The Circadian Rhythm Of Sleep: What it is and How it Affects Your Sleep
February 07, 20227 min read
Circadian Rhythm Of Sleep: Everything you need to know
Sleep is governed by our biological circadian rhythms that synchronize with nature's daily time clock composed of daylight and night or darkness. We instinctively tune our internal circadian rhythms to follow the rhythm of mother nature.
What is circadian rhythm?
Our internal biological systems function on circadian rhythms, which regulate our sleep-wake cycle over an average 24-hour period. Although internally regulated, our circadian rhythm is also influenced by our behavior and external environmental factors that affect our natural sleep patterns.
The circadian rhythm of an individual anywhere in the world is predominantly determined by their visual response to light and dark. The difference in daylight hours between the four seasons impacts our circadian rhythm, which is never constant but rather a response to light and other external influences.
The foundation of natural life is based on the fact that light promotes wakefulness and darkness promotes sleep; however, the complications of lifestyle choices, artificial light, and our ability to travel to different time zones play havoc with the natural order of our circadian rhythms.
Nearly every tissue and organ in our body functions on its biological clock, which is linked to the master clock in our brain that ultimately regulates our circadian rhythm.
Our circadian rhythm is regulated by a group of about 20 000 nerve cells called the suprachiasmatic nucleus (SCN) in the brain's hypothalamus region, which receives and responds to direct input from the eyes. To simplify circadian rhythm, our biological clock regulates our sleep pattern, but it also caters to the means to perform daytime activities optimally.
Early development of circadian rhythm in infants.
Babies are not born with a functioning circadian rhythm but have a weak sleep-wake rhythm connected to the mother. The SCN systematically processes light information detected through the eyes' retina that begins establishing circadian rhythms. The following are essential building blocks that form a large part of circadian rhythms:
Melatonin (a hormone that controls the sleep-wake cycle).
Cortisol (primary stress hormone).
Circadian rhythm and your infant
Establishing circadian rhythm in a newborn takes between 8 and 11 weeks. At 8 weeks old, a cortisol rhythm develops, melatonin develops at 9 weeks, and body temperature rhythm and circadian genes develop at 11 weeks.
The circadian rhythm established in infants is primarily influenced by exposure to light, including normal daylight and artificial light at night. A baby milestone that parents celebrate is the first time that their little one sleeps through the night. But many parents don't consider the impact of blue wavelength-rich artificial light on their child's early development, which should be a big concern.
A large TV screen mounted on the wall in the main bedroom that you share with your newborn for the first few months is a common feature in many homes. Everything is connected to the screen, including the soft baby lullaby music played to calm the little one into a state of sleep. Digital screens emit blue light, which interferes with our circadian rhythm.
I know you may think that when a baby's eyes are closed, all light is blocked. Do this in a dark room, push a small flashlight against the palm of your hand or at the tip of your finger below your fingernail. You will see how light can penetrate skin and tissue. This will give you an idea of how effective eyelids are at blocking light.
Medical professionals warn against the impact of light on newborns. What is known is that a change in the peripheral circadian genes has been linked to changes in blood pressure, airway inflammation, and immune response. Furthermore, the imprinted circadian rhythm of the newborn remains into adulthood.
Circadian entrainment is essential in newborns. Entrainment is the synchronizing of our internal biological clock with external environmental cues. For this reason, an infant needs to be exposed to daylight and evening that evolve into darkness. There must be a balance for effective synchronization to be locked in, and exposure to sunlight is the key.
As a side note, if an infant has a congenital cataract and is not treated immediately, vision will not develop, which will impede the establishment of the circadian rhythm. This also applies if the infant does not receive the appropriate day/night exposure.
Common factors that change circadian rhythms and affect sleep.
Sleep is essential to good health, both physical and mental health. A sleep routine is usually established to have the right amount of sleep in a 24-hour cycle to maintain good health.
We train our children from infancy to develop a healthy sleep routine which shows that we are aware of the importance of quality sleep; yet, sleep is the first thing we are willing to compromise when the going gets tough.
Reducing or disrupting sleep can have serious consequences, potentially throwing our circadian rhythms out of sync. Here are a few examples:
Changes or mutations in certain genes can affect our internal biological clocks.
