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Circadian science Lighting Shift Work Sleeping troubles

What do shift workers do & what might they do?

So you want to help shift workers feel better—sleep better, be safer, have fewer of the long term chronic health problems that go hand in hand with shift work. How do you do it? Where do you start?

As some of the most circadian-wrecked people around, shift workers have been the topic of no small amount of research. Yet one incontrovertible, “best” strategy has failed to emerge for what shift workers should do. There are plenty of reasons for this, but the short answer is: it’s complicated! There are a lot of possible shift schedules a person can be on, and a lot of variation from person to person in how those shifts will affect them. In this blog post, I’ll try to chip away at the complexity a bit by covering what’s currently known about strategies for shift work, and what shift workers might do in the future.

Rather conveniently, a lot of the ways you try to help shift workers can be framed as a choice between two alternatives. So let’s start with one of the biggest “versus” there is out there.

Homeostat vs Circadian Interventions

There are two main forces that conspire to make a person feel sleepy. One is your sleep hunger, or sleep homeostat—basically, a build up of “need for sleep” that accrues when you’re awake, and drains when you’re asleep.

Figure 1 from Bailey et al., 2018. The two process model has the sleep homeostatic (red line) getting bigger while you’re awake, and going down when you’re asleep. The entrance and exit to and from sleep is regulated by the body clock (black curves). Waking up in the middle of the night? It might be because your circadian clock isn’t quite aligned to where you want it to be.

The other is your body’s circadian clock, which sends an extra strong signal once a day to tell you to go to sleep. These aren’t the only things that make a person sleepy, but they explain a lot of the phenomena we see in shift work contexts. This way of thinking about sleepiness (homeostat plus circadian) is called the “two process model of sleep.”

You could classify the strategies around helping shift workers into two camps, based on which of these two forces—homeostat or circadian— they’re primarily targeting. If you want to have a low sleep homeostat going into the night shift, for instance, you probably want to sleep as close to before your shift as you can. So you might try staying up until 1:00 pm on the day after your shift, building up a ton of sleep pressure, then falling asleep for most of the afternoon and evening, waking up right when it’s time for work. Naps and caffeine would also fall under the header of “mostly targeting the sleep homeostat.”

Targeting the circadian clock, however, means moving your rhythms to promote sleep at a time you actually can sleep. This means phase shifting your clock, which can be achieved by doing the kinds of activities that matter to the clock (getting light exposure, avoiding light, exercise, etc.) at the right times.

These methods aren’t mutually exclusive by default, but they can be in conflict at times. A lot of what decides that is the direction you choose to move your clock in.

Advancing vs delaying the clock
Two directions for shifting the clock, from Burgess et al. 2002. Large white rectangles correspond to night shifts. Small white rectangles correspond to 3 hour pulses of bright light aimed at delaying (left) or advancing (right) the clock. The pulses move in time because the person’s circadian clock is shifting in response to the signals from the previous days.

A totally day-adjusted person will probably have their peak fatigue hours occur sometime in the early morning; say, 3:00 am. If they go on a night shift, those peak fatigue hours are happening right in the middle of work hours. (Not exactly ideal). So you could shift their rhythms so that their worst hours no longer happen at 3:00 am.

Way #1 to Achieve This: Shift them later, or delay their clock. Move it so they’re feeling the biggest circadian drive to sleep at, say, 9:30 am, after they’re home from work.

Way #2: Shift them earlier, or advance their clock. Move it so they’re feeling the biggest circadian drive to sleep at, say, 5:00 pm, or before they go to work.

Way #1, or delaying the clock, is often called “compromise phase position.” The idea is that it’s a compromise for the night shift life—you’re not totally shifting to a nocturnal schedule, but you are getting the time of day when your clock maximally promotes sleep to be outside your work hours. You can do this by blasting yourself with light in phase delay portion of your body’s daily rhythms, which for a person who’s still pretty adjusted to the day schedule is going to be in the afternoon and evening. Note that this is where we start to conflict a bit with the homeostat-targeting interventions: If you’re keeping yourself in a super bright environment in the hours before your shift, you’re probably not sleeping the whole time you’re at it.

