Abstract: Introduction: Impaired sleep is highly prevalent, especially due to irregular work shifts and extreme working conditions (e.g. astronauts). It affects the regeneration of the autonomic nervous system (ANS) and cognitive performance ability. A cooperation with the IBMP (Russian Institute of Biomedical Problems) was formed to identify a way to predict performance ability of astronauts after impaired sleep. As part of the pilot project ANSISS (Autonomous Nervous System in Sleep and Space), we aimed to identify ANS biomarkers with a non-invasive portable recording system that capture the effects of impaired sleep. Methods: A study protocol, assessing ANS parameters with a portable non-invasive polygraphy system, also practicable in space was developed. It was pilot tested under sleep laboratory conditions with two sleep alterations: sleep restriction (5 hours sleep and 3 hours wake bedtime) and sleep fragmentation (8 hours sleep, light on every hour). Twenty healthy male 74 XXIII International Symposium HUMANS IN SPACE Aerospace and Environmental Medicine 2021 V. 55 № 1/1 special issue participants (40 ± 7 years, BMI: 25 ± 2 kg/m3) underwent both sleep interventions in a randomized cross-over design with a washout phase of 10 days in between. Each sleep intervention consisted of four nights: a baseline night followed by the intervention night and two undisturbed recovery nights. ANS parameters were recorded with the portable polygraphy system Somnotouch RESP. Additionally, a full polysomnography, a psychomotor vigilance task, and questionnaires on well-being and sleep efficiency were completed. Results: Subjective and objective measures revealed that sleep restriction had a stronger effect on the subjects than sleep fragmentation, especially regarding the need of regeneration. During the restriction night, ANS parameter showed a shift towards higher sympathetic activity and lower parasympathetic activity during sleep with a recovery effect after waking up. The SDNN (standard deviation of normal to normal to normal interval), a parameter of the heart rate variability, significantly decreased in the restriction night from bedtime (median SDNN: 64.5ms, IQR 40.4/74.7ms) till being woken up after 5 hours of sleep (58.4ms, 42.2/74.9ms), and subsequently increased during the remaining three hours wake bedtime (70.3ms, 49.8/129.6ms; p < 0.01). Light sleep stages were more affected than the REM or deep sleep stage.The sleep restriction also showed a compensatory shift of the sleep phases (shorter sleep latencies, longer deep sleep phase, etc.), a tendency of a decrease in reaction time, subjective performance and subjective well-being with a subsequent recovery effect. Conclusion: Our pilot study revealed that especially sleep restriction had a strong negative effect with a need for recovery. Identifying ANS parameter using simple sensory technology of electrocardiography to adequately assess effects of impaired sleep is critical especially during extreme challenges such as in the cosmos before going out in space. The SDNN parameter of the heart rate variability may just be a suitable ANS biomarker and may add to a new decision-making instrument as to whether or not an activity with high psychological / physical stress can be justified. Next, the study protocol will be applied during isolation experiments lasting several months and simulating a space mission.

Cite: Laharnar N. , Glos M. , Zemann M. , Schagintweit J. , Fatek J. , Suvorov A.V. , Demin A.V. , Penzel T. , Fietze I.
ASSESSING AND COMPARING EFFECTS OF SLEEP RESTRICTION AND SLEEP FRAGMENTATION ON THE AUTONOMIC NERVOUS SYSTEM – A PILOT STUDY (ANSISS)
XXIII International symposium Human in Space 05-08 Apr 2021