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Circadian science Interviews Sleeping troubles

Interview with Dr. Amy Bender


Could you introduce yourself and tell us a little bit about what you work on?

I’m the Director of Clinical Sleep Science at Cerebra. We’re a sleep technology company focused on better diagnosis and treatment of sleep disorders, but also focused on work to help the everyday person sleep better. I lead our research department on initiatives related to those key areas of better diagnosis and treatment of sleep disorders and sleep improvement.

What got you interested in sleep in general, but also sleep and performance?

My aunt was a sleep technologist and she invited me out to her lab. She hooked up a patient with electrodes, and showed me the translation of those physiological signals onto the screen—I was instantly hooked. After that I pretty much called every sleep lab that I could when I got back home and found a place where I could volunteer.

As it turned out, the manager of the place I was volunteering at was on the hiring committee to hire the Director of the Sleep and Performance Research Center at Washington State University. So there was kind of a collaboration there already. They were looking for a sleep technologist, then ended up hiring me as a sleep technologist. At the lab we focused on sleep deprivation and the impact on cognition and the sleep EEG. I started off there for about 4 years as the sleep technologist and was fascinated by the science so I applied to graduate school.

I ended up getting into a dual Master’s PhD program focused on experimental psychology while continuing to work at the lab. Having the sleep technologist background that I do, I wanted to focus on the impact of sleep deprivation on the EEG. After my Masters and PhD I ended up doing a postdoc at the University of Calgary where I was focused on Canadian Olympic team athletes and how to improve their sleep. Because I was a former athlete myself (I played college basketball, Ironman, I did some mountaineering as well), there was kind of a love for sports and performance already. Doing that postdoc at the University of Calgary was like a combination of both of my passions. Since then I have worked with a number of college athletes, professional athletes, and Olympic athletes.

It seems like the importance of sleep for sports performance is getting more recognition these days. What shifts in perception have you seen in your career?

Well, I see more of an emphasis on sleep in sports teams for sure. Previously, the coach would only focus on things that they had control over with their players while at the facility. Things like sport-specific skills, conditioning, and strength. This has since expanded into nutrition on and off the field, sports psychology, and sleep. Once we started to realize how important sleep was for performance, I think the teams and athletes started listening. We still do have a long way to go, there’s only a handful of us out there working with teams and elite athletes and so I think it can certainly grow a lot more.

For example, Dr. Cheri Mah’s study on sleep extension in Stanford basketball players and how that impacted reaction time, mood, and sprint times—I mean people started to listen and I think we’re finally getting there. If a team or an athlete isn’t thinking about sleep, then they’re really missing out on a huge area of performance.

Our CEO actually wrote a blog post about this during the Olympics. Discussing how athletes can entrain to their new time zone and for their specific competition time.

Oh absolutely that is important, I recently went on a trip overseas, and it’s apparent. I tried to do all that I could to shift my rhythms earlier (I was traveling to Europe) so I was trying to get lots of light in the morning, get up earlier, block light at night, go to bed early, you know—just trying to shift my rhythms about three days before the trip. Even doing all that, being the sleep scientist that I am, I still had jet lag upon arrival. It was a quicker recovery, but still: people need to be thinking about If they’re traveling across time zones. They may bank on the fact that “I’ll get there a week ahead of time and I’ll be adjusted by the time the competition starts”, but I think the training leading into that competition is also important for being fresh and ready and alert. It’s definitely a factor for teams and athletes traveling across multiple time zones, and there’s a lot they can do ahead of time to help prepare for that.

We’re betting people ask you for sleep tips pretty regularly. Is there anything where you’re like “people still haven’t realized how big an impact this could have for them”?

You all are a circadian optimization company, and so one of the things is that light is so important. For example, I’m in my office right now in low light, it’s only between 100 and 200 lux, and so I think it’s important for people to understand that the indoor environment isn’t necessarily optimized for circadian optimization. Trying to get outside in the morning is key for me, even on a cloudy day where light could be up to 13,000 lux or so.

It’s important for people to get outside light and go on a walk in the morning to help entrain their circadian rhythms to be more on that normal schedule. Many people don’t realize it, they think that their office environment is perfect for light. But getting the right amount at the right time, starting in the morning, is very important. Then also trying to dim the lights at night and maybe wear blue light blocking glasses in the evening are good tips for people to follow.

There’s been some work looking at office lighting, having bright white light in the morning and then as the evening approaches kind of transitioning to more of that orange kind of sunset lighting. And they do find improvements in sleep, in performance, and even mood.

Like you mentioned, we’re a circadian rhythms company first and foremost, so we gotta ask: What do you think the future holds for circadian rhythms research in the world of elite performance? How about just overall health?

I think there’s a lot to uncover here, and in particular I’m really interested in the individual, their own chronotype, their own circadian rhythm, and optimizing training times based on when they would perform the best. For example, if they’re more of an early bird but they have evening competition, how can we optimize our circadian rhythms to shift more towards an optimal performance time in the evening? I think this is a fruitful area that has a lot to be explored, and there are hints of it in the research right now. I think we could do a lot more to shift circadian rhythms for optimal performance at a certain time.

A while back, there was a realization that strength and conditioning is important, and so sports teams would add a strength coach. Then there was a realization that nutrition is also important, so they would add a nutritionist to the team. Now (potentially) I think that you might see more sleep coaches helping out teams. There’s a lot of work out there that we aren’t necessarily taking advantage of and I think that could be an area where maybe more sleep coaches will pop-up for different teams and different athletes.

Any research you’re excited about or want to highlight?

At Cerebra, we’re working on developing a kind of a miniature EEG wearable device that you could potentially wear on the forehead or even measuring in-ear EEG with one of our partners that we are working with. We want to pair that with an app to be able to figure out for the individual what their triggers are for sleep quality. We have a way to measure sleep quality using ORP (which is a metric of sleep depth which micro-analyses the EEG). We did a study recently where we had 20 people do 20 nights with our current device while tracking their lifestyle factors such as, caffeine, exercise, alcohol use, and how much they got outside. We’re really seeing some interesting results with some of those lifestyle factors and how that impacts sleep quality, and also how that impacts next day performance. Additionally, we did a reaction time test for all those individuals, we’re just finding some really interesting results and I think we want to go way beyond the “general sleep hygiene” advice for people and make it more personal and individualized.

