RestEaZe: Low-power accurate sleep monitoring using a wearable multi-sensor ankle band

The well-recognized importance of adequate restful sleep for health and the high prevalence of disturbed sleep has produced wide-spread recognition of the clinical need and commercial potential for a practical cost-effective system to evaluate and support restful sleep at home. However, existing systems for sleep monitoring use wrist-worn devices that are shown to be inaccurate in measuring quality of sleep and ineffective as an aid for the diagnostic of sleep-related disorders such as RLS (Restless Leg Syndrome) and ADHD (Attention Deficit Hyper Activity Disorder). To address this gap in use of sensors in sleep medicine, in this paper, we present RestEaZe, a multi-sensor ankle band that can capture two leg movement phenotypes: Dorsiflexions that are correlated with sleep disorders such as RLS and ADHD, and Complex Leg Movements that are correlated with texture of sleep, namely sleep fragmentation and brief arousals. In this paper, we focus on the hardware and software architecture of the RestEaZe system, and present an algorithm that uses hierarchical sensing to reduce the power consumption of the ankle worn sensor. We show, through evaluation in the sleep lab and in the home setting that the RestEaZe system can last for 5 days on a single charge of a 400 mAh battery while collecting all the relevant leg movements.