What Is The Definition Of Circadian Rhythm (Body Clock)?

How To Maintain a Healthy Circadian Rhythm

The Master Clock

The master clock is what controls all of your body’s biological clocks, and it’s made up of 20,000 nerve cells that form a structure called the suprachiasmatic nucleus (SCN).⁴ The master clock syncs up all internal clocks.

This master clock is located in the hypothalamus, a part of the brain that controls many biological functions, like body temperature, thirst, and hunger. The system works by receiving information from our eyes like when it is light outside and when it is dark. Additionally, our body’s master clock is completely reliant and interwoven with the earth’s rotation.

Just as a refresher: Every 24 hours the earth rotates on its axis. When our part of the planet is facing the sun, that’s when we have daylight. When our part of the planet is facing away from the sun, it’s nighttime.

Our eyeballs, which are essentially an extended part of our brain, detect when it is light outside and when it is dark.⁵ This communication is sent directly to the master clock, which then lets all of the biological clocks in our body know what they should be up to, including whether it is time to be sleepy (it’s dark) or awake (it’s light).¹

Circadian Rhythm Disorders

As mentioned, your circadian rhythm is set by certain biological clocks. What if those clocks are running too slow or fast, though? What if those clocks take a trip from New York to Paris to Thailand in two weeks, and they don’t know what’s what?

This is where circadian rhythm disorders come in. Also called “sleep-wake cycle disorders,” this is when your body’s biological clocks are out of sync with your environment.⁶ Circadian rhythm disorders can be long-term, caused by things like aging, genes, or medical conditions. They can also be short-term, caused by things like jet lag or shift work.

1. Delayed Sleep-Wake Phase

A delayed sleep-wake phase disorder (DSWPD) is associated with people who refer to themselves as “night owls.” This is one of the most common circadian rhythm disorders and involves a delay in falling asleep.

Specifically, a person with this condition will have trouble falling asleep for two or more hours after a “normal” bedtime. (Usually, these people will fall asleep well after midnight.) This is because their body’s internal clock is sending alert signals, rather than “sleepy” signals, until late in the night.

These people will also usually have trouble waking up at an early hour in the morning because their bodies will not yet be producing those alert signals.

Interestingly, unless you have other sleep disorders like sleep apnea or insomnia, people with DSWPD tend to sleep well, in terms of duration and quality of sleep.⁷ The problem is the delay in getting to sleep, which makes it difficult to wake up for things like school or work.

2. Advanced Sleep-Wake Phase

They say the early bird gets the worm, and those with advanced sleep-wake phase disorder can certainly attest to this. The only problem is that people with an advanced sleep-wake phase disorder get tired early in the evening, and they’re often awake and staring at the ceiling before morning.⁶

There are some positives to being on this type of schedule. You can accomplish more by breakfast than most people do all day, but if you have a social engagement planned for the evening, you’re likely to feel tired, and your yawning could be mistaken for boredom.

If you find yourself on this type of schedule, avoid the temptation to take stimulants at night or sleeping pills at 3:00 a.m. Instead, think of ways you can use this to your advantage, perhaps even exploring a career that caters to this type of schedule, like medicine or fitness.

3. Irregular Sleep-Wake Rhythm

An irregular sleep-wake rhythm is much harder to adjust to than either a delayed or advanced one. This is because there’s no real pattern to it. Likely, the person has a weak internal clock, and so they get mixed messages from their body about when it’s time to feel drowsy or awake.

This might look like several short periods of sleep throughout the night or the need to take multiple naps throughout the day. You probably won’t feel rested after you sleep.⁶

As you can imagine, this makes work, school, relationships, and family life difficult.

4. Shift Work Sleep Disorder

Any working hours outside of the typical 9:00 a.m. to 5:00 p.m. schedule is considered shift work. While this could be something like 11:00 a.m. to 7:00 p.m., it’s often characterized as the “graveyard shift,” in which people are working overnight.