For example, I might be a high or a fast metabolizer of caffeine, and so a coffee at 1 p.m. won’t necessarily impact my sleep quality vs someone who may be more of a slow metabolizer – where it would impact their sleep quality. I think it’s really exciting for us to really try and personalize sleep optimization for different individuals.

Actually, I was listening to a recent podcast that Olivia (CEO of Arcascope) was a guest on, and she mentioned that sleep at night starts with what you do during the day. A lot of these activities, stressors, or anxiety that you experience during the day can then impact your sleep quality at night.

Actually, before I started working at Arcascope, I had no idea that what I did during the day impacted my ability to fall asleep and stay asleep. Having experienced sleeping troubles throughout my life, I wish I had this knowledge sooner!

For sure, that brings up an important point. If you are struggling with your sleep, and you have tried different things but it doesn’t seem to impact your sleep quality, try and get help from a sleep professional. If you’ve been struggling multiple times for weeks you’ve tried everything, don’t try and solve it on your own but really try and reach out to sleep professionals who can help.

Categories
Circadian science Sleeping troubles

Visualizing MESA, pt. 1

One of the things we’re interested in as scientists is what longitudinal, large-scale data collection can tell us about sleep. Along those lines, one of our research projects involves looking at how models of circadian rhythms, as well as different sleep regularity metrics, can help us understand different outcomes for different folks. And as part of all that, we wanted to make some pretty pictures.

We recently teamed up with Ryan Rezai, a data scientist and student at the University of Waterloo, to visualize some data from the Multi-Ethnic Study of Atherosclerosis (MESA). All the plots below were made by Ryan to showcase some of the high-level properties of the MESA dataset. We think that with beautiful, interactive datasets, the nuances of big data stories, like in MESA, can become a lot clearer. Let’s dive in!

Total sleep and outcomes of interest

How much does how much sleep you get correlate with your perceived sleepiness? Below shows average nightly sleep (from wrist actigraphy—a way of measuring sleep based on how much you move) and responses to the Epsworth Sleepiness Scale (ESS). Higher numbers mean more sleepiness. Right away there’s something interesting: this plot isn’t a line that starts high at low levels of sleep and goes straight down:

Instead, we see the famous U-shaped curves of sleep research. Short version of what we mean by that: lots of bad things (like sleepiness) are correlated with both short amounts of sleep and long amounts of sleep. One natural thing to think is that, for the extreme long sleepers, there’s something underlying both the bad thing and their propensity to sleep a lot (for instance, if you’re sick, you may sleep more and also generally feel sleepier all around). But it’s certainly the case that other things could be going on too, which is why it’s helpful to consider each case of a U-shape in isolation.

We’ll come back to that in a minute. In the meantime, here’s a case of a curve that looks… pretty flat:

This graph is showing total sleep from actigraphy, plus the fraction of respondents who said they had a diagnosis of a sleep disorder from a clinician. This is actually pretty weird: why is it highest for people who seem to have a lot of hours of sleep?

Our theory: This could be one of the pitfalls of wrist-acceleration sleep tracking. Any time you’re trying to measure someone’s sleepiness from their wrist, you run the risk of mistaking “them being very, very still but awake” for “them being asleep.” In this case, it may be that the people with the large amounts of sleep recorded are simply trying to fall asleep for longer (and staying mostly still for longer), but not actually managing to do it. That could mean that their recorded sleep is quite high, but their actual sleep is much lower. It could also be another explanation for what was going on with the U-shaped curve above: maybe some of the long sleepers in that plot weren’t true long sleepers.

Here’s one more interesting total sleep duration tidbit. The number of apnea events (from a night of polysomnography, or PSG) is much higher in people who were usually found to sleep a pretty long duration (around 10.5 hours):

You might expect this to be close to a straight line (with habitual short sleepers having shorter PSG nights and fewer hours in which to have an apnea event), but it doesn’t look particularly linear at all at the end there. Another suggestive hint that some people actigraphy is picking up as sleeping for a very long time probably aren’t sleeping very well after all. (And maybe also an indicator that there weren’t that many 10.5 hour sleepers in the dataset; see: widening standard error bounds around the line).

So let’s talk about actigraphic sleep

Disadvantages of using an acceleration-based device to track your sleep: It’ll probably mistake a lot of “awake but still” time for sleep. You’ll have questions, like the ones we had above, about how accurate it is for people who are immobile for a long time. Comes with the territory.

Advantages: it’s objective. It doesn’t care about being judged for saying you only slept two hours last night.

With these pros and cons in mind, a natural question to have is: how does an objective measure like actigraphy compare to subjective measures like “asking people how long they slept last night”? For starters, if they were perfectly correlated, you’d expect them to track along the line of slope one.

Spoiler alert: they don’t.

The orange curve shows self-reported versus actual sleep, while the gray line shows the line of slope one. Those lines are not the same! Instead, we see people who sleep a long time according to actigraphy saying they sleep less than actigraphy expects, and people who sleep only a short amount according to actigraphy saying they sleep more than actigraphy is saying. These differences are pretty wild.

And there’s another interesting difference to explore here. Among people who say they don’t get a lot of sleep (subjectively), ESS scores are really high, suggesting profound sleepiness. For people who don’t get a lot of sleep according to actigraphy, not so much.

Moral of the story

Whenever you want to understand data, make a picture out of it first. Are our long sleepers sleeping a long time because they’re otherwise not doing well, or are they not even sleeping a long time at all? What effect does the choice of sleep measure—subjective or objective—have on our results? Only way to know is to try it out and see. And that’s what we’ll be doing in the coming posts in this series. Stay tuned!

With thanks to these resources:

Zhang GQ, Cui L, Mueller R, Tao S, Kim M, Rueschman M, Mariani S, Mobley D, Redline S. The National Sleep Research Resource: towards a sleep data commons. J Am Med Inform Assoc. 2018 Oct 1;25(10):1351-1358. doi: 10.1093/jamia/ocy064. PMID: 29860441; PMCID: PMC6188513.

