Should you trust the tracker data? Could it clue you in to underlying health conditions? Here’s what experts say about sleep-tracking devices.
Technology allows us to track more specific measurements of our health than ever before. Wearables can monitor daily steps, blood pressure, and now sleep. But experts warn that what you can learn from your sleep stats, at least currently, has its limits.
“The reality is that we live in an era in which we are obsessed with the notion of ‘quantify self,’” says Massimiliano de Zambotti, PhD, a principal scientist at the Human Sleep Research Program at SRI International, a nonprofit research center in Menlo Park, California. People don’t just want to wake up feeling rested; they want to see the numbers to prove it.
The popularity of sleep-tracking devices signifies the digital health revolution that’s currently underway, notes Dr. de Zambotti and the other coauthors of a review on the topic published in July 2019 in Medicine and Science in Sports and Exercise.
But there’s little guidance from the scientific sleep community regarding these tracking devices, which can lead to “confusion and controversy about their validity and application,” according to that review. De Zambotti and his colleagues argue, based on their analysis of available evidence, that more guidelines are needed around how personal sleep-tracking devices work to better utilize them for clinical use and research.
And some questions remain: What can currently available sleep-tracking devices tell us about our sleep and our health? And can tracking your sleep actually help you improve it? Here’s what sleep experts want you to know.
Sleep Trackers Are Not Medical Devices
While it’s nice to have a sense of how well you’re sleeping each night, the standard tracker you wear on your wrist is far from precise. According to a 2018 statement from the American Academy of Sleep Medicine (AASM), sleep trackers qualify as lifestyle or entertainment devices, which means they’re not regulated by the Food and Drug Administration (FDA).
“There is still no clarity on the requirements for considering a sleep device accurate,” de Zambotti says. The AASM says these devices and apps should be cleared by the FDA if the data is going to be used to treat or diagnose sleep issues, but that isn’t currently required.
It’s not to say that paying attention to how long you sleep each night is bad. “Sleep trackers generate awareness on the importance of sleep, and that is a positive thing,” de Zambotti says. But it’s probably too early days for your sleep tracker to necessarily indicate inconsistencies that would suggest someone has a sleep disorder or other health problem.
The Data May Not Be Accurate
Those numbers on your tracker may not be entirely correct. “The information users receive from these devices can be inaccurate and potentially create concerns and worry,” de Zambotti says. In some cases, trackers overestimate how much you sleep.
“Many sleep trackers use an accelerometer, a device that measures how much you move, to estimate sleep,” says Michelle Drerup, PsyD, director of behavioral sleep medicine at the Cleveland Clinic’s Sleep Disorders Center in Ohio. If you spend time in bed reading or scrolling through your phone, the lack of movement will likely register as light sleep.
Alternatively, if you wake up in the middle of the night and stare at the ceiling without moving, the tracker won’t register you’re awake. The data should be taken with a grain of salt, says Kelly Glazer Baron, PhD, a clinical psychologist with specialty training in behavioral sleep medicine and associate professor in the University of Utah’s department of family and preventive medicine in Salt Lake City. “They are getting better, but the trackers that only use movement, with no heart rate or other sensors, are really not able to pick up stages of sleep or even decipher between quiet wakefulness and sleep,” she says.
The Most Accurate Sleep Test Involves Monitoring Brain Waves
Testing in a sleep lab is far more precise than a movement-based tracker. Polysomnography (the type of test that sleep labs use) is considered the gold standard in measuring sleep, according to a study published in April 2019 in the journal Sleep. These sleep studies monitor brain wave activity, eye movement, muscle tension, movement, and breathing for accurate measurement of the four stages of sleep, Drerup explains.
A study published in 2018 in Chronobiology International compared polysomnography results with sleep data tracked by a Fitbit Charge 2 and found that the data was similar in regard to sleep-wake states and sleep-stage composition, but the Fitbit wasn’t great at detecting deep sleep. Another study, also published in April 2019 in Sleep, compared several sleep-tracking devices with polysomnography results: wearables, a mattress device, and a bedside device. The devices appeared to be successful at detecting sleep (they were 93.3 to 98.5 percent accurate, compared with polysomnography) but were not as good at detecting wakefulness (being only 28.3 to 50 percent accurate, compared with the polysomnography data).
