What Is Circadian Rhythm?

Any bodily process that occurs regularly on a 24-hour cycle is known as a circadian rhythm. The most common circadian rhythm is the sleep-wake cycle, and that’s what this article discusses. For simplicity, the sleep-wake cycle is called circadian rhythm in this article. In general, this cycle is controlled by exposure to sunlight and other bright lights.

Studies on the impact of circadian rhythm on health and cognition date back to at least the 1930s. One of the most famous studies was the “cave study” from 1962 in which Michael Siffre, a 23-year-old man, temporarily lived in a cave in the Alps. When he left the cave after almost two months, he thought it was only a little over a month later. Another famous study was known as the “bunker experiment” from 1966 in which people were kept in a bunker with no exposure to natural sunlight or clocks. After a few weeks, their circadian rhythms changed, and their sense of time was warped. Professor Till Roenneberg, one of the study’s workers, noted later that “Most people’s clocks, however, don’t run on a tight 24-hour schedule. It’s more like 25.”

Which Health Conditions Are Associated with Dysregulated Circadian Rhythm?

Not only can a disrupted circadian rhythm warp our sense of time, but it can also contribute to or exacerbate health conditions such as:

• Cancer
• ADHD
• Immune dysregulation
• Gastrointestinal disorders
• Other chronic health conditions

In addition, the International Agency for Research on Cancer of the World Health Group classifies shift work involving circadian disruption as probably carcinogenic to humans (Group 2A).

It’s hard to say which came first, the sleeping problem or the chronic health condition, but the fact is that “up to 75% of children and young people with neurodevelopmental, emotional, behavioural and intellectual disorders (NDEBID) are known to experience different types of insomnia, compared to 3% to 36% in normally developing population.” It is likely that many of these children have a dysregulated circadian rhythm, meaning that their bodies are out of sync with the natural, daily rhythms of the sun.

Melatonin and Blue Light

If sleep-wake cycles are out of sync with the sun’s rhythm, it is often due to the lack of melatonin around the age-appropriate bedtime. These bedtimes vary by age:

• Babies: 5:30-6:00pm
• Toddlers: 6:30-7:00pm
• Young children: 7:00-7:30pm
• Older children: 8:00-8:30pm
• Teenagers: 9:00-10:00pm
• Adults: 10:00-11:00pm

Melatonin is a hormone made by the pineal gland in the brain that helps the body fall asleep.
The pineal gland is exquisitely sensitive to light, and it associates blue light with dawn and orange/red light with sunset. Blue light is the shortest wavelength of visible light and thus has the most energy. It is the wavelength that is associated with being alert and awake.

Too much of the wrong color’s wavelength at the wrong time can add up to an inhibition of melatonin production and an out-of-sync sleep cycle. These days, people are bombarded with an excess of blue light from smartphones, tablets, computers, TVs, bright overhead lights, LED lights and most other electronics and lights. Remember that blue light is associated with being awake, and you can understand why blue light blocks the production of melatonin.

How to Reset Circadian Rhythm

Earlier Bedtime

An easy way to get in sync is to adhere to an earlier, age-appropriate bedtime. For very young children this means going to bed potentially before one or both parents come home from work. An earlier bedtime usually leads to an earlier wakeup time, typically around sunrise. If it’s hard to go to sleep earlier, forcing an earlier wakeup time can make it easier to fall asleep that same night, although it may be hard to stay awake during the day. Staying up past an age-appropriate bedtime leads to a “second wind”, which entails a rise in cortisol and adrenaline, making it difficult to sleep until the effects of these have worn off. A constant cycle of this can be a heavy contributor to chronic inflammation.

Limit Blue-Light Exposure to the Appropriate Time of Day

Blue light from natural sun exposure or even a lightbox in the early morning sends a signal to the brain that it’s time to wake up and be alert. This kind of bright light therapy is a fairly common approach to boost mood and depression. Getting some sun during the day helps as well. However, around sunset, begin limiting blue-light and bright-light exposure with the following steps:

• Turn off overhead lights; use dimmer side lights instead
• Use warmer color temperature lighting
• Limit or eliminate TV, video games, smartphones, tablets or other electronic devices too close to bedtime
• Wear blue-light-blocking eyewear at night when using devices with screens or LED lights
• Replace bedside lamp bulbs with blue-light-blocking (orange) bulbs
• Use blue light filters on devices (set screen color temperature to warm; also known as “night shift mode”)

About Maria Rickert Hong CHHC

Prior to working on Wall Street, she was a marketing specialist for Halliburton in New Orleans, where she also received her MBA in Finance & Strategy from Tulane University.

She is the author of the bestselling book Almost Autism: Recovering Children from Sensory Processing Disorder and the co-author of Brain Under Attack: A Resource for Parents and Caregivers of Children with PANS, PANDAS, and Autoimmune Encephalitis. She is a co-author of Reversal of Autism Symptoms among Dizygotic Twins through a Personalized Lifestyle and Environmental Modification Approach: A Case Report and Review of the Literature, J. Pers. Med. 2024, 14(6), 641.

Maria is also a Certified Holistic Health Counselor. Her work can be found on DocumentingHope.com, Healing.DocumentingHope.com, Conference.DocumentingHope.com and MariaRickertHong.com

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