Sleep tracking sounds like a dream. You get a gadget that tells you how you slept and then gives you tips on sleeping better and — boom — you’re better rested. As a parent of a young child, I know this is not how it would work for me, but I’ve been feeling desperate lately. If I’m sleeping less, then maybe with the help of a wearable, I could simply sleep smarter.

That’s how I got drawn into the promise of the Oura Ring, a $350 device you wear on your finger to track a number of different health metrics, including sleep. You’ve probably seen a celebrity wearing one in the tabloids. Mark Zuckerberg wears one to optimize his sleep.

The big problem is that wearables don’t come with any guarantees. This fall, we’ve seen these gadgets gain new abilities like detecting sleep apnea and working as hearing aids, making wearables seem more and more like medical marvels. However, research over the years has shown that doctors don’t currently find data from these devices very useful in a clinical setting, and left to their own devices, consumers might feel worse when using a wearable. The positive effects of sleep trackers, in particular, are difficult to nail down.

But if I just wanted a few data points to direct me toward better habits, surely a little ring couldn’t hurt. After spending a couple of days scouring medical journals in order to make a better decision about what a wearable could do for my sleep, however, I now feel more exhausted than ever. Buying a new gadget won’t fix that for a number of reasons. Nevertheless, if you’re thinking about using a wearable to improve your health, it’s helpful to know where the marketing stops and the proven benefits begin.

The Oura Ring 4, out this week, uses a variety of lights and sensors to measure your heart rate, respiration rate, blood oxygen, temperature, and movement. For an extra $6 monthly membership fee, you get access to things like detailed sleep analysis, advanced temperature monitoring, and reproductive health insights. The ring doesn’t have a screen; it connects to your phone via Bluetooth so you can see all your health data there.

The Oura Ring “is not a medical device.” This is the first thing the company’s PR team told me when I reached out to them for this article. In its marketing, however, Oura does bring up the potential health benefits often, and it promotes its medical advisory board prominently on its website. Jason Russell, Oura’s vice president of consumer software, explained that the company is tapping into a real demand.

“People want to understand their bodies and live long and healthy lives, but they don’t want another tech device to manage,” Russell said, flagging the discreteness of the Oura Ring.

You can also use your health savings account (HSA) and flexible spending account (FSA) funds to buy an Oura Ring, which is confusing since you’re only supposed to use those for medical and dental expenses. The Oura Ring does not have FDA clearance, although it can be used with the FDA-cleared Natural Cycles app for menstrual cycle tracking. According to some reviewers, it is especially useful for women for this very reason. Natural Cycles describes itself as “a hormone-free alternative to the pill that is 93% effective with typical use.”

This maze of regulations and clearances makes it hard to know if the Oura Ring, which is being marketed as a device that can improve your health, comes with real medical benefits. The same is true for other wearables, like the Apple Watch, which recently got FDA clearance for detecting sleep apnea. That’s on top of the device being FDA-cleared for detecting irregular heart rhythms and for recording electrocardiograms. (Smartwatches and fitness trackers from Google, Samsung, and Fitbit have similar clearances.) Even Apple AirPods Pro got clearance from the FDA this year for a new feature that turns them into “the first over-the-counter (OTC) hearing aid software device.”

None of these devices are FDA approved. There’s a difference between FDA approval, which is a very involved process, and the less rigorous FDA clearance. There’s also a third designation called “de novo classification” reserved for low-risk devices that don’t already exist in the market. (The new hearing aid feature on the AirPods Pro got this designation recently.) The FDA acknowledges that its name gets tossed around in misleading ways, so much so that it has a whole explainer on what FDA approval actually means.

So even though I can use this year’s leftover FSA dollars to buy an Oura Ring, the FDA has not put its stamp of approval on the device. Thanks to its partnership with Natural Cycles, the Oura Ring does enjoy a bit of that FDA-cleared glow, but that has nothing to do with the rest of its features.

In any case, you’d be forgiven for thinking a device you can buy with funds set aside for health care costs from a company that name-checks the FDA in its press release would lead to health benefits. When it comes to wearables, this isn’t always the case.

At the end of the day, you might not need a stamp of approval from a government agency to know whether a gadget is useful to you. I bought an Apple Watch not because I wanted something to alert me of an irregular heartbeat but because I liked getting notifications on my wrist. It’s easier to glance at a text message on my watch than it is to pull out my phone. The fitness tracking that comes with the watch is a bonus, and I can confidently say I move my body more because my watch tells me to.

Research suggests that smartwatches and other fitness trackers are best at this. A systematic review covering nearly 200,000 study participants published in the Lancet in 2022 found that wearables indeed improved physical activity and helped people lose weight. People who wore fitness trackers walked an extra 1,800 steps a day, on average. But they had little effect on other health markers, including blood pressure and cholesterol. A smaller meta-analysis in the BMJ, a peer-reviewed journal from the British Medical Association, showed similar conclusions: over 1,200 extra steps a day. Fitness tracking, it seems, leads to better fitness.

Sleep tracking is not so clear-cut. Whether it’s on your wrist, under your mattress, or wrapped around your finger, a sleep tracker will measure everything from your movement and body temperature to your heart rate and blood oxygen in order to determine how long you’ve slept and how well. The idea here is that by having more details about how you slept, you could link what you did before bed — say, rigorous exercise, drinking, or doomscrolling on your phone — with your quality of sleep. If bad habits lead to bad sleep, you can stop the bad habits.

Many sleep trackers will crunch all that data through an algorithm that spits out a score. (The Oura Ring’s app gives you three scores: one for sleep, one for activity during the day, and one for “readiness” which tells you on a scale of 1 to 100 how ready you are for the day.) Experts warn that these scores can be arbitrary, if not downright useless. Plus, most trackers can’t directly measure brain activity, which is the standard for diagnosing sleep disorders. Furthermore, obsessing over sleep data, scores, and metrics can actually increase anxiety and lead to worse sleep, according to a recent study from the American Academy of Sleep Medicine.

It’s possible that some of this data could come in handy in a clinical setting. Newer Apple watches can perform an ECG that’s roughly as good as what you’d get in a doctor’s office, according to one study. The problem is, for now, it’s not always easy for doctors to get access to the data collected by wearables. This is not to say that doctors aren’t optimistic about a future in which they can access that data. Many doctors tell their patients to buy wearables and use them to help manage disease, especially heart-related issues that devices like the Apple Watch are designed to detect.

Medical device or not, all wearables come with benefits and drawbacks, largely depending on how you use them. The Oura Ring rabbit hole I fell into left me feeling more confident about how I was using the one wearable I own, my Apple Watch. It also talked me out of buying an Oura Ring.

To be clear, I haven’t tried the new Oura Ring, and for now, I’m holding off. Even though I do have some FSA funds to spend before the end of the year, I think the sleep-tracking function would make me anxious in the long run.

At this phase of my life, sleeping smarter isn’t exactly an option. I simply need more hours in the day, and that gadget has not been invented yet.

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