Figure 4 from Burgess et al. 2002. This schedule is a compromise between work days and off days where the schedule on off days is still very late. Shaded rectangles are sleep windows, the large white rectangles represent five night shifts (11pm – 7am), and the L symbols are recommended times for light exposure. The black triangle markers show the timing of the core body temperature minimum, or the point at which your body sends its strongest signal for sleep.

Way #2, or advancing the clock, does not come with the same homeostat conflict. To advance the clock, a person still relatively well-adjusted to a day schedule would want to avoid evening/afternoon light and get tons of it in the morning. A “sleep after 1:00 pm” intervention in which people were also dosed with bright light in the latter part of their shift saw a 3 hour shift in the timing of the circadian rhythm biomarker, dim light melatonin onset (DLMO). In other words, you can target the homeostat right before a shift and promote an earlier phase shift at the same time.

Figure 1B from Chinoy et al. Black bars are scheduled sleep periods, gray bars are periods of dim light exposure, shaded bars are work shift hours, and white rectangles are periods of enhanced light during the night shift. By sticking the brightest light in the phase advance period for these people, their clocks should shift to better adjust them to sleeping from 1:00 pm to ~8 or 9:00 pm.

There’s evidence that both strategies can improve upon a baseline of undirected, “do what you want” advice to shift workers. Advancing the clock plays nicely with “sleep before shift” strategies, but you could also take a pre-shift nap, while mostly delaying yourself in the lead up to it. You could also try splitting your sleep—sleeping right after your shift, and then again right beforehand, and using your non-sleep time to steer your clock in one direction or another (though depending on what your personal time zone is, this may be a bit difficult—those hours might be times when you’re more or less insensitive to light).

So how do we begin to choose a strategy to recommend? Well, there’s one missing dimension to all the research touched on so far that we haven’t discussed yet.

Non-shift workers vs. shift workers

All of the shift working studies cited above looked at non-shift workers who were brought into the lab and put on simulated shift work protocols. Typically, being a shift worker was an exclusion criteria for the study: No real shift workers allowed.

There’s a very good reason for this, which is that shift workers have wonky circadian rhythms. You bring shift workers into a lab and look at their dim light melatonin onset timings, and you can see coverage over almost all the 24-hour clock. This means that you wouldn’t expect a nice clean scientific result to come out of putting them all on the same schedule: What’s good for someone would almost certainly be terrible for another. Focusing only on non-night shift workers (who are, it should be said, a good model for “just starting out on the night shift workers”) means you’re able to better parse a signal from the noise.

But it also means that you miss out on a very important piece of information: Namely, that only a tiny fraction of shift workers phase advance themselves in the real world. Many of them don’t follow particularly great strategies, but the ones who are better adapted tend to be very delayed.

From Gamble et al. 2011. Gray shaded areas are nigh shift work schedules, red shaded areas are typical sleep times. From a large number of responses, the Night Stay, Nap Proxy, No Sleep, Switch Sleeper, and Incomplete Shifter strategies were identified as categories. No Sleep and Nap Proxy shift workers tended to be worse adapted, while Incomplete Shifters and Switch Sleepers were better adapted.

This result comes from work in night shift nurses that looked at the different strategies that real nurses employ. In that research, the “most adapted” nurses were the ones who basically did this compromise phase position strategy, where they were very late types on their off days. Nurses who stayed up all night before a shift or napped during the day on their off days tended to be worse adapted— worse mood, increased cardiovascular risk, you name it. Counterintuitively, the least adapted nurses also tended to be older and more experienced on the job.

When you step back and think about shift work in a vacuum, the truly best strategy from a health perspective would probably be for shift workers to shift their lives entirely to align with night work, sleeping during the day even on the days they have off. In that sense, it would be like living in the United States but pretending you worked the same hours as a person living in Tokyo. With good enough blackout curtains and strong enough willpower to ignore the FOMO of diurnal life, you truly could fully adapt to a night-living lifestyle.

A tiny fraction of real shift workers do this. But most don’t, and the vast majority want to sleep at night during the days they’re not working. The better adapted nurses in the Vanderbilt study achieved this by being pretty extreme night owls on their days off. The poorly adapted nurses, the older ones who tended to stay up all night or nap on off days— they might be the ones to benefit most from a phase advancing schedule, which appears to have worse discoverability (nobody really does it in the real world) than the delaying schedules. In other words, if one direction isn’t working—as it appears not to for the ill-adapted shift workers—try going the other way.

