BackgroundWe investigate the potential usability of a novel in-the-ear electroencephalography recording device for sleep staging.MethodsIn one healthy subject we compare simultaneous earelectroencephalography to standard scalp EEG visually and using power spectrograms. Hypnograms independently derived from the records are compared.ResultsWe find that alpha activity, K complexes, sleep spindles and slow wave sleep can be visually distinguished using earelectroencephalography. Spectral peaks are shared between the two records. Hypnograms are 90.9% similar.ConclusionThe results indicate that ear-electroencephalography can be used for sleep staging.

Wrist-worn actigraphy sensors translate measurements of limb acceleration into temporal patterns of wakefulness and sleep. The Actiwatch combines actigraphy with light-sensing capabilities to improve sleep−wake classification (Harrison et al., 2019). Actigraphy is a complementary assessment tool that can help identify changes in sleep patterns specific to certain disorders (Sadeh, 2011), particularly insomnia, hypersomnia and disorders of circadian rhythm. Compared with polysomnography (PSG), binary sleep/wake classification from actigraphy has a sensitivity of 96.5% but only 32.9% specificity, and this is influenced by age, sex, insomnia and sleep/ wake timing (Marino et al., 2013).A U-shaped relationship between health and sleep duration has been suggested (Watson et al., 2015); sleep duration under 6 hr is associated with negative cardio-metabolic outcomes (Grandner et al., 2014). These associations have been challenged due to uncertainty about the causal link between long sleep duration and mortality, and because studies using objective sleep measurement find very few individuals sleeping more than 8.5 hr compared with studies relying on self-report measures (Kurina et al., 2013).Reasons for sleep diary inaccuracy include patients filling out the diary from memory at the end of the monitoring period (Stone et al., 2002). This underscores the importance of objective compared with subjective sleep measures. Actigraphy is valid compared with sleep diaries (Jungquist et al., 2015), and has the added advantage