What a Sleep Expert Thinks of Sleep Trackers

Tricia Ward


March 28, 2022

The pandemic not only disrupted sleep but may have also triggered an uptick in the use of wearable tech. Sleep tracking was featured at the Cardiovascular Health Tech virtual conference 2022, sponsored by the Institute of Electrical and Electronics Engineers (IEEE) Engineering in Medicine & Biology Society technical committee on Cardiopulmonary Systems and Physiology-Based Engineering.

Kelly Glazer Baron, PhD, MPH, DBSM

Medscape caught up with presenter Kelly Glazer Baron, PhD, MPH, DBSM, an associate professor at the University of Utah and a clinical psychologist specializing in behavioral sleep medicine.

This interview has been edited for length and clarity.

Are consumer sleep trackers mainly divided into "nearables" — things that you put at the side of the bed or under the pillow — vs wearables?

There are so many different devices these days. There are things that you put under your mattress or pillow; there are bedside recording devices; then there are headbands, rings, wrist-worn, all kinds of things.

At the conference, Philip de Chazal, PhD, (University of Sydney, Australia) described the evidence on sleep tracking smartphone apps as woeful. Would you agree with that?

Yes. I would agree if you're looking at how accurate they are at recording sleep, particularly compared with what we would define as the gold standard, which is a sleep study wherein you have electrodes on the scalp and you're measuring the electrical activity directly.

Devices that go under the pillow are extremely poor at deciphering sleep from wake time, which is really the main goal. They are best at detecting when you get into the bed and when you get out. But even then, there isn't good evidence that they do that accurately when there are two people in the bed.

Overall, they may give you a general gist of what's happening in terms of time in and out of bed, but we're doubtful on their recording ability to tell sleep from wake time.

Are the wrist-worn devices better for sleep tracking?

They're getting better. We've used wrist activity monitors in research for years. They use an accelerometer to measure movement, and then an algorithm determines whether an interval of time is called sleep or wake.

Recently, they've incorporated more sensors, such as heart rate, and they can more accurately decipher rapid eye movement (REM) sleep from non-REM. They're still not as good as doing a full sleep study. But they're getting closer.

If asked how you slept, most of us think we can answer without needing to look at a smartphone, but maybe not. Can you explain "paradoxical insomnia"?

You can't really know if you're sleeping because if you know you're asleep, then you can't be asleep because it's a state of unconsciousness. How people decide whether they had a good night's sleep probably depends on a lot of things about how they feel when they wake up in the morning or if they remember being up in the night.

Quality of sleep is not really something that people can directly ascertain. There is a selection of people who feel awake all night but they actually are sleeping. They feel that their sleep quality is poor: They're suffering, they have insomnia, but from the objective data, they are sleeping fine.

Is this related to non-REM stage 1 sleep, when you may not be aware that you're asleep

No. I'm talking about people who come into the sleep lab for an overnight study and get hooked up. And in the morning, they'll tell the tech I was awake all night, but the tech will see that their sleep was just fine.

There is a disconnect between how people perceive their sleep and how they actually sleep. For most people it's impossible to be completely accurate to know how much you're sleeping. Then there are some people who perceive it very differently.

Sleep trackers don't have the level of detail of sleep studies that use scalp electrodes. When we get into the details of sleep measurement, we're measuring 30-second epochs (sampling periods), where we look at broad measures of electrical activity. There is even more detail there that can be pulled out using other techniques, such as analyzing the spectrum of the EEG. For example, some studies have found a beta frequency in the EEG of people with insomnia, so even though they are sleeping, they often feel awake .

Basically, the subjective experience of sleep somewhat overlaps with the objective recording of what's happening on a sleep study, but not completely.

You said that first thing in the morning might not be the best time to assess your sleep — if you wake up groggy and are already thinking, The day is shot.

In general, people really feel worst in the morning. Their circadian drive is low, especially if they're a little sleep deprived. You shouldn't judge the day on the first hour after waking — most people are pretty cognitively impaired. I tell people they need some boot-up time.

You feel differently as the day goes on and even at different points of the day. There's a lull in the early afternoon because of your circadian dip and then we get a second wind in the evening. How you feel isn't one flat line; it's really a rhythm throughout the day

Would you say that consumer sleep trackers are okay for individuals to use to see a pattern but are maybe not accurate enough to use more globally in research?

I think there is a huge opportunity to understand sleep at a population level. For example, if there's been a hurricane or an earthquake or Superbowl Sunday, companies have an opportunity to look at the impact — say, daylight saving time and how it affects sleep across different countries, or men vs women, or different age groups.

There was a paper about sleep among hospital workers in Wuhan during the outbreak of the pandemic. That was a creative use of wearable devices to look at sleep in a large population.

Now, of course, the devices are not given out randomly; the people who buy them are probably a little bit healthier, maybe a little bit younger — that sort of thing. It is a biased sample

As you note, mobile health trackers tend to be used by the "worried well." Can you tell us about your paper that introduced the term "orthosomnia," or "a perfectionistic quest for the ideal sleep in order to optimize daytime function"?