Time now for my caveat that this is all, once again, pretty complicated. You can be an extreme night owl on your off days right up until the moment you have to work a 7am to 7pm shift. Your actions during your off days and off hours are constantly shifting your circadian profile, so that the thing that works for you one week might not work for you the next week. None of these studies could look at DLMO changing day-by-day in the real world, because none of them had the ability to track DLMO cheaply and in real-time. What do you want to prioritize—safety on the commute? Safety during shift? Ability to sleep well and feel good? Putting one of these above the other can give you a different answer. It’s a lot.

Enough already! What should I do?

Listen, if there was a one-size-fits-all easy solution to all of this, we wouldn’t have made an app for it. I would just have emailed everyone this blog post and done that thing where you brush your hands together in the international sign of “all done here.”

Here’s one rule-of-thumb, though: If you’re adjusted to a day schedule, and you’ve got a one-off night shift tonight before going back to the day schedule, you’re not going to be able to meaningfully shift your body’s circadian clock in the next 8 hours. You’re going to want to bank as much sleep as you can in the hours leading up to it and be aware of when your peak fatigue hours are going to occur. Our app can help you with that.

For everyone else, this is where our app comes in. Shift builds on this history of research to design plans unique to your body clock. You can choose which ones to try, and give feedback on the ones you like and don’t like. Want to help us move the needle on getting shift workers to a healthier place? Reach out for early access.

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Shift Work

A Space for Shift Workers

We’ve noticed a lot of shift worker communities online. I’m not talking about just a few here—I’m talking about hundreds. These communities also each tend to have thousands of active followers. Surprising, right? Until you remember that over 30 million people in the U.S. currently live with shift work.

From Instagram accounts to Twitter hashtags, Facebook pages to subreddits, it’s clear that shift workers are looking for spaces online to connect. Some of these communities are full of funny and relatable memes, hoping to get a few laughs out of their followers. Others are centered around giving general advice and support. When we took a closer look, we noticed something else: Questions and concerns from shift workers that (directly or not) involve circadian rhythms. That inspired us to start this very blog series. It also involves our favorite thing: helping people with science.

By addressing some of these FAQs that we see online, we hope to be an additional resource for the shift work community. If you have a question you would like us to answer next in this series, feel free to email us at inquiries@arcascope.com.

1: “I would experience this weird sensation where all the sudden I feel more tired around 1:30am – 3:30am, they tend to vary but it’s really annoying, not sure what is going on…”

Ah, we know exactly what’s going on here. Around 3am is an interesting time to be awake (and no, we’re not talking about the “witching hour”). It’s because your body’s internal clock is often trying its absolute best to force you into sleep around this time. If you continue to stay awake and push through it, your clock will eventually back off and stop sending quite so strong a signal for sleep. This is probably what’s going on with the “weird sensation” this particular shift worker is experiencing.

Another fact regarding this time of night is that, due to the strong urge your body is sending for sleep, your likelihood of making a mistake goes way up. Which is another reason why it’s so important to have an internal clock that is in sync with your unique work schedule. By adjusting your internal clock, you can eliminate this excessive sleepiness that occurs in the middle of the night and be more awake on your shift.

2 “I need to lose weight and I feel like it’s so much harder to do on night shift. Some of my coworkers don’t eat at all during shift but I end up getting hungry. Yet I also will wake up feeling snackish throughout the day so I basically end up eating round the clock with no “fast” like normal people have at night. So many people say intermittent fasting is the easiest diet but I can’t figure it out with this schedule.”

We reference your body’s “internal clock” frequently. This is your central circadian clock and it’s responsible for many of your internal functions throughout the day. But did you know that your stomach also has a clock of its own?

It’s true, and your stomach is better prepared to digest food at certain times of the day versus others. You can think of this as your “ideal meal window.” The time of this window depends on the signals that come from your body’s internal clock. In other words, your specific “best” meal window is unique to you. This is why it’s important to remember that there is no one-size-fits-all solution when it comes to timing your eating. But how do you know when that window is? Well, our app, Shift, has the answer for you.

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Circadian science Interviews Shift Work Sleeping troubles

Interview with Dr. Louise O’Brien

Thanks for letting us interview you, Dr. 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.

