June 15, 2024

Vitavo Yage

Best Health Creates a Happy Life

Circadian Rhythms and Their Impact on Sleep

6 min read

Sleep is among the many physiological processes in the human body directed by circadian rhythms, a collection of interrelated internal clocks that oscillate independently throughout the day. It isn’t surprising, then, that when a person’s circadian rhythms are off they may experience problems such as insomnia or daytime sleepiness.

If you’re dealing with sleep issues, understanding how circadian rhythms are established and how they can be thrown off can help you determine what steps to take to establish a healthy sleep schedule.

Nolwen Cifuentes / Getty Images

Factors That Affect Circadian Rhythms

Light and genetics are external factors known as zeitgebers (German for “time givers”) that are primary influencers of circadian rhythms. Certain health conditions may also affect circadian rhythms.

Sun and Light

Both sun and light are important to circadian rhythms because photosensitive cells in the retina are directly connected to the anterior hypothalamus gland in the brain where the suprachiasmatic nucleus (SCN), or the body’s pacemaker, is located. The SCN synchronizes many of the biological and physiological processes of the body, including sleep and wakefulness.

Sunlight entering the eye travels to the optic nerves, above which the X-shaped optic chiasm delivers the nerve signals to the SCN.

  • As morning sunlight increases at the start of the day, the visual system signals the SCN to activate receptors in the brain that stimulate the production of the stress hormone cortisol, leading to wakefulness and increased energy.
  • As sunlight decreases at the end of the day, the visual system signals the SCN to activate the pineal gland, the organ responsible for producing the sleep hormone melatonin.


Certain genes have been found to help maintain circadian rhythms independent of external influences. The first such gene, called CLOCK (Circadian Locomotor Output Cycles Kaput), was identified by Dr. Joseph Takahashi and colleagues in 1994.

Multiple genes that constitute the body’s core molecular clock have since been identified.

Health Conditions

Certain health conditions increase the risk of disrupted circadian rhythms, including:

Circadian Desynchronization

When a person’s internal clock is misaligned, circadian disorders such as delayed sleep-wake phase syndrome (an inability to fall asleep) and advanced sleep-wake phase syndrome (sleep occurs prematurely) can develop. The degree of desynchronization is largely dependent on an individual’s genetics and the extent to which day and nighttime patterns are interrupted.

Desynchronization can occur as a result of any number of circumstances such as:

  • Time zone changes: Jet lag is a familiar circadian rhythm disruptor for people who travel.
  • Daylight savings time: The loss of a single hour can have a short-term effect on circadian rhythms.
  • Total blindness: Research has shown that people who are blind from birth frequently have difficulty with their sleep-wake cycle because of the lack of environmental light cues. This can lead to a condition known as non-24 sleep-wake rhythm disorder (non-24 SWRD).
  • Lifestyle habits: Alcohol or illicit drug use, chronic caffeine intake, and nighttime exposure to artificial light (such as from a TV screen, smartphone, or very bright alarm clock) can disrupt circadian rhythms.

Non-24 sleep-wake phase disorder can also occur in sighted individuals, albeit rarely. The cause is not entirely clear, but it seems to affect those with extremely irregular work hours, including those with ongoing shift work. For people dealing with insomnia or non-24 SWRD, a nightly 5-to-10 milligram dose of melatonin may improve sleep patterns.

Overcoming Circadian Rhythm Disorders

Irregular sleep patterns can interfere with health and quality of life. For example, night shift workers often respond to the stress of their schedules by overeating (especially sugary and fatty foods), which can lead to weight gain and poor glucose control.

What happens when circadian rhythms are disrupted?

When circadian rhythms are disrupted, multiple metabolic changes have been observed, including increased body mass and waist circumference, elevated triglyceride levels, and poor cholesterol balance.

Ultimately, the best way to overcome circadian dysregulation is to reset your internal clock by taking steps to improve your sleep hygiene.

