7 Factors That Affect Your Natural Sleep-Wake Cycle

Your daily and nightly habits have more impact on your circadian rhythm than you realize.

There’s nothing quite like rolling out of bed in the morning after a good night’s sleep. You feel rested, alert, and ready to take on the day. But for many, falling into a deep sleep can feel nearly impossible. In fact, about 70 million Americans suffer from chronic sleep problems, according to the Centers for Disease Control and Prevention. And while this could be associated with certain health problems, sleep disorders, limited exercise, and other risk behaviors, for many it could mean there’s a disruption to their circadian rhythm.

What Is Your Circadian Rhythm?

Circadian rhythm is the body’s internal timekeeper. Its primary function is to organize when you feel alert and awake, and when you feel tired and ready for sleep. It also works to keep periods of wakefulness and sleepiness grouped together so that your awake time essentially occurs at once, and so does your sleep time. When this rhythm and sleep-wake routine is thrown off track, it can create significant sleep problems such as insomnia, issues with mental health, metabolism, brain fog, and more.

“Newborns don’t have a circadian rhythm, it develops over time,” says Patricia Pinto-Garcia, MD, MPH, medical editor at GoodRx. “This is why newborns go through so many cycles of sleep and wakefulness throughout the day. If we didn’t have a circadian rhythm, we’d keep a newborn schedule—sleeping every few hours. This would make it impossible to get through any meaningful activity—you’d fall asleep in the middle of work, a movie, or even a long drive.”

But there are several things outside your body that can influence your circadian rhythm. These are called zeitgebers, which is a German word that means “time-giver,” Dr. Pinto-Garcia explains. And while maintaining a consistent sleep schedule is the best way to honor your own circadian rhythm, there are several other, less-obvious zeitgebers that may be preventing you from getting a quality night’s sleep.

Top Factors That Impact Your Circadian Rhythm

Too much evening light.

Our brains need dim light to help set the stage for sleep, which allows for our brain’s natural melatonin production to help make us sleepy, explains Shelby Harris, PsyD, DBSM, clinical psychologist and sleep specialist. “If you’re out in the sunlight and then immediately decide to go to bed, you might struggle with winding down and falling asleep earlier,” she says. “The same goes for blue light, which is the wavelength that’s typically emitted from electronic devices, like phones, tablets, TVs, and computers.”

She recommends being thoughtful about your nighttime light and electronics exposure, and opting for using blackout curtains or a sleep mask if you have light still entering your room at bedtime. Also, consider limiting your use of electronics 30 to 60 minutes before bed.

Related: Is Your Bedroom Dark Enough? Sleeping With Ambient Light Can Harm Your Health, Study Finds

Not enough morning light exposure.

Your circadian rhythm is closely tied to light, the presence or absence of which signals wakefulness or sleepiness, respectively. So while you should be avoiding light as much as possible as you wind down at night, the opposite is true for when you wake up. Morning light exposure is crucial to help set your body’s circadian rhythm, because it resets your internal sleep clock that tells your brain it's time to get moving for the day. Research has even shown that as little as five minutes of light exposure in the morning can advance this clock and jumpstart your day.

“Natural light works better than indoor light, but if you can’t get outside or don’t have a window to sit near, then turn on all the lights to help wake your brain and body,” Dr. Harris says. This can look like eating your breakfast outside, taking a quick walk around the block, or just sitting in front of an open window while you read a book or meditate.

Too much caffeine.

Caffeine plays a major role in sleep and your body’s ability to tell when it’s tired. While you likely enjoy a cup (or three) of coffee each morning to help you feel energized and alert, too much caffeine later in the day can leave your body wired and confused about what time it is. This can throw your circadian rhythm off and have your body thinking it’s awake time, even though it’s time to be winding down.

Dr. Pinto-Garcia says that if you find you’re having a hard time going to sleep at night, feeling particularly restless, or overly tired during the day, consider limiting your caffeine to just the morning or cutting it out altogether. And if you can’t quit the habit of a nice beverage later in the day, opt for a cup of tea, which tends to have less caffeine than coffee and sodas.

Related: When Is the Best Time to Drink Coffee—And How Late Is Too Late?

Exercise timing.

