title: Microgravity reduces sleep-disordered breathing in humans.
abstract: 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.
authors.affiliation: Department of Medicine, University of California, San Diego, La Jolla, California 92093-0931, USA.
authors.forename: A R
authors.initials: AR
authors.lastname: Elliott
authors.forename: S A
authors.initials: SA
authors.lastname: Shea
authors.forename: D J
authors.initials: DJ
authors.lastname: Dijk
authors.forename: J K
authors.initials: JK
authors.lastname: Wyatt
authors.forename: E
authors.initials: E
authors.lastname: Riel
authors.forename: D F
authors.initials: DF
authors.lastname: Neri
authors.forename: C A
authors.initials: CA
authors.lastname: Czeisler
authors.forename: J B
authors.initials: JB
authors.lastname: West
authors.forename: G K
authors.initials: GK
authors.lastname: Prisk
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D017286:Polysomnography; D012119:Respiration; D012890:Sleep / Q000502:physiology*; D012892:Sleep Deprivation; D012893:Sleep Wake Disorders / Q000503:physiopathology; D013026:Space Flight; D014893:Weightlessness