  • Maintain a regular sleep schedule: Go to bed at the same time every night of the week and use an alarm to wake yourself up at the same time every morning.
  • Don’t take naps: Sleeping during the day decreases “sleep debt,” so that you need less sleep at night. This can interfere with a regular sleep routine.
  • Don’t watch TV or read in bed: Stop any form of entertainment and turn off all electronics (including cell phones) at least 30 minutes before bedtime.
  • Avoid caffeine and alcohol several hours before sleep: Caffeine can overstimulate you. Alcohol may help you fall asleep but is likely to cause sleep interruptions and morning grogginess.
  • Keep the bedroom dark: Turn off all lights and tightly close curtains or window shades. Replace window coverings that allow light to shine through with room-darkening shades. Note that sleep masks can prevent sunlight from entering the eye and impede the environmental signals meant to stir you when it’s time to wake up.
  • Turn down the thermostat: You’re likely to sleep more soundly in a room that’s cool. Even in winter, don’t pile on too many blankets.
  • Keep the room quiet: Sudden noises can cause momentary starts that interrupt otherwise restful sleep. If your partner snores loudly, explore anti-snore remedies or invest in a pair of earplugs.

When to See a Healthcare Provider

If faced with chronic insomnia and daytime sleepiness, ask your healthcare provider for a referral to a board-certified sleep physician who can help diagnose and treat your condition.


Circadian rhythms are a collection of interrelated internal clocks that wax and wane throughout the day. The causes of circadian rhythm disorders are not always clear, but it is known that irregular sleep patterns can interfere with health and quality of life. If you have sleep problems, try to reset your internal clock by taking steps to improve your sleep hygiene and talk with your healthcare provider for additional treatment options.

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Mure LS. Intrinsically photosensitive retinal ganglion cells of the human retina. Front Neurol. 2021;12:636330. doi: 10.3389/fneur.2021.636330

  2. Robertson-Dixon I, Murphy MJ, Crewther SG, et al. The Influence of Light Wavelength on Human HPA Axis Rhythms: A Systematic Review. Life (Basel). 2023 Sep 26;13(10):1968. doi: 10.3390/life13101968

  3. Vitaterna MH, King DP, Chang AM, et al. Mutagenesis and mapping of a mouse gene, Clock, essential for circadian behavior. Science. 1994 Apr 29;264(5159):719-25. doi: 10.1126/science.8171325

  4. Cox KH, Takahashi JS. Circadian clock genes and the transcriptional architecture of the clock mechanism. J Mol Endocrinol. 2019 Nov;63(4):R93-R102. doi: 10.1530/JME-19-0153

  5. National Heart, Lung, and Blood Institute. Circadian rhythm disorders causes and risk factors.

  6. Quera Salva MA, Hartley S, Léger D, Dauvilliers YA. Non-24-Hour Sleep-Wake Rhythm Disorder in the Totally Blind: Diagnosis and Management. Front Neurol. 2017;8:686. doi:10.3389/fneur.2017.00686

  7. Solaiman SS, Agrawal R. Non-24-hour sleep-wake circadian rhythm disorder in a sighted male with normal functioning. J Clin Sleep Med. 2018;14(3):483-4. doi:10.5664/jcsm.7008

  8. Bouillon-Minois JB, Thivel D, Croizier C, et al. The Negative Impact of Night Shifts on Diet in Emergency Healthcare Workers. Nutrients. 2022 Feb 16;14(4):829. doi: 10.3390/nu14040829

  9. Brainard J, Gobel M, Scott B, et al. Health implications of disrupted circadian rhythms and the potential for daylight as therapy. Anesthesiology. 2015 May;122(5):1170-5. doi: 10.1097/ALN.0000000000000596

Additional Reading

  • Almoosawi S, Vingeliene S, Gachon F, et al. Chronotype: Implications for epidemiologic studies on chrono-nutrition and cardiometabolic health. Adv Nutrition. 2018;10(1):30-42. doi:10.1093/advances/nmy070

  • Arendt J. Biological rhythms during residence in polar regions. Chronobiol Int. 2012 May;29(4):379-94. doi:10.3109/07420528.2012.668997

  • Kryger MH, Roth T, Dement WC. (2016) Principles and Practices of Sleep Medicine (6th Ed). St. Louis, Missouri: Elsevier Saunders.

Brandon Peters, M.D.

By Brandon Peters, MD

Dr. Peters is a board-certified neurologist and sleep medicine specialist and is a fellow of the American Academy of Sleep Medicine.


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