Biological Rhythms: The science behind the way we sleep

biological sleep rhythms

Everyone sleeps, but not everyone understands the science behind the way we sleep. Sleep is an important part of our daily functions and overall health and wellness. Educating ourselves on the biological rhythms behind the way our body responds to sleep will help us understand the importance of staying on a consistent sleep schedule, as well as implementing one for our children.

Follow the Biological Rhythms

The three main factors that influence our daily sleep are the circadian rhythm, the homeostatic sleep drive, and the mysterious ‘forbidden zone’.

The circadian rhythm (from the Latin meaning “around a day”) can be thought of as our internal clock, keeping us in sync with the natural cycle of day and night and telling us when to go to sleep and wake up. Virtually every living creature follows a circadian rhythm, which is influenced by three main factors:

Body temperature: typically, this rises during the day and drops as the night progress. Body temperature is at a minimum at around 6 hours after sleep onset.

Hormone levels: different hormones are released at various times of the day to aid the sleep/wake cycle; melatonin at night to promote drowsiness whilst cortisol (sometimes referred to as the ‘stress hormone’) is produced at its peak during the early morning hours, to promote wakefulness.  

Light and dark: the blue-ish hue of daylight literally acts as a wake-up call, telling the brain to stop producing melatonin. Darkness at night acts in the opposite way, preparing us for the night’s sleep.

The drive for sleep

After being awake for a long period of time, the urge to sleep becomes stronger and stronger. This phenomenon is known as the homeostatic sleep drive, and it creates a pull against our circadian rhythm, which tries to maintain wakefulness during the day. The homeostatic drive is very powerful in children, and the younger the child, the more influence it has. This is the reason children are better able to make up for lost sleep during a time where they should be awake. This being said, although it may be convenient, it should not be relied upon to make up for lost sleep on a daily basis.

If we don’t impose a sleep schedule, their circadian rhythm can become disrupted, confusing the body clock and creating fatigue and hunger at undesired times.

Entering the forbidden zone

This tension between our circadian rhythm and the homeostatic drive becomes greatest just before the onset of sleep, creating what’s been called the forbidden zone of sleep.  Typically occurring around 9 pm in adults1 (earlier for children), during this period, many people find it near impossible to fall asleep.  When putting your children to bed at night, it’s crucial to be aware of this phenomenon as you could find yourself fighting against your natural biological sleep timings.

Child sleep expert Richard Ferber, says “Awareness of the forbidden zone turns out to be critical for understanding and treating certain common sleep problems.”2 As the forbidden zone draws to an end, the circadian rhythm and homeostatic drive start working together, creating an overwhelming sense of fatigue which makes it harder for us to stay awake.

Surfing the wave

As a child sleep consultant, I am constantly explaining why there are ideal nap times for babies as well as an ideal bedtime. These times are considered ideal because they coincide with the child’s internal clock. When a child is put down for a nap, in order to produce quality sleep, the nap needs to occur at a time when the child is very drowsy and at the utmost readiness for sleep. Getting this right means the rest they will get during this nap to be restorative.

Understanding a child’s need for restorative sleep helps us as parents to make sure we are putting them down for a nap at the right crest of their biological sleep wave. The author and pediatrician Marc Weissbluth uses a surfing analogy to explain how to catch the best nap time for your little one.

“The magic moment is a slight quieting, a lull in being busy, a slight staring off, and a hint of calmness. If you catch this wave of tiredness and put the child to sleep then, there will be no crying. I like the analogy of surfing because timing is so important there, too; you have to catch the wave after it rises enough to be recognized but before it crashes.”3  

Take your time

Although we are all born with an innate biological clock, newborns take some time to establish their circadian rhythm. This is the reason for unorganized sleep under four months of age. But as the baby grows -and with the help of the parents – it starts to build more of a regular sleep/wake pattern, and over time, they start learning to sleep in sync with their internal rhythms. However, you must bear in mind that this internal timing system is genetically predisposed, allowing for individual variation and ensuring that no two children have exactly the same sleep patterns.

Educating ourselves on the way our internal clock influences our sleep helps us to make sure our family is getting the quality sleep they deserve. When proper rest is acquired, it, in turn, creates the opportunity for “optimal wakefulness”. If we set our children upon this productive sleep path, we are giving them the best opportunity to practice healthy sleep habits and lead a positive and constructive lifestyle.

Ferber, Richard. Solve Your Child’s Sleep Problems. London: Vermilion, 2013. Print.

Lebourgeois, Monique K., Kenneth P. Wright, Hannah B. Lebourgeois, and Oskar G. Jenni. “Dissonance Between Parent-Selected Bedtimes and Young Children’s Circadian Physiology Influences Nighttime Settling Difficulties.” Mind, Brain, and Education 7.4 (2013): 234-42. Print.

Weissbluth, Marc. Healthy Sleep Habits, Happy Child: A Step-by-step Program for a Good Night’s Sleep. New York: Ballantine, 2005. Print.

As seen on January 2014

About the Author
Diana Flutie

Diana Flutie


Diana Flutie is a Certified Child Sleep Consultant, and the founder of Big Sky Lullaby; a child sleep resource to help navigate the early years of pediatric sleep! At Big Sky Lullaby, we strongly believe that implementing a healthy sleep schedule and maintaining it throughout their early years, is one of the greatest gifts that we can give our child. After the birth of her son, Diana made it her mission to become an expert on child sleep patterns and behavior, making it the focus of her career. Diana has since become an avid child health enthusiast, (specializing in newborn to age 5) with a strong passion for implementing healthy and safe sleep habits, and helping other families do the same. Diana's programs are personalized to meet the specific needs of each client, while offering a high level of communication and support throughout the process. Big Sky Lullaby is proud to offer a military discount!

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  1. Pingback: It’s not Logical, Its Biological: The science behind the way we sleep | bigskylullaby

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