Olivia Walch is an investigator in the Department of Neurology at the University of Michigan and CEO of a tech start-up called Arcascope. Her research has been featured on CNN, NPR, and in The Atlantic, among other outlets. Beyond sleep research, she co-edited Political Geometry, a book on the mathematics of gerrymandering, and published comics with The Nib and Silver Sprocket. She is also the cartoonist of Imogen Quest, a webcomic that won her the “America’s Next Great Cartoonist” prize from the Washington Post.
What’s the big idea?
If you are dancing and can’t catch the beat, you are not dancing well. In this way, if your sleep doesn’t follow a regular pattern that matches your biological beat, then you are not sleeping well. To find the beat your body is wired to cycle through and not just step along with it but groove with that beat, it’s important to develop an intuition about how your circadian rhythms work to shape overall health.
Below, Olivia shares five key insights from her new book, Sleep Groove: Why Your Body’s Clock Is So Messed Up and What To Do About It. Listen to the audio version—read by Olivia herself—in the Next Big Idea App.
1. Sleep is like your heartbeat; rhythm is central to health.
Even if both beat 60 times a minute, you wouldn’t say an arrhythmic heartbeat was as healthy as a regular one. Yet, we do this all the time when it comes to sleep. We think that as long as we get eight hours a night on average—even if one night you go to bed at 8 pm and the next you stay up until 2 am—the rhythm doesn’t matter.
Except it totally does. A recent study found sleep regularity (how much your sleep schedule on one day resembles your sleep on the next day) to be a better predictor of mortality than sleep duration. Every day, a new study comes out linking sleep irregularity to hypertension, diabetes, cardiovascular disease, you name it.
Sleep regularity correlates with all these things because it correlates with circadian health. Specifically, when you have regular sleep, the signals you send to your body’s circadian clock are very rhythmic. When you give your clock rhythmic inputs, then it is more confident about when daytime is and when nighttime is, and it does a better job scheduling things that happen during the day, at night, and at all the times in between. One of those things is making you feel sleepy at bedtime, but other things include metabolism, DNA repair, and immune response. In general, you do better when your body does those things confidently at the right times versus muddling through them at all hours because of mixed signals.
2. Circadian rhythms are like being on a swing.
The same input can give you wildly different outputs depending on when it’s delivered.
When I say being on a swing, I mean a classic playground-style swing. In this analogy, that rhythm (swinging back and forth) is a stand-in for your circadian rhythms. The input, when you’re on a swing, is a push in the forward, outgoing direction. Biologically, that push in the outward direction can be anything that affects your clock’s sense of time. The biggest influence on your body’s sense of time is light exposure, but meal timing and exercise can also affect what time your body thinks it is.
Let’s go with light exposure since it’s the primary signal your clock pays attention to. Getting light exposure when your body expects it, during the day, is like a push in the forward direction when you’re heading forward. It helps reinforce your rhythm; it helps you get to a higher amplitude swing. But that same forward push when you’re on the backswing actively messes up your rhythm. You don’t want someone to give you a forward shove when you’re swinging backward. Similarly, when you’re entering your biological night, you don’t want a burst of light exposure—you want to continue in the dark. Just like how a forward push is good at some times, that burst of light exposure is critical for health only when you get it during your biological day.
“When you’re entering your biological night, you don’t want a burst of light exposure.”
This is both a simple point—if I get light during the middle of the night, it will confuse my brain and throw off my rhythms—and a hard one to internalize. We’re not primed to understand how the same thing can go from good to bad to good again as time passes. We don’t think of anything being more rhythmic as making us healthier. I chose the title Sleep Groove because groove—along with “getting in the swing of things”—is a concept that explicitly ties rhythmicity to positive outcomes. I think our way of understanding health writ large will change once we begin to think of not just sleep but all aspects of health, in terms of how much they’re grooving.
3. Circadian rhythms are like walking.
Circadian rhythms are robust, stretchy, able to entrain, and can be more or less in a groove. Let’s say I gave you a yellow shoe and a black shoe, and I told you to walk on a sidewalk with alternating yellow tiles and black tiles, with your yellow shoe hitting yellow tiles and black shoe hitting black tiles. If the tiles were well sized for your legs (not too long, not too short), you’d be able to adapt your stride to match this yellow-on-yellow, black-on-black pattern. This process of adapting your rhythms (your gait) to match the environment (the sidewalk) is something circadian scientists call entrainment. You’re able to stretch or shrink your walking pattern to match the size of the tiles, which is what I mean by stretchy. If I randomly put a puddle on the sidewalk that you had to step around, you could do that, throwing off your walking pattern temporarily, and then falling back into the pattern once you were around the puddle—which is what I mean by robust.
