Have you ever wondered how your body knows when it’s time to sleep?
Or when it’s time to wake up?
You might set an alarm to make sure you get up for the day. But there’s another clock that tells you when it’s time to stop sleeping and wake up.
And that’s your circadian rhythm.
A circadian rhythm is your body’s natural, internal clock. It regulates your sleep-wake schedule based on a 24-hour day.
Even if you’re unaware of it, your circadian rhythm is constantly running in the background. It affects both your physical health and mental fitness. Because of their massive effect on our types of sleep and overall well-being, it’s important to understand what circadian rhythms are.
Let’s take a closer look at how your body’s internal clock works and how you can maintain a healthy circadian rhythm.
What is a circadian rhythm?
If you’ve ever wondered, “What is circadian rhythm?” you aren’t alone.
Many people have heard terms like biological clock and sleep rhythm. But they still aren’t sure exactly what these phrases refer to or how these concepts work.
Circadian rhythms are 24-hour cycles that form part of the human body’s internal clock.
These rhythms operate in the background to perform essential processes and functions. This includes encouraging a regular sleep cycle. In fact, the sleep-wake cycle is one of the most well-known circadian rhythms.
Different systems of the body follow circadian rhythms that synchronize with a ‘master biological clock’ in the brain. Environmental cues like light and dark directly impact this clock. It's for this reason that circadian rhythms tend to follow the consistent cycles of day and night.
When they are correctly aligned, circadian rhythms promote healthy, consistent sleep. When they’re thrown out of balance, you can experience circadian rhythm sleep disorders. These include early waking, insomnia, and delayed sleep phase disorder.
How circadian rhythms work
Circadian rhythms work by governing the body’s processes. They ensure that these processes are optimized at numerous points during each 24-hour period.
All organisms have a circadian system. They help diurnal animals — animals that are active during the daytime — to wake with the sunrise. And they ensure that nocturnal animals only leave their burrows at night. Circadian timing also instructs flowers to open at ideal times for pollination.
The human circadian rhythm system coordinates our physical and physiological systems. It instructs our digestive systems to produce certain proteins. These proteins match the timing of our meals and regulate our endocrine systems.
Our wake rhythm is connected to the circadian pacemaker in our brains, made up of 20,000 neurons.
This 'master clock' is the suprachiasmatic nucleus (SCN) in our hypothalamus. Our genes instruct the SCN to send signals that regulate our body's activity during the day.
This SCN is extremely sensitive to light. This makes it an important environmental cue that influences how the SCN sends signals within the body.
Other cues that regulate the SCN’s activities are diet, exercise, social activity, and room temperature.
Do circadian rhythms affect sleep?
Circadian rhythms are most often mentioned in the context of wakefulness and sleep. Good sleep is essential for promoting good health and preventing diseases.
The sleep-wake cycle is one of the clearest examples of these rhythms in action. During each day, exposure to light prompts the SCN to send signals that keep us alert, active, and awake.
As night approaches, the eyes send a signal to the hypothalamic master clock.
This triggers the pineal gland to produce melatonin, the hormone that promotes sleepiness at night. These specialized signals continue during the night to keep us asleep until the morning light triggers a new cycle.
This is how our circadian rhythms align our sleeping patterns with the cycles of day and night. This alignment promotes a consistent cycle of sleep that helps us stay active during the day.
How can a circadian rhythm get out of sync?
There are many lifestyle, dietary, and health factors that can influence your circadian rhythms.
Here are some factors that can cause your biological clock to become out of sync.
1. Work shifts with erratic hours
Erratic shift work with poor work-life balance can change the body’s response to natural light-dark cycles. This can cause significant disruptions to your circadian rhythms and even cause shift work sleep disorder.
Working long hours at night places your sleep schedule at direct odds with natural daylight hours. If you work night shifts, you will need to train your circadian rhythms according to your new cycles. Minimize your exposure to sunlight to get enough sleep during the day and prevent burnout at work.
2. Caffeine
Caffeine can disrupt your sleeping patterns and keep you awake for longer than usual. The effects of caffeine last hours after you ingest it.
Limit your intake of caffeinated drinks like coffee in the afternoon. Always avoid all caffeine for at least four hours before bedtime.
3. Medications
Prescription medications can all affect sleep patterns to varying degrees. These include:
- Diuretics
- Clonidine
- Beta-blockers
- Sedating antihistamines
- Selective serotonin reuptake inhibitors (SSRIs)
4. Mental health conditions
Research in circadian rhythm psychology shows that disruptions in circadian rhythm are clear in people suffering from mental health conditions. People diagnosed with depression, anxiety, bipolar disorder, and schizophrenia are often affected.
Chronic stress can also disturb the biological clock. This is due to the overproduction of stress hormones like cortisol and adrenaline.
Research shows that resynchronizing circadian rhythms can improve symptoms of poor mental health.
5. Light exposure
Light signals the SCN to keep you awake and alert. This is especially true of the blue light emitted by electronic devices like smartphones and tablets. Even minuscule amounts of light can delay your circadian rhythm by two to three hours.
In a natural environment, there is little to no natural light present once the sun goes down. But nowadays, our homes are flooded with artificial light. Bright light can stimulate our brains to suppress melatonin production and keep us awake.