Chen X, Wang R, Zee P, Lutsey PL, Javaheri S, Alcántara C, Jackson CL, Williams MA, Redline S. Racial/Ethnic Differences in Sleep Disturbances: The Multi-Ethnic Study of Atherosclerosis (MESA). Sleep. 2015 Jun 1;38(6):877-88. doi: 10.5665/sleep.4732. PMID: 25409106; PMCID: PMC4434554.

The Multi-Ethnic Study of Atherosclerosis (MESA) Sleep Ancillary study was funded by NIH-NHLBI Association of Sleep Disorders with Cardiovascular Health Across Ethnic Groups (RO1 HL098433). MESA is supported by NHLBI funded contracts HHSN268201500003I, N01-HC-95159, N01-HC-95160, N01-HC-95161, N01-HC-95162, N01-HC-95163, N01-HC-95164, N01-HC-95165, N01-HC-95166, N01-HC-95167, N01-HC-95168 and N01-HC-95169 from the National Heart, Lung, and Blood Institute, and by cooperative agreements UL1-TR-000040, UL1-TR-001079, and UL1-TR-001420 funded by NCATS. The National Sleep Research Resource was supported by the National Heart, Lung, and Blood Institute (R24 HL114473, 75N92019R002).

 Interested in using acceleration to track sleep? We’ve got a software package for that.

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Circadian science Lighting Sleeping troubles

Official Company Stance on Permanent DST

NOOOOOO!!!!

Noooooooooooooooooooooooo!!!!!!















(To hear our actual stance on permanent DST, check out this blog post. Short version: we love getting rid of the seasonal time change, as long as we end up on permanent standard time, not permanent DST.)

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Circadian science Interviews Shift Work Sleeping troubles

Interview with Dr. Louise O’Brien

Would you mind introducing yourself to our audience—where do you work, what do you do?

I’m Louise O’Brien, an Associate Professor at the Division of Sleep Medicine, Department of Neurology, at the University of Michigan. My work focuses mostly on sleep disruption in pregnant women and its consequences. I’m also interested in treatments and therapies available to intervene to improve the health of women and babies.

Your work largely centers around sleep and its connections to pregnancy and maternal health. What led you to this field of study?

That’s a great question. Going back a long time ago when I was a graduate student, I was really interested in SIDS (Sudden Infant Death Syndrome) and why seemingly healthy babies died suddenly at night. So, I was spending a lot of time monitoring babies overnight to understand what was going on physiologically. That led me to really want to understand more about what happens during sleep, because I realized I’m doing all this nocturnal monitoring, and I really don’t know that much about sleep. That brought me to the United States—to become trained in sleep.

What are some of the things that are really well-known about how sleep affects pregnancy?

I think most pregnant women know that sleep can be quite disrupted during pregnancy. Healthcare professionals can dismiss this as normal, or it’s the body’s way of getting ready for a baby, etc. But I think we’re now learning that certain types of sleep disruption, such as frequent snoring or obstructive sleep apnea can actually lead to poor health outcomes for mom and baby. Poor maternal sleep can lead to high blood pressure or diabetes in the mom, and can also result in poor fetal growth, preterm birth, even an increase in c-section deliveries.

We are learning more and more with the work that we do. For instance, in recent years we’re learning that sleep behaviors, like sleeping on your back, appear to be related to poor outcomes such as stillbirth. A woman who has a stillbirth in late pregnancy has been shown to be more than twice as likely to have fallen asleep on their back. So, this is a relatively new area, and an area that we’re very interested in. I think that behaviors such as sleep position are particularly interesting to me because they can be changed. And If we can change behaviors, that offers an opportunity for intervention that could potentially reduce poor outcomes.

What are some of the current research questions around sleep, circadian rhythms, and pregnancy that are most exciting to you?

I’m becoming really interested in the timing of sleep. A lot of my previous research has been on sleep disorders, like obstructive sleep apnea, which is a medical condition that can be treated. We all sleep, but we don’t all have a sleep disorder. And so, what we’re learning from the general non-pregnant population is, even if we get sufficient sleep (7-8 hours as an adult), if that sleep is mistimed against your body’s natural rhythm there appears to be an increase in blood pressure. So, I’m interested to take those findings to the pregnancy population and to see if mistiming sleep during a critical developmental window for a fetus has adverse consequences which impact the health of the mom , and also the health of the baby. Because we know that what goes on in utero can sometimes have long term effects decades later, potentially even transgenerational, this is an important area that we really don’t know anything about. So the timing of sleep is something I’m really getting interested in. Because, again, we can change it.

The obvious place we see mistimed sleep is in shift workers, but they may not be able to change so easily because they’re working shifts, and they’re working against their body’s natural rhythm. That’s an extreme example, but we know that miscarriage is higher in shift workers than non-shift workers. So the question is, what is mistimed sleep against our body’s natural rhythm really doing?

Since we’re a company that does wearable analytics: What’s the current state-of-the-art for wearable tracking during pregnancy?

It’s not very good. I think with lots of wearables out there that claim to be able to track your sleep, the reality is that none of them are really validated against the gold standard- which is an overnight sleep study. There is an algorithm that has been validated against polysomnography, a type of sleep study, but none have been validated in pregnant women. So, we just really don’t know. While there are lots of things out there that claim to track your sleep, there is nothing out there that tracks it accurately in pregnant women. There is definitely an opportunity for growth in this area, absolutely. Wearables let you look in your app, and it says “REM sleep or deep sleep”, but how accurate is that? We really do not know. So many people have wearables, and I think if we can somehow harness that technology and validate it, then we have a real opportunity to see how sleep across gestation impacts maternal and fetal health. Now this is a window of opportunity. We should be doing this now, because we could then make a huge difference to the lives of mothers and babies if we just had this data.

People sometimes use sleep and circadian rhythms interchangeably, even though they’re not the same. Are there any circadian-specific angles to pregnancy and delivery outcomes that you think are particularly important to call attention to?