Your body’s clock is the same. For circadian rhythms, it’s not the color of tile your body is adapting to but the light exposure you get. Your natural day length—how often your circadian rhythms would repeat if you were cut off from all signals, like light and food timing—is probably a little longer than 24 hours, but your circadian clock adapts to match the lighting patterns in your environment the same way you can adapt how long your stride is on a sidewalk.
Or at least it tries to. Imagine I take that original sidewalk and change it so you’ve got a yellow tile, followed by a black tile, and then a shorter grayish tile that looks halfway between yellow and black. Step with the yellow foot on the yellow tile and the black foot on the black tile, I tell you, except now it’s kind of hard to do. You can still manage it, but you’re not taking strides of an even size with a consistent tempo. You’ve gone from walking in an easy, effortless groove to stepping. When we give our brains ambiguous day/night signals, our circadian clocks struggle to keep a rhythm going. It’s one of the reasons why Daylight Savings Time, which moves the light later in the day, is so disruptive to sleep and health.
4. Your sleep system is like a water cooler.
“Listen,” you might be saying, “this is all very well and good, but my problem is that I wake up in the middle of the night and can’t fall back asleep. What do multi-day patterns of light and dark have to do with me waking up on Tuesday at 3:40 am?”
You’ve probably been to a barbecue before, gone up to a water cooler to fill your glass, and noticed, as you’re pouring, that the level’s getting low. If it drops too low and falls below the level of the tap, your flow of water is going to stop. So, you tilt the water cooler toward you to keep the flow going and get a nice, long, uninterrupted pour.
“Your circadian clock tilts your system in favor of sleep during your biological night, allowing you to sleep longer than you would without the tilt.”
This is exactly what your circadian clock does during your biological night. Think of your sleep system as governed by two things: how “hungry” for sleep you are (how full your cooler is) and how much your circadian clock is promoting sleep (how tilted your water cooler is). Sleeping is when you drain the water cooler, and if your water level (sleep hunger) falls below the level of the tap, you wake up. Your circadian clock tilts your system in favor of sleep during your biological night, allowing you to sleep longer than you would without the tilt. It also tilts away from sleep at some times. If you’ve ever tried to scoot your bedtime up a few hours and been unable to do it, it could be because your circadian clock is tilting your sleep water cooler away from you, making it so that even though you’re pretty full of water (sleep hunger), the level is below the tap and you can’t fall asleep.
If you wake up in the middle of the night and can’t fall asleep again, here are three reasons why that might happen:
- You might have gone to sleep earlier than your clock expected. The tilt is still coming; it’s just late. If you stay in the dark and wait for it to hit, you might be able to fall back asleep.
- You might have gone to sleep later than your clock expected. The tilt could have come and gone already. In this case, it could be tough to fall back asleep, even if you try to wait. Try going to bed earlier the next day.
- Maybe you tilted at the right time, but it wasn’t a big enough tilt. It was a shallow, barely-there tilt. That can happen to older people or those who have lower amplitude rhythms. The theoretical way to boost amplitude is to get really bright light during the day and the darkest dark at night, at the same time every day. If you think you might not have enough of a circadian tilt to your sleep at night, send your brain clear, unambiguous day/night signals for at least two weeks and see what happens to your sleep.
5. Circadian rhythms are like an audio recording slowed way, way down.
We don’t understand how much of our health is rhythmic because the rhythms happen on a timescale too slow for us to really notice. But rhythms are fundamental to how our bodies work, even if we don’t always consciously register them.
Let’s bring it back to the heartbeat analogy. If you were performing chest compressions on someone in cardiac arrest, you wouldn’t do one push, sit back, and decide you’ve done everything you could. We intuitively understand that rescuing a heartbeat means giving it a clear rhythm of inputs to lock onto. The same goes for your sleep.
To rescue a grooveless sleep rhythm, there’s no one-time hack. You need to fundamentally change how you think about light, activity, and food to center rhythmicity. If you give your body enough time to find the beat, you’ll notice differences not only in how you sleep but also how you feel.
To listen to the audio version read by author Olivia Walch, download the Next Big Idea App today:
