What Is A Circadian Rhythm? - InlifeHealthCare

What Is A Circadian Rhythm?

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It is not a hidden fact that people experience a series of patterns when it comes to sleep. You might feel sleepy at specific points in a day without fail. These are different levels of sleepiness and alertness in a day, but did you know why this happens?

Two things contribute to this pattern: the circadian biological clock and sleep/wake homeostasis. Through this article, you will learn what a circadian rhythm is, how it brings in sleep disorders and what are the ways you can maintain a good circadian rhythm.

The sleep/wake homeostasis is a balance between sleeping and being awake that shows us a need for sleeping. This need is collected in our system, and it tells us whether it is time to sleep or wake up. This helps us maintain adequate sleep all through the night to compensate for the hours of being awake.

The first hormone that activates while going to sleep, is Melatonin. Melatonin levels increase after dusk and stay high throughout the darkness, promoting sleep. Melatonin levels in the blood typically scale up later at night in teenagers when compared to children and adults.

Since teenagers might have more difficulty while calling a day off and going to bed early to get enough sleep, keeping the lights dim at night as bedtime approaches can help them get better sleep. On the other hand, getting out into the bright light as soon as possible in the morning can help them wake up and feel fresh the whole day.

If this were the only therapeutic process that existed in us alone, we would be most alert as our day was starting. The longer we stay awake, the more is the feeling of wanting to fall asleep. This way, the sleep/wake homeostasis generates a force that balances sleep and wakefulness.

What Is A Circadian Rhythm?

The circadian biological clock is an internal clock known for regulating the timing of us going to sleep and staying awake throughout the day. Generally, a typical adult feels sleepy between 2 AM to 4 AM early in the morning and between 1 PM to 3 PM.

There is always a fluctuation to these time periods depending on whether you are a morning person or an evening person. When we have a sufficient amount of sleep, the dips that we experience at these time frames are less intense and becomes more intense when we are sleep deprived.

The circadian rhythm also makes us feel more proactive at specific points of the day, even if we stay up late for hours. On the other hand, the sleep/wake restorative process would otherwise make us feel more sleepy.

Sleep Cycle

The changes to this circadian rhythm happens during adolescence when most teenagers go through a sleep phase delay. This shift in teenagers’ circadian rhythm prompts them to automatically feel wide-awake at late hours in the night, creating difficulty for them to fall asleep before 11:00 PM.

Considering that most teenagers have early class timings and other commitments to fulfill, this sleep period delay can make it much more challenging to get the sleep they need. An average of 9.25 hours, but at least 8 hours is considered normal.

Thus, sleep deprivation can affect the circadian rhythm. For teenagers, the most powerful circadian “dips” manage to occur between 3 AM to 7 AM and 2 PM to 5 OM. The morning dip between 3 AM to 7 AM can even stay longer if one hasn’t had a sufficient sleep, and can sometimes also last until 9 AM or 10 AM.

What Controls The Circadian Clock?

The Suprachiasmatic Nucleus (SCN), a collection of cells in the hypothalamus in the brain control the circadian biological clock. It responds to dark and light signals.

The Circadian Clock

The light travels from the optic nerve of the eye to the SCN, sending signals to the internal clock that it is time to wake up. These signals are transmitted to other parts of the brain that control body temperature, hormones and other functions that play a role in making us feel awake or sleepy.

With the exposure to sunlight, these cells send signals to raise the body temperature and produce hormones like cortisol which is responsible for the metabolism in the body. It also pauses the discharge of other hormones like melatonin associated with sleepiness which is usually created when the SCN comes into contact with darkness.

What Disrupts The Circadian Rhythm?

The disruptions to the Circadian Rhythm are the general irregularities to our sleep cycle like jet lag, changes in shift timings at work, etc. As a result of these disruptions, one might find it difficult to thinking, performing normal activities or feeling unwell during jet lag or a sudden timing shift.

Work Life Imbalance

The above mentioned symptoms can also occur in everyday life where the circadian rhythm could be disrupted by staying awake for long or irregular hours. In order to maintain a good rhythm, it is essential to keep a regular sleep schedule and allow enough time for quality sleep.

Allowing these two vital biological components  — the sleep/wake restorative process and the circadian rhythm — to stay in balance help us perform at our best.

What Are Circadian Rhythm Disorders?

The most essential characteristic of circadian rhythm disorders is the constant or particular disruption of sleep patterns.

It is either a result of a malfunction in our so-called internal body clock or an apparent mismatch between this internal body clock and to what is happening in the external environment concerning the duration and timing of sleep.

As a result of this circadian mismatch, the individuals going through these disorders usually fret of insomnia at particular times and unnecessary sleepiness at some other times of the day, that results in interruptions at work, school, or social life.

In these disorders, patients have a standard sleep quality and duration with a 24-h circadian rhythm cycle, but the sequence is out of sync with desired or necessary wake times.

Less commonly, the period is not 24 h, and patients wake up and sleep later or earlier each day. Patients have no symptoms if they are able to follow their natural sleep cycle.

circadian rhythm disorders

The diagnosis of a circadian rhythm disorder is a challenging one and often requires a discussion with a sleep specialist. A detailed history of the sleep cycle for about a week or two might help gain more insight into the sleep log. It is also necessary to eliminate other sleep and medical disorders, like narcolepsy, which often imitates a delayed sleep phase disorder.

Repetitive circadian shifts due to frequent long-distance travel or rotating shift work timings are not only challenging to adapt to but also affect the sleep cycle vigorously.

Especially when these shifts switch in a counterclockwise path. The counterclockwise changes are those that move awakening and sleeping times to earlier ones.

