Detection of sleep apnea using smartphone-embedded inertial measurement unit

We previously demonstrated that sleep apnea (SA) can be detected using acceleration and gyroscope signals from smartwatches. This study investigated whether an inertial measurement unit (IMU) embedded in non-wristwatch devices, such as smartphones, can also detect SA when worn during sleep. During polysomnography (PSG), subjects wore an IMU-embedded GPS device (Amue Link^®) and/or smartphones (Xperia^® or iPhone^®) on their abdomen. Triaxial acceleration and gyroscope signals were recorded overnight. Data were split into training and test groups (2:1) for each device. An algorithm was developed in the training groups to extract respiratory movements (0.13-0.70 Hz) and detect respiratory events, which were validated in the test groups. IMU-derived respiratory events showed breath-by-breath concordance with PSG apnea-hypopnea events, yielding F1 scores of 0.786, 0.821, and 0.796, respectively. Regression model derived from IMU signals correlated with PSG AHI in the test groups (r = 0.90, 0.93, and 0.96), with limits of agreement of -16.7 to 25.9, -17.4 to 22.5, and - 18.4 to 20.5. Using cutoff values from the training groups, moderate-to-severe SA (AHI ≥ 15) was identified in the test groups with AUCs of 0.95, 0.98, and 0.94 and F1 scores of 0.89, 0.96, and 0.92, respectively. IMUs embedded in non-wristwatch devices, including smartphones, can quantitatively detect SA when worn during sleep.