Within the Apple Watch Series 10’s new sleep apnea detection feature

To find out if you have a sleep disorder like sleep apnea, it usually requires a night’s sleep that is uncomfortable for many. To do this, sensors are placed all over your body, even in your nose.

The Apple Watch can’t mimic a sleep study or diagnose sleep problems, and it doesn’t try to. But Apple wants to help people decide whether or not they should at least talk to their doctor about getting one.

The new Apple Watch Series 10, along with the Series 9 and Ultra 2, can detect signs of moderate to severe sleep apnea, a sleep disorder in which breathing stops and starts during the night that is estimated to 936 million adults worldwideThe new watch feature, which works by measuring movements on the wrist that are correlated with pauses in breathing, was cleared by the Food and Drug Administration on Monday. It will ship at launch on the Series 10 and will be available on other compatible watches with the release of WatchOS 11.

Check this out: How Apple’s Sleep Apnea Feature Works on the Apple Watch

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Of the approximately 30 million people in the U.S. with sleep apnea, which is linked to an increased risk of type 2 diabetes and other health complications if left untreated, only 6 million have been diagnosed, according to a 2022 article from the American Medical AssociationThat suggests many people aren’t aware they have the condition, which is where tools like Apple’s new sleep apnea notification could potentially help.

According to Dr. Matt Bianchi, a researcher with Apple’s Health Technologies team, it took more than 11,000 nights of sleep tracking to get it right.

“One of the ways we make sure we don’t make mistakes or misinterpret these movements is by collecting a huge amount of ground truth data on a wide variety of people who are sleeping in the lab, in a sleep center, or at home in their natural environment,” Bianchi said in a virtual interview with CNET about how Apple developed the feature.

Smartwatches are all about health tracking

In 2019, Apple CEO Tim Cook said CNBC that the company’s “greatest contribution to humanity” would be “about health,” and the Apple Watch has clearly played a major role in making progress toward that goal.

The Apple Watch started out nearly a decade ago as a luxury iPhone accessory, but over the past decade it’s evolved into a comprehensive health-monitoring device, able to detect irregular heart rhythms, hard falls, and changes in body temperature, among a host of other health and wellness metrics. Sleep apnea detection is another step in that direction.

“Even after a short period of time, we started hearing from users who were noticing things about their health and fitness that they might not have noticed before,” Deidre Caldbeck, Apple’s senior director of Apple Watch and Health product marketing, said of the Apple Watch’s health-tracking features. “So we started pulling on those threads.”

Apple isn’t alone; the announcement comes as rivals Samsung and Google are also pushing their own wearables with new health tracking capabilities. Samsung announced in July that its latest Galaxy Watches would be able to measure signs of sleep apnea, while Google’s Pixel Watch 3 can detect a drop in heart rate. Together, the updates are another sign that smartwatches are continuing to evolve into much more than just activity and exercise trackers.

“Smartwatches have always been about health and fitness, make no mistake,” Ramon Llamas, research director for the International Data Corporation, said via email. “The question is how far we can take it.”

How the Apple Watch Detects Sleep Apnea

Sleep apnea is usually diagnosed through a sleep study or a home sleep apnea test. A sleep study, or polysomnogram, involves wearing sensors to measure brain waves that occur during sleep stages, an ECG sensor to monitor heart activity, sensors to detect muscle and eye movements, respiratory sensors to monitor airflow, and a pulse oximeter to measure blood oxygen, according to the Cleveland Clinic. (My colleague Lexy Savvides experienced this firsthand when she explored how she could use technology to improve the quality of her sleep earlier this year.)

The main benefits of devices like the Apple Watch that can pick up signs of sleep apnea at home is that it gives doctors more nights of data to work with. Plus, it can encourage people to talk to their doctors before the condition worsens.

“We should welcome it [smartwatches] “As tools,” Dr. Rafael Pelayo, a sleep specialist and clinical professor at Stanford Medicine, told CNET’s Lexy Savvides.“If you do a sleep test, you get one night, maybe two nights.”

