Is Your Sleep Tracker Making You Sleep Worse?
The promise of sleep tracking technology is powerful and-at first blush-highly convincing: Good sleep is vital for good health. It can foster everything from waking concentration and creativity to gut recovery and immune system functionality. Yet it is difficult for many people to get a good sense of the quality of their sleep, unconscious as they are during it. They may not even realize how often they sacrifice sleep for other goals, or lose it to poor sleep hygiene-both common problems.
But if a wearable, bedside, or bed-integrated device can monitor their sleep, then the average person can get a sense of their sleep health-and make informed decisions about how optimize their sleep. Potentially, they can learn and benefit more from this in-the-wild, long-term tracking than they might from a traditional sleep study: one night in a lab, where they might not sleep in the same way they would at home.
This is likely why, as of 2018, around 10 percent of Americans regularly wore sleep trackers-or fitness trackers that also monitor sleep-to bed. It's also why people like Roy Raymann, the chief sleep science wonk for the app SleepScore, argue that “sleep tracking should become a habit, just like using your bathroom scale every day” to help monitor your health.
Yet for all the promise of sleep trackers, a number of health pros have started to speak out against them. “Many in the field are appreciative of the greater attention that these trackers have brought to the issue of insufficient sleep,” says Jamie Zeitzer, a circadian physiologist at the Stanford Center for Sleep Sciences and Medicine. Experts like Zeitzer, however, doubt the data these trackers give has real value to many users-and suspect that tracking could actually be detrimental to good sleep.
The limitations of sleep trackers
No one in the sleep science community is calling for the abolition of tracking tech. Many doubters, however, do think that we should perhaps lean away from them, or at least make people more aware of their limitations. Dalva Poyares and Ronaldo Piovezan, two sleep researchers based in Brazil, for instance, have been hosting presentations for medical professionals over the last year “to warn about the limitations of … these devices.”
A fair amount of this skepticism stems from longstanding doubts about just how accurate these devices are. No app or device measures sleep directly by monitoring brain activity, instead using proxies like heart rate and body movement. A phone app using audio to track movement could, the worries run, mistake a partner’s movement for your own. A wearable device could mistake tiny, natural sleep movements as a sign of wakefulness, or disturbed sleep. Any device could overestimate one’s sleep duration if you just lay still in bed, lowering your heart rate with calm, deep breathing, but remain awake.
These doubts have led to, among other things, a 2012 lawsuit against Fitbit for allegedly overestimating users’ sleep by a significant margin. There was also an entire edition of the academic journal SLEEP in 2015 focusing on trackers’ limitations, and a 2017 warning from Consumer Reports about the potential for misreported data in most tracking tech.
Every tracker manufacturer I spoke to argued that they take great pains to make sure their data is accurate. Fitbit, for instance, has sent some 60 people wearing their devices to independent sleep labs to validate their sleep duration data against the highest clinical standards-with favorable results, says Conor Heneghan, Fitbit's lead research scientist and head of innovation. And their tech continues to improve.
But many have doubts about the quality of studies validating tracker data. Piovezan and Poyares, for instance, argue that trackers seem to do a good job of measuring how long young and healthy users without sleep issues sleep per night, but may do a much worse job for those who actually have disordered or otherwise low-quality sleep. The accuracy of trackers even for healthy, young users varies wildly by brand, they add. In total, Poyares claims based on her research and readings of the evidence to date, “commonly used consumer grade sleep trackers tend to overestimate sleep duration and simultaneously underestimate the number and duration of nighttime awakenings.”
Things get even iffier, skeptics argue, when looking at more complex measures, like the amount of time people spend in a given sleep phase-something companies like Fitbit attempt to track. A few studies have determined that, when compared to sophisticated brain scans that accurately monitor sleep stages, trackers’ proxy measures (based on things like heart rate) seem to be way off.
How useful is sleep data?
Even if or when trackers do provide accurate data on the time you sleep, Zeitzer argues that information is functionally meaningless for many people. Sleep is complicated. The quality of your sleep and its effect on your waking life is about much more than just how long you sleep, or even how long you spend in a given stage of sleep per night. Pop science aside, Zeitzer says, we don’t even “know whether a specific amount of a specific stage of sleep has any meaning.” (Nor, he adds, do we actually know how to change how much time a person gets in a given sleep stage.)
