Sleep explained in exactly 500 words

Sleep is like your significant other. You’re fond of it, but you don’t really understand it.

From an evolutionary perspective, sleep is a strange phenomenon that transforms us into unconscious, ready-to-eat meals for predators. To compensate for the risks it exposes us to, it needs to have tremendous evolutionary benefits. Turns out - it does.

Sleep is like a magic pill that happens to be free. Not only does it make you more productive and less cranky, it also reduces your risk of diabetes, Alzheimer’s, obesity, and heart disease. 

Interestingly, the relationship between sleep and heart disease is tested annually during the switch to Daylight Savings Time - over a billion people wake up an hour earlier than usual, and reports of heart attacks spike the next day.

Types of Sleep

You experience two types of sleep each night - REM (Rapid Eye Movement) and NREM (Non-Rapid Eye Movement).

  • During REM sleep, your brain creates connections between its parts - like a man clearing a path from one area of your brainforest to another.

  • During NREM sleep, your brain transfers data from one part to another using the connections formed during REM sleep - like a bunch of people using the paths in your brainforest to get to a new place. 

While NREM sleep helps you remember stuff by shifting data from temporary to permanent locations, REM sleep increases the complexity of your brain and makes you more creative. 

Fascinatingly, our mastery of fire and its effect on REM sleep might be the reason for our dominance as a species. Fire kept predators at bay, and let us sleep on floors instead of trees. This allowed us to get deeper REM sleep, which strengthened the neural connections in our brains. As a result, we were able to perform complex tasks and maintain complex relationships needed for mass cooperation - and eventual dominance.

What makes you sleepy?

While you’re awake, a neurotransmitter called Adenosine builds up in your brain and makes you drowsy. When you sleep, Adenosine breaks down - and the cycle repeats when you wake.

Besides adenosine, your internal body clock (also known as your circadian rhythm) regulates your sleep cycle and makes you sleepy when it’s time for bed.

Not everyone’s a morning person.

Circadian rhythms differ among individuals. Adolescents have circadian rhythms that shift forward, so they're wired to sleep and wake up later than adults. If you're an adolescent reading this - the next time your mom calls you lazy, you know what to say (you’re welcome).

Even among adults, only 40% are naturally 'morning people'. Daily life is designed to favor these folks, while the rest of us repeatedly smash the snooze button on our alarm clocks.

Sleep is the easiest and cheapest way to improve our health, and we’d all benefit from making more time for it.

It's ironic that I write this, it's 4 AM, and I'm sleep deprived. But today, I'd advise you to do as I say, not as I do.


That’s it for this week.

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