Growth of lowland native children of European Ancestry during sojourn at high altitude (3,200 m)

Abstract

The moderate growth retardation frequently observed among children living at high altitude is usually assumed to result from hypoxic stress. However, such children are frequently from the poorer socioeconomic strata of their societies and may suffer malnutrition, poor hygiene, inadequate medical care, and overcrowding-factors also associated with growth retardation. The objective of this study was to determine if there is a statistically observable alteration in the growth of middle-class children of European ancestry during sojourn at high altitude. Semilongitudinal heightlweight measurements were gathered retrospectively from medical records of 18 boys and 17 girls who were born at low altitude, were well-nourished and clinically normal, and who had lived at Achoma, Peru (altitude 3,200 m), continuously for 9-36 months. Measurements were divided, by sex, into four cohorts: I(3-6 months at Achoma), I1 (6-12 months), 111 (12-18 months), and IV (18-24 months); initial, presojourn, height and weight were also obtained. All heights and weights were normalized with age-specific reference values. Changes in Z scores (AZ) during sojourn were calculated for each subject by subtracting the score of the presojourn value from those of cohorts I-IV. Paired t-tests revealed, among the boys, a significant decline in Z score for weight during sojourn in

Mechanisms and Limits of Induced Postnatal Lung Growth

“…However, the stimulatory effect progressively diminishes with duration of exposure, suggesting that severe hypoxia may not extend the upper limit of alveolar growth at maturity but merely accelerates the rate of its attainment, and the ultimate lung dimension may be determined predominantly by thoracic size. Because both somatic growth and the age of epiphyseal closure tend to be retarded at high altitude (108), lung growth of high-altitude guinea pigs may continue beyond the reported observation period. In contrast, dogs raised from age 2 to 14 months at 3,100 m (137) show significantly larger lung volumes, septal tissue volumes, and Dl than matched control animals raised to maturity at sea level; differences persist 9 months after returning to sea level.…”

“…Native Tibetan newborns show higher arterial oxygen saturation than Han newborns whose mothers had resided at high altitude for approximately 2 years (107). Whereas somatic growth is slowed and perhaps prolonged at high altitude (108,109), native highlanders show larger vital capacities and thoracic volumes than lowlanders regardless of ethnic origins (110)(111)(112)(113)(114)(115)(116). Where measured, Dl is also increased in native highlanders as well as persons born and raised at sea level who subsequently move to high altitude as adults (116,117).…”

Lung Structure and the Intrinsic Challenges of Gas Exchange

“…Thereafter, mechanical interactions between the lung and thorax diminish and both the lung and the thorax stop growing. Extending the age at which epiphyseal union occurs may explain the enhancement of lung growth observed during chronic residence at high altitude by allowing a longer period of thoracic growth (317). Following epiphyseal union in adulthood, lung growth may be reinitiated if sufficiently intense intrathoracic mechanical stimuli are reimposed and space is available for expansion, for example, following pneumonectomy.…”

“…This effect represents evolutionary adaptation to cope with oxygen-poor environments. Whereas severe hypoxia inhibits somatic growth (104, 317), postnatal exposure to a moderate altitude ( < 4000 m) has been shown to accelerate lung growth ( discussed below ). Space for the expanding lung is provided by passive rib cage expansion and caudal displacement of the diaphragm (194).…”

The effects of chronic hypobaric conditions

“…Im Folgenden wurden ähnliche Untersuchungen an europäi-schen Kindern durchgeführt, welche in großen Höhen in Südamerika und den Vereinigten Staaten aufwuchsen. Bei den Bewohnern großer Höhen wurden hierbei einerseits ein verlangsamtes Körperwachstum, eine geringere Kör-pergröße sowie ein geringeres Körpergewicht, andererseits aber durchschnittlich größere Thoraxdimensionen und eine bessere Lungenfunktion sowie höhere Hämato-krit-und/oder Hämoglobinwerte im Vergleich zu den Flachlandbewohnern festgestellt [11][12][13][14]. Alle in diesem Zusammenhang durchgeführten Untersuchungen weisen jedoch den Nachteil auf, dass die in große Höhen emigrierte Populationen zwar mit Populationen gleichen Alters und gleicher Rasse verglichen wurden, dass aber ansonsten keine größere genetische Verwandtheit zwischen den untersuchten Populationen bestand.…”