| BackgroundThe equilibrium of metabolism of human body is disrupted in a hypoxic environment,which results an increase in catabolism rate. Body composition investigation is a branch ofhuman biology. Currently, many metabolism related diseases are believed to be related tochanges of human body composition[1].Previous study found that several indexes of human body composition were changedafter exposure to high altitude or hypobaric hypoxic environment. The effect varied amongdifferent people. With prolonged exposure, the effect is still persistent[2].Acute mountain sickness (AMS) is a common high altitude illness, which oftenhappens in people who newly travel to high altitude and have not fully acclimatized tohigh altitude environment. The symptoms of AMS are benign, but if not treated properly,it can develop into a life threatening disease-high altitude cerebral edema (HACE)[3].The contributing factors of development of AMS include altitude, ascent rate and individual susceptibility [4]. In an altitude of3000-4000m, the incidence of AMS is25%-84%[5]. Previous investigation indicated that the metabolic and body-compositionchanges in high altitude were different among different ethnicities[6]. One randomizedtrial found that nutritional supplementation cannot prevent the change of bodycomposition, which supports that this change has an inert property, and is very similar tocharacteristics of AMS[7].A hypobaric chamber-based study found that obesity is a risk factor for AMS[8].However, the majority of the people traveling to high altitude have a normal weight, andthe incidence of AMS is mostly calculated from people with a normal weight. Identifyingthe risk factors in this group of people has a broader significance and applicable value.Therefore, we hypothesized that body composition changes in early exposure couldpredict development of AMS. There have not been studies of continuous observations onhuman body composition at high altitude. In the current study, we observed the bodycomposition at both low land and high altitude, and analyzed the relations between bodycomposition and occurrence of AMS.ObjectiveObserving the body composition changes at low land and1-3days at high altitude,and analyzing the relations between body composition and occurrence of AMS.Methodslongitudinal study. Participants were young male adults (n=108). They ascended from236m to3658m by train. The body composition were analyzed by using bioelectricalimpedance method (Inbody720，Biospace，Korea). The parameters measured include:general parameters (height, weight, body mass index (BMI), arm circumference (AC), armmuscle circumference (AMC), waist circumference (Waist_Cir), visceral fat area (VFA),basal metabolic rate (BMR)), and molecular parameters (water, fat, protein and minerals).The symptoms of AMS were assessed by using the Lake Louise scoring system. AMS wasdefined as the total Lake Louise score>=3, and presence of headache. The relationsbetween AMS and body composition parameters were analyzed by using t-test method. The relation between the body compostition at the first at high altitude and the accurenceof AMS was analyzed by binary logistic analysis.Results1. Changes of body composition at high altitude(1) General parametersWeight: on the first day at high altitude, the weight loss was0.41kg (t=1.94,p=0.058). On the second and third day, the weight losses were (t=3.59, p=0.001)、0.75kg(t=3.11, p=0.003).BMI: on the first day at high altitude, the BMI loss was0.14(t=1.88, p=0.064). Onthe second and third day, the BMI losses were0.28(t=3.47, p=0.001)、0.26(t=3.03,p=0.004).AC: on the first day at high altitude, the AC loss was0.15cm (t=1.63, p=0.109). Onthe second and third day, the AC losses were0.33cm (t=3.77, p<0.001)、0.35cm (t=3.76,p<0.001).AMC, Waist_Cir, VFA, BMR: on the1-3days at high altitude, the AMC losses were-0.06cm,0.05cm,0.04cm (p>0.05); Waist_Cir,-0.8cm,0.05cm,0.33cm (p>0.05);VFA,-1.0cm2,2.12cm2,2.41cm2(p>0.05); BMR,7.46kcal,5.70kcal,0.22kcal(p>0.05).