As these devices came out, more people were coming into the clinic and shoving their data in front of us saying, "I don't feel well, and I don't sleep 7 hours." They were focused on this specific number. Back when we wrote this paper, the devices were primarily movement-based (now the devices are a bit more accurate). Some would say, "My sleep is light and it's not deep." We'd do a sleep study that showed that they have deep sleep, but they would still believe their device even though the device really wasn't able to classify sleep accurately.

We even found people making their sleep worse because of the device. For example, trying to get the number higher by spending more time lying in bed trying to sleep which is the opposite of what you want someone with insomnia to do. These people held the data so tight and really felt that it characterized their experience, even though we sleep medicine practitioners didn't find it very accurate and felt that it was somewhat unhelpful to their treatment.

A sample hypnogram depicting sleep stages of a normal, healthy adult.

What advice would you give the harried primary care physician presented with a patient's hypnogram or sleep pattern?

As someone once pointed out to me, it's a conversation opener about their sleep. Did they buy the device because they're worried about their sleep? It's unlikely that you can glean anything clinically useful from the data.

I briefly look at it to see the duration of their sleep, the regularity in their sleep pattern — the pattern of awakenings during the night might suggest that they have some insomnia. But it doesn't take the place of clinical assessment for conditions like sleep apnea: Are they snoring? Are they unrefreshed?

I had a patient in the orthosomnia study who was given a sleep tracker by a family member. He brought the data to his doctor who ordered a sleep study that found he had sleep apnea. He would say, "The device diagnosed my sleep apnea." But that wasn't actually the case; it just opened the conversation and the clinician said, "Well, let's order a sleep study."

The device told him he wasn't getting much sleep and then the sleep study told him it was apnea.

Right. It's impossible to pick up sleep apnea. Some of the latest devices have some oximetry reading but it is not a clinically validated oximetry that could diagnose sleep apnea.

When these first came out I thought I'd get more referrals. So far, I haven't had a single person come in and ask if they have sleep apnea. If you have a patient saying, "Hey, I'm worried about my oxygen level and here's my data," then the clinician should consider whether they need a sleep study for sleep apnea.

You did a survey that suggests that clinicians are less keen on these devices than consumers. Conor Heneghan of Fitbit/Google also mentioned a study using the Fitbit Charge and a SleepLife portal. The patients were very engaged but only one physician (out of 49) logged into the portal to look at the data.

Our survey of sleep professionals (which we need to publish) showed that they were wary of the data. They found it frustrating in some ways because it took time out of the clinical encounter.

Some of them said that parents are putting trackers on their children and then catastrophizing their children's sleep.

Is there such a thing as an ideal hypnogram or does it vary by individual?

I would say that it depends on a lot of things. If you think about a hypnogram from a sleep study, the patient is not sleeping in their home environment and it's only one night. There's a range of what would be considered normal, and it's related to your sex and your age.

One night is not going to be sufficient to characterize your percentage in this or that sleep stage. Our patients come in saying, "I'm not getting enough REM." But there isn't a sleep disorder called lack of REM; there's no treatment for that. It's probably pretty normal for them or maybe they're taking medications that suppress their REM, such as antidepressants.

The tech world is very interested to sense REM properly and to display it. But on the treatment side of things, there's not much that we do with that data. We're more interested in the consolidation of their sleep, the duration of their sleep, breathing-related sleep disorders, those sorts of things.

Is there any reason to be concerned about the amount of REM sleep in terms of outcomes? We know that poor sleep can lead to bad cardiovascular outcomes, but has any of that correlated to sleep stage?

There are studies where they've experimentally deprived people of certain stages of sleep, but they're not very useful in the real world. We're looking at sleep holistically: Do you have a good sleep pattern? Any breathing-related sleep disorders? Insomnia? We don't treat sleep by the stage.

Any concern that people who are focused on a device may be ignoring the basic tenets of good sleep hygiene?

If people are doing things that are obviously bad for their sleep, like working too late, not exercising enough, sleeping in on weekends to compensate for being up late during the week, or probably the biggest thing contributing to insomnia —stress. A device itself won't fix those things but it could show you the evidence.

If somebody really has a sleep disorder, then sleep hygiene alone is probably not going to be enough. They're going to need to engage in a more extensive program to improve their sleep, such as cognitive-behavioral therapy for insomnia.

Is there anything else you want to mention?

I don't want to leave with a reputation of being against sleep trackers. I think they are a great opportunity for people to get excited about and learn about their sleep and try to improve it. We have a lot to learn about what people want from their data and how we can use that data to improve people's sleep.

As providers, we can engage with our patients — sleep is an automatic process, but improving sleep takes some effort. Buying a device is not going to automatically make you sleep better. It takes work to establish a better sleep pattern, it may require some cognitive-behavioral therapy or treating a sleep disorder. That takes some work.

Kelly Glazer Baron, PhD, MPH, DBSM, reported no conflicts of interest.

Tricia Ward is an executive editor at Medscape who primarily covers cardiology. She has a smart watch but has never used it to track her sleep (it's usually charging overnight). You can follow her on Twitter  @_triciaward

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