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Related Experiment Video

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Polygraphic Recording Procedure for Measuring Sleep in Mice

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Sleep Is Compromised in -12° Head Down Tilt Position.

Alessa L Boschert¹, David Elmenhorst^2,3, Peter Gauger¹

¹Department of Muscle and Bone Metabolism, German Aerospace Center (DLR), Institute of Aerospace Medicine, Cologne, Germany.

Frontiers in Physiology

|May 2, 2019

Summary

Head down tilt (HDT) posture, simulating microgravity, moderately reduces deep sleep and REM sleep while increasing light sleep. Subjective sleep quality also declined, though participants reported comfort, suggesting the body can largely compensate for HDT effects.

Keywords:

bed rest head down tilt polysomnography simulated microgravity sleep

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Area of Science:

Physiology
Sleep Science
Space Medicine

Background:

Cerebrospinal fluid (CSF) circulation and cranial perfusion are interconnected with sleep.
Head down tilt (HDT) simulates microgravity by reducing cranial perfusion.
The impact of HDT on sleep quality and physiological parameters requires investigation.

Purpose of the Study:

To assess the effects of -12° head down tilt (HDT) on sleep parameters.
To investigate the relationship between HDT, cranial perfusion, and venous system changes.
To evaluate subjective sleep quality during simulated microgravity.

Main Methods:

Cross-over study involving 11 male subjects exposed to horizontal and -12° HDT positions for 21 hours.
Polysomnography used to measure sleep stages (N3, REM, light sleep), efficiency, latency, and arousals.
Ultrasound measurements of the internal and external jugular veins assessed venous system changes.

Main Results:

Significant reductions in N3 (deep sleep) and REM sleep durations (-25.6 and -19.1 min, respectively) during HDT.
Increase in light sleep (N1/2) duration (+33.0 min) and a decrease in subjective sleep quality (-1.3 points on a 9-point scale) during HDT.
Ultrasound revealed increased cross-sectional areas of the internal jugular vein, suggesting venous congestion, while frontal skin thickness remained unchanged.

Conclusions:

Simulated microgravity via -12° HDT moderately impairs sleep architecture, particularly deep and REM sleep stages.
Venous congestion in the jugular veins occurs during HDT, potentially influencing cranial fluid dynamics.
Despite physiological changes, subjects reported comfort, indicating a degree of physiological compensation for HDT-induced effects.