I would go back to this idea of mistimed sleep. You can get sufficient sleep and still have poor outcomes, potentially if your sleep is mistimed. We’re learning that in the nonpregnant population now. So, the timing of when we sleep is really important. We already know that getting insufficient sleep is bad for us, but we just assume if we get 7-8 hours of sleep we must be fine. But, if we mistime that, then maybe we’re NOT so fine. I think this is a really interesting area, and how does that relate to pregnancy? We just don’t know, the data is not there. But, I think that this is going to be the next niche area.

Some literature that’s coming out now is adding another layer on top of that. For instance, our diet—WHEN we eat. What’s the impact of eating late at night or mistiming our eating, and how does that affect pregnancy? I think this is a more complicated area that’s going to get a lot of work in the next decade. This is where the field is going to go, and I would like to think that we would be in there somewhere you know, making some inroads into this really important area. I think it’s crucial that we understand what’s going on with our timing, and our eating, and how that’s impacting our own health and the health of that developing baby. Timing is everything, right?

Anything else you’d like to highlight, from your own work, or as an area that needs more attention?

One of the things I would like to mention is: how does sleep play into disparity in healthcare and disparities in outcomes? So for instance, we know that minority women have worse outcomes than caucasian women, we also know that minorities in general tend to have poorer sleep. How does this whole sleep, pregnancy, and disparities play together? That’s a little bit unknown at this point. This is another area that I think is really important—is there a role for sleep and addressing sleep issues in being able to improve outcomes for minority pregnant women? Outside of pregnancy, we know that minorities in general have worse sleep than caucasians, especially Black women. We also know that Black women have worse pregnancy outcomes. For instance, they have double the risk of having growth-restricted babies, and also have higher risk of preterm birth. Nobody’s really looked at pulling sleep into that. We’re looking at two parallel angles, and what I think we need to do is bring these things together to see if there is a role for sleep in these poor outcomes. Because if there is, then we can intervene.

Interested in beta testing our app? Send us an email!

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Circadian science Sleeping troubles

Naps, part one.

The first thing I want to say about naps is that I’m almost always for them. Naps can help you recover from sleep deprivation. Naps are good.

But let’s talk about that almost always. When might you want to avoid napping? 

Well, maybe you’re trying to shift your personal time zone and are at a point in your internal circadian day where getting light exposure will be very, very helpful to achieving that shift. Closing your eyes to take a nap will block photons from reaching your retina, which means your brain won’t have the photic momentum it needs to push through a shift in your rhythms. Probably not a big setback if the nap is short, but a multi-hour nap at the wrong time could end up slowing down how quickly you adjust.

Or maybe you really, really need to be alert right at the moment when you’d be waking up from a nap. In that case, you might worry about sleep inertia, the phenomenon of general grogginess and impaired performance that can persist for several hours after waking. This, too, might make you want to hold off on a nap. 

And then there is the classic “I napped, ergo, I cannot sleep now.” Your transition into sleep is driven both by your circadian clock as well as your accumulated “hunger for sleep” (or sleep drive). Feed that hunger for sleep right before bed, and you might not have enough sleep pressure built up to flip your switch from on to off. This is one of the reasons why avoiding naps in the evening is a common component of cognitive behavioral therapy for insomnia

So: You’re sleepy. You’ve got other stuff to do today. Do you take a nap? If so, how long? 

Answer: You probably want a ten minute nap. 

This, like all science boiled down to a single tidbit, is a big ole simplification. It matters what your internal time is (does your body think it’s day or night?) and what your recent sleep/wake history is. 

But multiple studies have found that a 10 minute nap during the day improves performance right off the bat, while longer naps mean that you have to sink time into recovering from your nap after you wake up. A 20 or 30 minute nap in these studies was still found to be better than staying awake, but participants could still be shrugging off the effects of sleep inertia more than two hours after waking, while a 5 minute nap was generally not enough for much of an effect.

Would you ever want to take a longer nap? You might, if your goal is not so much “perform better for the next two hours” as it is “don’t fall asleep in the next ten hours.” In a classic study from 1986, researchers kept subjects up all night, let them take a morning nap, and then measured how readily they fell asleep at different points over the rest of the day. Here, a 15 minute nap was barely better than no nap at slowing down how rapidly people fell back asleep, while a 60 minute nap had alerting effects that persisted 4 to 8 hours later. The benefits didn’t keep increasing past 60 minutes, though: a 120 minute nap didn’t get you anything more than a 60 minute one did. 

Another reason to consider a longer nap is memory. People who get a 60 minute nap do a better job at remembering words they’ve been exposed to than people who don’t get a nap. That said, a 6 minute nap is also enough to see a significant memory boost— for one tenth the time investment. 

In conclusion: You probably want a short nap. You might want a longer nap, though, if you don’t need to be super alert for the next few hours, but you do need to stay awake later in the day. 

Lastly, you might benefit from a nap, even if you don’t think of them as particularly helpful for you. The benefits of napping that show up in objective reaction time tests often aren’t reflected in how people subjectively rate their own sleepiness. You might get more of a boost from naps than you think, and you may also need less of a nap than you’d expect to see that boost.

Much of this blog post was helped along by this review. Thanks to the authors for the great resource!

Categories
Circadian science Interviews Sleeping troubles Technology

Interview with Dr. Cathy Goldstein

We sat down to talk with Dr. Goldstein on what she sees as the future of wearables in the sleep clinic. Enjoy!

Thank you for taking the time to meet with me today! Could you take a minute to introduce yourself and say a little about what your job is?

Cathy Goldstein, MD. I’m a neurologist, Associate Professor of Neurology here at Michigan Medicine, and my clinical practice is entirely in sleep medicine.

You’ve done work with [Arcascope CEO] Olivia on wearables, and you’re heavily involved in the AASM and consumer sleep technologies. Where do things stand today for consumer sleep technology and wearables, and where do they need to go?

These devices really started becoming prominent about 8 years ago. I remember I was right out of my fellowship at that time, and I thought, wow, these will be so awesome for when a patient sees me in the clinic: I have all these questions about their sleep and sleep timing, and how they sleep on the weekdays vs weekends vs vacation, and they’re in the position of having to try and remember what their problems have been over the long time they’ve been waiting to see me. 