Trackers May Encourage Technology Use Before Bed
One downside to wearing a device or using a sleep-tracking app is that it might prompt you to pick up and start using a smartphone or other screened device before bed, which is a drawback because the light from your phone and other screens can make it tougher to fall asleep.
If your smartphone or another device is near you in bed so it can track your sleep, you may be more likely to hear alerts for incoming texts and emails when trying to fall asleep, Drerup says. The ideal bedroom setting is device-free. “Devoting the bed and bedroom to being a calm, relaxed environment is essential for having a healthy relationship with sleep,” Drerup says.
Sleep Trackers May Help You Detect Certain Sleep Patterns
The main health benefit of trackers is they can help you recognize patterns for behaviors that may affect your health. “Using a sleep tracker can be helpful if you are trying to extend or lengthen sleep time because you don’t allow enough time for sleep due to a busy schedule or a tendency to binge-watch Game of Thrones before bedtime,” Drerup says. They can be a reality check for how many hours of shut-eye you are actually logging every night — and how many days in a week or month you are cutting your rest short.
Drerup adds that trackers can be particularly helpful for people who suffer from insufficient sleep syndrome, which involves not allowing enough time in bed to get an adequate amount of sleep. If it takes you awhile to fall asleep or you wake up throughout the night, a tracker might alert you to how much sleep you’re actually missing out on.
Don’t Rely on Them to Identify Sleep Disorders and Other Health Issues
The landscape around sleep trackers is changing, and the technology is quickly improving. Currently, many of the commercially available sleep trackers are not designed (or FDA-approved) to diagnose sleep disorders or other health problems.
Devices like the Belun Ring, for example, have the FDA’s approval for use as a pulse oximeter, which measures your pulse rate and the oxygen level in your blood. The ring can be used at home or in a hospital, but it is not used as a tool by doctors to diagnose sleep apnea. It does generate sleep reports that can help identify and track potential symptoms of sleep apnea, but Drerup says, in most cases, your sleep tracker isn’t going to detect sleep apnea, insomnia, or any other sleep disorder.
For Some People, Use of Sleep Trackers May Worsen Sleep Struggles
Interestingly, sleep trackers can even make insomnia worse if people (in an attempt to sleep longer) end up spending more time in bed lying awake. “It may seem counterintuitive, but part of the behavioral treatment for chronic insomnia is to actually spend less time in bed trying to sleep,” Dr. Baron says (spending too much time in bed not sleeping can actually train the brain to associate your bed with not sleeping or unsuccessfully trying to fall asleep).
Also, know that using a sleep tracker might be counterproductive for your sleep health if you avoid asking your doctor about trouble with sleep or feeling fatigued because your tracker hasn’t picked up a problem (even though you’re experiencing symptoms, like taking awhile to fall asleep), de Zambotti says. Trackers could vastly improve in the next few years and change this paradigm, he adds. “Being able to predict diseases and monitor disease progression — on a large scale, inexpensively, passively, and timely — could soon be reality,” de Zambotti says, but generally, trackers are not there yet.
Currently, doctors are trained to screen for and diagnose sleep problems and disorders using in-office tests, laboratory sleep studies, and medical histories. They’ll need more training before they can use sleep tracker data as a stand-in for these current processes or to help their patients interpret that data in a meaningful or useful way, de Zambotti says. “I believe that training should be provided to healthcare practitioners on how to communicate with patients showing up to their clinics to ask about their wearables data,” he says. “It seems to be an extremely common occurrence.”
Tracker Data May Be a Game Changer for Sleep Researchers
Knowing your sleep last night was 20 minutes shorter than your nightly average generally doesn’t have sweeping implications for your health overall. You’d need more context about your sleep and lifestyle habits to actually identify a problem, and de Zambotti adds, “that’s even if the information is accurate and reflects true sleep.”
But the information from these popular devices does present a potentially huge opportunity for sleep researchers. The previously mentioned AASM statement, for example, notes that these devices could allow researchers to gather larger data sets about sleep and health trends that could identify previously unrecognized links between sleep and disease or health outcomes.