepy. In the morning, when the SCN detects light, it tells the brain to slow the production of melatonin so we can wake up more easily
Because of this, our bodies generally know when it’s time to wake up and when it’s time to go to sleep for optimal functioning. Understanding this natural cycle can go a long way in helping us sleep better without resorting to unpleasant interventions like addictive sleeping pills and jarring alarms.
What Throws Your Circadian Rhythm Out of Whack?
Unfortunately, our modern lives have introduced many sensory inputs that can disrupt how our circadian rhythms affect sleep.
Artificial light, exposure to blue light from electronics, noisy streets, caffeine, stress, and alcohol can all disrupt our circadian rhythms. There are also internal factors that can cause circadian rhythm disruptions, including our genes and our hormones.
What Happens When Your Circadian Rhythm is Disrupted
Our bodies are impressive in their ability to respond to input from the environment in order to make life easier and more comfortable.
But when our natural sleep-wake process is disrupted, we can suffer from circadian rhythm sleep disorders. These disorders occur when our internal sleep-wake cycle is no longer aligned with the external dark-light cycle.
Jet lag and shift work are two common sleep disorders caused by that misalignment. But while these two circadian rhythm sleep disorders can be cured over a relatively short period of time, disruptions to our natural sleep-wake cycle can also lead to more persistent sleep disorders that cause headaches, nausea, irritability, and even depression.
How to Reset Your Circadian Rhythm
It’s not only frustrating when we can’t fall asleep easily or awaken naturally, it can also be detrimental to our health.
Luckily, a circadian rhythm reset is possible.
Keeping a regular sleep schedule is the best way to maintain or reset a healthy circadian rhythm. That’s because going to bed around the same time every night and waking up around the same time every day — even on the weekends — creates a sleep-wake cycle your body can learn to predict.
If you need to change your sleep schedule, regular exposure to sunlight first thing in the morning can help you acclimate. If that’s not possible, using a lightbox or a sunrise simulator can help establish a new pattern for your internal clock to follow.
Proper exercise can also help reset your circadian rhythm because it gets your body good and tired during the day so you’re ready to fall asleep without a problem at night.
Caffeine is a popular option for helping us wake up each morning — and most people regularly enjoy a morning dose of caffeine, even when their circadian rhythms are perfectly aligned with their sleep cycles. But caffeine also wears off and can impact our body’s natural ability to become alert if we rely on it too heavily.
Those who regularly travel across time zones are familiar with the practice of forcing themselves to stay awake in order to reset their circadian rhythms. By staying up until dark, even if your body wants to hit the hay at 3 p.m., you can realign with the natural light-dark cycle.
The Bottom Line on Circadian Rhythms
Our circadian rhythms are usually capable of adjusting on their own. But the more we can align ourselves with the rising and setting of the sun by getting outside, getting exercise, and maintaining a regular sleep schedule, the less intervention is necessary.
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