The Influence Of The Special Environment Of The Antarctic On The Physiological Psychology Of The Members

Background Prolonged residence in Antarctica is characterized by exposure to isolated,confined,and extreme(ICE)environment.Winter-over expeditioners at research stations often exhibit a complex of psychophysiological symptoms,which varied by stations and sociocultural backgrounds.The aim was to understand the different patterns of psychophysiological responses provoked by environmental stress.Methods We conducted a longitudinal assessment of mood and endocrine function in two groups of Chinese expeditioners who were deployed to sub-Antarctic(Great Wall Station,62°S,N=12)and Antarctic(Zhongshan Station,66°S,N=16)from December 2003 to 2005.Measures of mood,thyroid function,the levels of plasma catecholamine,and circulating interleukins were obtained at departure from China,mid-winter(Antarctica),end of winter(Antarctica),and return to China,respectively.Results The Zhongshan Station crew experienced significant increases in fatigue,anger,tension,confusion,and decrease in free thyroxine(FT4),norepinephrine(NE),and epinephrine(E)during the winter,increase in thyrotropin(TSH)and total triiodothyronine(TT3)when returning,whereas their counterparts at Great Wall Station only experienced increased TT3 after deployment.Moreover,compared with the Great Wall Station crew,the Zhongshan Station crew exhibited greater increase in anger,greater decrease in FT4,total thyroxine(TT4),NE and E over the winter,and greater increase in TSH when returning.Conclusion Chinese expeditioners who lived and worked at the Antarctic station and the sub-Antarctic station for over a year showed different change patterns in mood and endocrine hormones.Negative mood and endocrine dysfunction were positively associated with the severity of environment.The study is a supplement to scientific knowledge on psychophysiological variation under ICE environment,which has certain applied value for the development of preventive countermeasures or interventions.Background.Residence at Zhongshan Station(69°22’24"S,76°22’40"E)for over one year exposes Chinese winter-over members to marked changes of light-dark cycle(polar days to polar nights),in addition to geographic and social isolation.This extreme environment may increase the risk of circadian rhythm desynchrony and sleep disturbances,induce Seasonal Affective Disorder(SAD),adversely affect living quality and working performance.Hence,it is necessary and important to evaluate the circadian status and sleep parameters during temporary Antarctic residence,to provide scientific data for medical prevention and treatment,as well as logistic management.Since Antarctic is a natural laboratory for long-term investigation into physio-psychological adaptation of a small group in extreme environment,it could be used for reference for other similar circumstances such as space missions.Methods.The subjects were the 27th,29th,and 30th winter-over expeditioners residing at Zhongshan Station for over 1 year.Sequential urine samples in 48 hours were obtained at four periods:departure,before winter(Antarctic),mid-winter(Antarctic)and end of winter(Antarctic).Sequential saliva samples in 24 hours were obtained at each month during winter period.6-sulphatoxymelatonin(aMT6s)in urine and melatonin in saliva were assayed using ELISA.The concentration data were analyzed by a cosine curve-fitting method,and the peak phase was chosen as biomarker of circadian rhythm.Objective sleep parameters were measured by wrist actigraphy or polysomnography(PSG)at four periods:departure,before winter,mid-winter and end of winter.Subjective sleep quality were evaluated by Pittsburgh Sleep Quality Index(PSQI).Morningness/Eveningness Questionnaire(MEQ)and Seasonal Pattern Assessment Questionnaire(SPAQ)were completed.Results.Circadian rhythm-The urinary aMT6s rhythm of 27th crew was delayed during residing at Antarctic(P<0.05),while the salivary melatonin rhythm of 30th crew was delayed in polar days(P<0.05).Sleep-The actigraphy results showed that,the sleep onset,sleep offset and mid-sleep time of 27th crew were delayed(P<0.05),with no change in total sleep time,sleep efficiency,and sleep latency.PSG results showed that the sleep architecture of 29th did not alter significantly.PSQI results suggested that the subjective sleep quality of 30th crew decreased,and their sleep were disturbed with affected daytime performance.Seasonal mood and behavior-The three crews had higher seasonality(P<0.01)in mid-winter.The number of SAD subjects were:0(27th crew),2(29th crew),2(30th crew).The number of S-SAD subjects were:2(27th crew),2(29th crew),1(30tth crew).Chronotype-The three crews had greater eveningness preference or later chronotypes(P<0.01)in mid-winter.Conclusions.Winter-over expeditioners at Zhongshan Station experienced problems as follows:delayed circadian rhythm and sleep phase,reduced subjective sleep quality,later chronotype,higher seasonality and incidence of SAD and S-SAD.An appropriate combination of artificial bright light during dark winter months and a strict social schedule are recommended in a winter-over station in Antarctica.The study provided fundamental but novel data of circadian status and sleep of Chinese expeditioners.Further investigations on light therapy or melatonin treatment are needed.Background Antarctic is the largest plateau on the earth.In 2009,China established Kunlun Station(80° 25’ S,77° 6’ E,4087m)at Dome A,which is the highest station in Antarctic with the harsh environment of hypoxia,extreme cold,and low humidity.Lowlanders may experience a series of physiological changes,however,in some individuals,acclimatization fails resulting in acute mountain sickness(AMS),in which sleep disturbance is one of the symptoms.Sleep disorders may not only adversely affect subjective mood but also impair cognitive function and daytime vigilance if sufficiently severe and prolonged.Hence,it is necessary and important to investigate AMS prevalence,sleep structure,sleep-related breathing disorder,and oxygen saturation of Chinese expeditioner at Kunlun Station,in order to provide scientific data for medical prevention and treatment,and help them to better adapt to such extreme environment.Methods The study was carried out on the 31st Chinese Antarctic Inland Expeditioners to Dome A.Daytime oxygen saturation was measured by figure pulse oximeter for 12 times(N=27).AMS symptoms and score were evaluated by Lake Louise Scoring System(N=27)in the first 7 days.The golden standard--polysomnography(PSG)was used to evaluated sleep,once at Kunlun Station and twice at sea level(before ascend and after descend),and the following signals were recorded:EEG,EOG,EMG,thoracic and abdominal breath effort,nasal air flow,as well as nocturnal oxygen saturation.Results The AMS prevalence at Kunlun Station was 55.6%(15/27)。The lower daytime oxygen saturation was,the worsen AMS symptoms were.Compared with sea level values,slow wave sleep reduced(P<0.01),with no change in total sleep time(TST),sleep latency and sleep efficiency.Total respiratory events and apnea hypopnea index increased(P<0.05),most of which were central type.Periodic breathing was prevalent,and its percentage in TST was increased(P<0.01).The oxygen desaturation index greatly increased(P<0.01).The nocturnal mean and minimal oxygen saturation fell(P<0.05).The values returned to normal after descent.Conclusion Under the "hypoxic,cold,isolated" environment of Kunlun Station,more than half of expeditioners experienced AMS.Their sleep architecture changed and deep sleep reduced.Apneas were prevalent,with almost exclusively of periodic breathing type.Daytime and nocturnal oxygen saturation were decreased,and the latter was lower.The strict physical screening examination and pre-acclimatization training before departure to Antarctica is imperative.Oxygen supply equipment is recommended to be maintained and used properly in living chamber or room to benefit the expeditioners’ safety,work productivity and general well-being.The results were of value in extending the knowledge on the changes in sleep and breathing on Antarctic plateau.