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Have you ever laid awake at night, jealous of your spouse who is out by 10 and up at 6 every day like clockwork? Maybe you've experienced the dreaded jet lag, or noticed a dip in your energy just after lunch? If any of this sounds familiar, you've got your circadian rhythm to thank! You might have heard it called the circadian clock, circadian cycle, internal clock, or sleep-wake cycle. No matter what name you give it, it has a massive impact on your alertness throughout the day.
Read on to learn more about how the circadian rhythm works, what you can do if your internal clock is malfunctioning, and tips and tricks to keep your body in sync with the world outside.
The circadian rhythm is your body's way of regulating your sleep patterns. It's hard-wired into your brain from birth and naturally runs on a roughly 24-hour cycle that controls when you feel sleepy and when you are alert. Your circadian clock affects nearly every part of your body, including the release of hormones, your body's temperature, and even your digestive system!
Humans aren't the only creatures who rely on a circadian cycle to tell them when to sleep, either - circadian rhythms exist in almost every living thing on earth! So, if you find yourself in a post-lunch slump, you're in good company. Most adults will experience the biggest dips in energy in the middle of the night (from 2:00 to 4:00 AM) and just after lunch (from 1:00 to 3:00 PM), but you might vary from this by a couple of hours if you're a morning lark or a night owl. You might find that your circadian rhythm changes as you age, too! For example, teenagers tend to stay up later and wake up later, while the older generation is more likely to follow an "early to rise, early to bed" mentality.
Your circadian rhythm can be thrown out of whack by a few late nights, daylight savings time, shift work, or even something as simple as a change in the seasons. If you're all caught up on sleep, you won't feel the effects of your circadian rhythm as strongly - but if you are even a little sleep-deprived, you'll notice a big difference in your energy levels throughout the day!
Melatonin is the hormone responsible for helping you fall asleep and stay asleep. When it gets dark outside, your eyes send a signal to your brain that says that it's time to start feeling tired. Your brain then sends a signal to your body to produce melatonin, which in turn makes you feel sleepy.
In the natural world, the sun emits blue light in the morning and afternoon before tapering off in the evening. This blue light signals your body to stop producing melatonin, so you feel more alert. That's why your circadian rhythm tends to mimic the cycle of day and night - and why it's so hard for shift workers to fall asleep during the day! It's also the reason why using blue-light emitting devices like cell phones, computers, and television screens at night can have such a drastic effect on your ability to fall asleep at bedtime. When you use these devices at night, you're essentially tricking your body into thinking that it's still light out!
People who travel across time zones often and people who do shift work are some of the most at-risk for a disrupted circadian rhythm. Jet lag exposes you to light at times that your body isn't used to, and shift work forces you to sleep at times you would normally be awake, and vice versa.
If you travel often, you may have heard of this trick: As soon as you get on the plane to travel to a new time zone, or even the day prior to leaving, set your watch to the new time and try to live as though you're already there. By sleeping a bit earlier or staying up a bit later the night before, you can help to get your body in sync with the new location ahead of time, so you're not as tired when you arrive! Either way, it may still take you a few days to adjust.
Shift work is a bit more difficult to manage. Luckily, your circadian clock is somewhat flexible and you can adapt to a new schedule given enough time! If your work schedule requires you to sleep during daylight hours, try to limit your exposure to the daylight and outside noise as much as possible to "trick" your body into thinking it's nighttime. Light-blocking window fixtures and earplugs are an absolute must-have for those of us who have no choice but to sleep during the day!
Now that you know how the circadian rhythm works, it's easy to see how an irregular schedule can throw the whole system out of whack. Luckily, there's hope! Here are a few tips and tricks you can use to get things back in working order: