Circadian rhythm is the internal clock that regulates the body’s sleep and wake cycles over a 24-hour time period. The brain’s master clock receives sunlight and darkness signals, and makes us feel alert or sleepy accordingly. (1) These signals trigger other biological clocks throughout the body to activate hormone release, hunger cues, and other important bodily functions.
In addition to natural stimuli, the circadian rhythm is guided by such influences as artificial light, meal times, bedtime routine, and stress levels. Though the internal clock is designed to respond to environmental cues, it can be controlled — and reset — by human beings. (2)
Note: The content on Sleepopolis is meant to be informative in nature, but it shouldn’t be taken as medical advice, and it shouldn’t take the place of medical advice and supervision from a trained professional. If you feel you may be suffering from any sleep disorder or medical condition, please see your healthcare provider immediately.
Sleep-Wake CycleAn alternating biological pattern that consists of approximately 16 hours of daytime wakefulness and eight hours of nighttime sleep.
When A Circadian Rhythm Should Be Reset
The circadian rhythm is sensitive to disruption and inconsistency. If sleep and wake times fluctuate or meal times shift, the internal clock may become desynchronized from other biological functions.
The circadian rhythm may need to be changed or adjusted due to:
- Jet lag after traveling to a different time zone
- A new job or school schedule
- A class or other activity with an early morning start time
If they occur on occasion, these types of life changes may disturb the circadian rhythm only temporarily. (3) However, repeated disruptive behaviors or certain health conditions can lead to severe circadian rhythm dysfunction. These behaviors might include:
- Regular travel across time zones
- Night shift or rotating shift work
- Use of certain medications or drugs
- A genetic predisposition to circadian rhythm disorders (4)
A disrupted sleep schedule may become severe enough to be considered a sleep disorder. Studies suggest up to 3 percent of the adult population suffers from a circadian rhythm sleep disorder (CRSD) (5). Types of CRSD’s include:
A readjustment of the circadian rhythm may be necessary to treat a circadian rhythm disorder or to help prevent related health complications, (8) such as:
- Other sleep disorders
Dementia and certain cancers are associated with numerous types of chronic sleep dysfunction, including disturbance of the circadian rhythm.
Shift WorkWork that occurs outside the traditional daytime work schedule. Shift work may include working overnight, rotating between day and night shifts, or working partly during the day and partly at night.
11 Ways To Reset A Biological Clock
To adjust a sleep schedule, the biological clock and circadian rhythm must be reset. Sleep experts recommend consistency during the adjustment process, as well as the following behaviors:
- Dim the lights. Darkness signals the brain to release melatonin, a hormone that promotes sleepiness. (9) Light signals the brain to shut down melatonin release, promoting energy and wakefulness. To help shift the circadian rhythm, dim the lights a few hours before bed to signal to the brain it’s time to wind down
- Change meal times. The circadian rhythm responds to food consumption by priming hormones, enzymes, and digestive systems for activity in the morning and afternoon. (10) Shifting breakfast, lunch, and dinner times an hour earlier or later may help move the body’s internal clock backward or forward
- Exercise earlier in the day. Muscles have their own internal clocks, and tend to function better during the day than at night. Daytime exercise may help adjust the circadian rhythm, while nighttime exercise may promote wakefulness and poor sleep.(11) Studies reveal that daytime exercise may also benefit general health more than working out in the evening (12)
- Adjust bedtime. To fall asleep earlier, experts suggest slowly adjusting bedtime until the desired hour is reached. Doctors typically recommend moving sleep time back in small increments of 15 minutes. Because advancing sleep times may be more difficult than delaying them, professional help can be helpful in some cases (13)
- Do not nap. Napping can make it harder to fall asleep at night. To combat daytime fatigue, some experts recommend a light workout instead of taking a nap. Exercise may temporarily reduce the feeling of sleepiness while increasing sleepiness at bedtime (14)
- Get up at the same time every morning. Later weekend sleep and/or wake times or an erratic weekday schedule can disturb the circadian rhythm. Consistency and predictability are key to a healthy sleep schedule and balanced body clock (15)
- Avoid exposure to light before sleep. Exposure to artificial light at night can shift the body clock to a later schedule, causing disruption of the circadian rhythm. It may be helpful to avoid bright light from any source close to bedtime, and dim indoor lights whenever possible (16)
- Don’t eat too close to bedtime. Food consumption before bed may signal the brain to stay awake by activating digestive organs and release of insulin and other hormones. (17) Avoid eating a substantial meal at least two hours before going to sleep
- Try light therapy. Bright-light therapy involves timed exposure to bright light in the morning, and is typically done under a doctor’s care. Bright-light therapy may be particularly helpful for those suffering from a circadian rhythm disorder (18)
- Consider professional help. If at-home techniques fail to restore the circadian rhythm, consultation with a sleep specialist or therapist may be useful. Cognitive behavioral therapy, a short-term therapy technique that encourages healthy sleep by altering negative thought patterns, is often successful at readjusting the biological clock (19)
- Look at science. Sleep science is a rapidly growing field, and our understanding of sleep has increased markedly in the last few decades. One recent study discovered a “reset” button for the brain’s biological clock, which stimulated and suppressed the SCN’s neurons that emulate day and night activity levels and forced the clock to reset. (20) Though the experiment was conducted on mice, such studies may lead to treatments for circadian rhythm sleep disorders in humans in the near future
Last Word From Sleepopolis
We each have a biological schedule that plays a significant role in when we feel tired and awake. A well-balanced body clock promotes healthy sleep patterns and the smooth functioning of other bodily processes, such as hunger cues and energy levels.
Travel, work, and stress may make it difficult to maintain consistent sleep and wake times. A desynchronized circadian rhythm can result in sleep deprivation, circadian rhythm disorders, and increased risk for certain health conditions. With healthy sleep strategies in place, we can restore the body’s circadian rhythm and improve health and well-being.
- LeGates T.A., Fernandez D.C., et al. Light as a central modulator of circadian rhythms, sleep and affect. Nature Reviews Neuroscience, Jun 11, 2014
- Schroeder A and Colwell C. How to fix a broken clock. Trends in Pharmacological Sciences, Oct 2013
- Farhud, D. Circadian Rhythm, Lifestyle and Health: A Narrative Review. Iranian Journal of Public Health, Aug 2018
- Jones C, Huang A, et al. Genetic Basis of Human Circadian Rhythm Disorders. Experimental Neurology, July 2012
- Zhu L and Zee P. Phyllis C. Zee. Circadian Rhythm Sleep Disorders. Neurologic Clinics, Nov 1, 2013
- Ferri P, Guadi M, et al. The impact of shift work on the psychological and physical health of nurses in a general hospital: a comparison between rotating night shifts and day shifts. Risk Management and Healthcare Policy, Sep 14, 2016
- Herxheimer A. The prevention and treatment of jet lag. British Medical Journal, Feb 2003
- Takaesu Y. Circadian rhythm in bipolar disorder: A review of the literature. Psychiatry and Clinical Neurosciences, Sep 2018
- Gooley J, Chamberlain K, et al. Exposure to Room Light before Bedtime Suppresses Melatonin Onset and Shortens Melatonin Duration in Humans. Journal Of Clinical Endocrinology And Metabolism, Mar 2011
- Asher G, Sassone-Corsi P, Time for food: the intimate interplay between nutrition, metabolism, and the circadian clock. Cell, Mar 26, 2015
- Peek C, Levine D. Circadian Clock Interaction with HIF1α Mediates Oxygenic Metabolism and Anaerobic Glycolysis in Skeletal Muscle. Cell Metabolism, Oct 2016
- Chatterjee S and Ma K. Circadian clock regulation of skeletal muscle growth and repair. F1000Research, Jun 30 2016
- Sharkey K, Carskadon A. Effects of an Advanced Sleep Schedule and Morning Short Wavelength Light Exposure on Circadian Phase in Young Adults with Late Sleep Schedules. SleepMed, Aug 2011
- Buxton OM, L’Hermite-Balériaux M. Daytime naps in darkness phase shift the human circadian rhythms of melatonin and thyrotropin secretion. American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, Feb 2000
- Kang J and Chen S. Effects of an irregular bedtime schedule on sleep quality, daytime sleepiness, and fatigue among university students in Taiwan. BMC Public Health, Jul 19, 2009
- Tosini G, Ferguson I, et al. Effects of blue light on the circadian system and eye physiology. Molecular Vision, Jan 24, 2016
- Kajimoto J, Matsumura R, et al. Potential role of the pancreatic hormone insulin in resetting human peripheral clocks. Genes Cells, May 23, 2018
- Dodson E and Zee P. Therapeutics for Circadian Rhythm Sleep Disorders. Sleep Medicine Clinics, Dec 1, 2011
- Gradisar M, Dohnt H, et al. A Randomized Controlled Trial of Cognitive-Behavior Therapy Plus Bright Light Therapy for Adolescent Delayed Sleep Phase Disorder. Sleep, Dec 2011
- Cao R, Gkogkas C, et al. Light-regulated translational control of circadian behavior by eIF4E phosphorylation. Nature, April 2015