title: Sleep during an Antarctic summer expedition: new light on "polar insomnia".
abstract: Sleep complaints are consistently cited as the most prominent health and well-being problem in Arctic and Antarctic expeditions, without clear evidence to identify the causal mechanisms. The present investigation aimed at studying sleep and determining circadian regulation and mood during a 4-mo Antarctic summer expedition. All data collection was performed during the continuous illumination of the Antarctic summer. After an habituation night and acclimatization to the environment (3 wk), ambulatory polysomnography (PSG) was performed in 21 healthy male subjects, free of medication. An 18-h profile (saliva sampling every 2 h) of cortisol and melatonin was assessed. Mood, sleepiness, and subjective sleep quality were assessed, and the psychomotor vigilance task was administered. PSG showed, in addition to high sleep fragmentation, a major decrease in slow-wave sleep (SWS) and an increase in stage R sleep. Furthermore, the ultradian rhythmicity of sleep was altered, with SWS occurring mainly at the end of the night and stage R sleep at the beginning. Cortisol secretion profiles were normal; melatonin secretion, however, showed a severe phase delay. There were no mood alterations according to the Profile of Mood States scores, but the psychomotor vigilance test showed an impaired vigilance performance. These results confirm previous reports on "polar insomnia", the decrease in SWS, and present novel insight, the disturbed ultradian sleep structure. A hypothesis is formulated linking the prolonged SWS latency to the phase delay in melatonin.NEW & NOTEWORTHYThe present paper presents a rare body of work on sleep and sleep wake regulation in the extreme environment of an Antarctic expedition, documenting the effects of constant illumination on sleep, mood, and chronobiology. For applied research, these results suggest the potential efficiency of melatonin supplementation in similar deployments. For fundamental research, these results warrant further investigation of the potential link between melatonin secretion and the onset of slow-wave sleep.
authors.affiliation: VIPER Research Unit, Royal Military Academy, Brussels, Belgium; nathalie.pattyn@rma.ac.be.|Department of Experimental and Applied Psychology, Vrije Universiteit Brussels, Brussels, Belgium.|Human Physiology and Sports Medicine, Vrije Universiteit Brussels, Brussels, Belgium.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Pattyn
authors.affiliation: VIPER Research Unit, Royal Military Academy, Brussels, Belgium.|Department of Experimental and Applied Psychology, Vrije Universiteit Brussels, Brussels, Belgium.|Sleep Unit, CHU Brugmann, Brussels, Belgium; and.
authors.forename: Olivier
authors.initials: O
authors.lastname: Mairesse
authors.affiliation: VIPER Research Unit, Royal Military Academy, Brussels, Belgium.|Sleep Unit, Department of Pneumology, Universitair Ziekenhuis Brussels, Brussels, Belgium.
authors.forename: Aisha
authors.initials: A
authors.lastname: Cortoos
authors.affiliation: VIPER Research Unit, Royal Military Academy, Brussels, Belgium.|Department of Experimental and Applied Psychology, Vrije Universiteit Brussels, Brussels, Belgium.
authors.forename: Nele
authors.initials: N
authors.lastname: Marcoen
authors.affiliation: VIPER Research Unit, Royal Military Academy, Brussels, Belgium.
authors.forename: Xavier
authors.initials: X
authors.lastname: Neyt
authors.affiliation: Human Physiology and Sports Medicine, Vrije Universiteit Brussels, Brussels, Belgium.
authors.forename: Romain
authors.initials: R
authors.lastname: Meeusen
mesh_terms: D000064:Acclimatization / Q000502:physiology; D000339:Affect / Q000502:physiology; D000864:Antarctic Regions; D001143:Arousal / Q000502:physiology; D002940:Circadian Rhythm / Q000502:physiology; D005101:Expeditions; D006801:Humans; D006854:Hydrocortisone / Q000378:metabolism; D008029:Lighting; D008297:Male; D008550:Melatonin / Q000378:metabolism; D017286:Polysomnography / Q000379:methods; D011597:Psychomotor Performance / Q000502:physiology; D012463:Saliva / Q000378:metabolism; D012621:Seasons; D012890:Sleep / Q000502:physiology*; D012892:Sleep Deprivation / Q000503:physiopathology*; D007319:Sleep Initiation and Maintenance Disorders / Q000503:physiopathology*
chemical_list: D008550:Melatonin; D006854:Hydrocortisone
keywords: Antarctica; chronobiology; cortisol; field study; melatonin; polysomnography; sleep