Circadian Rhythms: What’s The State of Your Body’s Clock?

If you find yourself tossing and turning at bedtime or staring at the ceiling in the middle of the night, a circadian rhythm imbalance may be to blame! The circadian rhythm is your body’s internal “clock” that dictates your sleep-wake cycles over a 24-hour period.

Governed by your physiological response to darkness and light, your circadian rhythm is responsible for inducing sleepiness in the evening and wakefulness in the morning. However, an imbalance in this system can have a significant impact on many areas of your health, from sleep to the development of chronic conditions. (18)

What is your circadian rhythm?

Your circadian rhythm is the biological clock that regulates your sleep-wake cycle. It also plays a role in the regulation of several other body functions, such as appetite, hormone production, body temperature, and cell growth. (14)(18

While the hypothalamus acts as “mission control” for your circadian rhythm, environmental factors provide signals that turn these biological functions on or off. The main factors influencing your circadian rhythm are daylight and darkness. Even minor changes in your exposure to daylight (e.g., daylight savings) can speed up, slow down, or even reset your circadian rhythm. (18)

Did you know? Cells grow and repair themselves more quickly throughout the night when DNA-damaging UV rays are not present. (14)

Circadian rhythm disruption

Going to sleep at the same time and waking at the same time each day typically keeps your circadian rhythm humming along without a hitch. However, changes in your schedule, time zone, a sleepless night, and other factors can upend this biological clock. Factors that can disrupt your circadian rhythm include:

• Aging (5)
• Alcohol (7)
• Alzheimer’s disease and dementia (12)
• Bipolar disorder (1)
• Changing time zones
• Menopause (20)
• Pregnancy (4)
• Staying up all night
• Sleeping in too long
• Substance abuse (10)
• Technology (e.g., bright light, device screens) (21)

Circadian rhythm disorders

Circadian rhythm dysfunction can be temporary, but chronic disruption can affect nearly every physiological function in the body and is associated with serious health consequences, including cognitive impairment, mood disorders, cardiovascular disease, type 2 diabetes, non-alcoholic fatty liver disease, and kidney problems. (6)(27)

The most common feature of circadian rhythm disorders is a disruption in normal sleep patterns. This can result in insomnia and daytime sleepiness. (27) The most common circadian rhythm disorders are described below.

Advanced sleep phase disorder

Often occurring in middle age, advanced sleep phase disorder is characterized by excessively early rising and an early bedtime. (27) For example, a person with this disorder may fall asleep between 6:00 and 9:00 p.m. and wake between 1:00 and 5:00 a.m.

Delayed sleep phase disorder

This disorder is the opposite of advanced sleep phase disorder and affects approximately 15% of teenagers. People with delayed sleep phase disorder tend to fall asleep very late, often as late as 2:00 a.m., and have difficulty waking up in the morning. (2)

Jet lag

Travelers often find that rapidly changing time zones, especially when travelling internationally, can disrupt normal sleep patterns. The disruption in your sleep-wake cycle becomes worse with each time zone crossed, especially when traveling from west to east. Although jet lag is temporary, it can take several days to adjust to a new time zone. (11)

Non-24-hour sleep-wake disorder

This disorder commonly impacts those with total sight loss and sensitivity to light, but it can also affect some sighted people. Many experience this circadian rhythm disorder due to the inability to distinguish light from dark. It can cause a serious lack of quality sleep at night and excessive sleepiness during the day. (19)

Shift work disorder

People who work overnight or shifts that frequently rotate find that their schedules conflict with the body’s natural circadian rhythm. This can result in getting up to four hours less sleep than the average person and may lead to chronic insomnia and excessive sleepiness. The true prevalence of sleep work disorder isn’t well known, but evidence suggests that more than one in five shift workers experiences sleep wake disorder. (25)

Did you know? Exposure to screens, such as your TV, cell phone, or computer, up to an hour before you go to bed can increase cortisol levels and reduce the effectiveness of the body’s sleep hormone, melatonin. (24)

How to reset your circadian rhythm

There are simple strategies that can help to reset your sleep-wake cycle. However, if you continue to suffer from insomnia or other sleep problems, it’s wise to seek support from an integrative health practitioner.

1. Bright light therapy

One of the easiest ways to regulate your sleep-wake cycle is by exposing yourself to bright light via a lightbox. The box sits on top of a table and houses several tubes that produce extremely bright light—about 10,000 lux. Bright light stimulates cells in the retina that connect to the hypothalamus. Scientists believe that, by activating the hypothalamus at the same time every day, you can restore your normal sleep-wake cycle and increase your mental well-being. (8)(13) Exposure to 30 to 45 minutes of light early in the morning can decrease daytime sleepiness and activate your body’s natural circadian rhythms. (16)

2. Chronotherapy

This is a relatively new type of sleep therapy in which bedtime is progressively delayed by two- to three-hour increments each day until you can fall asleep at the desired bedtime. During one trial of 66 patients with delayed sleep phase disorder, researchers found that chronotherapy, also known as phase-advance therapy, resulted in a 100% success rate while in a controlled environment, with 54% of the patients maintaining a healthy sleep-wake cycle after being discharged. (22) However, despite its possible effectiveness, chronotherapy is complex and may be difficult to do on your own at home.

3. Melatonin

Melatonin is a natural hormone produced by the body that plays a key role in regulating your sleep-wake cycle. The production and release of melatonin is connected to the time of day, increasing when it’s dark and decreasing when it’s light. However, your body’s natural melatonin production declines with age and may not be sufficient if you have a circadian rhythm disorder. (9)

Melatonin supplements have been shown to help synchronize the circadian rhythm and improve the onset, duration, and quality of sleep. (26) One British review reported that nine out of the ten studies evaluated by researchers found that taking supplemental melatonin decreased jet lag in people crossing five or more time zones. It was also noted that supplementation worked best when taken close to the local bedtime at the destination. (11) Another review that appeared in the journal Sleep found that taking melatonin effectively advanced the sleep-wake rhythm in people with delayed sleep phase disorder. (23)

4. Sleep hygiene

Consistently practicing good sleep hygiene can help you overcome some circadian rhythm disorders, particularly when used in conjunction with melatonin supplementation. (3) Keep a regular bedtime, power down electronics at least 30 minutes before turning in, sleep in a cool, dark environment, and wake up at the same time every day. (17) You can also use some relaxing essential oils, such as lavender oil, to help ease you to sleep. (15)

The bottom line

Your circadian rhythm controls your biological schedule over a 24-hour cycle. However, when this system is disrupted, it can adversely impact your health and quality of life. Taking a proactive approach to circadian disorders can get you back in rhythm and foster better health and performance every day.