Head-Down Tilt Bed Rest Studies as a Terrestrial Analog for Spaceflight Associated Neuro-Ocular Syndrome

Joshua Ong, Andrew G. Lee, Heather E. Moss

Research output: Contribution to journalReview articlepeer-review

38 Scopus citations


Astronauts who undergo prolonged periods of spaceflight may develop a unique constellation of neuro-ocular findings termed Spaceflight Associated Neuro-Ocular Syndrome (SANS). SANS is a disorder that is unique to spaceflight and has no terrestrial equivalent. The prevalence of SANS increases with increasing spaceflight duration and although there have been residual, structural, ocular changes noted, no irreversible or permanent visual loss has occurred after SANS, with the longest spaceflight to date being 14 months. These microgravity-induced findings are being actively investigated by the United States' National Aeronautics Space Administration (NASA) and SANS is a potential obstacle to future longer duration, manned, deep space flight missions. The pathophysiology of SANS remains incompletely understood but continues to be a subject of intense study by NASA and others. The study of SANS is of course partially limited by the small sample size of humans undergoing spaceflight. Therefore, identifying a terrestrial experimental model of SANS is imperative to facilitate its study and for testing of preventative measures and treatments. Head-down tilt bed rest (HDTBR) on Earth has emerged as one promising possibility. In this paper, we review the HDTBR as an analog for SANS pathogenesis; the clinical and imaging overlap between SANS and HDTBR studies; and potential SANS countermeasures that have been or could be tested with HDTBR.

Original languageEnglish (US)
Article number648958
Pages (from-to)648958
JournalFrontiers in Neurology
StatePublished - Mar 26 2021


  • astronaut
  • countermeasures
  • head-down tilt bed rest
  • microgravity
  • optic disc edema
  • space medicine
  • spaceflight associated neuro-ocular syndrome
  • terrestrial analog

ASJC Scopus subject areas

  • Neurology
  • Clinical Neurology


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