Jet lag is an instant change in the light-dark cycle that results from people traveling to a different time zone. It will take a few days of sunlight exposure to get back into sync with the natural environment.
Light, especially blue light from digital devices at night retard the secretion of melatonin, confusing our internal biological clocks. This shifts our circadian rhythm, so we fall asleep later and get up later in the morning.
Shift work where day and night shifts are regularly interchanged can severely impact circadian rhythms.
Unhealthy sleep habits also disrupt your circadian rhythm, like going out late and waking up early, not having a fixed sleep routine, eating and drinking caffeinated drinks late at night, being involved in mentally stimulating activities, and sleeping with pain or in an uncomfortable bed.
4 reasons your circadian rhythm may be out of whack
Drastic changes that affect our internal biological clocks will lead to sleep disorders and cascade into chronic health conditions that include obesity, diabetes, depression, bipolar disorder, and seasonal affective disorder, among other health risks.
Underlying medical conditions related to sleep disorders may affect circadian rhythms. These include:
Delayed sleep phase syndrome. Going to sleep later and wake later.
Advanced sleep phase disorder. Going to sleep earlier and waking earlier.
Irregular sleep-wake disorder. No regular sleep rhythm leads to sleep-wake disruptions.
Non-24-hour sleep-wake disorder. Circadian rhythm is not synchronized to a 24-hour day, and there are periods of sleepiness and insomnia.
Easy ways to keep your circadian rhythm in check
Establish a sleep routine. Go to bed and wake up at the same time every day. Your sleep routine should be adhered to over weekends as well. If you get good quality sleep every night, you will not need to catch up on weekends which is a futile exercise, to begin with.
Control exposure to light. You should also have a pre-sleep routine 2 hours before you go to bed, limiting the amount of light you're exposed to. The digital screen gives off intense blue light that confuses your circadian rhythm, as do fluorescent lights, so installing dimmer switches in your home is wise. Glasses that block blue light will help install blue light reduction apps on your digital devices. Your pre-sleep routine should include calming activities like reading or meditation.
A dose of early morning light. Going outside early in the morning is a strong trigger to help regulate your circadian rhythm.
Avoid stimulants late in the day. Caffeine and other stimulants will throw your circadian rhythm out of sync.
Take short naps. If you feel tired during the day, there is no harm in taking a quick nap but keep it short. Long naps will interfere with your sleep routine.
Check your diet. Avoid eating big heavy meals, especially late in the day. Have three moderate meals per day, starting with breakfast, the most important meal.
Lifestyle. Modify your lifestyle to accommodate quality sleep that supports your circadian rhythms. Quit smoking and limit your alcohol consumption. Take up an active hobby like rowing or join a sports club to ensure you're getting enough exercise. Regular outdoor activities help to regulate your sleep-wake rhythm and promote healthy sleep. Give your sleep environment a makeover, so it's quiet, dark, and cool. Lastly, invest in quality bedding designed to give you a peaceful night's rest.
Seek help. Sleep disorders negatively affect circadian rhythms and can lead to more pressing health issues like strokes, heart attacks, hypertension, and psychosis, to mention a few. If you are experiencing a sleep disorder like sleep deprivation, it may take medical intervention to help you restore your circadian rhythm. Don't hesitate to call your doctor.
Research on the circadian rhythm of sleep.
Although much research on our circadian rhythms has been conducted, researchers are discovering new and innovative ways to treat conditions like PTSD (Post Traumatic Stress Disorder) by focusing on how our circadian rhythms regulate fear memory and stress response.
By better understanding the interaction between the circadian system and fear memory processing in the brain.
Research on how circadian rhythms regulate brain processes is an area of science not extensively explored.
However, recent studies show the circadian system's critical role in many different neurological disorders like schizophrenia, eating disorders, drug addiction, and alcoholism.
The many different research topics on the circadian system have provided startling evidence of how intertwined circadian rhythms are in every facet of our being. Quality sleep appears to be the spinoff of a healthy synchronized circadian rhythm system.
Good health starts with a set sleep routine, and we should endeavor to be more disciplined in how we install good sleep habits in our children, but we as adults must lead by example.