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. 2016 Jan 7:2:15019.
doi: 10.1038/npjmgrav.2015.19. eCollection 2016.

Circadian misalignment affects sleep and medication use before and during spaceflight

Erin E Flynn-Evans  1   2   3 , Laura K Barger  1   2 , Alan A Kubey  1 , Jason P Sullivan  1 , Charles A Czeisler  1   2
Affiliations

Circadian misalignment affects sleep and medication use before and during spaceflight

Erin E Flynn-Evans et al. NPJ Microgravity. .

Abstract

Sleep deficiency and the use of sleep-promoting medication are prevalent during spaceflight. Operations frequently dictate work during the biological night and sleep during the biological day, which contribute to circadian misalignment. We investigated whether circadian misalignment was associated with adverse sleep outcomes before (preflight) and during spaceflight missions aboard the International Space Station (ISS). Actigraphy and photometry data for 21 astronauts were collected over 3,248 days of long-duration spaceflight on the ISS and 11 days prior to launch (n=231 days). Sleep logs, collected one out of every 3 weeks in flight and daily on Earth, were used to determine medication use and subjective ratings of sleep quality. Actigraphy and photometry data were processed using Circadian Performance Simulation Software to calculate the estimated endogenous circadian temperature minimum. Sleep episodes were classified as aligned or misaligned relative to the estimated endogenous circadian temperature minimum. Mixed-effects regression models accounting for repeated measures were computed by data collection interval (preflight, flight) and circadian alignment status. The estimated endogenous circadian temperature minimum occurred outside sleep episodes on 13% of sleep episodes during preflight and on 19% of sleep episodes during spaceflight. The mean sleep duration in low-Earth orbit on the ISS was 6.4±1.2 h during aligned and 5.4±1.4 h (P<0.01) during misaligned sleep episodes. During aligned sleep episodes, astronauts rated their sleep quality as significantly better than during misaligned sleep episodes (66.8±17.7 vs. 60.2±21.0, P<0.01). Sleep-promoting medication use was significantly higher during misaligned (24%) compared with aligned (11%) sleep episodes (P<0.01). Use of any medication was significantly higher on days when sleep episodes were misaligned (63%) compared with when sleep episodes were aligned (49%; P<0.01). Circadian misalignment is associated with sleep deficiency and increased medication use during spaceflight. These findings suggest that there is an immediate need to deploy and assess effective countermeasures to minimize circadian misalignment and consequent adverse sleep outcomes both before and during spaceflight.

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Conflict of interest statement

LKB has previously received research support from Cephalon, NFL charities, Sysco and San Francisco Bar Pilots. She has received consulting/lecture fees or served as a board member for Alertness Solution, Ceridian, Davis Joint Unified School Board, San Jose State University Foundation, Pugot Sound Pilots, Sygma and Torvec. EEF-E is an employee of NASA Ames Research Center; AAK has a patent, REM-Sleep Directed Visual Alarm System and Method, issued. CAC has received consulting fees from, or served as a paid member of scientific advisory boards for Amazon.com, Inc., A2Z Development Center, Inc., Bose Corporation, Boston Red Sox, Cleveland Browns, Institute of Digital Media and Child Development, Jazz Pharmaceuticals, Inc., Koninklijke Philips Electronics, Merck Sharpe and Dohme, Novartis, Purdue Pharma, Quest Diagnostics, Samsung Electronics, Teva Pharmaceutical Industries, and Vanda Pharmaceuticals; owns an equity interest in Somnus and Vanda Pharmaceuticals; and receives research/education support from Philips Respironics, Mary Ann and Stanley Snider through Combined Jewish Philanthropies, National Football League Charities, Optum, San Francisco Bar Pilots, Schneider National, Simmons, Sysco. CAC receives royalties from McGraw Hill, Houghton Mifflin Harcourt Philips and from Respironics for the Actiwatch‐2 and Actiwatch‐Spectrum devices used in this research. CAC’s interests were reviewed and are managed by Brigham and Women’s Hospital and Partners HealthCare in accordance with their conflict of interest policies. The Harvard Medical School, Division of Sleep Medicine and the Brigham and Women’s Hospital, Division of Sleep and Circadian Disorders (LKB, EEF-E, CAC) have received unrestricted educational gifts and endowment funds from Boehringer Ingelheim Pharmaceuticals, Inc., Cephalon, Takeda Pharmaceuticals, Sanofi-Aventis, Tempur-Pedic, Walmart, Proctor and Gamble, Optum, Bose, Vanda Pharmaceuticals, Inc., Apria Healthcare, ResMed Foundation, Teva Pharmaceutical Industries, Ltd., Wake Up Narcolepsy, and Sepracor. CAC is the incumbent of an endowed professorship provided to Harvard University by Cephalon, and holds several process patents in the specialty of sleep and circadian rhythms (e.g., photic resetting of the human circadian pacemaker). CAC has served as an expert witness on various legal cases related to Celadon, Crete Carrier Corporation, Citgo, sleep and circadian rhythms, including matters related to Celadon, Crete Carrier Corporation, Citgo, Bombardier, Fedex, HG Energy, Michael Jackson’s mother and children, Purdue Pharma, Stric Lan LLC, Valero, and United Parcel Service.

Figures

Figure 1
Figure 1
Representative raster plots for three astronauts during spaceflight. Plots show sleep (black boxes) and circadian temperature minimum estimates (circles) derived from actigraphy over 100 days of data collection during spaceflight. Day 1 begins in the upper left corner. Data are plotted by clock time as indicated on the lower axis.
See this image and copyright information in PMC

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