And the problem with a sleep log [that someone fills out manually] is that it’s hard to keep up with every day. In this busy world, you need more of a passive degree of tracking, particularly over time. So when wearables came out I was like, wow, you know, wouldn’t it be cool if when the patient shows up I can just take a look at their data in the last six months and see their sleep patterns. 

The problem as far as adoption has gone, is that we don’t know how accurate they are at tracking sleep. So, there’s a medical grade version of consumer trackers called “actigraphy”, although they’re not completely accurate, we KNOW how accurate they are. And so, particularly in science and medicine, what is known is better and less scary—even if the performance isn’t great— than the unknown. 

There are a lot of unknowns in regard to consumer-targeted sleep tracking because there’s not a lot of peer-reviewed literature about the performance of these. It’s growing, but even when the accuracy does get reported in a paper, oftentimes the algorithms change with updates, or the hardware changes a little bit with each iteration. The big thing is—we just don’t know. And that’s really prevented adoption in research and clinical practice, unfortunately. 

What are the biggest misconceptions about sleep wearables that you see out in the world?

The biggest misconception is that they’re totally inaccurate, that they’re inferior to actigraphy for some reason, because the data that we have so far doesn’t necessarily suggest that. For many of these devices, we just don’t know, but the ones that we do know about appear to perform similarly. 

I’d say the other misconception is people say, “My watch tracks my sleep.” Your watch doesn’t track sleep: your watch tracks your heart rate or your pulse, and your watch tracks movement. And then, math estimates your sleep from that device. So, that’s a big misconception of people telling me in the clinic, “My device is telling me I don’t have REM, so my sleep is really bad.” Sleep stages like REM, NREM  are polysomnography EEG constructs. So, to use a consumer wearable sleep tracker’s components of dream sleep, light sleep, deep sleep, interchangeably with PSG-defined states— we’re just not there yet in my opinion. 

I do think the estimates are getting better, and they do use properties of heart rate variability that we know change in the different sleep stages, but still, those [stages] are defined by brainwaves and eye movements. So, it’s very hard to recapitulate that. The question is, “Do we even need to track that on a daily basis?” What we’re really looking for, and what the clinical and research world wants, is to track on a longitudinal basis— objectively— just sleep-wake patterns day to day.

How do sleep trackers fit in with sleep clinics right now?

People sometimes think that doctors just don’t want to look at sleep wearable data because we don’t like it—that’s not true. A lot of us love seeing this data and love seeing sleep patterns over time, particularly if a patient can tell me “Hey you know, you treated my sleep apnea with this CPAP machine, and look at the change in my wearable tracked sleep.” One of the massive problems, though, is that clinical practices are really, really busy. We have a lot of patients that need help, and we need to give everybody high-quality care. 

This means we have a high volume of work and most of our work takes place through something called the Electronic Health Record, and at this point, there is no real way to interface the data that comes from consumer wearable devices with that Electronic Health Record. So, we really don’t have a good way of integrating any of this into our clinical practice. It’s not that we are absolutely opposed to using this as an adjunct, particularly the ones that have some idea about performance, but we don’t really have a way of getting it in there to make it an easy part of our workflow. Patients will send me screenshots, or they will show me their app in the clinic. 

I think medicine moves slower than consumer-geared technologies for a multitude of reasons, including security issues, but I do think that one day we will get there. And again, we’re not using these as diagnostic tools; we’re using them as an adjunct to our clinical decision-making. So, as long as they are reasonably accurate, and we overall know how they work, I think a lot of doctors would like to adapt them into their practice as long as we have a way of seamlessly integrating that data into our workflow.

Do you think we’re going to see circadian rhythms enter the clinic more in the near future?

Yeah, and what I would hope is that they don’t just enter the sleep clinic, but they enter the wellness and general health area as well. I think a lot of us are doing all of our body systems a big disservice by living in desynchrony with both our central clock and peripheral clocks. 

When my friends and family ask, “What are some of the best things I can do for my sleep and circadian health?” I say “Wake up at the same time every single day.” That’s going to entrain your circadian phase. And hopefully, you’re eating in line with that (and you’re not eating when you’re supposed to be asleep), and when you’re getting light when you wake up. We are all undergoing mild degrees of circadian disruption by varying our wake-up time and getting as much light at night as we are.

Definitely. Especially with screens. I was one of the people who thought my phone screen couldn’t possibly affect my quality of sleep.

Exactly! And I think people are becoming more aware. I mean when you talk about intermittent fasting, that’s kind of a chronotherapeutic measure. It’s so simple, but people get so excited about it. It’s like yeah, don’t eat when your body is biologically prepared to be asleep.

You’re right that it’s incredibly simple, and I think people really respond to small changes that make a big effect on their health and wellness.

And it’s not magical, it’s timing. It’s literally all about timing.

What do you believe the future holds for sleep technology? What are you most excited about?

I’m just hopeful for a day where we change the way clinical evaluation works now, where a  patient might be waiting for me to see them for months and months, and then I see them, give them instructions, send them home with sleep logs so I can see how they’re doing, and tell them to come back to the clinic in 6 months because I’m booked out I can’t see them sooner. 

I want to get to a point where I see them, and at that initial point of care I know what their last 6 months of sleep looked like, and then I can come up with an intervention that’s precise for them and that’s also adaptive based on how their sleep looks in response to intervention. 

Then possibly, when they do go home, we can change that intervention, maybe in an automated way, maybe with me being able to interact with an app, whatever it may be – but instead of writing down instructions and giving people medications, we’re using the mobile application as a prescription to really make patient-specific interventions that are based on wearable data.

So, it’s important to make it less labor-intensive for the patient because then it’s less likely to be done correctly or be done at all.

Exactly, we’re talking about behavior change here. That’s one of the cornerstones of so many diseases we take care of in medicine: they’re due to things that with behavior change could be different, and behavior change is hard. One of the behaviors that we’re really, really good at in current society is working with our devices and our apps. So, I think it’s just a no-brainer as far as delivery goes, I think it’s really time to make this stuff an adjunct and a helper in healthcare.

What have you seen in the clinic in the age of COVID? 

