title: Sleep Quality Changes during Overwintering at the German Antarctic Stations Neumayer II and III: The Gender Factor.
abstract: OBJECTIVE
  Antarctic residence holds many challenges to human physiology, like increased psycho-social tension and altered circadian rhythm, known to influence sleep. We assessed changes in sleep patterns during 13 months of overwintering at the German Stations Neumayer II and III from 2008 to 2014, with focus on gender, as many previous investigations were inconclusive regarding gender-based differences or had only included men.
  
  
  METHODS
  Time in bed, sleep time, sleep efficiency, number of arousals, sleep latency, sleep onset, sleep offset, and physical activity level were determined twice per month during seven overwintering campaigns of n = 54 participants (37 male, 17 female) using actimetry. Data were analyzed using polynomial regression and analysis of covariance for change over time with the covariates gender, inhabited station, overwintering season and influence of physical activity and local sunshine radiation.
  
  
  RESULTS
  We found overall longer times in bed (p = 0.004) and sleep time (p = 0.014) for women. The covariate gender had a significant influence on time in bed (p<0.001), sleep time (p<0.001), number of arousals (p = 0.04), sleep latency (p = 0.04), and sleep onset (p<0.001). Women separately (p = 0.02), but not men (p = 0.165), showed a linear increase in number of arousals. Physical activity decreased over overwintering time for men (p = 0.003), but not for women (p = 0.174). The decline in local sunshine radiation led to a 48 minutes longer time in bed (p<0.001), 3.8% lower sleep efficiency (p<0.001), a delay of 32 minutes in sleep onset (p<0.001), a delay of 54 minutes in sleep offset (p<0.001), and 11% less daily energy expenditure (p<0.001), for all participants in reaction to the Antarctic winter's darkness-phase.
  
  
  CONCLUSIONS
  Overwinterings at the Stations Neumayer II and III are associated with significant changes in sleep patterns, with dependences from overwintering time and local sunshine radiation. Gender appears to be an influence, as women showed a declining sleep quality, despite that their physical activity remained unchanged, suggesting other causes such as a higher susceptibility to psycho-social stress and changes in environmental circadian rhythm during long-term isolation in Antarctica.
authors.affiliation: Center for Space Medicine and Extreme Environments Berlin, Institute for Physiology, Charité Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Mathias
authors.initials: M
authors.lastname: Steinach
authors.affiliation: Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany.
authors.forename: Eberhard
authors.initials: E
authors.lastname: Kohlberg
authors.affiliation: Center for Space Medicine and Extreme Environments Berlin, Institute for Physiology, Charité Universitätsmedizin Berlin, Berlin, Germany.|Department of Biomedical Sciences for Health, Università degli Studi di Milano, Milan, Italy.
authors.forename: Martina Anna
authors.initials: MA
authors.lastname: Maggioni
authors.affiliation: Center for Space Medicine and Extreme Environments Berlin, Institute for Physiology, Charité Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Mendt
authors.affiliation: Center for Space Medicine and Extreme Environments Berlin, Institute for Physiology, Charité Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Oliver
authors.initials: O
authors.lastname: Opatz
authors.affiliation: Center for Space Medicine and Extreme Environments Berlin, Institute for Physiology, Charité Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Stahn
authors.affiliation: Center for Space Medicine and Extreme Environments Berlin, Institute for Physiology, Charité Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Hanns-Christian
authors.initials: HC
authors.lastname: Gunga
mesh_terms: D056044:Actigraphy; D000328:Adult; D000864:Antarctic Regions; D001143:Arousal / Q000502:physiology; D001823:Body Composition; D015992:Body Mass Index; D002940:Circadian Rhythm; D004780:Environment, Controlled; D005260:Female; D005858:Germany / Q000208:ethnology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009043:Motor Activity; D012044:Regression Analysis; D012108:Research Personnel / Q000706:statistics & numerical data; D012621:Seasons; D012737:Sex Factors; D012890:Sleep / Q000502:physiology*; D012892:Sleep Deprivation / Q000453:epidemiology; D012934:Social Isolation; D013472:Sunlight; D014851:Wakefulness / Q000502:physiology