6. Travel and jet lag
Jet lag is a physiological condition that happens when we travel across time zones. This kind of long-distance travel can cause changes to our body's circadian rhythms.
For example, if you travel from a GMT0 time zone to a GMT +6 zone, you may feel like the time is six hours earlier than local time. This can disrupt your sleep pattern, which can take weeks or even months to correct.
7. Changes in genes
At least 15 ‘clock genes’ are thought to make up our circadian clock. Differences in these genes are what cause each person to have their own biological clock.
Certain underlying genetic conditions can also change your circadian rhythms. Examples include delayed sleep phase syndrome and irregular sleep-wake disorder.
These kinds of conditions can make it difficult to maintain regular sleep patterns.
8. Unhealthy sleeping habits
Poor sleep hygiene can extend your sleep rhythm, keeping you awake for longer. This can further disrupt your circadian rhythms.
Unhealthy sleeping habits include:
- Using electronic devices late at night
- Not following a set sleep schedule
- Eating and drinking late at night
- Long nighttime awakenings (segmented sleep)
Health effects of having disruptions to circadian rhythms
Research shows that irregular circadian rhythms can have negative health impacts. It also shows how adjusting them can prevent health issues such as anxiety and Alzheimer’s disease.
Deep sleep, also called slow-wave sleep, is necessary to calm overactive regions of the brain.
On the other hand, sleep deprivation can trigger increased anxiety. It can also trigger issues like chronic inflammation when the brain or circadian rhythm genes don't get enough slow-wave sleep.
Let’s look at six negative effects that disruptions to circadian rhythms can have on our bodies.
1. Cardiovascular issues
Sleeping for less than five hours each night is a common sign of circadian rhythm disruption. This lack of sleep is associated with the development of hypertension.
This is because sleep deprivation promotes systemic inflammation. This is the root of many lifestyle diseases such as heart disease. Over time, these irregular rhythms can lead to progressive cardiovascular disease.
2. Metabolic changes
Circadian rhythms don't only govern our sleep. They also affect our appetites, digestion, and endocrine function as well.
If these signals become interrupted, you could experience a sluggish metabolism. In extreme cases, changes in the circadian cycle are associated with an increased risk of obesity and high blood pressure.
3. Memory issues
Your brain processes and stores essential information during sleep. Sleep deprivation can negatively impact your ability to store and recall long and short-term memories.
4. Impaired immunity
Impaired sleep cycles will reduce your body’s ability to produce antibodies and fight off infections. This can leave you with a weakened immune system and more prone to viruses and bacteria.
5. Endocrine disruptions
Irregular circadian rhythms can lead to problems with the endocrine system. This is the system of the body responsible for your hormones.
Endocrine disruptors can put you at risk of developing endocrine disorders and imbalances. These include hypothyroidism, type II diabetes, premenstrual syndrome, and other related issues.
How to maintain a healthy circadian rhythm
Follow these tips to maintain a healthy and consistent circadian rhythm.
1. Seek out the sun
Enjoying natural daylight in the morning encourages your brain to stop producing melatonin.
As soon as your alarm goes off, open the blinds or go outside to enjoy some sunshine. This will regulate your biological clock. Spending time in nature is also a great self-care practice to kickstart your day the right way.
2. Follow a sleep schedule
Depending on where you are in the world, melatonin production begins at around 9 pm and slows at 7:30 am. Try to base your sleep schedule around these intervals.
Give yourself an extra hour to wind down before bedtime. This can help align your circadian rhythms.
Add good habits like mindfulness, reflection journaling, or breathwork to your nightly sleep schedule. These kinds of relaxing wellness activities prepare your body and mind for a good night’s rest.
3. Avoid caffeine after certain hours
Caffeine can keep you awake for hours after ingestion. This is why it’s important to limit your caffeine intake at least four hours before your bedtime.
4. Limit light before bed
Artificial light from televisions, smartphones, and indoor lights can trick the brain into thinking it’s still daytime. This delays the production of melatonin, which delays your sleep.
Switch off electronic devices at night. Use built-in night light settings to reduce the amount of blue light you are exposed to if you do need to use your phone.
You can also invest in blue-light-blocking glasses that help keep your natural body clock regulated.
5. Daily exercise
Studies have found that scheduling workouts for a certain time of day can improve your body’s sleep cycles. This helps you to feel refreshed and alert the next morning.
On the other hand, exercising very late in the evening can delay your biological clock and lead to insomnia.
6. Reserve your bedroom for sleep
Using your bedroom for activities other than sleep trains your brain to expect activity whenever you’re in the room. Reserve your bedroom for sleep to avoid this.
7. Limit naps
Naps can be rejuvenating if your energy levels are low and you’re feeling physically exhausted. But they can disrupt your sleeping patterns, especially if you tend to nap later in the day.
If you do need to nap, it’s best to do so before 2 pm to ensure that you do not experience insomnia later at night.
Maintain healthy circadian rhythms for your well-being
Our internal clock plays an undeniably crucial role in regulating our sleep cycles. As well as rest, our circadian rhythms affect our hormone balance, digestion, body temperature, and physical and mental health.
Manage your biological clock using the tips mentioned above to enjoy consistent sleep. Getting regular, high-quality rest will have you ready to take on the world.
Get in touch with a BetterUp coach for more advice on optimizing your circadian clock and taking care of yourself.
