Sleep deprivation and glymphatic system dysfunction as a risk factor for SANS during long-duration spaceflight

Area of Science:

• Neuroscience
• Space Medicine
• Ophthalmology

Background:

• Spaceflight Associated Neuro-ocular Syndrome (SANS) affects 70% of astronauts on long-duration missions.
• Current SANS theories involve fluid shifts, increased intracranial pressure, and enlarged perivascular spaces (PVS).
• The glymphatic system (GS), comprising PVS, facilitates cerebrospinal fluid (CSF) and metabolite exchange in the central nervous system (CNS).

Purpose of the Study:

• To explore the connection between circadian disruption and glymphatic dysfunction as a potential cause of SANS.
• To highlight sleep deprivation's role in impaired glymphatic clearance in astronauts.
• To identify potential countermeasures for SANS prevention.

Main Methods:

• Literature review of studies on SANS, glymphatic system function, and sleep-wake cycles.
• Analysis of terrestrial research linking sleep deprivation to impaired brain clearance.
• Correlation of astronaut sleep problems with potential glymphatic dysfunction.

Main Results:

• Sleep significantly enhances glymphatic fluid flow and clearance compared to wakefulness.
• Sleep deprivation in astronauts is well-documented and may impair glymphatic efficiency.
• Impaired glymphatic clearance due to sleep loss could contribute to SANS development.

Conclusions:

• Circadian disruption and subsequent glymphatic dysfunction are potential contributors to SANS.
• Sleep deprivation may lead to long-term neuro-ocular effects in astronauts.
• Enhancing sleep quality and duration could be a practical countermeasure against SANS.