Sleep of Andean high altitude natives

Summary The structure of sleep in lowland visitors to altitudes greater than 4000 m is grossly disturbed. There are no data on sleep in long-term residents of high altitudes. This paper describes an electroencephalographic study of sleep in high altitude dwellers who were born in and are permanent residents of Cerro de Pasco in the Peruvian Andes, situated at 4330 m. Eight healthy male volunteers aged between 18 and 69 years were studied. Sleep was measured on three consecutive nights for each subject. Electroencephalographs, submental electromyographs and electro-oculograms were recorded. Only data from the third night were used in the analysis. The sleep patterns of these subjects resembled the normal sleep patterns described by others in lowlanders at sea level. There were significant amounts of slow wave sleep in the younger subjects and rapid eye movement sleep seemed unimpaired.     

Comparison of cisternal and lumbar cerebrospinal fluid pH in high altitude natives

Samples of cisternal or lumbar cerebrospinal fluid were obtained from 20 young male volunteers born and living at high altitude (3500 to 4800 m). The pH, carbon dioxide and oxygen tensions, and bicarbonate concentration were measured and compared with those in the arterial and jugular venous blood. A consistent difference between the two CSF compartments was noted, particularly a lower pH (0.05), a higher PCO2 (7 Torr), and a lower PO2 (7 Torr) at the lumbar site. Mean bicarbonate concentration was not significantly different at the two sites. The main factor is PCO2, which controls the pH variation. These differences were more marked in high-altitude natives than in man at sea level. The existence of a consistent inhomogeneity of CSF acid-base content emphasizes the inaccuracy of using lumbar CSF pH to estimate the ECF pH as regulator of pulmonary ventilation and determinant of cerebral blood flow.     

Population genetic aspects and phenotypic plasticity of ventilatory responses in high altitude natives

Highland natives show unique breathing patterns and ventilatory responses at altitude, both at rest and during exercise. For many ventilatory traits, there is also significant variation between highland native groups, including indigenous populations in the Andes and Himalaya, and more recent altitude arrivals in places like Colorado. This review summarizes the literature in this area with some focus on partitioning putative population genetic differences from differences acquired through lifelong exposure to hypoxia. Current studies suggest that Tibetans have high resting ventilation (V (E)), and a high hypoxic ventilatory response (HVR), similar to altitude acclimatized lowlanders. Andeans, in contrast, show low resting V (E) and a low or "blunted" HVR, with little evidence that these traits are acquired via lifelong exposure. Resting V (E) of non-indigenous altitude natives is not well documented, but lifelong hypoxic exposure almost certainly blunts HVR in these groups through decreased chemosensitivity to hypoxia in a process known as hypoxic desensitization (HD). Together, these studies suggest that the time course of ventilatory response, and in particular the origin or absence of HD, depends on population genetic background i.e., the allele or haplotype frequencies that characterize a particular population. During exercise, altitude natives have lower V (E) compared to acclimatized lowland controls. Altitude natives also have smaller alveolar-arterial partial pressure differences P(AO2) - P(aO2) during exercise suggesting differences in gas exchange efficiency. Small P(AO2) - P(aO2) in highland natives of Colorado underscores the likely importance of developmental adaptation to hypoxia affecting structural/functional aspects of gas exchange with resultant changes in breathing pattern. However, in Andeans, at least, there is also evidence that low exercise V (E) is determined by genetic background affecting ventilatory control independent of gas exchange. Additional studies are needed to elucidate the effects of gene, environment, and gene-environment interaction on these traits, and these effects are likely to differ widely between altitude native populations.     

Different adaptation patterns of antioxidant system in natives and sojourners at high altitude

Comparative studies on the adaptation pattern of antioxidant status among high altitude natives and acclimatized sojourners are very scanty. The aim of the present study was to compare the differences in antioxidant profile between two groups of active male volunteers, i.e. native highlanders (HAN, n = 66) in their natural hypoxic environment with that of sojourners (SOJ, n = 81) from sea level (SL) after 4 weeks of stay at an altitude of 4560 m. Blood samples of SOJ were collected at SL and HA. Same was collected from HAN once at HA. HAN had significantly higher SOD activity and significantly lower catalase, GPX and GR activities than SOJ at HA. Ratio of GSH/GSSG was also significantly higher in HAN than SOJ at HA. In SOJ, antioxidant profile showed an upregulation after HA stay but it was not effective to reduce the levels of oxidative stress markers. Therefore, it can be stated that lifelong exposure to hypoxia has beneficial adaptive effects on antioxidant system in HAN. Similarly, acclimatization to HA also has beneficial preconditioning effects on antioxidant system in SOJ, but, may not be sufficient to ameliorate oxidative stress completely. Transient increase in metabolic rate due to hypoxia may be a causative factor for excess free radical generation among sojourners at HA.     