It’s no secret that exercise is full of wonderful benefits for your body, and studies have even shown that it can improve the quality and length of your slumber. But the time of day you get in a good sweat can play a major role in your body’s natural circadian rhythm. Dr. Pinto-Garcia says that exercising is a cue to your body that it’s time to stay awake, and because aerobic exercises, like running, swimming, and biking stimulate earlier melatonin release, this can shift your circadian rhythm forward. And for the early birds who exercise outdoors, the added benefits of early morning sun exposure can help stabilize your circadian rhythm and make it easier to fall asleep.

But while some research has found that evening exercise may negatively affect sleep quality for early risers, night owls might benefit from it. “It’s important to point out that some people have naturally advanced or delayed circadian rhythms,” Dr. Pinto-Garcia says. “These aren’t medical conditions and they are completely normal. If you’re a natural night owl or early bird, there’s nothing wrong with your circadian rhythm. If your natural rhythms aren’t causing you any trouble, there’s no reason to worry.”

So if you find yourself completely wired and recharged after a late-day or early evening workout, consider switching your exercise time to the morning or early afternoon to ensure your circadian rhythm is functioning at its best, and so you can wind down faster. And if you don’t have any trouble winding down for bed after an evening workout, stick to what works for you.

Related: When Is the Best Time to Exercise? We Asked Fitness Experts

Irregular sleep habits.

For those who work the night-shift, have a newborn, or sometimes have to pull all-nighters, your sleep patterns can be thrown off. Our bodies aren’t designed to change abruptly from one schedule to another (hello, jet lag), so taking a more gradual route will pay off in the long run.

While it’s not always possible, the more you can think ahead and shift one to two weeks in advance, the better, says Dr. Harris. “Once you have a consistent bed-wake time established, then work on adjusting your current sleep-wake schedule earlier by 15 minutes every one to two days. So, if you’re going to bed at midnight and wakening at 8am, move it to 11:45 p.m. to 7:45 a.m. for a day or two, then 11:30pm-7:30am and so on until you match up with your ideal sleep schedule.”

And if you don’t have the time to gradually adjust your schedule over a few days or week—say after a long trip in another time zone, and you have to get back into your normal routine—another approach would be taking 3 to 5 mg of melatonin an hour before your desired bedtime, Harris adds. (Melatonin is not a magic sleep aid or necessary vitamin to be taken nightly, however—only occasionally, for a few days, as needed).

A disjointed or rushed nightly routine.

For the majority of folks, sleep isn’t triggered by an on/off switch. It’s something we have to encourage and ease into gradually, instead of thinking we can crash into bed and immediately doze off. So, there needs to be some separation between day and night, and allowing for a short, simple wind-down routine can be really helpful to let your brain know that sleep is coming soon, Harris explains.

“There’s no such thing as an ideal wind-down routine,” she says. “Whatever you find quiet, calm, and relaxing in dim light, and ideally without electronics, is the goal, and moving closer to the bed or bedroom is fantastic.”

Work on being as consistent as possible and know that not every night will have a full wind-down routine. And if you’re curious what temperature is optimal for better sleep, cooler rooms have been shown to provide a deeper, more restorative sleep.

Related: Yes, There's an Ideal Temperature for Sleep—and Here's Why It Matters

Substance abuse and certain mental health conditions.

Everyday lifestyle factors like those mentioned above should help “reset” your circadian rhythm, but other factors like excessive alcohol or substance use can negatively influence the natural sleep cycle too.

“Some drugs can cause you to stay up later, like stimulants, and other things can cause you to fall asleep too early, like marijuana or pain medication,” says Harris. “The same goes for any mental health that makes it more difficult to stay on a consistent sleep-wake pattern, like bipolar disorder, depression, or anxiety.”

When Should You Talk to a Doctor or Sleep Specialist?

It's normal and common to have problems getting to sleep or staying asleep sometimes, but if you find yourself struggling for more than three weeks to get on a consistent schedule and have trouble concentrating or severe daytime drowsiness, you should consult with your doctor or sleep specialist. They will be able to better diagnose your specific symptoms and help you understand what exactly is going on Not addressing sleep concerns can lead to more severe side effects like an increased risk of sleep deprivation.

"Chronic sleep deprivation can increase your risk of medical problems like heart disease, kidney disease, diabetes, stroke, and depression," Dr. Pinto-Garcia says. "It can also increase your risk for accidents and injuries both on the job and at home. There are sleep specialists who can help you find ways to work with your circadian rhythm and optimize your sleep."

Related: How to Fall Back Asleep After Waking Up in the Middle of the Night

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