- Hi, I'm Melissa Knauert.
Today, I'm gonna tell you
about the sleep and circadian systems,
and how they work together to create ideal sleep timing,
and therefore, the ideal sleep quality
and how you can use tips and tricks to move them around
and sleep the best you can given your schedule.
So sleep is really interesting.
The timing of sleep,
and immediately related to that,
the quality and length of sleep is related to two systems.
And so, we call them Process C and Process S.
Process S is sleep process.
And all that says is really, from the time you get up
until the time you go back to sleep,
you're slowly accumulating more and more sleepiness.
And so as you can imagine, if you've been awake for an hour,
you don't have a lot of sleepiness.
If you've been awake for 30 hours,
you have a lot of sleepiness.
But every day combating that, and I often say, in tandem,
is the circadian drive,
which you could also call the awake drive.
And so when you start in the morning,
your circadian drive is essentially off.
And then slowly through the day, it builds.
And as it builds, it makes you more and more awake.
And you can imagine it almost balancing out
or combating that sleepiness
so that in the afternoon, though there are some dips,
we know about the afternoon lull,
you really don't get sleepier and sleepier.
But then, suddenly, right before bedtime,
the circadian system turns off,
and it stops alerting us, it stops promoting awakeness.
Now, all of a sudden, you have this unopposed sleepiness
and you feel very tired.
And we call this either the sleep gate or sleep pressure,
and that's what allows us to go to sleep.
And then, as the night goes on,
the circadian system stays off.
And as it stays off, you can continue to sleep
and go through the normal cycles of sleep architecture
all the way till morning.
That time when the circadian system is off,
we call that biologic night or circadian night.
And aligning when we want to sleep with that biologic night
is one of the key parts of sleep hygiene
and the key parts of sleep health.
The circadian system going on during the day to alert you
and then off at night to allow you to sleep
is really important.
And the way that the circadian system knows to do that,
that's through things we call zeitgebers or time givers.
And so the external cues in our environment,
light, dark, feeding, exercise,
transmit into the suprachiasmatic nucleus,
which is our master clock, the central clock in our brain,
to say, "It's day. It's night."
And so it's a very layered,
and I almost often say, networked control system.
And so I think the traditional view of circadian
is this top-down master clock tells everything what to do.
And there's clocks in every cell of the body.
What's becoming more and more apparent
is that there's a lot of feedback in this network.
When we eat and the clocks in the stomach
see that we've eaten food,
they say, "Hey, brain, it's morning, we're getting food."
And so there's this sort of constant tug and pull
between the clocks to orient the body.
If you're thoughtful, you can move it, but it's hard.
And so we have some biology,
we also have the sum total of all the signals.
And so, obviously, sunlight is really powerful.
And so if you endeavor to trick your body
into thinking that night is day and day is night,
you need to do a lot of careful planning
around the fact that there's sun outside.
All of us have deadlines and work late.
We all have jet lag and travel.
All these things are common.
And really, shift work is referring to the idea
that you are trying to work when your body wants to sleep.
You're trying to work during that biologic night
and you're trying to sleep during biologic day
when your circadian system is on and alerting.
And so neither of those work very well.
So if you can imagine, I said,
well, if you wanna work at night and you're a day person
and you've got your regular sleep schedule
and you've got it all worked out,
and you say, "Okay, my sleep is 11:00 to 7:00,
and I do it every day of my life,
and I'm all set, I'm all regular.
That's when my biologic night is, I have great sleep."
Okay, now, you need to work at night.
You can then thoughtfully stay up later and later.
And as you stay up later and later,
you expose yourself to light,
maybe you eat some late snacks, maybe a little exercise,
maybe you do some activities,
and you can shift that 11:00 to 7:00
to midnight to 8:00, to 1:00 to 9:00, and so on.
It's easier for us.
There's some, as you might guess,
some complexity underlying that.
It's easier for us to push later,
which is why, often, our folks
who are really savvy with shift work
know that you need to rotate, we call it rotating forward.
But you can stay up later and later,
expose yourself to those daytime zeitgebers,
the light, the feeding, the exercise.
Trick your body into pushing that circadian night later.
And when you do that,
you're able to work during what I call clock night,
and you're able to sleep during clock day
because you've pushed that biologic night
very intentionally.
Understanding that our behaviors create
this time period when we sleep better is really helpful.
And then understanding
that if we want to, and we're thoughtful, we can move it.
So if we say, "You know, I normally sleep this time.
I know I'm gonna sleep best."
And then say, "You know what?
I've got a night shift coming up.
I have an overnight, I have an evening shift coming up.
I'm gonna intentionally shift it."
And it's very intuitive.
It's the daytime activities,
the light, the eating, the exercise, that can move it later.
And so understanding that,
at least, you can gain some advantages.
But also when you can't sleep,
you're not frustrated 'cause you know what's going on.