An Ethiopian pattern of human adaptation to high-altitude hypoxia

Abstract

We describe, in Ethiopia, a third successful pattern of human adaptation to high-altitude hypoxia that contrasts with both the Andean "classic" (erythrocytosis with arterial hypoxemia) and the more recently identified Tibetan (normal venous hemoglobin concentration with arterial hypoxemia) patterns. A field survey of 236 Ethiopian native residents at 3,530 m (11,650 feet), 14-86 years of age, without evidence of iron deficiency, hemoglobinopathy, or chronic inflammation, found an average hemoglobin concentration of 15.9 and 15.0 gdl for males and females, respectively, and an average oxygen saturation of hemoglobin of 95.3%. Thus, Ethiopian highlanders maintain venous hemoglobin concentrations and arterial oxygen saturation within the ranges of sea level populations, despite the unavoidable, universal decrease in the ambient oxygen tension at high altitude.

Fig. 1.

Hemoglobin concentration distributions of U.S. sea level and Ethiopian and Tibetan high-altitude males coincide and contrast with the higher hemoglobin concentrations of Andean males. Cumulative frequency distribution of hemoglobin concentration of Ethiopian high-altitude, U.S. sea level, and Tibetan and Andean high-altitude males.

Fig. 2.

Hemoglobin concentration distributions of U.S. sea level and Ethiopian and Tibetan high-altitude females coincide and contrast with the higher hemoglobin concentrations of Andean females. Shown is the cumulative frequency distribution of hemoglobin concentration of Ethiopian high-altitude, U.S. sea level, and Tibetan and Andean high-altitude females.

Fig. 3.

Oxygen saturation distributions of U.S. sea level residents and high-altitude Ethiopians coincide and contrast with lower oxygen saturations of high-altitude Tibetan and Andean residents. Cumulative frequency distribution of oxygen saturation of Ethiopian high-altitude, U.S. sea level, and Tibetan and Andean high-altitude samples.