Prevalence of sleep deficiency and use of hypnotic drugs in astronauts before, during, and after spaceflight: an observational study - PubMed (original) (raw)

Observational Study

Prevalence of sleep deficiency and use of hypnotic drugs in astronauts before, during, and after spaceflight: an observational study

Laura K Barger et al. Lancet Neurol. 2014 Sep.

Abstract

Background: Sleep deprivation and fatigue are common subjective complaints among astronauts. Previous studies of sleep and hypnotic drug use in space have been limited to post-flight subjective survey data or in-flight objective data collection from a small number of crew members. We aimed to characterise representative sleep patterns of astronauts on both short-duration and long-duration spaceflight missions.

Methods: For this observational study, we recruited crew members assigned to Space Transportation System shuttle flights with in-flight experiments between July 12, 2001, and July 21, 2011, or assigned to International Space Station (ISS) expeditions between Sept 18, 2006, and March 16, 2011. We assessed sleep-wake timing objectively via wrist actigraphy, and subjective sleep characteristics and hypnotic drug use via daily logs, in-flight and during Earth-based data-collection intervals: for 2 weeks scheduled about 3 months before launch, 11 days before launch until launch day, and for 7 days upon return to Earth.

Findings: We collected data from 64 astronauts on 80 space shuttle missions (26 flights, 1063 in-flight days) and 21 astronauts on 13 ISS missions (3248 in-flight days), with ground-based data from all astronauts (4014 days). Crew members attempted and obtained significantly less sleep per night as estimated by actigraphy during space shuttle missions (7·35 h [SD 0·47] attempted, 5·96 h [0·56] obtained), in the 11 days before spaceflight (7·35 h [0·51], 6·04 h [0·72]), and about 3 months before spaceflight (7·40 h [0·59], 6·29 h [0·67]) compared with the first week post-mission (8·01 h [0·78], 6·74 h [0·91]; p<0·0001 for both measures). Crew members on ISS missions obtained significantly less sleep during spaceflight (6·09 h [0·67]), in the 11 days before spaceflight (5·86 h [0·94]), and during the 2-week interval scheduled about 3 months before spaceflight (6·41 h [SD 0·65]) compared with in the first week post-mission (6·95 h [1·04]; p<0·0001). 61 (78%) of 78 shuttle-mission crew members reported taking a dose of sleep-promoting drug on 500 (52%) of 963 nights; 12 (75%) of 16 ISS crew members reported using sleep-promoting drugs.

Interpretation: Sleep deficiency in astronauts was prevalent not only during space shuttle and ISS missions, but also throughout a 3 month preflight training interval. Despite chronic sleep curtailment, use of sleep-promoting drugs was pervasive during spaceflight. Because chronic sleep loss leads to performance decrements, our findings emphasise the need for development of effective countermeasures to promote sleep.

Funding: The National Aeronautics and Space Administration.

Copyright © 2014 Elsevier Ltd. All rights reserved.

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Conflict of interest statement

Conflicts of Interest

Dr. Barger has previously received research support from Cephalon, Inc., non-public sponsors of research. She consults for Alertness Solutions and San Jose State University Foundation.

Dr. Flynn-Evans is now an employee of NASA Ames Research Center. This research was completed before she moved from Brigham and Women’s Hospital to NASA Ames..

Dr. Kubey has a patent, REM-Sleep Directed Visual Alarm System and Method, issued.

Dr. Walsh reports grants from Fujitsu Ireland and personal fees from Irish Centre for Manufacturing Research, outside the submitted work.

Mr. Ronda has nothing to disclose.

Dr. Wang has no conflicts to report.

Dr. Wright reports grants from NASA, during the conduct of the study; grants from Philips, Inc, personal fees from Takeda Pharmaceuticals, personal fees from Zeo, Inc, personal fees from Northwestern University American Waterways Operators Towboat Project, outside the submitted work.

Dr. Czeisler has received consulting fees from or served as a paid member of scientific advisory boards for: Teva Pharmaceutical Industries Ltd.; Koninklijke Philips Electronics, N.V.; Purdue Pharma LP; and Vanda Pharmaceuticals, Inc. Dr. Czeisler owns an equity interest in Vanda Pharmaceuticals, Inc. and receives royalties and research support from Philips Respironics, Inc. The Harvard Medical School Sleep and Health Education Program has received Educational Grant funding from Cephalon, Inc., Takeda Pharmaceuticals, Sanofi-Aventis, Inc. and Sepracor, Inc. Dr. Czeisler is the incumbent of an endowed professorship provided to Harvard University by Cephalon, Inc. and holds a number of process patents in the field of sleep/circadian rhythms (e.g., photic resetting of the human circadian pacemaker). Since 1985, Dr. Czeisler has also served as an expert witness on various legal cases related to sleep and/or circadian rhythms.

Figures

Figure 1

Figure 1

Mean sleep duration was significantly less on shuttle missions and during the SL-90 and L-11 pre-flight data collection intervals than during the post-flight data collection interval (marked with asterisks; p < 0·0001). The box plot indicates the median with a line, the 25th and 75th percentiles with the bottom and top of the box, respectively, and the10th and 90th percentiles as error bars. The dots are individual subjects with means outside lower than the 10th or higher than the 90th percentile.

Figure 2

Figure 2

Percentage of nights with total sleep time (actigraphy) less than 6 hours in space shuttle (light gray; n=77 shuttle mission-crewmembers) and ISS (dark gray; n=21 ISS crewmembers) crewmembers during three terrestrial data collection intervals, inflight and on the nights before EVAs (Space Shuttle only). 95% confidence intervals are indicated.

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