Abstract
STUDY OBJECTIVES: Actigraphy, the tool of choice for assessment of sleep phase disorders, is insensitive to movement-free waking. This study aimed to determine whether the detection of waking could be performed by recording instrumental responses to haptic stimuli delivered by a low-cost device. METHODS: Twenty adults underwent 2 nights of laboratory polysomnography (PSG) while wearing a fingerless glove under which a stimulating actigraph ("Wakemeter") was apposed to the palm. The Wakemeter, controlled by a tablet computer, delivered gentle, haptic stimuli every 10 minutes during the sleep period. If a stimulus was detected, the participant squeezed the Wakemeter. Stimulus times, response times and movements were streamed to the tablet. Concurrent PSG data were scored blind to stimuli and responses. Self-reported sleep quality ratings were collected each morning. RESULTS: The Wakemeter was acceptable to 19 of 20 participants, and effects on self-reported and objective sleep were small. The probability of a response to the stimulus during a wake epoch was high regardless of movement. In contrast, actigraphy magnitude distributions were indistinguishable across epochs scored wake without movement versus sleep, confirming a known limitation of actigraphy. A simple method for calculating sleep efficiency from responses to the stimuli yielded estimates that were highly correlated with PSG-derived estimates (rho = .69, P < .001). CONCLUSIONS: Behavioral responses to haptic stimuli detected epochs of movement-free wake during the sleep period and may augment actigraphy in the low-burden estimation of sleep efficiency. Acceptability of the method over longer recording periods remains to be established.