Circadian Rhythm: Everything You Need to Know

Most of us hear about circadian rhythms only when we experience sleep issues. Indeed, the sleep-wake cycle is linked to our circadian rhythms, but there’s much more to the story.

To understand circadian rhythms, imagine your body is tied to a master clock that keeps all internal processes optimized for a 24-hour cycle.

The sleep-wake cycle is just one of the processes regulated by this master clock. If it’s off, a lot of processes are delayed, and your health may be affected. This explains, for instance, insomnia.

What Is the Circadian Rhythm?

The circadian rhythm meaning comes from the Latin “circa diem,” which translates as “around the day.” In other words, “circadian rhythm” means what happens in your body during 24 hours. All living things have such a rhythm, including plants and animals.

Our circadian rhythm is influenced by various external factors, the most important being light.

How Does the Circadian Rhythm Work?

The mental and physiological systems in our body are regulated by biological clocks, the eyes included. But they all receive orders from the master clock in the brain.

This master clock is in an area of the brain known as the hypothalamus, in the suprachiasmatic nucleus (SCN).

Rather than shouting orders to the various organs under its control, the so-called clock genes in the brain send out chemical signals.

Circadian Rhythm Examples

When it gets dark, the master clock knows that it’s time to prepare for sleep. It orders the body to produce melatonin, the hormone that helps your body relax and fall asleep.

But when it registers light, the master clock knows it’s daytime and orders the production of hormones like cortisol, to keep you alert. This is why using screens late into the night can make it hard to fall asleep.

Another circadian rhythm example concerns digestion. Your body knows when you normally eat, so it prepares in advance by producing digestive enzymes to break down the food.

Metabolism and the mechanism regulating body temperature are also linked to circadian rhythms. Even our mental health is linked to circadian rhythms. Imbalances in our circadian rhythm, particularly in the sleep-wake cycle, are associated with an increased link of developing depression, bipolar disorder, or dementia.

More recently, research has found that problems with the circadian rhythm may cause eye health issues resulting from poor sleep.

What Factors Disrupt the Circadian Rhythm?

Factors that influence the circadian rhythm can be both internal and external. Let’s take a closer look at the most important of them.

Working in Shifts

People working in shifts are faced with many problems as their circadian rhythm is seriously off-balance. This is most obvious when you first start out working in shifts and you force yourself to stay alert while the master clock keeps sending signals that it’s time to sleep. You can get used to this sort of life, but it will still affect your circadian rhythm.

Jet Lag

When you travel to a country in a different time zone, your circadian rhythm will be seriously impacted. Sticking to its 24-hour cycle, the master clock will tell the body to prepare for sleep even if it’s broad daylight outside.

The master clock will catch on to the light signals, but you can expect it to be lagging for a few days.

Screens and Other Artificial Light Sources

Screens emit artificial light, which can trick the circadian rhythm into thinking it’s earlier in the day than it actually is. Blue light can suppress the production of melatonin.   

Blindness

People who are blind miss out on the most important clue that regulates our circadian rhythm—light. The blind learn to adapt to the rhythm that regulates the activity of those around them, but they remain prone to sleep problems. Their sleep hours can shift back and forth by hours.

Stress

When you’re under a lot of pressure, your body produces lots of cortisol, the hormone that helps us cope with stress. Cortisol is also what helps stay alert, which explains the disruptions to the sleep-wake cycle.

Genetic Factors

Certain mutations or changes in the genes involved with the circadian rhythm can set off the biological clocks regulating activities in certain systems. More research is needed for us to better understand these genetic factors.

Advanced Sleep Phase Disorder

This is a rare condition and that tends to affect mostly the elderly. People with advanced sleep disorder feel tired early in the evening and eventually go to sleep only to wake up very early the next day.

Delayed Sleep Phase Disorder

This type of disorder is associated with night owls, people who stay up very late and sleep till midmorning or until noon. Delayed sleep disorder is influenced by habits, but it can also be caused by internal factors.

Teenagers, for instance, may keep odd hours and sleep until noon if left to themselves. Hormonal changes likely contribute to this sleep disturbance.

Young woman sleeping during the day

How to Reset Your Circadian Rhythm

In many cases, disruptions to the circadian rhythm are caused by our lifestyle choices. Here are a few tips to help you reset your circadian rhythm.

Establish a Sleep Routine

If you have a sleep disorder, the first step is to go to bed at the same hour every night. It’s not as simple as brushing your teeth and turning off the light, though. You must allow some time for your body to relax and release melatonin.

Avoid Digital Screens

As we’ve seen, digital screens emit blue light which can mess up your internal clock. If you have trouble sleeping, stop checking your phone and turn off your computer at least one hour before your bedtime.

When you struggle with insomnia, the worst thing you can do is checking the hour on your phone as this confuses your brain even further.

Limit Alcohol and Coffee Consumption

For a good night’s sleep, it’s essential to limit your alcohol, caffeine, and nicotine consumption in the evening. These substances are all stimulants and can keep you alert when you should be drifting off to sleep.

For instance, it’s recommended to stop drinking coffee six hours before your set bedtime, so the body eliminates all traces of caffeine by that time.

Get Plenty of Sun and Exercise

To keep your body clock in sync, go out and enjoy the sunshine every day. Exposure to natural light enforces your circadian rhythm.

Also, 20 or 30 minutes of exercise help you consume energy and regulate your body clock. Don’t go to the gym in the evening as the endorphins released during physical exercise will keep you awake.

Avoid Naps

Even if you feel tired, it’s best to avoid quick afternoon naps. Yes, they might give you enough energy to get more stuff done late in the afternoon and the evening. But sleeping during the day offsets your circadian rhythm.

Takeaway

Disruptions in your circadian rhythm can affect your entire body as well as specific organs such as the eyes. To keep your eyes healthy, you want to try as much as possible not to offset your internal clock. Good sleep is crucial for healthy vision.