ABSTRACT
<p><b>OBJECTIVE</b>Aim of our study was to compare hematological parameters in Tibetan natives with those in Han migrants living on the Tibet plateau in order to determine the potential effects of age, gender, and ethnicity on hematological response to hypoxia.</p><p><b>METHODS</b>Blood hemoglobin (Hb, g/dl), hematocrit (Hct, %), red blood cells (RBC,10(6)/mm3) were measured in 3 588 healthy Tibetan natives and 3 371 Han migrants ranging in age from 5 to 72 years, living at a mean altitudes of 2 664 m, 3 813 m, 4 525m and 5 226 m.</p><p><b>RESULTS</b>Hemoglobin (Hb) concentration analysis was made by multiple regression equations relating hemoglobin to altitude and age. For 2 093 Han males, Hb = 9.612+ 0.001440xaltitude+ 0.06148xage. For 1 948 Tibetan males, Hb =12.202+ 0.000462xaltitude+ 0.02893xage. For 1 278 Han females, Hb = 10.858+ 0.000939xaltitude+ 0.02632xage. For 1 640 Tibetan females, Hb = 11.402+ 0.000626xaltitude+ 0.00412xage. Each of the four equations was statistically significant (P < 0.001), and had variance (r2) of 0.86 or more, indicating that altitude and age accounted for at least 85% of the variation in hemoglobin levels. The coefficients for altitude and for age were higher (P < 0.05) in Han males than in Tibetan males and higher (P < 0.05) in Han females than in Tibetan females. The Tibetan postmenopausal females had higher Hb values than premenopausal females only presented at altitude above 4 000 m while this phenomenon was beginning at altitude of 2 664 m among Han females.</p><p><b>CONCLUSION</b>We conclude that gender and increasing age in Tibetans are associated with lower hemoglobin values than those in Han at high altitude, and we speculate that genetic factors seems to be important.</p>
Subject(s)
Adolescent , Adult , Aged , Child , Child, Preschool , Female , Humans , Male , Middle Aged , Young Adult , Altitude , Asian People , Ethnicity , Hematocrit , Hemoglobins , Hypoxia , Ethnology , Tibet , Transients and MigrantsABSTRACT
Mean hemoglobin (Hb) concentration of about 3 500 subjects derived from 17 studies of Himalayan highlanders (Tibetans, Sherpas, and Ladakhis) was compared with lowlanders (Chinese Han, Indian Tamils) lived in the Himalayas, and European climbers during Everest expeditions as well as Andean natives. The results found that Hb concentration in Himalayan highlanders was systemically lower than those reported for Andean natives and lowland immigrants. These comparative data demonstrated that a healthy native population may successfully reside at high altitude without a significant elevation in Hb, and the lower Hb levels of Himalayan highlanders than those of migrated lowlanders and Andean natives are an example of favourable adaptation over the generations. In addition, excessive polycythemia has frequently been used as a marker of chronic mountain sickness (CMS). Altitude populations who have a higher Hb concentration also have a higher incidence of CMS. The low Hb in Himalayans suggested as showing adaptation over many generations in Tibetan stock. Recent work in Tibet, suggested that Tibetans there may have adapted to high altitude as a result of evolutionary pressure selecting for genes which give an advantage at altitude. All of the population genomic and statistical analysis indicated that EPAS1 and EGLN1 are mostly likely responsible for high altitude adaptation and closely related to low Hb concentration in Tibetans. These data supported the hypothesis that Himalayan highlanders have evolved a genetically different erythropoietic response to chronic hypoxia by virtue of their much longer exposure to high altitude.