If your Apple Watch alerts you to sleep apnea, here’s what it means and what to do next

CNN
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Apple Watches, which are already multi-tool smart devices, added another interesting feature last month: a sleep apnea detection app.

Sleep apnea is a condition that causes the sleeper’s breathing to stop when the throat muscles relax too much and the airway collapses. This can result in loud snoring that the sleeper may not even notice. Usually a partner or roommate will address the problem first.

The condition is associated with a variety of health problems, particularly wear and tear on the cardiovascular system, including high blood pressure, stroke, heart attack, heart failure and cardiac arrhythmias such as atrial fibrillation. It is also associated with dementia and daytime sleepiness. And people with sleep apnea are also more likely to be involved in traffic accidents.

Millions of people are thought to suffer from this breathing disorder but have not yet been diagnosed, and experts say the new app could be a valuable tool in directing people to medical care. Sleep apnea notification is available on the latest Apple Watches Series 10 and some older models after a software update.

However, as with any new technology, the sleep apnea feature has limitations and can have unintended consequences, including poorer sleep, if someone focuses too much on the information or worries about the results.

“We see this phenomenon called orthosomnia. These are people who are overly concerned about their sleep data and how they can maximize and improve their sleep. And they sometimes go to extremes,” said Dr. Robson Capasso, chief of sleep surgery at Stanford University School of Medicine.

In search of an ideal night’s sleep, they may resort to risky supplements or extreme diets.

However, new ways to monitor sleep don’t necessarily have to be a source of stress.

“I think this is a great tool. It just needs to be implemented properly,” Capasso said.

Apple Watch’s new feature uses the device’s accelerometer, which measures movement, and Apple says it’s so sensitive that it can detect even very slight wrist movements that correspond to breathing at night.

However, since this is an opt-in feature, it must be enabled to work.

To detect sleep apnea, the watch measures breathing disorders during sleep for 30 days. If there are at least 10 sessions with breathing pauses and at least five of them have an unusually large number of pauses, the watch sends a notification to the user.

How well does the feature work?

Apple tested it on nearly 1,500 people, some of whom breathed normally while sleeping and others who suffered from varying degrees of sleep apnea. Each wore the watch for at least 30 nights and also completed a more conventional home sleep study for at least two nights using a monitor that recorded a variety of factors, including nasal pressure, blood oxygen, posture, breathing effort, heart rate and leg movement.

Researchers used data from this home sleep study to determine each person’s apnea-hypopnea index, which is the number of times breathing stops or decreases per hour. The researchers then compared the watch’s performance with measurements taken during the sleep study.

In general, Apple’s testing found that the watch picked up any degree of sleep apnea about 66% of the time. It was more accurate at detecting severe severe sleep apnea and correctly alerted users about 89% of the time. About 43% of the time, users were correctly alerted to moderate respiratory problems.

Apple said it adjusted the watch’s algorithm to avoid giving false alarms that could throw off users, and that appears to have worked. The new warning did not tell normal sleepers that they had sleep apnea 100% of the time.

So if you receive a warning message, you can be fairly confident that the result is genuine and further consultation with your GP or a sleep specialist is required. However, if you don’t receive a notification, that doesn’t necessarily mean you’re in the clear. You may still have sleep apnea, especially if you have other symptoms that suggest it.

The company’s study was neither peer-reviewed nor published in a medical journal. But in mid-September, the US Food and Drug Administration approved the marketing of the sleep apnea feature on Apple Watches.

There are other wearable devices that also promise to help people find out if they have sleep apnea, but the fact that this is an Apple entry has gotten some attention.

“It’s come up so often in conversations,” Dr. Jing Wang, clinical director of the Mount Sinai Integrative Sleep Center. “I’ve become more aware of it.”

Wang says the way the watch works is different from the steps it takes to make a diagnosis. The watch relies on wrist movements, but it starts with symptoms.

“What else have you experienced other than the watch saying this or your tracker saying that?” Wang said.

In particular, the watch does not ask about symptoms. It also doesn’t use the pulse oxygen feature, which has disappeared from some Apple watches due to an ongoing patent dispute.

Wang says typical things that tip her off to sleep apnea include loud snoring – although not everyone who snores has apnea – a partner who says they can’t sleep because of the noise, or who has heard their bedmate at night has stopped sleeping, a patient who reports waking up choking or wheezing, and someone who says they wake up tired or feel exhausted during the day. Morning headaches, high blood pressure and memory problems could also play a role, she says.

After this conversation, she would order a sleep study if she felt it was necessary. These can be done at home or in a sleep laboratory, which usually requires an overnight stay in a hospital or sleep center. Sleep studies record several variables, including blood oxygen, breathing rate, pauses in breathing, and nighttime awakenings.

The Apple Watch has some of these features, but the company hasn’t included them in the sleep apnea feature. If this had been the case, it may have been better able to detect mild and moderate cases of apnea, says Dr. Eric Topol, a cardiologist, founder and director of the Scripps Translational Research Institute.

“When her watch had pulse oximetry — now lost — it would have provided useful data, at least in people of color,” Topol wrote in an email. Studies have shown that wearable oxygen-detecting devices called pulse oximeters are not as accurate in people with darker skin, leading to a demand for better devices tested on more diverse populations.

“Unlike home tests or sleep labs that continuously measure oxygen saturation, the Apple Watch algorithm is based on acceleration measurements of movement, which would explain its low sensitivity.”

It might not be such a big deal that the clock isn’t as sensitive, Stanford’s Capasso said.

Even in full sleep studies, the answers are not clear. The main measure of a sleep study — the apnea-hypopnea index, or AHI — doesn’t always correlate with symptoms, he said. And not all cases of sleep apnea need treatment.

Capasso says it’s common for a patient to stop breathing and a lot of oxygen drops, he knows they need to be treated with a continuous positive airway pressure (CPAP) machine.

The machine is a “glorified air compressor” that delivers a steady flow of air through a mask to keep the airway open while you sleep.

“There is ample evidence that in these patients with frequent drops in oxygen there is a closer association with future clinical outcomes, particularly cardiovascular outcomes,” he said.

If he has a patient with an AHI that falls into the mild to moderate category and they also have daytime symptoms of sleepiness and brain fog, he might also try CPAP.

However, not everyone has success with these machines. Half of patients prescribed this therapy don’t use it as they should, Capasso said.

For some people with mild apnea, the key to better recovery may lie in other options, such as weight loss – which often cures the problem in overweight or obese people – and addressing poor sleep hygiene.

“It takes a lot of time to change bed-related habits,” he said.

For younger adults with sleep apnea who are not overweight, he might look for anatomical features such as the size of their jaws and tonsils, which may also be a factor.

Ultimately, he says, he considers a person’s age and the severity of their illness when deciding how aggressively to approach treatment.

Capasso believes Apple Watch notifications will be helpful for people who live alone or don’t have easy access to sleep studies and specialists.

“It can be a pretty good screening tool,” he said.