Sleep Trackers: How Accurate Are They Really?Feb. 2, 2021 - Katie McCallum
We all know that getting plenty of sleep is important. Still, many of us feel perpetually tired.
In fact, a recent poll conducted by the National Sleep Foundation (NSF) found that almost half of us feel sleepy at least three days a week. Yikes.
Given how elusive a good night's rest seems to be for many of us, it's only natural to look for ways to better our sleep.
But, when considering whether you should be tracking your sleep, what you're probably really wondering is: Are sleep trackers actually accurate?
"Tracking sleep via a smart watch or wearable device is becoming more and more popular. On the one hand, this is a good thing. Having a grasp on your sleep habits can be the first step toward improving your sleep. On the other hand, many of these devices provide a lot of information — much of which may not be very accurate — without helping you actually turn this data into better sleep," explains Dr. Ali Sawal, primary care practitioner at Houston Methodist.
This doesn't mean tracking your sleep is a waste of time, but it does help to know what you can and can't rely on when it comes to sleep metrics and wearable devices.
How sleep trackers work
Most wearable devices that track sleep devote quite a bit of battery power to assessing it. While each wearable device varies slightly, the two primary measurements being collected all night are your movement and your heart rate.
"The heart rate measurements are used to try to infer which stage of sleep you're in at a given time," explains Dr. Sawal. "The movement information is used to determine whether you're asleep or awake, as well as whether your sleep is restful or restless."
These measurements are then processed through algorithms and neatly bundled into (sometimes confusing) panels of dashboards that help you understand your sleep.
Each particular device's sleep dashboard looks different, but the metrics generally include:
- Wake time
- Time spent asleep
- Time spent in each sleep stage
- Heart rate while asleep
- Overall sleep score
Speaking of your sleep dashboard, when it's in the red more often that not, you may start to wonder whether you have a sleep disorder...or if your sleep tracker just isn't accurate.
Sleep trackers can't detect sleep apnea or diagnose other sleep disorders
The most important thing to know about tracking your sleep via your smart watch or a comparable device is that the information provided isn't clinical in nature. Meaning, it cannot be used to diagnose sleep apnea, insomnia, narcolepsy or any other sleep disorder.
"If you're concerned about your sleep, discuss your concerns with your doctor. You can show your doctor the sleep data your tracker provides, and your doctor may certainly use this data to determine whether you might benefit from undergoing a sleep study, but the data is not comprehensive or reliable enough to diagnose a sleep disorder," says Dr. Sawal.
A sleep study, also called a polysomnogram, is the benchmark of assessing sleep, and it is what experts rely on to analyze a person's sleep patterns and identify what's causing sleep disturbances. These studies measure:
- Your brain waves
- Eye and leg movement
- Breathing patterns
- Blood oxygen levels
So, are sleep trackers even helpful?
"First and foremost, it's important to understand that the data collected by wearable sleep trackers are very indirect measurements of your sleep. A lot of extrapolation has to happen between collecting those measurements and providing an assessment of your sleep," says Dr. Sawal.
With this imperfect science in mind, you may want to be particularly wary of the more complex metrics, such as sleep quality, sleep scores or readiness ratings. In addition, Dr. Sawal says that time spent in various stages of sleep isn't likely to be very accurate, either.
However, what most wearable devices are pretty reliable at measuring inclides: when you went to sleep, when you woke up and the total time you spent asleep. While these metrics might not sound all that flashy, this information can be very beneficial for identifying factors that lead to poor sleep.
"Most people don't need a sleep study to understand why they're not getting quality sleep. This is because the majority of people experience bad sleep as a result of poor sleep habits — either they're not getting enough sleep or they're not being consistent with their bedtime," explains Dr. Sawal. "Knowing how much sleep you're getting may seem like a very simple metric, but it can help you assess your sleep habits and correct them if needed."
Which sleep tracker is best?
There are many sleep tracker options on the market, and each uses its own proprietary sensors and algorithms to monitor and report on your sleep. So, which is best?
Dr. Sawal says this is pretty subjective, but he does have some advice on what not to look for.
Many sleep trackers provide beautiful curves that depict your journey through each stage of sleep each night. But — even after casting aside the inaccuracies within these measurements — this information doesn't actually help solve your sleeping problems.
"A sleep tracker that just spits out a ton of data but doesn't help you actually translate this data into making the adjustments that lead to better sleep isn't providing you much benefit," explains Dr. Sawal. "You can't will yourself to spend more time in deep sleep just because your watch is telling you it's not happening."
Instead, Dr. Sawal recommends looking for a tracker that simplifies the data and actually helps you improve your sleep habits.
"It's quality over quantity here. Focus on finding a sleep tracker that simply helps you understand if you're getting enough sleep — what time you went to bed, what time you woke up and how many hours you spent asleep," recommends Dr. Sawal. "Over time, this information can help you spot problems with your sleep habits. And, you can take the other, extraneous data with a grain of salt."
In addition, consider a tracker that integrates with your other smart devices to help you actually improve your sleep behaviors via:
- Alerting you when it's almost time to go to bed
- Scheduling a wind-down routine that can help you relax before bedtime
- Prompting you to consider your sleep environment, such as the room's temperature, noise level and darkness
- Tracking when you exercise and drink caffeine or alcohol
Getting quality sleep starts with your sleep habits, also to referred to as sleep hygiene.
"You want to optimize your sleep hygiene in order to fall asleep and hopefully stay asleep until it's time to wake up," explains Dr. Sawal. "Practicing sleep hygiene means going to bed around the same time every night, as well as utilizing your bed only for sleep — not other tasks such as watching TV or reading, or working in bed. In addition, sleep hygiene also means avoiding things like screen time and alcohol right before bed, or even eating a late dinner, as these force your brain neurochemistry to stay alert and awake."
Given all of this, Dr. Sawal says that the most helpful sleep tracker is the one that informs you of your sleep habits and helps coach you to improve or maintain the behaviors that lead to better sleep.