As you can imagine, this sort of schedule has a big impact on your circadian rhythm because you’re sleeping during daylight hours when your body naturally receives its wakefulness signals and working through the night when your body naturally wants to sleep. As a result, the health problems reported among shift workers are numerous and can include ulcers, heart disease, and pregnancy issues.⁸

Scientists are actively working on ways to make this less of a detriment to our health, but in the meantime, if you must live with this type of schedule, try to maintain the same schedule, even on your days off.

5. Jet Lag

Flying long distances through multiple time zones can wreak havoc on your body’s internal clock. Even a difference of just a couple of hours is enough to throw your schedule completely off.

Depending on which direction you’re traveling, you may be extra tired or not tired at all when you arrive at your destination. Then, when morning comes, you’re either going to be up early or struggling to get up on time.

Symptoms don’t stop with sleep issues either. According to the Mayo Clinic, jet lag can cause daytime fatigue, an inability to focus, digestion issues, a general feeling of being unwell or sick, and changes in mood.⁹

Generally, it is thought that traveling east might make jet lag more severe than traveling west, but either way, there are some things you can do to prevent jet lag from being too severe:

• Arrive to your destination early
• Get plenty of sleep before your trip
• Stay hydrated as dehydration can make jet lag symptoms worse
• Gradually adjust your sleep schedule before your trip
• If it is nighttime at your destination, try to sleep on the plane
• If it is daytime at your destination, try to stay awake

How To Maintain a Healthy Circadian Rhythm

Maintaining a Healthy Circadian Cycle

The easiest way to keep your circadian rhythm on track is to practice good sleep hygiene and maintain a regular schedule for sleeping, including on weekends. This won’t necessarily be easy –it will take dedication and practice – but here are some tips to make it a little bit simpler:

• Get enough sleep: In general, we require seven to nine hours of sleep per night. Figure out what your ideal number is and plan to get that amount each night by counting those hours backward from the time you’ll have to wake up in the morning. For example, if you have to wake up at 7:00 a.m. and you know that you work best with eight hours of sleep, you’ll need to prioritize going to bed by 11:00 p.m. at the latest.
• Maintain regular sleep hours: Maintain this same sleep schedule (11:00 p.m. to 7:00 a.m., for example) on weekdays and weekends. This consistency is important as it trains your body to get back into its regular circadian rhythm.
• Avoid late afternoon naps: If you’re not getting enough sleep at night, you’re more likely to take a nap in the late afternoon or evening. Unfortunately, this will further throw your sleep schedule off, so if you need to nap, it’s best to do so early in the day.
• Avoid electronics right before bedtime: Blue light from your phone and television will disrupt melatonin production.¹⁰ Melatonin is the hormone that induces sleep, so if you don’t have enough of it in your system, it’s going to take you longer to fall asleep. Try to give yourself at least one or two hours before bed without screens.
• Limit caffeine: That post-lunch cup of coffee could be messing with your circadian rhythm. Caffeine can stay in your system for up to 9.5 hours.¹¹ With this in mind, plan to stop drinking caffeinated drinks by noon each day. If you really need that almond milk latte to get you through the afternoon, consider half-caf.
• Limit alcohol: Even though alcohol might make you feel drowsy, studies show show that it actually disrupts the quality of sleep you’re getting.¹² That same research suggests that, in any amount, alcohol delays the initial onset of REM sleep and reduces the total amount of time you spend in REM sleep through the night.
• Take a morning walk: Light is the most powerful external trigger to sync our circadian rhythm. The combination of sunshine, fresh air, and movement is a powerful combination to wake you up and energize you for the day ahead.
• Keep a dark sleeping environment: As we mentioned earlier, light disrupts melatonin production. Even turning on the bathroom light in the middle of the night can throw off your circadian rhythm. If you live in an area where there are bright street lights or lights from surrounding buildings, make sure you draw your shades, or better still, invest in some blackout curtains or an eye mask.
• Exercise regularly: Exercise is vital for physical and mental health, but did you know it’s important for sleep as well? Research shows shows that regular exercise improves sleep quality and duration.¹³ In terms of getting your circadian rhythm back in order, working out in the morning sunshine would be ideal (combining the benefits of early morning light and exercise), but if that’s not possible, just pick the time of day that works best for you.