Apple Watch Sleep Apnoea notification.
He says every motion in our body is connected.
“So let’s say I sneezed. You could see that in a motion detector at your wrist, even though you don’t think of that as a ‘wrist problem’.”
Similarly, when we’re lying very still at night, even the motion of breathing can be felt at the wrist by the accelerometer within the watch.
By wearing the device for at least 10 nights over 30 days (for the Samsung device, it’s for at least two nights in a 10-day period), it captures our unique patterns, training the machine-learning algorithms to detect breathing disturbances.
“And if we see consistent elevations of that metric over time, that’s when you earn yourself a notification,” Bianchi says.
“We don’t want to react to every blip or bad night that occasionally happens. We want to make sure that if we’re poking you to go to the doctor … it’s really a consistent finding, that it’s accurate.”
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How accurate are they?
When developing tests, researchers dance between its sensitivity, which is crucial for minimising false negatives (missing cases of OSA), and its specificity, which is essential for minimising false positives (incorrectly diagnosing OSA when the person does not have it).
This varies from device to device.
“They’re always in trade off,” Bianchi says. “We know that when we favour specificity, that comes at a cost of sensitivity.
“And so we dial the knobs purposefully to reduce false positives … False positives can really compromise trust and flood the system.”
In a clinical validation study of more than 4500 adults across more than 11,000 nights, Apple demonstrated a sensitivity of 66.3 per cent and specificity of 98.5 per cent (the Samsung Galaxy Watch’s sleep apnoea feature has demonstrated a sensitivity of 82.7 per cent and a specificity of 87.7 per cent).
Early detection may improve treatment outcomes. Credit: Getty Images
What’s the point?
Neither the Apple Watch tests, nor the Samsung tests (or any other at-home device) replace a formal diagnosis. So why use them?
Not everyone with OSA has the classic symptoms, such as daytime sleepiness and snoring. And given we normalise fatigue, they may not realise it’s an issue.
However, OSA is associated with increased all-cause mortality, and untreated, it increases the risk of cardiovascular disease and stroke, type 2 diabetes, cognitive impairment, depression and motor vehicle crashes.
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Bianchi hopes that wearables can raise awareness and prompt people to act.
“Maybe you were thinking about [going to your doctor], but you were on the fence. Now you’ve got some inspiration to be more intentional about it,” he says. “I think that’s where we thought we could hope.”
Moira Junge, chief executive of the Sleep Health Foundation, says OSA is the No.1 issue that sleep doctors deal with.
Wearable tests make sense on many levels, including early detection, identifying patterns over an extended period of time, and encouraging treatment.
“We see it as a very positive step, and there is certainly a place for this new technology,” Junge says.
Christopher Gordon, a professor of sleep health at Macquarie University, is more circumspect.
“The consumer-based wearables have increasing sophistication in the way they measure people’s health and the detection of health conditions,” he says.
Despite some receiving TGA approval for the identification of sleep apnoea, he stresses that they can’t be a substitute for the diagnosis.
And although Bianchi points out that the person controls their data on Apple and can decide whether to share it with their doctor or not, what happens with health data in an ever-evolving space remains a concern for Gordon.
“I suspect there will need to be government regulation about how health data is controlled by wearables private companies, especially as it relates to privacy, an individual’s risk of disease and whether this is used in formal diagnosis and monitoring of patients’ conditions.”
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