I’ve seen a dichotomy. I mean I don’t think we’ve ever collectively (people my age, middle age, most of my patients) have gone through a stressor like this. So, there are quite a few people who had significant insomnia; there are people that had COVID that had major health disruptions during and following that, including fatigue during the day. Then there are people who actually had marked improvements in their sleep because they can sleep according to their clock, and they have more time due to less commute and so they can extend their sleep a bit. 

There have actually been patients who go off alertness-promoting medications, and are a bit happier with their sleep. There was a great article about a gentleman who had always felt confined to the service industry because he was a night owl. He was always kind of stuck, like a bartender/server, and during COVID (because hours were more flexible with work from home), he was able to go into other industries and have regular hours at the time he selected, and have a more stable work path. Which is what he wanted. You know, we shouldn’t chronotype shame people. Just because you’re biologically late you shouldn’t be at a disadvantage in life, and that’s helped a lot of people’s sleep.

It’s nice to hear some good news come out of the year 2020. That’s all the questions I had lined up, but do you have anything you would like to add?

I think there’s also, what can wearables NOT do. So, we don’t know how accurate the oximetry is yet, we don’t use this as a way to diagnose sleep apnea, I don’t think that sleep staging is something we should rely on. It’s that sleep disordered breathing, is not really something we have not been able to pick up yet, so when people have some episodes of sleep snoring or gasping, feeling sleepy during the day – even if your wearable says you sleep great, that is a limitation and you should still see your doctor.

So, if you feel something isn’t right, it’s best to go in and talk to your doctor.

Exactly, trust your body. The manifestation of diseases is how you feel, not just how your numbers are. 

Categories
Circadian science Sleeping troubles

Take a Break (From Social Jet Lag)

Why do you go to sleep when you do? 

Sure, there’s a big part of it that’s physical: You go to sleep because you’re sleepy. But you might also stay awake, even when you’re on the verge of collapsing from fatigue because you have work to get done. Or because your neighbor is practicing a percussion solo at 2:00 am. Or because there’s something mildly fun happening on the internet.

It’s like you’re caught in a tug of war, with your body on one side and eighteen different kinds of social pressure on the other. When your body finally triumphs and drags you into sleep, it’s winning out over incoming texts from friends, the snare drum next door, and that interesting passage in the book you’re reading. Team Body can get a boost from a stronger circadian signal for sleep, but it can also be helped along by that responsible part of our brains that tells Team Social Pressure to pack it up and go home, since “We have to get up early tomorrow, folks.”

The absence of this internal chiding is why people tend to stay up later on the weekend than on the weekdays, which shifts their circadian clock’s timekeeping, which makes it so they can’t fall asleep early enough on Sunday, which makes them end up feeling like a right proper Garfield on Monday. This is called social jet lag, and it’s been linked to lots of bad things

But what if we had a very, very long weekend? In other words: how do we sleep when we’re on break? 

I’m going to talk about this through the limited lens of a paper I was an author on in 2017, with collaborators at the University of Chicago. We looked at how people’s Twitter activity patterns changed as a function of where they were living and the time of the year. Tweeting isn’t the greatest proxy for sleep and wake, but we can at least conclude that if someone is posting a tweet, they’re probably—though not necessarily—awake.

You can make plots like the below, where the blue lines show the (normalized) amount of tweets at any point in time over the course of the day, on weekdays (dark blue) versus weekends (light blue). 

When the lines are low, less tweets are happening then. When the lines are high, more tweets. In the plot on the left that shows February tweeting, you can see a huge difference between weekday and weekend tweeting. In the plot on the right, for August, the minimum points for tweeting (the troughs) are nearly the same.

I remember seeing this and thinking, “Ah-ha! Seasonality effects! Human behavior is changing because the sun is changing over the year!” This, I thought, would be very interesting to report on. 

Then somebody on the team (one of my brilliant co-authors), wondered if it wasn’t just that people were more likely to be on vacation in August than in February. 

Reader, it was totally that.

Or, at the very least, we found some pretty compelling data to suggest that the reason why “Twitter social jet lag”— the difference between the trough in tweeting on weekends versus the weekdays— was higher in February than in August was not because of the sun being different in those two months, but people’s social responsibilities being different in those two months. 

Just look at the timing of the weekday tweeting trough versus the week of the year (red line), alongside the timing of big K-12 holidays (yellow) in Orange County, FL:

Sure looks to me like every time the kids go on break, people’s tweeting activity shifts later in the day. (You see this in other counties, too).

It’s true that tweeting in 2017 might have been disproportionately done by younger people. But this still means that, according to this proxy for sleep and wake, their social jet lag was decreased. They didn’t have to get up early for school or work, so they didn’t, and there wasn’t much of a difference between their weekdays and weekends. 

Which is a good thing! Don’t get me wrong: society is still set up in a way that punishes night owls more than early birds. But having your sleep be more consistent, and not jaggedly interrupted by the weekend, is healthy. 

This December, as we cruise towards that glorious week between Christmas and New Year’s, the sleep of those of us on vacation time will probably shift later, like we’re in one big, endless weekend. Wednesday will look like Saturday. Sunday night and Monday morning will be no big deal. 

The problem comes when we go back. Because if Twitter activity patterns are to be believed, the coming months are some of the worst in terms of “jet lagging” ourselves on the weekend.

So with the holidays coming up, take the time to rest and sleep in a nice, consistent way. Then keep it going into January. This will mean quashing down the parts of you that push for staying up late on Friday and Saturday as much as you can. But it will also mean that one of the best things about the way we seem to sleep on break will carry forward with you into the new year: better weekday-weekend sleep regularity. 

Oh, and by the way: this sleep regularity? In some ways, it might even be more important to your health than sleep duration. But more on that after the break. 

Categories
Circadian science Lighting Sleeping troubles

No, we shouldn’t make DST Permanent

I recently got some blackout curtains for my bedroom. This was pretty long overdue: about thirty feet from my bedroom window is a cheerfully bright, energy-efficient street lamp, which—while great when I’m taking the dog out for a nighttime stroll—is the photic equivalent of somebody standing in my azaleas and playing “Seventy-Six Trombones” while I’m trying to sleep. 

