title: Sleep and the endogenous melatonin rhythm of high arctic residents during the summer and winter.
abstract: The seasonal extremes of photoperiod in high latitudes place particular strain on the human circadian system. Arctic residence has been associated with poor sleep in both summer and winter. The goal of the work reported here was to study the circadian rhythms of individuals living in the high Arctic by measuring sleep variables and the timing of melatonin production. Two research trials were conducted in the built environment of CFS Alert (82° 29' 58″ N). Participants wore motion logging devices (actigraphs), which measure ambient light as well as motion, for 1week to provide data on sleep quantity, quality and light exposure. On the penultimate day of each trial, the participants were maintained together in a gymnasium with lounge chairs and saliva was collected at regular intervals to measure melatonin and assess the dim light melatonin onset (DLMO), offset (MelOFF), 50% rise and fall times of the whole profile and total production. In general, sleep duration was found to be significantly different between the January and June data collections at CFS Alert, with participants in June sleeping 50min on average less each day compared to their January counterparts. In June sleep was mistimed in many subjects relative to circadian phase as evidenced by the melatonin rhythm. Exposure to bright evening light was the most likely causal factor and should be avoided in the Arctic summer. The Arctic summer represents a particularly challenging environment for obtaining sufficient sleep. This has implications for the cognitive performance of staff during work hours.
authors.affiliation: Defence Research and Development Canada, Toronto, ON, M3K2C9, Canada.
authors.forename: Michel A
authors.initials: MA
authors.lastname: Paul
authors.affiliation: Defence Research and Development Canada, Toronto, ON, M3K2C9, Canada. Electronic address: ryan.love@drdc-rddc.gc.ca.
authors.forename: Ryan J
authors.initials: RJ
authors.lastname: Love
authors.affiliation: Defence Research and Development Canada, Toronto, ON, M3K2C9, Canada.
authors.forename: Andrea
authors.initials: A
authors.lastname: Hawton
authors.affiliation: University of Surrey, Guildford, Surrey GU2 7XH, United Kingdom.
authors.forename: Josephine
authors.initials: J
authors.lastname: Arendt
mesh_terms: D056044:Actigraphy; D000328:Adult; D001110:Arctic Regions; D002940:Circadian Rhythm / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008550:Melatonin / Q000032:analysis*; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology*; D012463:Saliva / Q000737:chemistry; D012621:Seasons; D012890:Sleep / Q000502:physiology*; D055815:Young Adult
chemical_list: D008550:Melatonin
keywords: Circadian rhythms; Dim light melatonin onset; Fatigue; Polar regions