The accuracy of the THIM wearable device for estimating sleep onset latency

STUDY OBJECTIVES:THIM is a wearable device designed to accurately estimate sleep onset. This article presents two studies that tested the original (Study 1) and a refined (Study 2) THIM sleep onset algorithms compared to polysomnography (PSG). METHODS:Twelve (Study 1) and twenty (Study 2) individuals slept in the laboratory on two nights where participants underwent THIM-administered sleep onset trials with simultaneous PSG recording. Participants attempted to fall asleep whilst using THIM, which woke them once it determined sleep onset. RESULTS:In Study 1, there was no significant difference between PSG (Mean, M = 1.94 min, SD = 1.32) and THIM-sleep onset latency (M = 2.05 min, SD = 1.38) on the first or second night, p > .07. There were moderate correlations between PSG and THIM on both nights, r(s) > .57, p < .001. On 23.74% of trials, PSG-sleep onset could not be determined before THIM ended the trial. With a revised THIM algorithm in Study 2, there was no significant difference between PSG (M = 3.41 min, SD = 2.21) and THIM-sleep onset latency (M = 3.65 min, SD = 2.18), p = .25, strong correspondence between the two devices, r(s) > .73, p < .001, narrow levels of agreement on Bland-Altman plots, and significantly less trials where PSG-sleep onset had not occurred (10.24%), p = .04. CONCLUSIONS:THIM showed a high degree of correspondence and agreement with PSG for estimating sleep onset. Future research will investigate whether THIM is accurate with an insomnia sample for clinical purposes.