Feasibility of In-Ear Single-Channel ExG for Wearable Sleep Monitoring in Real-World Settings

Automatic sleep staging typically relies on gold-standard EEG se-
tups, which are accurate but obtrusive and impractical for everyday
use outside sleep laboratories. This limits applicability in real-world
settings, such as home environments, where continuous, long-term
monitoring is needed. Detecting sleep onset is particularly rele-
vant, enabling consumer applications (e.g. automatically pausing
media playback when the user falls asleep). Recent research has
shown correlations between in-ear EEG and full-scalp EEG for var-
ious phenomena, suggesting wearable, in-ear devices could allow
unobtrusive sleep monitoring. We investigated the feasibility of
using single-channel in-ear electrophysiological (ExG) signals for
automatic sleep staging in a wearable device by conducting a sleep
study with 11 participants (mean age: 24), using a custom earpiece
with a dry eartip electrode (Dätwyler SoftPulse) as a measurement
electrode in one ear and a reference in the other. Ground truth
sleep stages were obtained from an Apple Watch Ultra, validated
for sleep staging. Our system achieved 90.5% accuracy for binary
sleep detection (Awake vs. ... mehrAsleep) and 65.1% accuracy for four-
class staging (Awake, REM, Core, Deep) using leave-one-subject-out
validation. These findings demonstrate the potential of in-ear elec-
trodes as a low-effort, comfortable approach to sleep monitoring,
with applications such as stopping podcasts when users fall asleep.