Morphological growth and thorax dimensions among Tibetan compared to Han children, adolescents and young adults born and raised at high altitude.

BACKGROUND: Studies comparing the growth of indigenous high-altitude Aymara children and children of low-altitude European descent who have been born and raised at high altitude in the Andes have provided evidence for genetically-determined differences in thorax growth, as well as for population differences in height, weight and other measures of overall size. Comparable studies now can be undertaken in Asia because of the growing number of Han Chinese who have been born and raised at high altitude on the Qinghai-Tibetan Plateau. AIM: The study compares the growth of indigenous Tibetan children and children of Han descent who have been born and raised at the same high altitudes, and under similar socio-economic conditions. SUBJECTS AND METHODS: Measurements of stature, sitting height, weight, triceps and subscapular skinfolds, upper arm muscle area, transverse chest diameter, anterio-posterior chest diameter, and chest circumference were taken on 1439 Tibetan and Han males and females between the ages of 6 and 29 years who were born and raised 3200 m, 3800 m or at 4300 m in the high altitude province of Qinghai in western China. RESULTS: Han-Tibetan differences in body size do not occur systematically for any measurement, for any age group, or for either gender; nor is there a systematic pattern of body size differences between 3200 m and 4300 m. This indicates that there are no differences in general growth between the two groups at high altitude in Qinghai, although both groups grow more slowly than urban children at low altitude in China. On the other hand, Tibetan males possess significantly deeper chests than Han males, and Tibetan females possess significantly wider chests than Han females. Tibetans of both sexes possess significantly larger chest circumferences than Han males and females. CONCLUSIONS: Although genetic similarities cannot be ruled out, comparable dietary stress is a likely explanation for the similar and slow morphological growth of Han and Tibetans at high altitude. However, Han-Tibetan differences in thorax dimensions are likely a consequence of population (genetic) differences in the response to hypoxia during growth.

Growth of Qinghai Tibetans living at three different high altitudes.

This study compares the stature, weight, skinfolds, upper arm muscle area, and chest dimensions of Tibetan children, adolescents, and young adults who were born and raised, or who had lived from infancy, at 3,200 m, 3,800 m, and 4,300 m in Qinghai Province, People's Republic of China. While the individuals measured in Qinghai are among the tallest and heaviest Tibetans reported in the literature, they are nevertheless smaller and lighter than well-off children living at low altitude. The pattern of size variation among Tibetan males and females measured at the three high altitudes, along with evidence of a secular trend at 4,300 m, suggests that nutrition may significantly effect growth at high altitude. Only minor differences in thorax dimensions exist between Tibetan males and females measured at 3,200 m and 3,800 m. However, Tibetan males at 4,300 m possess slightly narrower and deeper chests (during and after adolescence) than males at 3,200 m and 3,800 m. Since individuals from 3,800 m and 4,300 m belong to the same local populations, this characteristic is unlikely to be genetically determined. However, it may be related to differences in the degree of hypoxia or to the influences of other environmental conditions.

Smoking and pulmonary function in five Solomon Island populations.

The relationship between smoking and lung function was examined in a large sample of healthy Solomon Island Melanesians and Polynesians as part of a multidisciplinary study carried out in 1985 and 1986. Comparisons are made between samples of smokers and non-smokers to determine if smoking is associated with a reduction in pulmonary function among males and females between 25 and 75 years of age. The results of this study indicate that cigarette smoking causes significant reductions in the pulmonary function of these populations. In addition, a clear difference in pulmonary function between males and females, as well as a general reduction in female FEV1 values, suggests that cooking smoke inhalation may be operating as a possible risk factor to the pulmonary health of women. Further research is needed to quantify exposure to smoke of both males and females and relate this measure to declines in pulmonary function.

Effects of acculturation and age on the exercise capacities of Solomon Islanders.

Submaximal exercise tests were carried out on 197 females and 290 males from five populations in the Solomon Islands to determine how acculturation affects the fitness of different age and sex groups. Males and females in the least acculturated group show the highest fitness levels, reflecting strenuous work patterns. Subjects from the most acculturated groups exhibit the lowest levels of fitness, a consequence of their more sedentary life-styles. Unexpectedly, older females in these groups show exercise capacities that are equal to those of younger women. This may be a consequence of generational differences in the practice of traditional activities, such as those associated with gardening. Groups ranked intermediate in acculturation show variable patterns. For some age and sex groups, modernization has reinforced and even intensified strenuous activity patterns, resulting in high levels of fitness. For others, modernization has promoted inactivity and/or altered dietary patterns, resulting in increased body fat and low levels of fitness.

Cultural factors affecting the demographic structure of a high altitude Nepalese population.

PIP: Surveys were undertaken to study the fertility of Sherpa and Tibetan women living at altitudes over 3400 meters in Nepal. 2 teams independently collected demographic data during 1970 and 1971. Of all women who reported their ages to be 15 years and older, 348 (37.0%) provided menarchial data, 294 (31.2%) related the age at which they first became pregnant, and 420 (44.6%) replied to questions on the number of live births, neonatal deaths, infant deaths, child deaths, and the number of living children. The average completed fertility (4.77 live births) and estimated crude birthrate (31-33/1000) are low relative to low altitude peasant populations as well as to high altitude Andean peasants. Environmental phenomena (hypoxia, iodine deficiency) may be associated with retarded menarchial age and high infant mortality, but the major factors causing the low fertility seem to be cultural rather than environmental. Traditional ceremonial requirements delay the age at marriage until the mid or late twenties. Male and female celibacy is promoted by religious practices. Migrant females and women married to migrant males report reduced fertility. This is possibly due to poor nutrition and health care. Nonmigrant women living in villages participating extensively in the cash economy have greater access to the growing market economy, health care, and education and report higher numbers of live births and fewer child deaths.^ieng

Effects of hypoxia, heat, and humidity on physical performance.

The effects of hot, humid environment were compared with the effects of high altitude on the physical performance capacity of Ne-palese residents by measuring oxygen uptakes and heart rates at various work rates. The following groups of men were selected: 66 residents of a hot and humid environment in the Terai at sea level; 24 residents and 16 sojourners at 3,8000 m. The maximal oxygen uptake of the sea-level residents was, on the average, 2.55 1.min-1, at which a maximal heart rate of about 200 beats/min was reached. The sojourners at 3,800 m showed a higher maximal oxygen uptake (2.94 1. min-1) at their maximal heart rate of about 175 beats/min. The residents of 3,800 m achieved a similiar oxygen uptake as the sojourners, but did not show a similar maximal heart rate limitation, suggesting that they were capable of achieving a higher maximal oxygen uptake. This study shows that hot, humid environment at sea level is as much incapacitating as is hypoxia at high altitude.