The Apple Watch is packed with sensors, including the ability to take an ECG. Versions of the Apple Watch sold outside the US can also measure blood oxygen, but that feature is no longer available on devices sold in the US due to a patent dispute with health technology company Masimo.

Still, there’s one Apple Watch sensor that plays a primary role in picking up potential signs of sleep apnea: the motion-detecting accelerometer. Your chest vibrates as you breathe during the night, and those subtle movements are reflected in your arm so they can be detected on your wrist using the watch’s accelerometer, Bianchi says. These measurements manifest as a new metric called respiratory disturbances, which is recorded in the Apple Health app. The feature works the same whether or not you have an Apple Watch with the blood oxygen feature.

“When you have a pause in your breathing, where you breathe more shallowly or stop breathing for 20 or 30 seconds, that can be read out and detected by machine learning algorithms,” Bianchi said.

The chips in the Apple Watch Series 10, Series 9 and Ultra 2 are also a big part of what powers the Apple Watch’s sleep apnea detection, Caldbeck said, which is why the feature is only available on those models. An algorithm analyzes breathing disruption data on the watch and sends an alert if signs of sleep apnea are present.

“It’s the ability to take the accelerometer data, process that data on the device and make sure that we get accuracy and that we hit our performance targets,” Caldbeck said. “And so we really needed that combination.”

But sleep apnea isn’t the only reason you might experience breathing disturbances at night; factors like alcohol consumption, congestion from illness, and your sleeping position can also play a role. That’s why the Apple Watch looks for breathing disturbances over a 30-day period before sending that notification.

However, you only need to wear the watch for a minimum of 10 nights within that time frame for the feature to work. That 10-night minimum is the right balance between being realistic (not everyone wears their watch to bed religiously every night) and getting enough data.

“We don’t want to respond to the occasional three days of a long weekend or a short illness,” Bianchi said. “We want to make sure we capture what is truly you.”

11,000 nights of sleep data

As part of the clinical validation process, Apple collaborated with academic medical centers, hospital systems and clinical research organizations to collect sleep data from more than 11,000 nights.

Additionally, it collected an additional 1,500 nights of sleep data as part of the FDA regulatory process, which Bianchi says is the largest validation study submitted to the FDA for approval of a sleep apnea technology. In addition to these steps taken as part of the clinical validation process, Apple also has its own internal sleep lab for prototyping and developing its sleep-tracking features.

One of the biggest challenges was ensuring that Apple had a large enough and diverse dataset to account for all the potential failures of the technology.

“Any validation at the clinical level, anything that meets the regulatory standard, gives us the confidence we need to be able to say we stand behind this feature, that’s a step further,” Bianchi said.

People with a compatible Apple Watch can view nighttime breathing disturbances in the Health app on their iPhone, regardless of whether they receive an alert. Because some breathing disturbances are considered typical, Apple labels breathing disturbances as “elevated” or “not elevated,” with an elevated number of disturbances over multiple nights potentially indicating sleep apnea. The alert also encourages users to have a conversation with their doctor and provides an easy way to export the relevant data.

How Apple communicates and provides context around these measurements is especially important now as the Apple Watch and other wearables become sophisticated enough to detect potential health issues. paper published in the Cardiovascular Digital Health Journal in August 2020 suggests that smartwatches may be contributing to health-related anxiety, citing one example of a 70-year-old woman who believed smartwatch notifications were a sign of “worsening heart function.” She took 916 ECGs over the course of a year.

Smartwatch maker Withings is also trying to address this concern by providing clinical assessments of heart health data from board-certified cardiologists as part of its recently announced Cardio Check-Up function.

But when it comes to sleep apnea, doctors like Pelayo hope it will be possible to detect the problem even sooner in the future.

“I really want something to pick up the mild sleep apnea,” he said. “That’s hopefully where the future lies for us.”