Body composition of high altitude natives on descent to the plains: A densitometric,hydrometric, and anthropometric evaluation

Summary Body density was experimentally determined at a field location at 3,920 m on 32 medically fit and active high altitude native males using a water displacement technique. Stature, body weight and the bony widths at the elbow, wrist, knee, and ankles; and thickness of skin folds at eight sites were measured. Based on body density and bony widths, body fat, total body water (TBW), mineral mass and total cell solids (TCS) were calculated.Similar measurements were made on another group of 16 high altitude natives after one months stay in Dehli (200 m). TBW of 11 of these subjects was experimentally determined by the oral administration of 200 Ci of tritiated water. This group of subjects was physically less active in Delhi. At high altitude the natives consumed a balanced diet which provided 20.21 MJ, but in the plains the diet provided only 15.69 MJ though it was nutritionally balanced.In spite of the reduced calorie intake this group showed greater fat content in Delhi than the group located at high altitude. These men were also hyperhydrated. Hyperhydration of the lean body could be an adaptive response of the high altitude natives to the new environment. Due to the disturbed state of hydration of the lean body of these men in the plains, use of Siri's formula for the computation of total body fat is questioned.     

Effect of developmental and ancestral high altitude exposure on chest morphology and pulmonary function in Andean and European/North American natives

Chest depth, chest width, forced vital capacity (FVC), and forced expiratory volume (FEV1) were measured in 170 adult males differing by ancestral (genetic) and developmental exposure to high altitude (HA). A complete migrant study design was used to study HA natives (Aymara/Quechua ancestry, n = 88) and low altitude (LA) natives (European/North American ancestry, n = 82) at both altitude (La Paz, Bolivia, 3,600 m) and near sea level (Santa Cruz, Bolivia, 420 m). HAN and LAN migrant groups were classified as: N^th generation migrants, born and raised in a non-native environment; child migrants who migrated during the period of growth and maturation (0–18 yrs); and adult migrants who migrated after 18 years of age. Chest depth, FVC, and FEV1 measures were larger with increasing developmental exposure in both HAN migrants at LA and LAN migrants at HA. Developmental responses were similar between HAN and LAN groups. FVC and FEV1 measures were larger in HANs vs LANs born and raised at HA to suggest a genetic effect, but were similar in HANs and LANs born and raised at LA. The similarity of HAN and LAN groups at LA suggests that the genetic potential for larger lung volumes at HA depends upon developmental exposure to HA. Additional data for females (HANs at HA, n = 20, and LAN adult migrants to HA, n = 17) show similar differences as those shown between male HAN and LAN groups. Am. J. Hum. Biol. 11:383–395, 1999. © 1999 Wiley-Liss, Inc.     

Ventilatory capacity among highland Bods: a possible adaptive mechanism at high altitude

Ventilatory capacity (forced vital capacity, forced expiratory volume and maximal voluntary ventilation) among Highland Bods (3514 m altitude) was higher than in an ethnically similar population residing at a lower altitude in Kulu Valley (1500--2200 m). Increased ventilatory capacity appears to have developed among native highlanders as a consequence of a biological response to high altitude. Numerous factors such as low oxygen pressure, increased work-load and minimal air pollution may explain these findings.     

Ventilatory capacity among highland Bods: a possible adaptive mechanism at high altitude

Ventilatory capacity (forced vital capacity, forced expiratory volume and maximal voluntary ventilation) among Highland Bods (3514 m altitude) was higher than in an ethnically similar population residing at a lower altitude in Kulu Valley (1500–2200 m). Increased ventilatory capacity appears to have developed among native highlanders as a consequence of a biological response to high altitude. Numerous factors such as low oxygen pressure, increased work-load and minimal air pollution may explain these findings.     

Effects of long-term acclimatization in lowlanders migrating to high altitude: comparison with high altitude residents

The physiological response to submaximal and maximal exercise was assessed in lowlanders and Tibetans at low (500 m above sea level) and high altitude (HA, 3 680 m). The times spent at HA by the lowland migrators was 8 days (n = 60), 7 months (n = 60, same group), 15 months (n = 29) and 27 months (n = 29). After the 15-month stay at HA, the maximal oxygen uptake ( O_2max) and maximal heart rate of the lowland migrators almost reached those of the HA native residents (Tibetans, n = 57), but their total work capacity and the gross efficiency () of mechanical work remained lower than those of the Tibetans. The rate of O_2max achieved at 90 W by the Tibetans was lower than that of the lowland migrators. It was concluded that, at HA, the lowlanders regained much of the aerobic capacity which they had lost initially. However, they did not attain the same gross mechanical efficiency as the Tibetans, who seemed to be at an advantage in respect of work at HA.     

