Smartwatch Flagged 94% of Serious Sleep Apnea, With False Alarms

Jeff's Daily Pick. A Samsung Galaxy Watch caught about 94% of moderate to severe sleep apnea in 147 adults tested against a sleep lab at Stanford. Specificity was about 67%, so roughly 1 in 3 people below the threshold got flagged anyway. A screen, not a diagnosis.

In the United States, researchers at Stanford University tested the sleep apnea feature of a Samsung Galaxy Watch against the reference exam, an overnight sleep study in a lab (polysomnography). The study was published on August 27, 2026 in the Journal of Clinical Sleep Medicine and promoted by the American Academy of Sleep Medicine on October 13. Obstructive sleep apnea often goes undiagnosed because lab testing is costly and hard to schedule.

Who was tested

The team enrolled 152 adults aged 22 or older who either already had a diagnosis of moderate to severe apnea or scored high on the STOP-Bang screening questionnaire. Of those, 147 completed both lab nights, for 1,850 hours of recorded sleep. Average age was 54. Each person wore a Galaxy Watch 6 for a first night in the lab, at least three nights at home, then a second lab night. The target was moderate to severe apnea, defined as 15 or more breathing events per hour.

The numbers

The watch's overall accuracy score (area under the curve) was 0.94. At Samsung's default threshold, sensitivity was 94.1% (95% CI 84.1% to 98%): it caught almost every person with moderate to severe apnea. Specificity was 66.7% (95% CI 51% to 79.4%): about one in three people below the threshold were flagged anyway. When the researchers moved the threshold to 25.95 events per hour for this group, sensitivity fell to 82.4% and specificity rose to 94.9%. Among people with a high hypoxic burden, a measure of how deep and long the oxygen drops are, the watch sorted everyone correctly at the default setting.

Samsung's sleep apnea feature received De Novo authorization from the FDA in February 2024. This study adds independent lab comparison, but in a high risk group. Our explainer on what sleep trackers really measure covers the general limits of wrist data, and our piece on the Genio implant trial looks at treatment for people whose apnea is confirmed.