Understanding sleep rhythms: It’s not logical, it’s biological

Given that we spend a third of our lives in slumber, it’s surprising that very few of us understand the biological processes that dictate our waking and non-waking hours. Sleep is a vital contributor to our overall health and wellbeing so learning a little about the science of sleep will help us realize the importance of staying on a consistent sleep schedule, for both parents and children.

Follow the rhythm

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 progresses. 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 wakeup 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 adults ((Disorders of the sleep-wake cycle in adults. P. M. Sedgwick Postgrad Med J. 1998 March; 74(869): 134–138.)) (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 their 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.” ((Ferber, Richard. Solve Your Child’s Sleep Problems. London: Vermilion, 2013. Print.))

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

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 un-organized 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 up on this productive sleep path, we are giving them the best opportunity to practice healthy sleep habits and lead a positive and constructive lifestyle.

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