Humans at high altitude: hypoxia and fetal growth

High-altitude studies offer insight into the evolutionary processes and physiological mechanisms affecting the early phases of the human lifespan. Chronic hypoxia slows fetal growth and reduces the pregnancy-associated rise in uterine artery (UA) blood flow. Multigenerational vs. shorter-term high-altitude residents are protected from the altitude-associated reductions in UA flow and fetal growth. Presently unknown is whether this fetal-growth protection is due to the greater delivery or metabolism of oxygen, glucose or other substrates or to other considerations such as mechanical factors protecting fragile fetal villi, the creation of a reserve protecting against ischemia/reperfusion injury, or improved placental O₂ transfer as the result of narrowing the A-V O₂ difference and raising uterine Pv_O2$P{v}_{{\text{O}}_2}$. Placental growth and development appear to be normal or modified at high altitude in ways likely to benefit diffusion. Much remains to be learned concerning the effects of chronic hypoxia on embryonic development. Further research is required for identifying the fetoplacental and maternal mechanisms responsible for transforming the maternal vasculature and regulating UA blood flow and fetal growth. Genomic as well as epigenetic studies are opening new avenues of investigation that can yield insights into the basic pathways and evolutionary processes involved.     

高原地区居民的体成分与形态学变化

高原地区居民的体成分与形态学有什么变化及其原因如何,这是一个崭新的命题。本文介绍了体成分的概念,对高原环境中血红蛋白和红细胞压积,脂类,激素,酶,肌及水的变化做了概括,总结了人的生长发育,身高,体重,胸径,围度,皮褶厚度等体质变化,分析了高原缺氧,遗传以及社会经济文化,民族,年龄,健康等对高原居民的体成分和形态学变化的影响,提出今后对高原缺氧状态下体成分和形态学变化及其原因应进一步探讨。     

Anthropometric somatotype of Bod girls: A comparison of high and low altitude populations

The high altitude environment is known to influence the morphophysiology of man in a variety of ways. Its possible impact on somatotype of adolescent girls has not been investigated so far. For this purpose 348 female Bods, from 10 to 18 years old, have been somatotyped from high altitude (n = 176) of Ladakh (3,534 m) and low altitude (n = 172) of Kullu Valley (1,500–2,200 m). The results of the study reveal greater mesomorphy and ectomorphy in the high altitude Bod girls than in ethnically similar low altitude Bod girls of comparable age. The study has accorded the differences in the somatotypes to the high altitude stresses. Striking similarities in boys and girls in terms of higher mesomorphy and ectomorphy in the highlander Bods than the coeval lowlanders confirm the hypothesis that the high altitude environment influences the somatotype components.     

Chest dimensions of European and Aymara children at high altitude

This study compares the chest dimensions of European children raised at high altitude with those of Andean natives. The samples consist of 216 children between 8 and 14 years who attend the private French School in La Paz, Bolivia and 253 Aymara children of the same age who reside in the rural country of Arncoraimes, Bolivia. Compared to the Aymara children, the European children have larger chest depths and chest widths, but have smaller chest dimensions relative to stature. There is no difference between the two groups in the ratio of chest width to chest depth. The small relative chest size of the European children further expands the range of variation in chest dimensions among high altitude populations.     

Variation in hemoglobin concentration among samples of high-altitude natives in the Andes and the Himalayas

This paper presents data on hemoglobin concentration in a rural Andean sample at 3,800–3,900 m and incorporates them into a review intended to evaluate possible sources of the range of variation in mean hemoglobin concentration among samples obtained at high altitude. Between 3,400 and 4,000 m, rural Himalayan highlanders average 1.4 gm/dl lower mean hemoglobin concentration than rural Andean highlanders. With respect to potential causes of anemia, it is concluded that the relatively low values of rural Himalyan populations are not explicable by lower hypoxic stress or different techniques of obtaining and analyzing blood samples and are probably not explicable by nutritional deficiency and disease. With respect to potential causes of polycythemia within Andean populations, it is concluded that the somewhat higher values of some mining and urban samples of Andean higlanders may not be due to the mining occupation per se but may be due partly to the inclusion of European and mestizo (with at most 500 years of high-altitude ancestry) along with Amerindian highlanders (with millenia of high-altitude ancestry) as well as to the inclusion of highlanders living well above their own habitual altitudes of residence. The Andean polycythemia is probably not due to obesity, high androgen levels, or frequent intermittent hypoxemia during sleep. The effect of heavy smoking cannot be evaluated. Further work on hematological adaptation to high altitude must pay special attention to sample characteristics.