If you wear a smart watch or smart ring to bed, checking your sleep data may have become as routine as checking the weather.

How long did you sleep? How restful was it? What was your heart rate? And, perhaps most importantly, what does your device think of your sleep?

As wearables become more sophisticated, some can even flag breathing patterns consistent with sleep apnea. That can be useful information, but Dr. Mas Takashima, an otolaryngologist at Houston Methodist, says there’s an important distinction to remember: A wearable may flag a potential problem, but it can’t diagnose sleep apnea.

“Where wearables have the most value right now is they can help identify that there potentially could be an issue,” says Dr. Takashima.  “And when that happens, that can be a really good signal that it’s time to talk to your doctor.”

How can a wearable tell you something might be wrong while you sleep?

Traditional sleep medicine has generally relied on a relatively short window of information.

A patient notices symptoms, talks to a doctor and undergoes a sleep study, either at home or in a sleep laboratory. That test provides detailed information about what happens during a particular night.

Wearables offer something different: lots of data over a long period.

“The benefit of wearables is that they can potentially give us weeks to months to years of data in the patient’s natural environment,” says Dr. Takashima. “An in-lab sleep study essentially provides a snapshot of one night of sleep.”

That longitudinal information may reveal recurring patterns that aren’t obvious from one night alone.

The devices themselves are only part of the equation. Increasingly sophisticated algorithms can analyze huge amounts of sensor data and look for deviations or patterns that may suggest something unusual is happening during sleep.

That’s particularly useful because you probably aren’t aware of what your breathing is doing while you’re asleep.

What can wearables tell you about your sleep?

Today's wearables can collect an impressive amount of information while you sleep. Depending on the device, that might include heart rate, blood oxygen levels, movement and breathing patterns, as well as estimates of how long you slept and the stages of sleep you experienced.

The key word, though, is estimates.

Not every number displayed on your sleep dashboard has been clinically validated. In fact, Houston Methodist experts have previously cautioned that metrics such as heart rate and oxygen readings tend to be more reliable than proprietary "sleep scores" generated by wearable devices.

What about the Apple Watch sleep apnea alert?

Some wearable features have moved beyond general wellness tracking.

The U.S. Food and Drug Administration has cleared Apple's Sleep Apnea Notification Feature, which analyzes Apple Watch sensor data for breathing disturbances that may be consistent with moderate to severe sleep apnea. The feature is intended for adults who haven’t already been diagnosed with the condition.

The watch analyzes breathing-disturbance patterns over 30 days rather than judging based on a single night. If the pattern repeatedly appears elevated, the user may receive a notification suggesting that they talk with a health care provider.

The FDA specifically states that the feature is not intended to diagnose sleep apnea — and that not receiving a notification does not mean you don’t have it.

“Don’t say, ‘Well, my watch says I don’t have sleep apnea,’ if you’re still having all these symptoms. You still need to get that evaluated.”

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Dr. Mas Takashima, otolaryngologist

How accurate is the wearable data?

Wearables can provide an impressive-looking dashboard of numbers each morning: sleep stages, restfulness, recovery scores, readiness scores and other proprietary measurements.

But not every number deserves equal weight.

Dr. Takashima recommends paying closer attention to metrics that have undergone clinical validation, such as breathing disturbances, physiological and movement patterns and blood oxygen, rather than assuming every score generated by an app has the same medical significance.

“There are so many different numbers and data that you can get from these wearables,” he says. “Defining what data set you really should be paying attention to is important.”

Look for patterns, not perfection.

What should you do if your wearable says you may have sleep apnea?

First, don't panic — but don't ignore the alert either.

Make an appointment with your primary care doctor, sleep medicine specialist or ENT physician and bring whatever information your device allows you to share.

Some devices can generate reports showing several weeks or months of breathing data. Apple, for instance, allows users who receive a sleep apnea notification to export a report to share with their doctor.

Also tell your physician about any symptoms your device can't measure, particularly:

• Loud or persistent snoring

• Waking up choking or gasping

• Excessive daytime sleepiness

• Morning headaches

   

• Feeling unrefreshed despite getting enough hours of sleep

• A bed partner noticing pauses in your breathing

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Your doctor's next step may be a formal sleep study.

“Typically, we’ll get a formal sleep study on those patients to validate that,” Dr. Takashima says.

A sleep study provides much more detailed information about breathing, oxygen levels and sleep physiology than a consumer wearable can.

What if your sleep study is normal, but your wearable keeps showing a problem?

This is one situation where having months of wearable data may prove especially useful.

A sleep study captures a single night, and people don't necessarily sleep exactly the same way every night. If someone remains very symptomatic despite a negative test — and their wearable consistently shows abnormal patterns — Dr. Takashima says that additional information may give physicians a reason to investigate further.

That might include taking a more detailed history, reviewing a sleep diary or asking a spouse or bed partner what they've observed.

The same principle works in the opposite direction too: a reassuring wearable reading shouldn't override persistent symptoms.

Sleep apnea notifications and similar technologies are screening tools, not substitutes for medical evaluation.

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The best way to use a wearable for sleep

Think of your watch or ring as a smoke detector rather than a fire investigator.

It may notice a pattern worth paying attention to. It can collect information night after night in the environment where you actually sleep. And it may give you information you otherwise never would have known to bring up with your doctor.

But figuring out why the pattern is occurring still requires medical evaluation.

That's particularly important with sleep apnea because treatment isn't necessarily one-size-fits-all. CPAP may be appropriate for some patients, while others have anatomical issues — such as nasal obstruction or another area of airway collapse — that warrant further evaluation and potentially different treatment.

For now, Dr. Takashima sees wearables as another piece of information physicians can put alongside symptoms, physical examination findings and formal testing.

“We’re typically not making clear-cut clinical decisions based upon wearable information alone,” he says.

But if the device on your wrist repeatedly tells you something looks unusual, it may be worth listening — and then asking your doctor to help figure out what it means.