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


Tick tock, 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, it may need a tune-up! At its most basic, your body clock—technically known as your circadian rhythm—dictates your sleep/wake cycles over a 24-hour timeframe.

Governed by your physiological response to darkness and light, your circadian rhythm is why you feel sleepy in the evening and why you wake up in the morning. But a glitch in this system can throw your circadian rhythm out of balance, and that can have serious consequences for everything from getting a good night’s sleep to increasing your risk for certain health conditions.

woman sleeping in bed

Your body has its very own internal clock that governs your sleep/wake cycles.

What is the circadian rhythm?

Your circadian rhythm is the biological clock that governs everything from when you sleep, when you wake up, to when you eat. It also orchestrates the ebb and flow of your hormones, influences your body temperature, and plays a role in the timing of cell growth.

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 (think daylight savings time) can speed up, slow down, or even reset your circadian rhythm. (1)

Did you know?
Cells grow and repair themselves more quickly during the day when natural light is plentiful. (2)

Circadian rhythm disruption

Your circadian rhythm is a creature of habit. Going to sleep at the same time and waking at the same time day in and day out typically keeps it humming along without a hitch. But changes in your schedule, time zone, or even just one sleepless night can upend this biological clock. Things that can disrupt your circadian rhythm include:

  • Aging (3)
  • Alcohol (4)
  • Alzheimer’s disease or dementia (5)
  • Bipolar disorder (6)
  • Changing time zones
  • Menopause (7)
  • Pregnancy
  • Staying up all night
  • Sleeping in
  • Substance abuse (8)
  • Technology (bright light, device screens)

Circadian rhythm disorders

Sometimes a hiccup in your circadian rhythm is temporary. But chronic disruption can affect nearly every physiological function in the body and lead to serious health consequences. These include cognitive impairment, mood disorders, cardiovascular disease, type 2 diabetes, non-alcoholic fatty liver disease, and kidney problems. (9)(10) Even short-term disruption can cause a circadian rhythm disorder.

The most common feature of circadian rhythm disorders is a disruption in normal sleep patterns. This can result in insomnia and daytime sleepiness. Here are the most common circadian rhythm disorders:

Advanced sleep phase disorder

Often prevalent in the elderly, advanced sleep phase disorder is marked by excessively early rising and an early bedtime.(11) 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 percent of teens. (12) 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 for work or school.

Jet lag

Travelers often find that rapidly changing time zones, especially during international travel, 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. (13)

Non-24-hour sleep-wake disorder

Although it does impact those with total sight loss and sensitivity to light, 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. Although it primarily impacts those with a total loss of sight and sensitivity to light, it can also affect some sighted people. (14)

woman working on her laptop looking at bright screen

Shift work is one of the most common circadian rhythm disorders.

Shift work disorder

People who work the night shift or work 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. According to the Cleveland Clinic, up to 40 percent of all shift workers experience this sleep-disrupting disorder. (15)

Did you know?
Looking at screens—whether it’s 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. (16)

How to reset your circadian rhythm

Many times, simple strategies can help to reset your sleep/wake cycle. While this is relatively easy for some disorders like jet lag, if you continue to suffer from insomnia or other sleep problems, it’s wise to seek a healthcare professional’s help.

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 boost your emotional wellbeing. (17)(18)

Research also shows that light positively influences serotonin, the brain’s “feel-good” neurotransmitter. Getting 30 to 45 minutes of light first thing in the morning is also more effective than light therapy later in the day because early-morning light simulates sunrise and activates your body’s natural circadian rhythms. (19)

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 percent success rate while in a controlled environment with 50 percent of the patients maintaining a healthy sleep/wake cycle after being discharged. (20) But, even though chronotherapy may seem like a simple, drug-free way to re-establish a healthy sleep-wake cycle, it can be difficult to do on your own at home.

Melatonin

Melatonin is a natural hormone produced by the body that plays a key role in 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.

Melatonin supplements have been shown to help synchronize the circadian rhythm and improve the onset, duration, and quality of sleep. (21) One British study review reported that nine out of the ten studies that researchers evaluated found that taking supplemental melatonin decreased jet lag in people crossing five or more time zones. And it worked best when taken close to the local bedtime at the destination. (22) 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)

man in bed looking at tablet device

Blue light from your devices can raise cortisol levels and interfere with your natural circadian rhythm.

Sleep hygiene

Consistently practicing good sleep hygiene can help you overcome some circadian rhythm disorders, particularly when used in conjunction with melatonin supplementation. (24) Keep a regular bedtime, power down electronics at least two hours before turning in, sleep in a cool, dark environment, and wake up at the same time every day. You can also use some relaxing essential oils to help ease you to sleep.

The bottom line

Your circadian rhythm controls your biological schedule day in and day out. But when that rhythm is out of whack, it can adversely impact your daily life. Taking a proactive approach to circadian disorders can get you back in rhythm and foster better health and performance every day.

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