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Neuroscience Journal
Volume 2013, Article ID 254090, 10 pages
http://dx.doi.org/10.1155/2013/254090
Clinical Study

Circadian Levels of Serum Melatonin and Cortisol in relation to Changes in Mood, Sleep, and Neurocognitive Performance, Spanning a Year of Residence in Antarctica

1National Centre for Antarctic and Ocean Research, Ministry of Earth Sciences, Headland Sada, Goa 403 804, India
2Department of Medicine, B.L. Taneja Block, Maulana Azad Medical College, Bahadur Shah, Zafar Marg, New Delhi 110002, India

Received 24 August 2012; Revised 1 October 2012; Accepted 17 October 2012

Academic Editor: Marcos Gabriel Frank

Copyright © 2013 Madhumita Premkumar et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Background. Altered circadian cortisol and melatonin rhythms in healthy subjects exposed to an extreme polar photoperiod results in changes in mood and sleep, which can influence cognitive performance. Materials and Methods. We assessed the circadian rhythm of 20 subjects who wintered over at Maitri ( S, E), India’s permanent Antarctic station, from November 2010 to December 2011. Serum cortisol and melatonin levels were measured by radioimmunoassay at 8 am, 3 pm, 8 pm, and 2 am in a single day, once each during the polar summer and winter photoperiods. Conventional psychological tests, Depression, Anxiety, and Stress Scale (DASS-42), Epworth Sleepiness Scale (ESS), and a computerized neurocognitive test battery were used to measure mood, sleep, and cognitive performance. Results. The mean scores for DASS42 were higher during midwinter suggesting the presence of “overwintering.” Mean diurnal cortisol levels during summer and winter were comparable, but the levels of melatonin were markedly higher during winter. Higher 8 am melatonin levels were associated with better sleep quality, lower depression scores, and better performance in tasks like attention, visual memory, and arithmetic. Conclusion. Timing of artificial light exposure and usage of melatonin supplements in improving sleep and cognitive performance in expedition teams are of future research interest.