Sleep RR-Interval U-patterns and Their Correlation to Movement Events

Abstract

Sleep analysis has received an ever-increasing attention in recent years, with works demonstrating the negative physiological consequences of sleep deprivation such as hypertension, cognitive impairment, etc. While numerous studies have been performed in the context of sleep analysis, ECG-based ones have relatively received less attention. The aim of this work is to investigate the relation between a phenomenon called ”U-patterns” and their possible correlation to movement events in the context of sleep deprivation. U-patterns take place in the RR-interval time series during sleep. As their name suggests, these patterns present a U-shaped decrease-increase in RR-intervals, with a duration lasting from 20 to 40 seconds together with a minimum decrease of 15% in the local RR-interval mean value. Over a span of 17 days, 15 healthy subjects (7males, 22.1 ± 1.7 yrs.) participated in a study of three subsequent stages. First, a baseline phase of seven days, during which the subjects slept normally. Immediately after, a sleep deprivation phase with a duration of three days, during which participants slept only three hours per night. Finally, in a 7-day recovery phase subjects went back to their normal baseline sleeping routine. Subjects underwent polysomnography (PSG) data acquisition while sleeping. U-patterns were extracted from RR-intervals while movement events were extracted from different PSG channels. Their relative temporal layout was studied to determine whether U-patterns are caused due to subject movement during sleep or vice versa. Results show that Upattern/movement events are correlated, always initiated by U-patterns with movement events terminating before the termination of their respective U-patterns.