Believe it or not, it’s not just your alarm clock that tells you when to wake up in the morning. Your body’s internal clock, or circadian rhythm, uses internal and external cues to signal your brain when it’s time to sleep and wake each day. But sometimes, your body clock might fall out of sync with a normal sleep schedule. This may cause you to turn into a night owl or an early bird, or to suddenly feel tired at different times during the day. There are a number of reasons why this might happen, but the good news is there are often ways to take back control of your circadian rhythm.
The circadian rhythm is what guides the physical, mental, and behavioral changes a person goes through within a 24 hour cycle. It’s controlled by a part of the brain called the hypothalamus and is largely influenced by the perception of light through the eyes (source). In other words, your circadian rhythm will signal you to feel drowsy when it’s dark outside, and wakeful when daylight emerges.
When the sun goes down, your brain will begin to produce the sleep hormone melatonin, slowing down your metabolism and internal systems like your temperature and blood pressure to prepare for sleep. And when the sun comes up, your eyes will register this (yes, even when they’re closed), signaling the brain to cease melatonin production and kickstart your metabolism for the day (source). Although light exposure has perhaps the biggest effect on the circadian rhythm, it can also be influenced by external cues like meal times, exercise, and the temperature (source).
In adults, a sleep-wake cycle consists of roughly 16 hours of awake time and about 8 hours of sleep (although it can fluctuate from person to person depending on different biological factors and individual sleep needs). But sometimes, your regular sleep-wake cycle may fall out of sync with environmental cues, causing a circadian rhythm disorder. According to the National Heart, Lung, And Blood Institute, signs that your body clock is out of sync may include:
One very common example of a circadian rhythm shift that people experience regularly is daylight saving time. Although subtle, advancing the clock one hour forward puts your body clock out of sync with the actual clock, causing you to feel wide awake when your usual bedtime rolls around. Luckily, a time shift this small is easy enough for the body to resolve on its own within a few days.
More extreme shifts in sleep-wake cycles can occur as a result of jet lag or shift work, the Sleep Foundation notes. If we take a look at shift work, where a person works during dark hours or works an irregular schedule, external cues like light and physical activity do not match up with the body’s biological sleep drive. Over an extended period of time, this results in sleep deprivation and more of the symptoms mentioned above.
If you’re experiencing some of the symptoms above, particularly a sleep schedule that isn’t getting you a full night’s worth of quality sleep, your circadian rhythm may be in need of a reset. Fortunately, there are environmental adjustments you can make to help recalibrate your body clock.
As we mentioned earlier, light exposure has the biggest effect on your circadian rhythm. Soaking in some sunlight is the obvious (and best) choice, but if you must be inside for most of the day, the CDC advises that exposing yourself to bright artificial light can also help tell your body when it’s time to be awake. Short-wavelength blue light that’s emitted by LED lights and most electronics is especially good at suppressing melatonin and encouraging the body to stay awake. But research has shown that blue light’s stimulating effects can last a few hours, so try to avoid your devices, TV, and bright LED lighting in the evening hours.
In the hours approaching bedtime, your metabolism is preparing to slow down so sleep can soon be initiated. You can help this process along by eating your dinner at least 3 hours before bedtime. Keeping that meal on the modest side is also recommended, so your body can more easily digest the food without disrupting your sleep.
Moderate caffeine consumption in the morning can actually be a helpful tool in shifting your circadian rhythm. However, timing is key. Since the effects of caffeine can last for several hours, it’s best to avoid it during the second half of your day. Too much at the wrong time could make it difficult to fall and stay asleep at nighttime.
Physical activity is another important cue you can use to get your circadian rhythm back on track. Exercising regularly and at the same time of day will help you feel more alert during wake hours and it’ll also further encourage your body to maintain a schedule. Just be sure to finish your workout at least an hour before bedtime so you’re not too energized right before it’s time for lights out.
As you can probably already tell, doing certain things at the same time each day is especially helpful when it comes to resetting your circadian rhythm. And your bedtime and morning wake time are no exception. Laying your head down at the same time each night and waking up at the same time each morning will help your body to align with a desired schedule. Over time, your body clock will naturally tell you when it’s time to wake up. (Although an alarm clock is still a good backup plan!)
If you’re attempting to adjust your sleeping hours to an earlier or later time period, you can do so gradually by changing your bedtime a half hour every few days until you’ve reached your desired time.
Somewhat like caffeine, naps can be beneficial in helping you recharge throughout your day, but they must be used in moderation and at the right time. Long or late afternoon naps can inhibit your ability to go to sleep at your regular bedtime. A 20-30 minute power nap in the early afternoon is recommended to relieve just enough daytime sleep pressure without throwing off your nighttime sleep cycle.
For more information and resources on the circadian rhythm, we encourage you to read the following:
Circadian Rhythms by the National Institute of General Medical Sciences
Do You Need to Reset Your Circadian Rhythm? by Cleveland Clinic
What Are Circadian Rhythm Disorders? by the National Heart, Lung, And Blood Institute
Can You Change Your Circadian Rhythm? by the Sleep Foundation
Effects of Light on Circadian Rhythms by the CDC
Blue light has a dark side by Harvard Health Publishing
How Long to Wait Between Eating and Bed by Verywell Health
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