Dr. Matt Walker

So we can do it one of two ways.

So my way is to say, I keep you on a diurnal, nocturnal sort of schedule where you're awake during the day and you sleep at night, but I'm going to selectively deprive you of just your deep sleep at night.

So you're still sleeping and you're still spending the night timeness in bed.

which is not the shift work version, but I can block or not block.

I can significantly reduce your growth hormone because I selectively deprived you of sleep.

Or I can do the opposite, which is the shift work approach, which is I'm not going to deprive you of sleep.

You're going to sleep during the day.

but now I have held sleep constant.

So in my version, I have held nighttime-ness constant and I've manipulated sleep.

In your version, the shift worker, we've done the opposite.

We've held sleep constant, thus sleeping during the day, but we've manipulated nighttime-ness.

And now, as you said, yes, they will release some growth hormone, even though that's not the natural time on the 24-hour clock when we would see growth hormone released.

Why?

Because they are getting sleep, because it's a somewhat sleep-dependent process.

But they're not going to necessarily release as much, in part because they're not experiencing sleep at nighttime phases.

Right.

So you can elegantly separate those two out.

And that's why it's not quite one or the other, but it seems to be both.

Certainly it's a sleep sensitive.

I would say sleep sensitive is a very good way of describing it.