Sleep Tracking Devices

By Jessica Thomas, MPH

In recent years, there has been a dramatic increase in the purchase of devices that monitor sleep quality and quantity. This is driven by increased marketing efforts and a heightened understanding by consumers of the importance of sleep for overall health. To gain more knowledge on these devices, we spoke with Dr. Timothy Morgenthaler, the Director of the Center for Sleep Medicine at Mayo Clinic in Rochester, Minnesota. Drawing on his 25 years of professional experience, he enlightens us on wearables and "nearables" and their role in sleep medicine.

Wearables and Nearables: Understanding What They Are

No matter what type of device a person decides to buy, it’s important to remember that all devices have the same fundamental goal: to collect information and offer insight into the amount of sleep a person gets and the quality of their sleep.

Wearables are the category of devices that you are likely most familiar with. They come into direct contact or touch with the person using them. Think of devices like Apple Watches and FitBits. Many devices commonly considered smartwatches and activity trackers now include sleep tracking technology.

"Nearables" are devices that come near a user without directly touching them. For example, these devices could use sensors or pads placed directly under a person’s mattress. While some devices are clearly placed very near to the user, Dr. Morgenthaler cautions to not emphasize the "near" part of nearables. He notes that as technology improves, these devices can likely be placed farther and farther from the individual.

Not All Products Are Created Equally

There has been an explosion of new products available in the wearable and nearable markets in recent years. Many consumers struggle to separate the good devices from the not-sogood. Dr. Morgenthaler notes that this could be challenging even for medical providers since there is a lack of peer-reviewed studies that compare products. Even when studies do exist, they are often based on earlier, less relevant generations of the device since technology is evolving so quickly.

Numerous factors may explain the quality differences between devices. One driving factor is that different devices use different technologies to collect patient data. For example, Dr. Morgenthaler notes that wrist-based wearables tend to focus on activity as their baseline. Algorithms then use the information to create conclusions. However, these algorithms may vary dramatically from company to company, which can also play a role in quality differences.

Next Generation Data Collection Offers More Information

Movement-based measurements are typical in many wearables. Newer models, however, also collect other information, such as heart rate. Changes in heart rate and/or pulse rate can give insight into whether a person’s sleep is disrupted or not. It can also provide information, at least to a limited degree, on which sleep stage a person is in.

Nearables also collect data based on a person’s movement. For example, sensors placed under a person’s mattress can measure whether a person is tossing and turning during the night based on subtle pressure changes in the mattress. This tossing and turning can be a sign of disrupted or low-quality sleep. The sensors in under-mattress nearables are usually finely calibrated and can detect even slight pressure changes, such as those that could result from snoring.

Not all nearables collect information based on movement or activity, though. Some nearables use infrasonic sound waves to collect information about heart rate and breathing rate, as well as other physiological data. Other, simpler nearables use a microphone to detect sounds during the night, including snoring.

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The Challenges of Nearables and Wearables

While nearables offer invaluable information about sleep quality and quantity, they are not perfect. For example, they may detect noises that another person in the room (not the device user) is making. They may also pick up background noise that is entirely unrelated to a person’s sleep. It’s a careful balancing act to get the sensitivity of sensors precisely right.

There are also potential problems that affect the quality of information from wearables. Some wearables may have too sensitive of a threshold that records everything as a movement, even if it is not really a movement. At the same time, other wearables may lack sufficient sensitivity and movement may be missed.

Problems also occur when the algorithms for the collected information incorrectly evaluate the data. Many companies have worked to improve their algorithms and correct the errors, but it’s not always perfect. Updating algorithms can also take extensive time. Some companies seem to be better at this process than others, based on Dr. Morgenthaler’s evaluation.

Final Words of Wisdom from Dr. Morgenthaler

When asked for his conclusions

The good news is that most devices available on the market do a relatively good job of estimating how much a person is sleeping each night and when they are falling asleep. Information about the total amount of sleep is one of the most important pieces of evidence that a provider may need to start treating sleep disturbances. The information generated from these at-home devices often closely mirrors what doctors find from inpatient sleep studies. Currently, though, overnight tests, such as sleep studies, are undoubtedly more scientifically rigorous

Consider This Cautionary Note

Dr. Morgenthaler emphasizes that wearables are much less accurate at determining sleep stages. For instance, some users might be concerned when their wearable tells them that they are not getting enough REM sleep. It’s important to consider that this conclusion may not be correct since it hinges on differentiating heart rate variability from stage to stage.

Reassuringly though, sleep stage information is frequently not integral in driving treatment protocols, according to Dr. Morgenthaler. However, it may be challenging to communicate this limitation to wearable users, who are often quite attached to the data they receive from their devices.

About

wearable and nearable devices, Dr. Morgenthaler describes them as the ultimate double-edged sword for both medical providers and users. People who use these devices often come to doctors with lots of data from their devices. Although this data can be helpful in starting conversations, it can also take time to sort out what information is truly meaningful.

The most important thing that Dr. Morgenthaler wants wearable and nearable users to know is that these devices can be great starting points. At this point, however, they should never replace a thorough clinical evaluation from a skilled sleep practitioner. He also cautions that buyers need to carefully sort through the large variety of available options and focus (when possible) on buying a device that has been independently scientifically tested