Microgravity reduces sleep-disordered breathing in humans

Ann R. Elliott, Steven A. Shea, Derk Jan Dijk, James K. Wyatt, Eymard Riel, David F. Neri, Charles A. Czeisler, John B. West, G. Kim Prisk

Research output: Contribution to journalArticlepeer-review

58 Scopus citations


To understand the factors that alter sleep quality in space, we studied the effect of spaceflight on sleep-disordered breathing. We analyzed 77 8-h, full polysomnographic recordings (PSGs) from five healthy subjects before spaceflight, on four occasions per subject during either a 16- or 9-d space shuttle mission and shortly after return to earth. Microgravity was associated with a 55% reduction in the apnea-hypopnea index (AHI), which decreased from a preflight value of 8.3 ± 1.6 to 3.4 ± 0.8 events/h inflight. This reduction in AHI was accompanied by a virtual elimination of snoring, which fell from 16.5 ± 3.0% of total sleep time preflight to 0.7 ± 0.5% inflight. Electroencephalogram (EEG) arousals also decreased in microgravity (by 19%), and this decrease was almost entirely a consequence of the reduction in respiratory-related arousals, which fell from 5.5 ± 1.2 arousals/h preflight to 1.8 ± 0.6 inflight. Postflight there was a return to near or slightly above preflight levels in these variables. We conclude that sleep quality during spaceflight is not degraded by sleep-disordered breathing. This is the first direct demonstration that gravity plays a dominant role in the generation of apneas, hypopneas, and snoring in healthy subjects.

Original languageEnglish (US)
Pages (from-to)478-485
Number of pages8
JournalAmerican journal of respiratory and critical care medicine
Issue number3
StatePublished - Aug 1 2001
Externally publishedYes


  • Airway collapse
  • Arousals
  • Gravitational effect
  • Obstructive sleep apnea

ASJC Scopus subject areas

  • Pulmonary and Respiratory Medicine
  • Critical Care and Intensive Care Medicine


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