Circadian Rhythm: What It Is, How It Works & What Affects It (2024)

What is circadian rhythm?

Your circadian rhythm is the pattern your body follows based on a 24-hour day — it’s the name given to your body’s internal clock. This rhythm tells your body when to sleep and when to wake up. It also affects several other body processes, like your hormones, digestion and body temperature. It’s like you have a tiny conductor inside your body, orchestrating a 24-hour symphony of biological processes.

Your body sets your circadian rhythm naturally, guided by your brain. But outside factors, like light, can affect the rhythm, too. For example, when light enters your eye, cells send a message to your brain that it can stop producing melatonin (a hormone that helps you sleep).

How does circadian rhythm work?

Your circadian rhythm makes sure your body’s processes perform optimally at different points during a 24-hour period. “Circadian” in Latin means “around or approximately” (circa) “a day” (diem).

Your circadian rhythm coordinates the physical and mental systems throughout your body. For instance, your endocrine system controls hormones like cortisol for energy expenditure, and your digestive system creates proteins to match the timing of your meals.

Your circadian rhythm connects to an internal clock in your brain. This internal clock is located in a tiny cluster of cells known as the suprachiasmatic nucleus (SCN). The SCN is in a part of your brain called the hypothalamus. Throughout the day, internal clock genes in the SCN send signals to control the activity throughout your body.

The SCN is sensitive to light. Light influences the signals that the SCN uses to coordinate circadian rhythms in your body. That’s why circadian rhythms closely relate to day and night.

Circadian rhythm in babies, toddlers and children

Newborns typically don’t develop a circadian rhythm until they’re a few months old. That’s why their sleep patterns tend to be erratic in those first few days, weeks and months. A baby’s circadian rhythm begins to develop as they experience changes to their bodies and adapt to their new environment.

Babies usually start to produce and release melatonin when they’re about 3 months old. Cortisol development occurs between 2 months and 9 months. Once toddlers and children develop a circadian rhythm, they should have a pretty regular sleep schedule, getting nine to 10 hours of sleep each night.

Circadian rhythm in teenagers

During their teen years, your child may experience a sleep phase delay, which is a shift in their circadian rhythm. When they were younger, they had early bedtimes (8:00 p.m. or 9:00 p.m.).

But your teen may not get tired until much later now. Their melatonin level may not rise until around 10:00 p.m. or 11:00 p.m. And as they’re going to bed later, they need to sleep later into the morning. Teenagers still need nine to 10 hours of sleep a night.

Circadian rhythm in adults

If adults practice healthy habits, they should have a consistent circadian rhythm. If you follow a regular schedule and get seven to nine hours of sleep at night, your bedtime and wake time should remain stable.

People over the age of 60 may notice their circadian rhythm changing as they get older. You may go to bed earlier and wake up earlier, too. This is a typical part of aging.

What can affect your circadian rhythm?

Light and dark have the biggest effect on your circadian rhythm. But many other things can influence it, including:

• Food intake.
• Stress.
• Physical activity.
• Temperature.
• Overnight or off-hour work shifts.
• Travel.
• Certain medications.
• Mental health conditions.
• Health conditions involving your head or brain.
• Poor sleep habits.

Circadian rhythm disorders

Sometimes, changes to your circadian rhythm can be a sign of a more serious health condition like a circadian rhythm disorder. These types of disorders include:

• Delayed sleep phase syndrome: This type of disorder affects people known as “night owls.” It means you go to bed and wake up two or more hours later than most people.
• Advanced sleep phase disorder: Advanced sleep phase disorder is the opposite of delayed sleep phase syndrome. You fall asleep three or more hours before most people and then wake up very early. It’s largely seen in elderly patients with cognitive impairment/dementia.
• Jet lag: Jet lag is a condition that occurs when you travel over three or more time zones by airplane. You may experience insomnia, extreme tiredness (fatigue) and other symptoms.
• Shift work sleep disorder (SWSD): SWSD occurs when you work a job that has untraditional or unpredictable hours. It can cause insomnia, trouble staying asleep and inappropriate sleepiness.
• Irregular sleep-wake disorder: In this condition, your body can’t set a regular wake and sleep schedule.

What happens if your circadian rhythm is disrupted?

Maintaining your circadian rhythm is very important to your health. If you experience a circadian rhythm disruption and can’t get an adequate amount of sleep, you may develop certain short-term and long-term health issues.

Short-term circadian rhythm disruptions may result in:

• A delay in healing wounds.
• Changes to your hormones.
• Digestion issues.
• Fluctuations in your body temperature.
• Lack of energy.
• Memory loss.

Circadian rhythm disruptions can lead to long-term health conditions in many different body systems, including your:

• Cardiovascular system.
• Metabolism.
• Gastrointestinal system.
• Endocrine system.
• Nervous system.

How can I fix my circadian rhythm?

To reset your circadian rhythm, your body needs to follow a healthy 24-hour schedule. Use the following tips to stay on track:

• Try to stick to a daily routine.
• Go outside when it’s light out to boost your sense of wakefulness. Treatment using light occurs in the morning specifically, and is important to avoid chronic sleep deprivation as part of treatment, which makes things exponentially worse.
• Get some form of daily physical activity.
• Foster a restful sleep environment. Make sure you’re sleeping on a supportive mattress in a room with a comfortable temperature and proper lighting.
• Avoid caffeine, nicotine and alcohol, especially in the evenings.
• Limit your screen time before bedtime, as the blue light can disrupt your ability to fall asleep. Instead, try meditating or reading a book.
• Don’t take a nap in the late afternoons or evenings.

When should I see my healthcare provider?

There are many reasons you may want to speak to your healthcare provider about an issue with your circadian rhythm. If any of the following affect you for a long period of time, make a call to your provider’s office:

• Difficulty getting enough sleep every night.
• Trouble falling asleep easily.
• Waking up throughout the night.
• Problems waking up in the morning.
• Extreme fatigue during the day.