Your circadian rhythm is your sleep-wake pattern over the course of a 24-hour day.

It helps control your daily schedule for sleep and wakefulness. Most living things have one. Circadian rhythm is influenced by light and dark, as well as other factors. Your brain receives signals based on your environment and activates certain hormones, alters your body temperature, and regulates your metabolism to keep you alert or draw you to sleep.

Some may experience disruptions to their circadian rhythm because of external factors or sleep disorders. Maintaining healthy habits can help you respond better to this natural rhythm of your body.

There are several components that make up your body’s circadian rhythm. It is one of four biological rhythms in the body.

Cells in your body

First, cells in your brain respond to light and dark. Your eyes capture such changes in the environment and then send signals to different cells about when it’s time to be sleepy or awake.

Those cells then send more signals to other parts of the brain, which activate other functions that make you more tired or alert.

Hormones play a role

Hormones like melatonin and cortisol may increase or decrease as part of your circadian rhythm. Melatonin is a hormone that makes you sleepy, and your body releases more of it at night and suppresses it during the day. Cortisol can make you more alert, and your body produces more of it in the morning.

Other hormones that play a role in alertness and circadian rhythm include:

  • vasopressin
  • acetylcholine
  • insulin
  • leptin

Other factors

Body temperature and metabolism are also part of your circadian rhythm. Your temperature drops when you sleep and rises during awake hours. Additionally, your metabolism works at different rates throughout the day.

Other factors may also influence your circadian rhythm. Your rhythm may adjust based on your work hours, physical activity, stress and anxiety, and additional habits or lifestyle choices.

Age is another factor that influences your circadian rhythm. Infants, teens, and adults all experience circadian rhythms differently.

Newborns do not develop a circadian rhythm until they are a few months old. This can cause their sleeping patterns to be erratic in the first days, weeks, and months of their lives. Their circadian rhythm develops as they adapt to the environment and experience changes to their bodies. Babies begin to release melatonin when they are about 3 months old, and the hormone cortisol develops from 2 months to 9 months old.

Toddlers and children have a fairly regulated sleep schedule once their circadian rhythm and body functions mature. Children need about 9 or 10 hours of sleep a night.

Teenagers experience a shift in their circadian rhythm known as sleep phase delay. Unlike in their childhood years with early bedtimes around 8 or 9 p.m., teenagers may not get tired until much later in the night.

Melatonin may not rise until closer to 10 or 11 p.m. or even later. That shift also results in a teenager’s need to sleep later in the morning. Their peak sleepy hours at night are from 3 to 7 a.m. — or maybe even later — but they still need the same amount of sleep as children.

Adults should have a pretty consistent circadian rhythm if they practice healthy habits. Their bedtimes and wake times should remain stable if they follow a fairly regular schedule and aim for 7 to 9 hours of sleep every night. Adults likely get sleepy well before midnight, as melatonin releases into their bodies. As adults, we reach our most tired phases of the day from 2 to 4 a.m. and 1 to 3 p.m.

Older adults may notice their circadian rhythm changes with age, and they begin to go to bed earlier than they used to and wake in the wee hours of the morning. In general, this is a normal part of aging.

Sometimes it is not possible to follow your circadian rhythm, and your lifestyle needs and internal clock clash. This can occur because of:

  • overnight or off-hours work shifts that go against the natural light and dark times of day
  • work shifts with erratic hours
  • travel that spans the course of one or more different time zones
  • a lifestyle that encourages late-night hours or early wake times
  • medications
  • stress
  • mental health conditions
  • health conditions like brain damage, dementia, head injuries, or blindness
  • poor sleep habits — not having a regular sleep schedule, eating or drinking late at night, watching screens too close to bedtime, or not having a comfortable sleeping space

How are circadian rhythms related to jet lag?

Jet lag occurs when you travel over several time zones quickly, and your body is not aligned to the time of your new environment. Your circadian rhythm is attuned to the place where you left, and it has to readjust. This may result in feeling tired during the day or feeling wide awake at night.

You may experience other changes that impact your well-being until your circadian rhythm normalizes again. It may take a day or up to a week to feel acclimated to the new time zone. It typically takes a day for each hour you shift to regulate your sleep-wake cycle.

You may even experience mild symptoms of jet lag when clocks fall backward or forward for daylight saving time. The disruption may not last too long, but your body may need a few days to adjust.

You may experience disruptions to your circadian rhythm, but you can get it back on track. Here are some tips for promoting a healthy 24-hour schedule:

  • Try to adhere to a routine each day.
  • Spend time outdoors when it’s light outside to boost your wakefulness.
  • Get enough daily exercise — 20 or more minutes of aerobic exercise is generally recommended.
  • Sleep in an environment that promotes rest with proper lighting, a comfortable temperature, and a supportive mattress.
  • Avoid alcohol, caffeine, and nicotine in the evenings.
  • Power down your screens well before bedtime and try engaging in an activity such as reading a book or meditating.
  • Don’t nap late in the afternoon or evening.

Sometimes alterations to your circadian rhythm may be the sign of a more serious condition like a circadian rhythm sleep disorder. Two of these disorders are advanced sleep phase and delayed sleep phase. You may be more susceptible to these if you work an irregular shift, have low vision, or are a teenager or older adult.

Delayed sleep phase disorder occurs when you go to bed and awaken 2 hours or more after most people. You may think of yourself as a “night owl.” Teenagers and young adults are more prone to this condition.

Advanced sleep phase disorder is the opposite of delayed sleep phase disorder. You actually fall asleep a few hours before most people and then awaken very early in the morning.

Disorders related to your circadian rhythm may result in having difficulty falling asleep at night, waking frequently throughout the night, and waking and not being able to go back to sleep in the middle of the night.

Symptoms related to these conditions include:

Other conditions that are tied into your circadian rhythm include:

  • jet lag, caused from traveling over several time zones quickly
  • shift work disorder, caused by an off-hours job or a job with unpredictable hours
  • irregular sleep-wake disorder, caused by an inability to set a regular sleep and wake schedule

Treating these conditions may include a variety of approaches. You may try to:

Maintaining your circadian rhythm is vital to your health. If you experience a disruption to your circadian rhythm and struggle to get the proper amount of sleep, you may experience both short-term and long-term effects to your health.

Disruption to your circadian rhythm can cause health conditions in several parts of the body in the long term. This includes your:

  • organs
  • cardiovascular system
  • metabolism
  • gastrointestinal system
  • skin

You may also be more susceptible to diabetes, obesity, and mental health conditions.

Short-term disruptions to your circadian rhythm may result in:

  • memory issues
  • lack of energy
  • delayed wound healing
  • changes to your hormone cycle that may impact fertility
  • problems with your digestion and bowels
  • shifts in your body temperature

There are several reasons you may want to talk to a doctor about an issue with your circadian rhythm. If you experience one of these issues for a prolonged period, consider making a doctor’s appointment:

  • have trouble achieving adequate sleep every night
  • cannot fall asleep easily
  • awaken several times a night and fail to get quality sleep
  • have trouble waking up
  • feel extremely tired during waking hours

Your circadian rhythm is your body’s natural way of keeping to its 24-hour body clock, helping your body operate on a healthy sleep-wake schedule. Living a healthy, active lifestyle that promotes proper rest will help you maintain this important component of your body.

See a doctor if you experience prolonged difficulties sleeping or extreme fatigue during the day to find out how you can realign with your circadian rhythm and get proper rest.