What is circadian rhythm?

Circadian rhythm refers to the natural, internal process that regulates the sleep-wake cycle and repeats roughly every 24 hours. It influences many physiological processes, including hormone release, eating habits, and digestion, all of which play a role in how we function during waking and sleeping hours. Our bodies' circadian rhythms are primarily adjusted by exposure to light and darkness, which act as signals to help align our internal clock with the external day-night cycle.

For instance, the hormone cortisol, which promotes alertness, is regulated by the circadian clock and peaks around the time we wake up. Conversely, melatonin, which promotes sleep, is produced when darkness falls, helping us wind down and prepare for sleep. Disrupting this rhythm by exposure to light at night or darkness during the day can lead to difficulties in falling asleep and other health issues 1 2.