(2) Molecular parametersFat: on the first day at high altitude, the fat loss was0.05kg (t=0.20, p=0.837). Onthe second and third day, the fat losses were0.55kg (t=2.17, p=0.034)、0.74kg (t=2.76,p=0.008).Water: on the1-3days at high altitude, the water losses were0.20kg (t=1.59,p=0.117),0.16kg (t=1.45, p=0.152)、0.01kg (t=0.08, p=0.936).Protein: on the first day at high altitude, the protein loss was0.07kg (t=1.99,p=0.050). On the second and third day, the protein losses were0.04kg (t=1.23, p=0.222)、0.01kg (t=0.05, p=0.961).Minerals: on the first and second day at high altitude, the minerals losses were0.08 kg (t=5.26, p<0.001)、0.06kg (t=4.14, p<0.001). On the third day, the minerals loss was0.01kg (t=0.90, p=0.371).2. The relations between body composition and occurrence of AMSFrom low land (Ya’an, Sichuan) to high altitude (Lhasa, Tibet), the incidence of AMSin the first three days is25.9%(28/108). The parameters of body composition in AMS andnon-AMS were compared.(1) General parameters and AMSWeight: on the1-3days, the weight losses in AMS group were1.3%,2.1%,1.8%; thethe weight losses in non-AMS group were0.3%,1.8%,2.0%(p>0.05).BMI: on the1-3days, the BMI losses in AMS group were1.3%,2.1%,1.7%; the theBMI losses in non-AMS group were0.3%,1.0%,0.9%(p>0.05).AC: on the first day, the AC loss in AMS group was1.5%, and the AC loss innon-AMS group was0.1%(p<0.05). On the second and third day, the AC losses in AMSgroup were2.0%,2.1%, and the AC losses in non-AMS group were0.8%,0.8%(p>0.05).AMC: on the1-3days, the AMC losses in AMS group were0.1%,0.4%,0.7%; theAMC losses in non-AMS group were-0.4%,0.1%,-0.1%(p>0.05).Waist_Cir: on the first day, the Waist_Cir loss in AMS group was1.5%, and theWaist_Cir loss in non-AMS group was0.1%(t=2.27, p=0.027). On the second and thirdday, the Waist_Cir losses in AMS group were1.2%,1.6%, and the Waist_Cir losses innon-AMS group were-0.1%,-0.1%(p>0.05).VFA: on the1-3days, the VFA losses in AMS group were0.7%,4.6%,4.5%; theVFA losses in non-AMS group were-7.5%,-1.6%,0.4%(p>0.05).BMR: on the1-3days, the BMR losses in AMS group were-0.1%,0.1%,-0.1%; theBMR losses in non-AMS group were0.7%,0.1%,0.1%(p>0.05).In the dinary logistic analysis of AMS and above indexes, it was found that AMC wassignificantly related to AMS (p=0.033).(2) Molecular parameters and AMSFat: on the1-3days, the Fat losses in AMS group were3.6%,7.0%,7.2%; the Fatlosses in non-AMS group were-4.9%,0.2%,2.9%(p>0.05). Water: on the1-3days, the Water losses in AMS group were-0.1%,0.1%,-0.2%; theWater losses in non-AMS group were0.8%,0.6%,0.1%(p>0.05).Protein: on the1-3days, the Protein losses in AMS group were0.2%,0.1%,0.1%;the Protein losses in non-AMS group were0.9%,0.6%,0.1%(p>0.05).Minerals: on the first day, the Minerals loss in AMS group was0.8%, and theMinerals loss in non-AMS group was3.1%(t=2.15, p=0.036). On the second and thirdday, the Minerals losses in AMS group were1.4%,-0.3%, and the Minerals losses innon-AMS group were2.3%,0.8%(p>0.05).In the dinary logistic analysis of relations between AMS and the above indexes, itwas found that minerals was significantly related to AMS (p=0.048).ConclusionWithin the1-3days at high altitude, body weight, AC, protein, fat and minerals werereduced significantly; low-altitude measurements of body composition indexes wereunrelated to AMS; for the people having a normal range of BMI, arm circumference, waistcircumference and mineral content measured at high altitude areas may be related to AMS.These parameter may be helpful to identify the early phase of AMS. |
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