What is the Circadian Rhythm?




The circadian rhythm oftentimes referred to as the biological clock, is a biological process that all living organisms experience, and which is controlled by exposure to light. The circadian rhythm is responsible for such things as the sleep-wake cycle in animals, the opening and closing of flowers, and even the production of new cells in simple life forms like fungi and molds. The existence and study of the circadian rhythm has been documented as far back as the 18th century when astronomer Jen Jacques d'Ortuous de Marian noted his plants opening and closing with the cycle of light and dark, and the leaves opening towards the sun. He then, out of curiosity placed the plants in total darkness and observed that they continued to open and close with the light cycle in the absence of total darkness- indicative of an internal clock. 

Your circadian rhythm is able to be influenced by artificial light. It is this ability to be influenced that can be a healthful benefit to us. 

Examples of positive influence would be the use of artificial light to boost productivity and alertness by being exposed to light in the white to blue spectrum. Light in the 5000k to 6500k range has been shown to boost mental acuity and productivity in the workplace and in schools. This particular spectrum of light mimics midday sun, which coincides with our most productive time of day.  On the other end of the spectrum, warmer color temperatures in the 2700k to 3000k range have a calming effect and can help people to unwind and relax prior to sleep. 

Another positive effect of light on the circadian rhythm is the use of full spectrum light in the treatment of season affective disorder. During winter months, exposure to natural light in the 5000k-6500k range is limited due to shortened days which can often be cloudy. This causes a disruption in the circadian rhythm which leads to feelings of malaise. With regular exposure to full spectrum lighting from such products as light therapy boxes, or full spectrum lamps, the circadian rhythm can be maintained and the effects of seasonal affective disorder minimized.  

These color temperature ranges, when used during appropriate times, will reinforce the circadian rhythm and make the sleep/wake cycle function smoothly. 

If these light spectrums and exposure to them are used out of sync with our circadian rhythm there can be sleep/wake cycle disruptions as you would expect. Recent studies show that exposure to the bright white/blue light in the 5000k-6500k spectrum in the evening can interfere with the ability to fall asleep. 

So to recap, in its simplest form, the circadian rhythm is your internal clock that helps regulate your sleep-wake cycles. And it can be influenced both positively, and negatively with the use of artificial light. 

The importance and understanding of the circadian rhythm recently gained international attention when in 2017, the Nobel Prize in Physiology or Medicine was awarded to three individuals for their work on understanding the genetic mechanisms behind the circadian rhythm.