Altered sleep spindles and slow waves during space shuttle missions

Dominik P. Koller,Jason P. Sullivan,Derk-Jan Dijk,Vida Kasanin,Laura K. Barger,Charles A. Czeisler,Erin E. Flynn-Evans

doi:10.1038/s41526-021-00177-1

Abstract

Sleep deficiencies and associated performance decrements are common among astronauts during spaceflight missions. Previously, sleep in space was analyzed with a focus on global measures while the intricate structure of sleep oscillations remains largely unexplored. This study extends previous findings by analyzing how spaceflight affects characteristics of sleep spindles and slow waves, two sleep oscillations associated with sleep quality and quantity, in four astronauts before, during and after two Space Shuttle missions. Analysis of these oscillations revealed significantly increased fast spindle density, elevated slow spindle frequency, and decreased slow wave amplitude in space compared to on Earth. These results reflect sleep characteristics during spaceflight on a finer electrophysiological scale and provide an opportunity for further research on sleep in space.

Highlights

Sleep deficiencies among astronauts have been reported across spaceflight missions for decades[1]
The effects of melatonin were not of primary interest to our study, we controlled for the administration of the hypnotic drug with our statistical models (Linear mixed-effects models; linear mixed-effects models (LMM))
To understand the differences in global sleep measures of our cohort of astronauts compared to previous studies, we investigated their sleep period time (SPT) and total sleep time (TST), as well as changes in sleep stages between the three experimental conditions

Summary

Introduction

Sleep deficiencies among astronauts have been reported across spaceflight missions for decades[1]. Most studies using self-reports based on subjective ratings and objective measures through actigraphy and electroencephalography (EEG; scalp-attached electrodes monitoring brain activity) have indicated reduced sleep quality, sleep duration, sleep efficiency, sleep period time (SPT), and physical restedness, as well as increased sleep latency[2,3,4,5,6,7]. Some evidence from spaceflight studies supports this concern, indicating inflight increases in fatigue[9] and decrements in performance on certain cognitive tasks, such as memory-search[10], tracking abilities and time-sharing efficiency[11,12], dual-task performance[13], and word recall[3]

Objectives

Methods

Results

Conclusion