Hemoglobin concentration of high‐altitude Tibetans and Bolivian Aymara

Abstract

Elevated hemoglobin concentrations have been reported for high-altitude sojourners and Andean high-altitude natives since early in the 20th century. Thus, reports that have appeared since the 1970s describing relatively low hemoglobin concentration among Tibetan high-altitude natives were unexpected. These suggested a hypothesis of population differences in hematological response to high-altitude hypoxia. A case of quantitatively different responses to one environmental stress would offer an opportunity to study the broad evolutionary question of the origin of adaptations. However, many factors may confound population comparisons. The present study was designed to test the null hypothesis of no difference in mean hemoglobin concentration of Tibetan and Aymara native residents at 3,800-4,065 meters by using healthy samples that were screened for iron deficiency, abnormal hemoglobins, and thalassemias, recruited and assessed using the same techniques. The hypothesis was rejected, because Tibetan males had a significantly lower mean hemoglobin concentration of 15.6 gm/dl compared with 19.2 gm/dl for Aymara males, and Tibetan females had a mean hemoglobin concentration of 14.2 gm/dl compared with 17.8 gm/dl for Aymara females. The Tibetan hemoglobin distribution closely resembled that from a comparable, sea-level sample from the United States, whereas the Aymara distribution was shifted toward 3-4 gm/dl higher values. Genetic factors accounted for a very high proportion of the phenotypic variance in hemoglobin concentration in both samples (0.86 in the Tibetan sample and 0.87 in the Aymara sample). The presence of significant genetic variance means that there is the potential for natural selection and genetic adaptation of hemoglobin concentration in Tibetan and Aymara high-altitude populations.

Genetic determinants of Tibetan high-altitude adaptation

“…It has been hypothesized that genes specifically involved in the HIF pathway could underlie adaptive changes in high-altitude populations (Beall et al 1998;Moore 2001;Rupert and Koehle 2006;Bigham et al 2009;Rupert 2010). Recent genome-wide analyses provide the first lines of evidence in support of genetic adaptation to high altitude (Beall et al 2010;Bigham et al 2010;Simonson et al 2010;Peng et al 2011;Wang et al 2011;Xu et al 2011;Yi et al 2010).…”

“…Native high-altitude populations, however, exhibit a unique suite of heritable traits that afford tolerance to hypoxia (decreased oxygen tension) (Beall 2000;Moore 2001;Beall 2007). Compared to lowland visitors and high-altitude native Andean groups, Tibetans living at high altitude exhibit elevated nitric oxide levels, increased resting ventilation and hypoxic ventilator response, and greater birth weights at high altitude (Beall et al 1998;Moore 2001;Wu et al 2005;Beall 2007). They also have hemoglobin (Hb) levels similar to those expected at sea level (Beall et al 1998;Moore 2001;Wu et al 2005;Beall 2007), in contrast to high blood viscosity caused by polycythemia, which is a typical response to hypoxia and a hallmark of chronic mountain sickness (CMS) (Monge 1976;Vargas and Spielvogel 2006).…”

Limits on Inferring Genetic Adaptation to High Altitude in Himalayan and Andean Populations

“…Compared to fully acclimatized lowlanders at HA, Tibetans have a high resting VE, lower levels of hemoglobin concentration [Hb], and similar resting arterial oxygen saturation (SaO 2 ) (Beall, 2000a and b;Beall et al, 1998;Beall et al, 1997a;Beall et al, 1997b;Winslow et al, 1989;Zhuang et al, 1993). Andeans, in contrast, have the same or lower resting VE compared to lowlanders, a similar [Hb], and higher levels of resting and exercise SaO 2 (Beall, 2000a and b;Beall et al, 1999;Brutsaert et al, 2000;Winslow et al, 1989).…”

Effects of high altitude and sea level on mean platelet volume and platelet count in patients with acute coronary syndrome

“…Adaptive phenomena involve cardiovascular and hematologic parameters [28,29]. In our study, hemoglobin and hematocrit levels were significantly higher in patients who experienced an acute coronary event at higher altitudes.…”