I’ve definitely started sleeping longer since I’ve gotten them. But I’ve also noticed that they’ve made it so I need to be even more careful about my other sources of light at night. The reason? They don’t just block my light at night. They also block light in the morning.

I’m thinking about this because it’s almost the end of daylight savings time, and, once again, there’s talk of making it permanent. As a quick guide: Daylight savings time (DST) is the one where the clocks move forward (so it’s lighter at night), while standard time is the one where the clock moves back (darker at night). The “Sunshine Protection Act”, introduced by Florida senator Marco Rubio, encourages states to observe a permanent version of DST, with the argument being that lots of good things could come out of just chilling it with the time change. 

Permanent daylight savings time means not having to change the clocks, and not having to experience that gnarly “lose an hour” in the Spring. It means no confusion about how many hours offset we are from the time in the U.K. and no struggling to remember if you should say EDT or EST when you’re trying to coordinate a Zoom meeting across time zones. As a programmer, I’m generally in favor of anything that makes the totally miserable experience of interacting with dates and times in code even marginally easier. 

But it also means—and I’m talking about permanent daylight savings time here—lots and lots of dark in the mornings. 

This is bad. It’s bad because light at night is fundamentally different from light in the mornings, because our bodies are fundamentally different at night than they are in the mornings.

Note: This picture does not apply if you’re a shift worker, a recent traveler, or otherwise circadianly weird.

Light in the morning does a couple things, but one of the most important ones is that it “advances” our circadian rhythms. It tells our internal clock that night is over and it’s time to get a move on. It makes it easier to fall asleep at night. 

And if you get a lot of light in the morning, it eventually advances you to the point where… it stops advancing you. You enter the part of your daily rhythm where light delays your clock. A sort-of “slow down, what’s the rush” period of your internal rhythm that starts in the mid-afternoon for most people and continues into the early morning.

More light in the morning: The permanent standard time solution.

And that slowdown period is the problem. Because while light in the morning is hitting you in the advance region, which you eventually get advanced out of, light at night is hitting you in the delay region, which is like a temporal sand trap. When you get light exposure in the delay region, your clock gets slowed down, which means you spend more time in the delay region. Which means you don’t feel tired as quickly, which means you get more light, which means you spend even more time in the delay region. It’s a feedback loop that spins out of control. It might be the reason that night owls exist

Permanent DST (gasps in circadian horror)

So if we adopt permanent DST, we’re adopting a schedule where we get more light during the hours most people call night, and much less light in the hours we consider morning. We’re setting ourselves up to fall into the delay region sand trap: More light in the night, making us stay up later and get delayed, and far less light in the AM hours to counteract it. 

This is what tanked permanent DST the first time we tried it. I’m not sure why this doesn’t always get brought up as the very first point against permanent DST, but we’ve totally done it before. In 1973, anywhere from 57-73% of people supported staying on DST during the winter. So they did it, in January of 1974. By the time February and March rolled around, only 19-30% of people still thought it was a good idea, while 43% said it was actively bad. 

What changed? People experienced what happens to your body when you have to kick off your day in the dark of night. They drove to work and caught the bus to school, while the sun waited to rise until 8:00 am. They didn’t like it, and rolled the decision back before the next winter came around. 

You might say, “well, time is a fake idea. Who says you have to start your day before 8:00 am?” This is a fair point. We could, societally, shift the normal times we do things to match whatever schedule we wanted. In China, where the entire country is on the same time zone, places like Kashgar (in the far west) have shifted their normal operating hours to reflect the fact that the sun might not come up until 10 am. 

But it’s a lot tougher to change social standards of when school and work “should” start in every town in the country than it is to pass a bill changing the time that appears on your phone. Which is why we shouldn’t do it: Permanent DST will put us on schedule where our traditional social standards for when things should happen are at odds with our biology, sabotaging our sleep and circadian health.


If we want to stop the whiplash of changing the clocks twice a year, why not do permanent standard time? I’m in favor of this. It reduces confusion the same way permanent DST does, but without the corresponding damage to our internal rhythms. Sure, it might mean that 9:00 pm is dark, even in the summer. But darkness at the right times is a healthy thing. And from a safety perspective, there are lots of street lamps and other sources of light at night these days that are very good at their jobs. 

Which brings it back to me and my blinds: I’ve needed to be more careful about my other sources of light at night lately because my blackout curtains mean I don’t get woken up by the sun. That’s not a big problem: I can wake up in the dark and yank them open myself, like one of the townsfolk in the first song in Beauty and the Beast

But if I get too much light at night from non-streetlamp sources, like watching Succession on my computer or looking at Succession memes on my phone, my ability to wake up in the dark in the morning is going to be less reliable, jeopardizing my exposure to that vital morning light. And I’m lucky that there’s even morning light to get: with permanent DST, I could be hopping on my first calls of the day while the sky is still black outside. 

My point is that social pressures already make it hard for us to get the darkness we need at night (let’s face it, screens are fun) and the light we need in the morning. We shouldn’t make it harder for ourselves with a change to a system that’s already failed once. Permanent daylight savings time is a no-go. Permanent standard time? Call me. 

Categories
Circadian science Sleeping troubles

Measuring Sleep Regularity

What is sleep regularity and why is it important?

Sleep regularity is a gauge of how consistent a person’s sleep patterns are, based on the day-to-day variability in their sleep–wake times. In general, having poorer sleep regularity, or irregular sleep patterns, has been shown to lead to many adverse outcomes in metabolism, mental health, and cognitive performance. Low sleep regularity has even been linked to increased inflammation. In order to avoid these and other complications, you want to increase your sleep regularity by aiming to get into bed at the same time every night.

How can we score sleep regularity?

There are at least five different metrics that can be used to quantify sleep regularity, each capturing different aspects of it and useful in its own way. The five measures of sleep regularity that we’ll look at in this blog post are listed below:

Traditional/Overall Metrics:

  • Individual Standard Deviation (StDev)
  • Interdaily Stability (IS)
  • Social Jet Lag (SJL)

Newer Metrics:

  • Composite Phase Deviation (CPD)
  • Sleep Regularity Index (SRI)

Traditionally, the most common overall metrics that have been used to assess sleep regularity are quantified by measuring sleep deviations in sleep patterns from an individual’s average. Examples of overall metrics are StDev and IS, both of which compare sleep from each day to an average sleep–wake pattern, and SJL, a metric that compares two average sleep patterns (workdays and free days).

