A new crop of consumer technology devices can measure your sleep. What's next for sleep-tracking tech? (Timothy Krause)
The alarm starts ringing as you're in the midst of deep sleep. Your limbs feel like lead, eyelids are glued shut, and even basic communication isn't feasible until that first cup of coffee.
We've probably all experienced that feeling, of being abruptly woken up when we really want to be asleep. Now, a handful of technology companies are developing sophisticated wearable devices that are capable of detecting when you're ina lighter stage and waking you then.
Sleep-tracking technology has made major strides in the past five years, although it's still in its early days. Some wearable-makers that offer sleep tracking are aiming to target the 70 million Americans with chronic sleep problems, including insomnia and night terrors, while others are focused on helping people optimize their slumber.
To find out what will be possible in the near future, KQED sat down with Dr. Matthew Diamond, a San Francisco sports medicine physician, member of the National Sleep Foundation's Sleep Technology Council and the medical director at Misfit. This interview with Diamond has been condensed and edited for brevity.
As a sports medicine doctor, why are you so interested in wearables and sleep tracking?
It's really important to me to understand how people are sleeping, especially if they have neck pain or back pain. During sleep, the body produces a hormone that is essential to the healing of muscles and joints.
How have doctors like yourself historically measured sleep -- and what's possible now?
For decades, the sleep study involved going into a sleep lab and hooking a patient up to 50 different wires. It's a very artificial environment, but that's the standard in understanding how we sleep. Now, a device from a consumer technology company like Jawbone or Misfit can give you pretty reliable information without the hassle. These devices contain sophisticated sensors and can be worn on the body.
How do these consumer devices track sleep?
The most commonly-used sensor that you'll find in these devices is an accelerometer, which measures movement. This may seem basic but it's valuable as our body transitions through different stages of sleep.
A normal night of sleep is actually quite a journey that takes us from light sleep to medium sleep to deep sleep and then back to lighter sleep -- and this happens in cycles that last from 90 minutes to two hours. Each stage is associated with a movement pattern. Everything should slow down in the deeper stage, when blood pressure gets lower and our movement diminishes. The sensors in these devices can pick up on this and help us understand how restless the sleep is overall.
Aside from movement-tracking, are there other sophisticated methods to track sleep?
Some devices contain sensors that also measure heart rate, which can allow for even more accurate understanding of your sleep. Another fascinating technology called "BCG," which stands for ballistocardiogram, picks up on vibrations created by the pulsing of the heart. This was a method used by cardiologists before the invention of more sophisticated technologies like the ultrasound. Using similar technology, sensors in the bed can pick up on the force created by the vibration of each heartbeat.
What are the best available methods to measure your sleep?
You can wear a tracker on the wrist, but the downside is that these devices are energy hungry. The Apple Watch, for instance, is not ideal for sleep-tracking as most people charge it overnight. There are also the sensors that can be placed in the bed from companies like Withings and Misfit. It is a thin ribbon sensor that you can put on a mattress -- it can detect the movement of the heart and your breathing.
Who should track their sleep: Athletes, people with sleep troubles or just about anyone?
If you are an active person, it's worth putting on an activity tracker even just for a week. You might notice, for instance, that at the end of the day you are only 20 percent towards your activity goal because you've been holed up in the office. The same is true for sleep tracking. It's easy to fool yourself that you're sleeping fine if you're not paying attention. Sometimes if you're feeling a bit off, it can be tough to attribute that to poor quality sleep without the objective data.
When will we be able to use these sensors to wake up at the optimal time?
With the more advanced digital sleep sensors it's possible today to set a smart alarm to wake you in the lighter stages of sleep rather than the deeper stages. This has the benefit of making you feel less groggy in the immediate period after awakening. But I would caution against using a device to wake up too much earlier than you need to.
What will be possible in the next 3 to 5 years when it comes to sleep tracking?
We're seeing the sensors and electronics becoming more energy efficient. They won't need to be charged as frequently. We're also seeing more sophisticated ways to analyze heart rate, including heart rate variability. If you see a lack of variability for a patient with heart disease, that might suggest that their nervous system isn't working correctly.
Similarly, you can get information from sleep-tracking on whether someone is over-exerting themselves. We'll be able to tell with some confidence whether a person is over-training and exercising too much. If you set unrealistic goals for activity levels, deep sleep will be diminished and interrupted.
Today, we see professional athletes wearing chest straps overnight to get this data, but that's very cumbersome and may interfere with sleep. My hope is that alternative methods will be easier to use and less expensive in the future.
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