Sleep and Circadian Systems - Yale Medicine Explains

Transcript

• 00:00- Hi, I'm Melissa Knauert.
• 00:02Today, I'm gonna tell you
• 00:02about the sleep and circadian systems,
• 00:04and how they work together to create ideal sleep timing,
• 00:08and therefore, the ideal sleep quality
• 00:10and how you can use tips and tricks to move them around
• 00:13and sleep the best you can given your schedule.
• 00:18So sleep is really interesting.
• 00:20The timing of sleep,
• 00:21and immediately related to that,
• 00:23the quality and length of sleep is related to two systems.
• 00:27And so, we call them Process C and Process S.
• 00:30Process S is sleep process.
• 00:33And all that says is really, from the time you get up
• 00:36until the time you go back to sleep,
• 00:37you're slowly accumulating more and more sleepiness.
• 00:40And so as you can imagine, if you've been awake for an hour,
• 00:43you don't have a lot of sleepiness.
• 00:44If you've been awake for 30 hours,
• 00:45you have a lot of sleepiness.
• 00:47But every day combating that, and I often say, in tandem,
• 00:51is the circadian drive,
• 00:52which you could also call the awake drive.
• 00:55And so when you start in the morning,
• 00:56your circadian drive is essentially off.
• 00:59And then slowly through the day, it builds.
• 01:00And as it builds, it makes you more and more awake.
• 01:02And you can imagine it almost balancing out
• 01:04or combating that sleepiness
• 01:06so that in the afternoon, though there are some dips,
• 01:09we know about the afternoon lull,
• 01:11you really don't get sleepier and sleepier.
• 01:13But then, suddenly, right before bedtime,
• 01:16the circadian system turns off,
• 01:17and it stops alerting us, it stops promoting awakeness.
• 01:22Now, all of a sudden, you have this unopposed sleepiness
• 01:24and you feel very tired.
• 01:25And we call this either the sleep gate or sleep pressure,
• 01:28and that's what allows us to go to sleep.
• 01:30And then, as the night goes on,
• 01:32the circadian system stays off.
• 01:33And as it stays off, you can continue to sleep
• 01:36and go through the normal cycles of sleep architecture
• 01:39all the way till morning.
• 01:41That time when the circadian system is off,
• 01:43we call that biologic night or circadian night.
• 01:45And aligning when we want to sleep with that biologic night
• 01:49is one of the key parts of sleep hygiene
• 01:51and the key parts of sleep health.
• 01:56The circadian system going on during the day to alert you
• 01:59and then off at night to allow you to sleep
• 02:01is really important.
• 02:02And the way that the circadian system knows to do that,
• 02:05that's through things we call zeitgebers or time givers.
• 02:09And so the external cues in our environment,
• 02:11light, dark, feeding, exercise,
• 02:14transmit into the suprachiasmatic nucleus,
• 02:17which is our master clock, the central clock in our brain,
• 02:20to say, "It's day. It's night."
• 02:22And so it's a very layered,
• 02:23and I almost often say, networked control system.
• 02:26And so I think the traditional view of circadian
• 02:28is this top-down master clock tells everything what to do.
• 02:32And there's clocks in every cell of the body.
• 02:34What's becoming more and more apparent
• 02:36is that there's a lot of feedback in this network.
• 02:39When we eat and the clocks in the stomach
• 02:42see that we've eaten food,
• 02:43they say, "Hey, brain, it's morning, we're getting food."
• 02:46And so there's this sort of constant tug and pull
• 02:49between the clocks to orient the body.
• 02:54If you're thoughtful, you can move it, but it's hard.
• 02:56And so we have some biology,
• 02:58we also have the sum total of all the signals.
• 03:01And so, obviously, sunlight is really powerful.
• 03:03And so if you endeavor to trick your body
• 03:05into thinking that night is day and day is night,
• 03:07you need to do a lot of careful planning
• 03:10around the fact that there's sun outside.
• 03:12All of us have deadlines and work late.
• 03:14We all have jet lag and travel.
• 03:19All these things are common.
• 03:21And really, shift work is referring to the idea
• 03:24that you are trying to work when your body wants to sleep.
• 03:27You're trying to work during that biologic night
• 03:29and you're trying to sleep during biologic day
• 03:32when your circadian system is on and alerting.
• 03:34And so neither of those work very well.
• 03:37So if you can imagine, I said,
• 03:39well, if you wanna work at night and you're a day person
• 03:42and you've got your regular sleep schedule
• 03:44and you've got it all worked out,
• 03:45and you say, "Okay, my sleep is 11:00 to 7:00,
• 03:48and I do it every day of my life,
• 03:50and I'm all set, I'm all regular.
• 03:52That's when my biologic night is, I have great sleep."
• 03:55Okay, now, you need to work at night.
• 03:56You can then thoughtfully stay up later and later.
• 04:00And as you stay up later and later,
• 04:02you expose yourself to light,
• 04:04maybe you eat some late snacks, maybe a little exercise,
• 04:07maybe you do some activities,
• 04:09and you can shift that 11:00 to 7:00
• 04:11to midnight to 8:00, to 1:00 to 9:00, and so on.
• 04:14It's easier for us.
• 04:15There's some, as you might guess,
• 04:17some complexity underlying that.
• 04:19It's easier for us to push later,
• 04:21which is why, often, our folks
• 04:23who are really savvy with shift work
• 04:25know that you need to rotate, we call it rotating forward.
• 04:27But you can stay up later and later,
• 04:29expose yourself to those daytime zeitgebers,
• 04:32the light, the feeding, the exercise.
• 04:34Trick your body into pushing that circadian night later.
• 04:37And when you do that,
• 04:38you're able to work during what I call clock night,
• 04:42and you're able to sleep during clock day
• 04:45because you've pushed that biologic night
• 04:47very intentionally.
• 04:50Understanding that our behaviors create
• 04:53this time period when we sleep better is really helpful.
• 04:57And then understanding
• 04:58that if we want to, and we're thoughtful, we can move it.
• 05:00So if we say, "You know, I normally sleep this time.
• 05:02I know I'm gonna sleep best."
• 05:04And then say, "You know what?
• 05:05I've got a night shift coming up.
• 05:06I have an overnight, I have an evening shift coming up.
• 05:09I'm gonna intentionally shift it."
• 05:11And it's very intuitive.
• 05:12It's the daytime activities,
• 05:14the light, the eating, the exercise, that can move it later.
• 05:17And so understanding that,
• 05:18at least, you can gain some advantages.
• 05:20But also when you can't sleep,
• 05:22you're not frustrated 'cause you know what's going on.