Dr. Matt Walker

Second, your sleep has a very specific pattern that has consequences to real life.

So let's say that you're someone who normally gives yourself an eight-hour sleep opportunity in bed.

But the next morning, based on what I've just told you, you say, okay, well, I want to, I'm going to get a jumpstart on the day or I've got an early morning flight.

So I'm just going to come up with numbers here.

I'm not suggesting that this is the ideal sleep schedule by any means, but just to make the numbers simple.

Let's say someone normally goes to bed at midnight and wakes up at eight.

So there's their eight-hour opportunity.

But today, they're going to wake up at 6 a.m.

rather than 8 a.m.

to get this push on the day.

How much sleep have they lost?

Well, technically, they've lost two hours of their eight-hour, so they've lost 25%.

That's not entirely true.

They may have lost 25% of their total sleep, but because of the strange structure of deep sleep first and then REM sleep later, they may have lost 60, 70, maybe 80% of their REM sleep.

So I only make this point because understanding how sleep is structured can have consequences.

I will come back to the 90 minutes, though.

It's fascinating.

We've often, and some people probably have heard this before, it's a 90-minute cycle.

Well, there's huge variability.

Some people can have a sleep cycle on average that's maybe 75 minutes.