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Circadian science Lighting Shift Work

Book of the Month (January)

The Circadian Code by Satchin Panda

In keeping with the theme of new beginnings, this January we introduced a book of the month. Join us as we work our way through books that highlight the importance of circadian and sleep health 😴 Up first: The Circadian Code by Satchin Panda of the Salk Institute for Biological Studies.

We’ve been fans of Dr. Panda’s work for a long time! For more on his research, check out our blog post on time-restricted eating.

Chapter 3: “A healthy lifestyle includes what and when you eat, when and how much you sleep, and when and how often you move. By focusing on the when, you are harnessing the power of your circadian code, which can compensate for those times when you make less than exemplary choices. Better still, by living in alignment with this internal rhythm, you reap even greater benefits that come along with making good lifestyle choices.”

This excerpt is definitely speaking our language. We love anything that sings the praises of a circadian-aware life. At Arcascope, we believe that everyone deserves to reap the benefits of living in alignment with their internal rhythm. Our app, Shift, will make it easy to do just that.

Chapter 4: “A short nap during the day is one way to repay your sleep debt. The only times when napping really works against you are when you are jet-lagged, if you are a true shift worker and you want to sleep at night, or if you are really trying to move your bedtime to earlier in the evening. In these instances, it’s better to build up your propensity to sleep at night, and then reset your clock the next morning. “

A great section to highlight. There’s a ton of focus on enough hours of sleep per day, and not enough focus on when those hours of sleep happen. Naps are great, but if you’re a shift worker or trying to shift your sleep earlier, a nap at the wrong time can throw you off course.

Chapter 4: “Small lighting changes can have a huge impact. I’m not suggesting we spend the evenings in a dark room until we go to bed There are many techniques and products that can help reduce our exposure to blue light. For instance, in the evenings, shut off overhead lights and use table lamps instead.”

Yep, this line resonated with us. Because it’s not all or nothing when it comes to living a healthier #circadian life. You don’t need perfect darkness in your evening home environment or constant sunlight during the day. Moderate, realistic changes to your daily routine can be enough to help put your body’s clock back on the right track, and our recommendations are designed with this principle in mind. We bet you’ll be surprised by how easy it is to live in alignment with your body’s clock and especially how many benefits come from doing so.

Chapter 5: ” Our brain clocks are most sensitive to light, but the clocks in our gut, liver, heart, and kidneys respond directly to food. Therefore, just like the first sight of morning light resets the brain clock and tells it that it’s morning, the first bite or first sip of coffee of the day tells the clocks in our gut, liver, heart, and kidneys to begin the day. If we change our routine from day to day, our clocks get confused.”

It makes sense to think that our bodies might be more prepared to handle food at some times (like when we’re awake), rather than others (like when we’re supposed to be asleep). And the same way light at night confuses and disrupts the central clock in our brain, so too could food around the clock confuse and disrupt the peripheral oscillators in our organs.

Chapter 8: “If you wear blue-light-filtering glasses, then you don’t have to change the light bulbs in your home or find apps for your laptop or television.”

Another reminder of how simple changes to our daily routine, like wearing glasses at certain parts of the day, can help out our body’s clock.

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Shift Work Sleeping troubles

Shift Work Disorder

What Exactly is Shift Work Disorder?

Shift work disorder, or SWD, is a type of circadian rhythm sleep disorder which is caused by working shifts that do not fall within the conventional working hours of around 9 am – 5 pm. These shifts overlap with periods of significant light sensitivity which can cause shift workers to be particularly vulnerable to having dysfunctional circadian rhythms.

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Shift Work

Living with Shift Work

It’s no secret that working night shifts does a number on your body.

From increased risks of cardiovascular disease, diabetes, and cancer, to excessive alcohol consumption and worsened nutritional intake, shift work is associated with a whole host of nightmarish health effects. 

The simple solution would seem to be to get rid of jobs that put people on work schedules that are brutal to their well-being. But society needs 24-hour emergency and healthcare workers to function, which means night shift work is here to stay.

It’d be great if there was a pill you could take to erase shift work’s negative effects. Unfortunately, there’s not much in the way of pharmacological solutions that work for shift workers at present. There is hope, however: non-pill solutions, like changing shift timings and light therapy, can offer relief to shift workers. In this blog post, we’ll cover what we know about what works for shift workers.