StDev: lower is more regular / StDev⬇ = Sleep regularity⬆

This score is just the standard deviation of your sleep metric of choice, like sleep onset, sleep offset, or sleep midpoint. The standard deviation captures the variation of a quantity from its mean. 

IS: higher is more regular / IS⬆ = Sleep regularity⬆

This metric uses sleep-wake data (can also use rest-activity data) over a period of days to measure the stability of a person’s sleep-wake rhythms. It does this by comparing the pattern of daily sleep activity to the average pattern across many days. 

SJL: lower is more regular / SJL⬇ = Sleep regularity⬆

Social jet lag is a metric that quantifies the mismatch in the average mid-sleep timing between workdays and free days. Negative SJL values represent earlier mid-sleep timing on weekends than weekdays while positive values indicate the opposite.

Two newer measures of sleep regularity are CPD and SRI. These two fall under the category of consecutive metrics, which means they measure variability in sleep–wake patterns between consecutive days. The circadian system makes adjustments daily, and consecutive metrics were developed in order to utilize day-to-day information and more accurately predict circadian disruptions associated with poor sleep regularity.

CPD: Lower is more regular /  CPD⬇ = Sleep regularity⬆

Composite phase deviation is a metric that was created with shift workers in mind. CPD quantifies circadian disruption where sleep is both irregular (rotating shifts) and mistimed (sleeping in daytime). This metric uses an individual’s chronotype to determine optimal timing of sleep. The chronotype then helps to quantify how “mistimed” they are. The regularity aspect is calculated using the difference between mid-sleep timing from one day to that of the prior day. In order for CPD to be derived it requires data that has one main sleep session per day or some other daily sleep variable, like sleep duration.

SRI: higher is more regular /  SRI⬆ = Sleep regularity⬆

The sleep regularity index is a measure based on binary sleep-wake time series. It measures the similarity of a person’s sleep-wake pattern from one day to the next. The scale for this metric ranges from 0 (random) – 100 (perfectly regular) and it represents the percentage probability that an individual will be in the same sleep/wake state at any two time points. It’s important to note that this metric does not account for total sleep time so a person that (hypothetically) sleeps 0% of the time will still be able to get an SRI value of 100.

So I’m regular, that means I’m healthy right?

Well, not quite. Depending on the kind of variability you have in your sleep patterns and the method used to record your sleep, different metrics may tell you very different stories regarding your sleep regularity. Context is very important when making a decision about which sleep regularity metric to use. 

Just think about what would happen if you increased the variability in your work week sleep timing, but maintained a consistent average. Your SJL score would stay the same, while your other metrics would likely shift to indicate greater variability. The ordering of days also matters. In Fischer et al. they shuffle days around to show how consecutive metrics can give you different stories on regularity than overall metrics do.  

In order to properly assess sleep regularity for yourself or your patients, it is necessary to understand the little things that go into calculating each of these sleep metrics. A variety of unknowns, such as the type of data being gathered or the length of the data set, can cause these metrics to disagree with each other. The good news is that you’ve got lots of options to choose from. 

This blog post is heavily based on “Measuring sleep regularity: Theoretical properties and practical usage of existing metrics” by Fischer et al. The authors didn’t have anything to do with the making of this post, but we want to thank them for writing an inspiring paper. 

This post was written by Arcascope’s intern, Ali Abdalla. Thanks, Ali!

Categories
Circadian science Sleeping troubles

What School Never Taught You

I woke up feeling groggy and lazy almost every day in the past school semester leading up to this summer.

I was already doing research on sleep at that point, and I had a general idea about what I was doing wrong, but when I tried to dive deeper into the hundreds of articles on sleep science, I just found myself getting tired and confused. The last few months working as an intern at Arcascope have taught me how to get in sync with my circadian rhythms and taught me of the many subtleties that are involved with supporting your circadian system.

When I started learning about sleep, I found myself asking friends about their habits and experiences with sleep out of curiosity. I quickly realized that almost everyone I talked to had experienced frustrating sleep problems at some point during their lives and had no idea how to deal with them because they were just never taught enough about sleep. I decided that I wanted to give them some of the knowledge that they will need to improve their sleep quality by reflecting on certain essential components of sleep that I have learned about throughout this past summer.

I want to begin this informational recap by stating what I think is the most important factor involved in getting good sleep: Get enough light and get it only when you are supposed to. Getting light, especially bright light, at the wrong times causes an advance or delay to your circadian clock which essentially means that you’re giving yourself jet lag without ever having to leave your room. Light is the strongest signal to the human circadian system and it can do some amazing things when used correctly. Bright light has the ability to affect the amplitude of your circadian clock, and if you time it right, can allow you to cross time zones faster than you otherwise would. However, this kind of entrainment schedule can be especially hard to follow given the pervasiveness of screen use at night. The presence of almost any light, particularly above 50 lux, has been shown to have a melatonin suppressing effect that can make the process of falling or staying asleep difficult.

Using light as effectively as possible is not just about timing and brightness but also about daily regularity. Previous light history has been shown to affect your circadian clocks current sensitivity to light, which makes paying attention to your light exposure important to maintain your healthy sleep habits. Poor sleep regularity has been linked to many health complications ranging from subdued cognitive performance all the way to inflammation. Recently, some new metrics have been created to quantify sleep regularity which may give clinicians the chance to make more well-informed decisions regarding recommendations for their patients’ sleep health.

The timing and brightness of light, as well as the regularity of your sleep schedule, are three components that have an immense influence on overall sleep health. My personal experience in school so far has left me lacking this key knowledge on how to promote my sleep efficiency. Learning about what to be cognizant of in regards to my sleep habits has greatly increased my alertness in the early morning, and I still have lots of room to improve upon my habits. The crux of my argument here is that just being aware of the things that can mess with your sleep will inherently allow you to avoid bad situations and improve the quality of your sleep.

This post was written by Arcascope’s intern, Ali Abdalla. Thanks Ali!