Developmental responses to high-altitude hypoxia in Bolivian children of European ancestry: A test of the developmental adaptation hypothesis.

The developmental adaptation hypothesis (DAH) proposes that highlanders adapt to their hypobaric hypoxic environment during growth and development. This report utilizes data on children (9.0-19.9 yr) of European ancestry residing in Santa Cruz and La Paz, Bolivia, to test selected aspects of the DAH. Previous tests of this hypothesis have been hampered by difficulties in controlling for socioeconomic and genetic influences. However, due to their high socioeconomic status and their relatively short history of residence at high altitudes, these factors can be reasonably well controlled in studies of European children. The data on European children are consistent with some but not all aspects of the DAH. First, examination of the available data on V̇O max (ml/kg/min) in European boys suggests that chronic exposure to hypobaric hypoxia results in an enhancement of the overall functional capacity of the oxygen transport system during adolescence, as predicted by the DAH. Second, chronic exposure to hypobaric hypoxia results in a delay in linear growth and maturation in European children, as well as in an enhancement of their lung volumes, also as predicted by the DAH. However, the effects of chronic hypoxia on linear growth, after controlling for health and nutritional status, are not as large as previously believed and, contrary to the expectations of the DAH, they need not be acquired through a distinctive pattern of growth during late childhood and adolescence. Instead, it appears that these patterns are established in European highlanders prior to 9 years of age and are then maintained, rather than accentuated, during later developmental periods.