For example, when rotating shifts from day time to night time and then to evenings or when traveling westward. The symptoms resolved over many days or a few weeks or months in some instances,  especially the elderly, as these rhythms regulate.

As a result of light being a strong synchronizing device of the circadian rhythms, exposure to bright sunlight or artificial light of 5,000 to 10,000 lux intensity after the coveted awakening time and the utilization of sunglasses to reduce the light exposure before the desired bedtime activity readjustment.

The following are common circadian rhythm disorders.

Advanced Sleep Phase Disorder

Usually seen in the elderly, it is a disorder recognized by usually going to sleep at early evening bedtimes between 6 PM to 9 PM and early morning awakenings at around 2 AM to 5 AM.

The people with this advanced sleep phase syndrome are “morning larks” and often complain of insomnia or early morning awakening as well as sleepiness ats late afternoons or early evenings.

Certain people with ASP can follow this early schedule to an extent. Missing a few hours of their evening sleep over a while can lead to chronic sleep deprivation. People with ASP still tend to wake up early even when deprived of sleep.

All these advanced sleep urges can be avoided with proper following of schedules with respect to work, family, friends and health.

Jet Lag

Jet lag is a result of the conflict between the waking up of the internal biological clock and a new time zone affecting the sleep pattern. People suffering from this condition find it hard to adjust and function appropriately in the new time zone they enter.

Jet Lag

It is easier to handle the jet lag while traveling from the west to the east rather than vice-versa. This is because it is easier to postpone sleep than to prepone sleep.

If feasible, travelers must shift their sleep-wake schedule little by little before their travel to approximate that of their destination, and after landing at the new region, they must make the most of exposure to daylight, especially in the morning during the day and exposure to darkness before bedtime.

Wake-promoting drugs and short-acting hypnotics may be used for short duration after arrival. Apart from that, reducing the number of time travelling trips should be done to maintain the overall health that runs on the basis of sleep.

Delayed Sleep Phase Disorder

This is a circadian rhythm disorder most common in young adults or teenagers where their “night owl” tendencies delay in sleep onset. This often occurs around 2 AM or later. If allowed to sleep in late, unusually as late as 3 PM, the chances of sleep deprivation to happen are less.

Nevertheless, earlier wake-up times in this condition can lead either to daytime sleepiness or impaired performance at work and school. As a result, the symptoms like being unmotivated, lazy, or performing weakly can be seen in people who are chronically late for morning obligations.

The people who have delayed sleep phase syndrome are usually most productive, alert, and creative late in the night. They are also termed as evening persons because of these traits.


It is a sleep disorder in which people feel excessive sleepiness in the daytime and uncontrollable occurrences of falling asleep during the daytime, even after getting sufficient sleep.

Sleep paralysis, hallucinations, excessive sleepiness, and in some cases it also causes episodes of partial or total loss of muscle control, often triggered by a strong emotion such as laughter called cataplexy.

Shift Work Disorder

It affects people who regularly interchange the shifts or work at night, also known as rotational shifts. Work schedule conflicts with the body’s natural circadian rhythm and some individuals have difficulty adjusting to the change.

Shift work disorder is identified by a constant or recurrent pattern of sleep interruption that results in insomnia or excessive sleepiness. Fixed-shift work, for example, a full-time night or evening is preferable. Rotating shifts should go clockwise like day to evening tonight. If not, it can affect the cycle of sleep.  

Nevertheless, it cannot be neglected that even fixed-shift workers could have difficulties due to daytime noise and light interfere with the quality of sleep. Workers often reduce their sleep times to take part in family or social occasions.

Shift Work Disorder

In order to maintain this sleep cycle and not letting interruptions come in the way, shift workers have to maximize their stay in bright light – sunlight for day workers or, specially constructed illuminated artificial lightboxes for night workers.

This should be done primarily at times when they should be awake and also ensure that the room is as dark and quiet as possible during sleep.

Donning sunglasses in the morning while commuting home in the expectation of sleep also serves as a useful thing. Using sleeping masks and white-noise tools seem helpful. Having Melatonin before bedtime can also help people with such disorders.

If the symptoms endure and interfere with the normal functioning and the judicious employment of hypnotics with a short half-life and wake-promoting drugs is suitable.

It is also important to make sure there is a balance between personal, professional, emotional and physical aspects of life for a harmonious sleep cycle that does not hinder the biological or circadian clock.

4 thoughts on “What Is A Circadian Rhythm?

  1. J.B.EMMANUEL says:

    I am a diabitic and 72 years.Even though
    I sleep from 10.30pm to 6am still feal sleepy through out the day some times uncontrollable please can you suggest a solution for this
    Once I receive a solution for this next I will take up for diabities

    • Mukta Agrawal says:

      Hello Emmanuel, day time sleep can be caused due to various reasons like increased sugar levels, B12 deficiency or it can be due to sleep apnea which is caused due to overweight. Until and unless we rule out the route cause I won’t be able to give you any suggestions. I advise you to have black coffee 1 per day and see how you are feeling.

  2. aewindia says:

    I am purchasing many medicines for weight loss of Inlife. But I am not getting results.
    Please give me diet plan and list of medicines for weight loss. I have main weight on my stomach.
    Ajeya Gupta. Age 57 years.

    • Mukta Agrawal says:

      Hello Ajeya, To give you a customized diet chart I need your complete details as below

      Please provide us with complete details and your daily routine with timings required for the customized diet chart.

      • Age
      • Gender
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      • Veg/Non-veg
      • Purpose of Diet Chart

      Please mail me the same at updates@inlifehealthcare.com and I will surely help you

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