Long-term exposure to microgravity impairs vestibulo-cardiovascular reflex

Area of Science:

• Cardiovascular physiology
• Neuroscience
• Space medicine

Background:

• The vestibular system regulates blood pressure during posture changes via the vestibular-cardiovascular reflex (VCR).
• Altered gravity environments, like spaceflight, may impact vestibular system sensitivity.
• Long-term microgravity exposure could reduce VCR sensitivity, potentially causing orthostatic intolerance.

Purpose of the Study:

• To investigate the impact of long-term spaceflight on human VCR function.
• To assess VCR's role in blood pressure regulation after returning from the International Space Station (ISS).

Main Methods:

• Human subjects were tested before and after a 4-6 month ISS mission.
• Galvanic vestibular stimulation (GVS) was used to assess VCR function during head-up tilt.
• Impaired VCR was identified when blood pressure response to head-up tilt was independent of GVS.

Main Results:

• A transient blood pressure increase during head-up tilt was observed pre-flight but absent 1-4 days post-flight.
• The VCR's ability to increase blood pressure was significantly impaired after spaceflight.
• VCR function returned to pre-flight levels within two months after returning to Earth.

Conclusions:

• Long-term microgravity exposure significantly impairs the vestibular-cardiovascular reflex (VCR).
• VCR impairment following spaceflight may be a contributing factor to orthostatic intolerance.
• Further research into VCR function is crucial for astronaut health during and after space missions.