What is Circadian Rhythm

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Have you ever noticed that you naturally tend to fall asleep at night and wake up in the morning? You may even rise at dawn. This is your body’s circadian rhythm, its natural sleep schedule set by your internal clock. Circadian rhythms are highly sensitive to light, which is why many people prefer sleeping in the dark.


How It Works

Human beings aren’t the only creatures on earth whose movements are influenced by the sun. Plants and other animals are also affected. The term “circadian” comes from a Latin phrase meaning “around a day.”

In humans, the body responds to a complex interplay of hormones and external factors when regulating its sleep schedule. Scientists are continuously studying what affects sleep patterns. In 2017, a team examining circadian rhythm in fruit flies won the Nobel Prize. Fruit flies are often used as test subjects because they’re easy to breed and have a similar genetic makeup to humans. The team discovered a protein that builds up in the flies’ cells overnight only to dissipate throughout the day. It’s believed that the Period and Cryptochrome genes serve this function in humans. (1) This process may affect the quality of your sleep.

Your circadian rhythm affects your mind and body, and although its effects may be most noticeable in your sleep pattern.

“Our physiology and behavior are shaped by the Earth’s rotation around its axis. This biological circadian system has evolved to help humans adapt to changes in our environment,”  a team studying the sleep/wake cycle wrote in 2020.

“Without this endogenous circadian clock, Homo sapiens would not be able to optimize energy expenditure and the internal physiology of the body.”


What Can Go Wrong

You might not be able to listen to your internal clock. This might because of work hours keeping you up at night, stress preventing you from fall asleep, or a lifestyle that promotes early or late hours. You may also notice changes with age.


If your circadian rhythm is out of sync, here are a few things you can try:

  • Exercise
  • Stick to a bedtime
  • Avoid long naps
  • Invest in a comfortable bed


Image source: Wikipedia


  1. Nangle, Shannon N et al. “Molecular assembly of the period-cryptochrome circadian transcriptional repressor complex.” eLife vol. 3 e03674. 15 Aug. 2014

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