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Sleep (Part 2): Circadian rhythm, Melatonin and Screens

When it is working properly, there is little doubt that the human brain is an amazing thing… even if you put aside all the knowledge it acquires or the emotional roller coaster rides that it manages to take us on over a human life!

At its most basic level, it’s doing some pretty nifty stuff. One of which is how it manages our sleep/wake cycle.

Most of us are aware of how much sleep we are supposed to be getting at night (just in case, sleep hours by age are listed below*) but did you know that your brain is hardwired to try and get you those minimum hours of sleep because our brains know how good for us those hours of shut-eye are.

Our circadian rhythm is a 24-hour cycle that is influenced by:

  • Environmental cues, such as light,

  • Lifestyle factors like exercise social activity, and

  • Internal hormonal cues like melatonin and cortisol production.

The circadian rhythm is set to match the day/night schedule of the environment

around us. It’s the body’s internal clock that:

  • Tells us to wake up early in the morning when the sun rises and tells us to feel drowsy when night falls.

  • Regulates our body temperature according to the time of day and

  • Suppresses or engages our digestive system depending on whether we are awake or asleep (ever wondered why we don’t normally feel hunger in the middle of the night? Because of our circadian rhythm…).

This is all done so that human beings can optimise energy expenditure. In this way, before the invention of electricity and artificial light, we were able to hunt for food during the day when we could see that buffalo herd off in the distance, and sleep at night in a cave safely away from predators who could see better than us in the dark.

When we are supposed to be going to sleep, the brain releases melatonin which is the hormonal reminder that this is the time you should be thinking about dosing off.

Don’t think of melatonin as a sleeping pill, it certainly won’t make you go to sleep, it’s the hormone that puts us in a state of calmness and slows respiration then encourages sleep.

Then, on the flip side in the morning, the brain releases the hormone cortisol which initiates “go-mode” and readies us for activity. And as you would expect, when one hormone goes up, the other goes down.

So, what does this brief biology lesson mean for your children?

FACT… All kids need sleep... however, we don’t all produce the same amount of melatonin, and if at regular levels, some can experience delayed melatonin release patterns that can run counter to the circadian rhythm. **

The next factor to consider is blue light. Sunlight is the biggest source of blue light however it’s also detected by the human eye through TVs, computer screens, smartphones, and tablets. Blue light stimulates that part of the brain that wants to keep us awake (the prefrontal cortex), so while seeing it emitted from sunlight in the morning is great…. seeing it emitted from the iPad at 9 pm at night when we are supposed to be settling into the calm before sleep, confuses our circadian rhythm.

So, if your child struggles falling asleep at night and device time is part of your child’s routine in the hour before bed, this may be worth raising at your next parent appointment to see if we can help tweak this habit. Also, consider having a chat about melatonin with your doctor.

*Recommended Sleep Hours by Age

Newborn 0-3 months (14-17 hours)

Infant 4-11 months (12-16 hours)

Toddler 1-2 years (11-14 hours)

Pre-school 3-5 years (10-13 hours)

School 6-12 years (9-12 hours)

Teen 13-18 (8-10 hours)

Adult 18+ (7 or more)

**There is also growing evidence that individuals with ASD or ADHD are amongst

those who experience shortfalls in melatonin activities, I.e., delayed onset or lower

overall production.


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