Have you ever wondered how your body knows that it’s time to go to sleep? Or why, even if you have big plans to dance the night away, your sleep-wake cycle isn’t always in your control? Our circadian rhythm is a 24-hour biological cycle that controls bodily functions like sleep, body temperature, and hormonal changes that occur throughout the day and night, based on sunlight or darkness.

How Do Circadian Rhythms Work?

The circadian rhythm is regulated by melatonin, a hormone produced by the pineal gland in the brain. (4) Activated by darkness, melatonin helps signal to the body that it’s time to wind down and sleep. This means that it can be interrupted by certain things in our environment like bright light, smartphone or TV screens, or lightbulbs. (5) When our circadian rhythm is off, we can experience symptoms like extreme sleepiness and fatigue during the day, decreased alertness, problems with memory and decision-making, and more. (6)

What Is a Natural Sleep-Wake Cycle?

Our sleep-wake cycle is our body’s natural rhythm that results in alternate periods of sleep and wakefulness and is regulated by our circadian rhythm. (8) This happens through a process known as “sleep pressure,” which just means that the longer you are awake, the more the body wants to sleep. The longer you stay up, the greater your sleep pressure. Sleep pressure decreases after a full night of sleep. (9)

This need to sleep is linked to a compound called adenosine in our brain that's basically our body's built-in sleep advocate. It builds up throughout the day and the longer we’re awake, the more it tells us to hit the pillow, until it’s basically shouting for us to hit the snooze button on the day. (11)

7 Ways to Reset Our Circadian Rhythm

If you’re experiencing disruptions in your slumber — maybe you just flew across the country, or had to work late — there are a few tricks you can try that promote restful sleep and can help you from disruptions:*

1. Take a melatonin supplement an hour or so before bedtime to support sleep and a normal circadian rhythm*.

2. Avoid alcohol, large meals, and caffeine before bedtime.

3. Be consistent with the time you go to bed each night and the time each morning you wake up. If you’re jet lagged, try to go to sleep and wake up based on the external clock where you are, even if your internal circadian clock hasn’t caught up yet.

4. Make sure your bedroom is quiet, dark, and relaxing. Play whale sounds. Get a water bed. Create a space that signals relaxation for your brain.

5. Remove electronic devices from the bedroom and try to avoid screens before bed.

6. Exercise and being physically active during the day can help you fall asleep easier at night.

7. Get out of the house. Time outside can keep your circadian rhythm functioning optimally, since it picks up signals of light and darkness. (9)

While there are often many factors out of our control when it comes to sleep, such as having small children to wake up with at night, working night hours, or participating in a 24-hour danceathon. There are small steps each of us can take to support our circadian rhythm and sleep cycle. We wish you lots (7-10 hours) of rest tonight!* (10)

References:

1. U.S. Department of Health and Human Services. (n.d.). Circadian rhythms. National Institute of General Medical Sciences.

2. Borbély, A. A. (1982). A two-process model of sleep regulation. Human Neurobiology, 1(3), 195-204.

3. Stolwijk, A. M., Straatman, H., Zielhuis, G. A., & Willemsen, W. N. (1998). Seasonal variation in sex ratio at birth: …. Human Reproduction, 13(12), 3350-3354.

4. Geoffriau M, Brun J, Chazot G, Claustrat B. The physiology …of melatonin in humans. Horm Res. 1998;49(3-4):136-41. doi: 10.1159/000023160. PMID: 9550114.

5. National Heart Lung and Blood Institute, U.S. Department of Health and Human Services,“How Sleep Works.”2022.

6. U.S. Department of Health and Human Services. (n.d.). What are circadian rhythm …?. National Heart Lung and Blood Institute.

7. American Psychological Association, American Psychological Association, “Apa Dictionary of Psychology.”

8. Centers for Disease Control and Prevention, Centers for Disease Control and Prevention,“Module 2. Sleep Pressure: Homeostatic Sleep Drive.” 31 Mar. 2020.

9. Centers for Disease Control and Prevention, Centers for Disease Control and Prevention,“Do You Get Enough Sleep?”12 Mar. 2021.

10. Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, “CDC - How Much Sleep Do I Need? - Sleep and Sleep...” 2 Mar. 2017.

11. “How Sleep Works - Your Sleep/Wake Cycle | NHLBI, NIH.”