Lauren is a board-certified adult-gerontology primary care nurse practitioner. Lauren has done NP clinical practicums focusing on the adolescent, adult, and geriatric populations in internal medicine, long-term care, and in outpatient oncology/bone marrow transplant. Lauren received a BA from Assumption University, a BSN from Massachusetts College of Pharmacy and Health Sciences, and her MS in Nursing from the University of Massachusetts at Lowell. She is certified by the American Academy of Nurse Practitioners (AANP).
Medically reviewed by Lauren Castiello, MS, AGNP-C

If you’ve ever chatted with someone about your sleeping habits, you may have heard the phrase “circadian rhythms.” It’s one of those scientific terms that shows up in common use occasionally — but may not be well understood. Everyone — every person and animal on the planet, in fact — has a circadian rhythm. So let’s take look and unpack this puzzling phrase to see what it means, and how it impacts your sleep.

What Is Circadian Rhythm?

A circadian rhythm is the internal clock established by your brain. Your brain will make note of when it is exposed to light and when it is exposed to darkness, creating a loose 24-hour clock to go by. The clockwork is quite fragile since, biologically, your brain has only been exposed to two variables to adjust it: sunlight and moonlight. Now, we have phone screens, televisions and even light fixtures that can easily influence our circadian rhythm. 

Two factors impact your circadian rhythms:

  • Light : As we’ve said, light is the primary trigger. Red-colored light affects your circadian rhythm the least, while blue lights affect it the most. This is the reason it’s not good to use your smartphone or other devices too close to bedtime. They emit blue light, which can hinder your ability to get to sleep.
  • Field of view: The more light your eyes can see, the more drastic the effects will be on your circadian rhythm. So, for example, your circadian rhythm will be more triggered to keep you awake when you’re outside on a sunny day than it might be if you’re working in a room with minimal lighting that hits your face only at an angle.

What’s the science behind circadian rhythms? Your hypothalamus, the portion of your brain responsible for the input from your eyes, responds to a group of neurons regarded as the suprachiasmatic nucleus (SCN). Your SCN determines what genes to prepare and encourages cells to work hard during wakefulness.

It also determines which genes to reduce or diminish entirely, so rest may occur. The genes play a role in reinforcing, resupplying and fortifying rest for cells. When you are awake, genes will begin to empower the neural network for wakefulness. When you sleep, this network is less of a priority, so your body focuses on your neural network to promote rest. 

Your exposure to ambient light will affect which genes behave accordingly. If you are watching TV at 2 a.m., but your bedtime is 10 p.m., your hypothalamus will interpret the ambient light as daylight and tell your body to continue to support the neural network for wakefulness.

How Does Circadian Rhythm Work?

Your circadian rhythm is just that — a rhythm, or cycle — and is designed ideally to work in conjunction with the sun, by triggering your body to create a sleep-wake cycle that keeps you healthy and well-rested. Of course, we’ve added elements that can throw that rhythm off, such as indoor lighting. But even with those disruptions, the circadian rhythm does a pretty good job of talking to the brain and telling you when to sleep.

For example, if you fly to a time zone six hours behind your usual time zone, your body will, at first, be adjusted to the time zone you normally rest in and not the new one. 

Despite your conscious regard for the time zone you are currently in, your body is instead adjusted to previously established exposure of ambient light and darkness, therefore impacting the hour at which you should be drowsy or even asleep. But after a day or two of disorientation, which we call “jet lag,” your circadian rhythm will effectively reset itself to reflect the light-dark patterns where you are, and your sleep will adjust to the new time zone. Your circadian rhythm may have negative impacts on your sleep if you are accustomed to a different periodic schedule for wakefulness and somnolence. If your circadian rhythm becomes maladjusted, you may find yourself sleeping at odd hours or even having difficulty sleeping as it is. This is something that is seen with shift workers, such as healthcare providers and long-haul truckers, who work irregular hours, and may be sleeping during the day. There’s even a name for it: shift work disorder.

What Are The Most Common Occurrences That Interrupt Circadian Rhythms?

There are a number of common factors that may upset the balance of your circadian rhythm — some of them are minor and will dissipate in a day or so. Others may require medical intervention to treat. Here are a few of the most common.

Jet lag: most people have had the experience of feeling tired and achy after a flight to another time zone. It’s natural, and in most cases, will only last a few days. According to research done by Harvard, expect it to take one day of recuperation for each time zone crossed. To help ease the way, try to rearrange your home schedule slightly in the days before the trip, and adopt the new schedule as soon as you arrive to your destination. Avoid alcohol and caffeine, and get out in the sun when you arrive, if possible.

Daylight savings time: It will take a day or so for your body to adjust when we turn the clock ahead or back. Try to stick to your schedule and avoid taking a long nap to compensate. Avoid coffee or alcohol within 4-6 hours of bedtime. Prepare for “springing forward” by going to bed 15 minutes earlier each night for four or five days beforehand.

Shift work disorder: as we mentioned above, this is common for those who work at unconventional hours, or those who put in longer than usual shifts, such as hospital workers, food service employees who work late nights, musicians, and more. Shift workers make up 20% of the workforce, and shift work disorder impacts 10-40% of those workers. One thing that can help shift workers is maintaining as regular a sleep schedule as possible, even on weekends, and ensuring that their bedroom, mattress, and bedding are as comfortable as possible.

Birth of a child: any weary new parent can attest to the fact that few things disrupt your sleep pattern as much as a newborn. To a certain extent, you’ll just have to wait this out until your child is sleeping through the night, but the Mayo Clinic has a few suggestions to help, including splitting duties with your partner and avoiding sleep when your child is in the bed with you.

Change in circumstances: even small changes in your life can disrupt the delicate balance of your circadian rhythms. During the pandemic, for example, there is evidence that people were, in the beginning, staying inside more than usual. Later in the pandemic, however, “quarantine fatigue” resulted in people being outside more than they commonly would. Both these extremes can cause disrupted sleep. The changes may be minor, but they are something to be aware of if you find yourself tossing and turning after a day spent at the beach or in a darkened movie theater.

Spotlight On College Student Sleep

One group that is particularly prone to disruptions in their circadian rhythms are college students. Pulling an all-nighter to study for an exam is, for many, a rite of passage, as is staying up late to study or, for some, to party. Another cause of sleep disruption may be a noisy dorm, with people coming and going at all hours. Although there may be no simple solutions, Villanova University offers the following tips:

  • Work on creating a schedule that gives you time for both study and leisure, as well as regular hours of sleep. This can be hard at first, but gets easier with practice.
  • Consider doing brief meditations before bedtime. A five minute meditation can lead to a full night’s worth of sleep.
  • Make your sleep environment as comfortable as possible. If you’re sleeping on a used, college-provided mattress, perhaps you can bring in your own. Adjust light so that your room is as dark as possible at night, and if you can adjust the temperature, make sure it’s on the cool side.

You may find, as well, that your campus has resources to help you address disruptions. Consider the following:

  • Talk to your RA or someone in your housing office to find out if there are designated “quiet dorms” that forbid noise after a certain hour. These are becoming increasingly common on college campuses.
  • Carve out some time to spend in the campus gym. Regular physical exercise (preferably done at least three hours before bedtime) can help your body to rest more peacefully at night.
  • Work with your advisor and the registrar to frontload your classes during the middle of the day, so that you don’t have to get up at the crack of dawn for an early-morning class, nor do you have to unwind after a night class that leaves your brain whirling when it should be preparing for sleep.

How To Reset Circadian Rhythms

It may sound like your circadian rhythm is so sensitive that it derails easily — and there’s some truth to that. Even a small change can cause a slight speed bump in your sleep patterns. In modern life, it’s easy to run into a situation where, say, you need to work late or are watching a great movie at 1 a.m. or have some other perfectly valid reason to not sleep on schedule.

If that’s the case, there’s no need for worry. Just as you can reset a clock or wristwatch, so, too, can you reset your body’s internal clock.

  • Take melatonin supplements: Melatonin is a chemical that already exists naturally in your body. This hormone is what helps you associate a decrease in light as the time to rest and an increase in light as the time to be awake. Unfortunately, melatonin decreases with age. Melatonin supplements can help you re-establish your circadian rhythm if you take them right before bed.
  • Establish consistent, healthy sleep habits: If your circadian rhythm has been disrupted, chances are you don’t have consistent and healthy sleep habits. You can remedy this by going to bed and waking up at the same time every day. Over time, your body will adjust to your new sleep schedule and re-establish your circadian rhythm.
  • Caffeine: As delicious as caffeine-infused drinks are, try to curb your intake at least several hours before you go to bed. Caffeine can take up to six hours to leave your body so curb your intake much earlier in the day.
  • Bright Light Therapy: Bright light therapy, or chronotherapy, can help with your sleep since lighting is strongly tied to how we rest. Consult with your physician on what the best course of action is for you, but you do not need a prescription to purchase a light therapy box. Set up your light near where you work or sit and let the light do it’s work. Be consistent when you choose to utilize light therapy.
  • Watch your meal schedule: when you eat has some impact on your circadian rhythm. For one thing, it’s a good idea to avoid eating too late in the evening and to avoid heavy meals at dinnertime. Your body’s digestive processes will still be rumbling away then when you go to bed, and may disrupt your sleep. If you need a late-night snack, consider a food that will help you sleep, such as bananas or turkey. 
  • Exercise regularly: exercise is good for your body overall, but there is ample evidence that regular exercise helps you fall asleep more quickly and has a positive impact on the quality of your sleep. According to John Hopkins Medicine, just 30 minutes of moderate-impact aerobic exercise (think: a brisk walk or active yoga class) will lead to a solid difference in sleep quality. 
  • Make adjustments to light: When you get up in the morning, it’s a great idea to get out in the sunshine as soon as you can, if possible. Morning light will trigger your circadian rhythms to tell your body that it’s time to rise and shine, and be active and productive. Likewise, dimming lights for an hour or so before bed tells your body the opposite, that it’s time to wind down to get some shut-eye.
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Final Thoughts

As enjoyable as it is to stay up late watching TV or playing video games, your body’s inner clock intuitively knows what is required to get the rest you need. Fortunately, if your circadian rhythm does get thrown off — perhaps you are traveling or taking a late shift at work — there are lots of ways to re-establish it and get settled into a consistent period of sleep. Consider utilizing light therapy, melatonin, and our other suggestions to reset your brain and get the rest you need. Consult with your doctor if you’re having trouble establishing a regular sleep pattern as you may have a circadian rhythm sleep disorder.