Astronauts well-being and possibly anti-aging improved during long-duration spaceflight

Area of Science:

• Space medicine
• Human physiology
• Chronobiology

Background:

• Understanding circadian rhythms is crucial for astronaut health during long-duration space missions.
• Previous research indicates potential disruptions in physiological functions due to the space environment.
• Assessing sleep quality and its relationship with physiological markers is vital for crew well-being.

Purpose of the Study:

• To evaluate changes in circadian rhythms of heart rate (HR), heart rate variability (HRV), and activity in astronauts during long-term space missions.
• To investigate the relationship between these physiological changes and sleep quality.
• To explore potential correlations between circadian rhythm parameters and environmental factors like magnetic field fluctuations.

Main Methods:

• Ten healthy astronauts underwent four measurement periods: before launch, and at two time points during space missions (ISS01, ISS02), and after return to Earth.
• Ambulatory 48-hour electrocardiograms (ECG) and 96-hour actigraphy were utilized.
• Sleep quality was assessed using sleep-related changes in activity, RR-intervals, and specific HRV components (HF, VLF, LF-band).

Main Results:

• Circadian amplitude of HR (HR-A) was significantly larger in space compared to Earth-based measurements.
• Sleep duration varied among astronauts in space; some increased sleep duration while others experienced a decrease.
• Sleep quality improved in a subset of astronauts (Group B), accompanied by an increase in sleep-related parasympathetic activity (pNN50).
• HR-A demonstrated significant correlations with the amplitudes of the magnetic declination index over 24-h, 12-h, and 48-h periods.

Conclusions:

• Long-term space missions are associated with altered circadian rhythms and varying effects on sleep duration.
• Improvements in sleep quality and increased parasympathetic activity were observed in some astronauts during spaceflight.
• Findings suggest a potential link between mission duration, physiological well-being, and exposure to magnetic field fluctuations, hinting at possible anti-aging effects.