In the end, the myriad variables that stack up to a healthy night’s sleep probably differ drastically from person to person, even if we can find population averages for, say, optimal sleep duration in a given age and gender bracket. Comparing yourself to those population averages, Zeitzer cautions, “may or may not have any bearing on your reality,” much less offer you any actionable sleep health advice.
The anxiety of knowing how you slept
Sleep data can also trigger deep and damaging anxiety in some consumers. Users have been talking for years about how tracking their sleep led to an obsession with data and their own sleep hygiene shortcomings. Ironically, this left them so distracted and worried they started to get less or worse sleep. In 2017, a team of researchers actually coined a term for the worst manifestations of this issue: orthosomnia, or an obsession with getting a measurably “correct” amount or type of sleep.
Researchers often worry about the negative effects of data when it comes to the nearly one third of adults who struggle on and off with insomnia symptoms and just under one tenth who cope with chronic insomnia. Many (but not all) of those people can benefit from accepting the amount and patterns of sleep they get, explains Zeitzer, rather than obsessing over sleep data or population averages. But it is possible (although not yet thoroughly proven) that tracking data could create sleep anxiety from nothing. For instance, if someone who used to feel well rested every morning suddenly sees that they’re not in line with their demographic’s sleep averages, they might start to feel viscerally as if they are sleeping poorly and obsess over reaching normalcy. It can be very tempting to trust hard data over our own knowledge of our bodies and how they feel.
Anxious folks may feel especially tempted to bring their sleep tracker data to their doctors to get help. Hannah Ruark, a spokesperson for sleep tracking app Sleep Cycle, argues that people bringing sleep tracker data to their doctors can be a good thing, helping them get a real and clear picture of their patients’ sleep. But given all the caveats and limitations sleep health pros have found with that data, this seems likely to be about as infuriating and counterproductive as a patient walking into an office with a WebMD printout.
On a more mundane level, Raymann argues, wearable trackers “might just create discomfort and as a consequence may disrupt sleep.” Phone based app trackers, meanwhile, encourage people to bring their phones to bed, which runs counter to best sleep hygiene practices. (The more tempted we are to use our devices in the hour or so before bed, typically the worse we sleep.)
The silver lining of sleep trackers
None of the skeptics I’ve spoken to went so far as to argue that trackers have no possible utility for anyone. Heneghan notes that most users seem to appreciate their Fitbits because they never realized how irregular their sleep schedules are, or how often they sacrifice sleep. It can help them, broadly, to think more about and prioritize sleep in their lives-and apps can give them general best-practice sleep hygiene advice. They can also act as journaling adjuncts, helping users track the impacts of lifestyle changes on rough sleep metrics.
Even if the data is not always accurate, Poyares acknowledges that some research has shown it can motivate some people to change their sleep behaviors for the better. And for all the people made anxious by tracker data, Heneghan argues, many could feel reassured by it. “If somebody is 65 years old and only sleeping five-and-a-half hours a night,” he says, “they might feel that they’re way off the norm. But then they see that for this age and gender that’s actually pretty typical.”
Tracker mnufacturers recognize the risk of provoking or exacerbating anxiety in some users. They say that anyone experiencing worse sleep or stress due to sleep quantification should set them aside-at least for a time. And sleep researchers, even skeptics, largely believe that trackers will become more and more accurate as their technology and analytic tools evolve. “One day, they will be good enough to help a doctor make a diagnosis faster and at less cost,” says Nitun Verma, a spokesperson with the American Academy of Sleep Medicine.
For now, skeptics argue, the accuracy and potential benefits of sleep trackers are highly limited in scope and scale. The risks of triggering anxiety in unsuspecting consumers-or of stoking a tendency to abandon our meaningful connections to our own bodies in favor of data-are real and worrying. This would suggest that perhaps they should think twice before blithely buying or trusting a tracker-and focus more on adhering to best sleep hygiene practices, while listening to their bodies.
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