Brain blood flow in Andean and Himalayan high-altitude populations: evidence of different traits for the same environmental constraint

• Published in: Journal of cerebral blood flow and metabolism Vol. 31; no. 2; pp. 706 - 714
• Main Authors: Jansen, Gerard FA, Basnyat, Buddha
• Format: Journal Article
• Language: English
• Published: London, England SAGE Publications 01.02.2011; Nature Publishing Group; Sage Publications Ltd
• Subjects: Altitude; Biological and medical sciences; Blood Flow Velocity - physiology; Bolivia; Brain Chemistry - physiology; Cerebrovascular Circulation - genetics; Cerebrovascular Circulation - physiology; Deuterium Oxide; Environment; Hematocrit; Humans; Investigative techniques, diagnostic techniques (general aspects); Medical sciences; Middle Cerebral Artery - physiology; Nepal; Nervous system; Neurology; Nitric Oxide - metabolism; Original; Oxygen - blood; Oxygen Consumption - physiology; Peru; Population; Ultrasonic investigative techniques; Ultrasonography, Doppler, Transcranial; Vascular diseases and vascular malformations of the nervous system; Bolivia; Peru; Nepal; adaptation; cerebral blood flow; high altitude; Andean; Himalayan; High altitude; Nervous system diseases; Constraint; Central nervous system disease; Cerebrovascular disease; Cerebral disorder; Blood flow; Encephalon
• ISSN: 0271-678X; 1559-7016
• DOI: 10.1038/jcbfm.2010.150

Humans have populated the Tibetan plateau much longer than the Andean Altiplano. It is thought that the difference in length of occupation of these altitudes has led to different responses to the stress of hypoxia. As such, Andean populations have higher hematocrit levels than Himalayans. In contrast, Himalayans have increased circulation to certain organ systems to meet tissue oxygen demand. In this study, we hypothesize that cerebral blood flow (CBF) is higher in Himalayans than in Andeans. Using a MEDLINE and EMBASE search, we included 10 studies that investigated CBF in Andeans and Himalayans between 3,658 and 4,330 m altitude. The CBF values were corrected for differences in hematocrit and arterial oxygen saturation. The data of these studies show a mean hematocrit of 50% in Himalayans and 54.1% in Andeans. Arterial oxygen saturation was 86.9% in Andeans and 88.4% in Himalayans. The CBF in Himalayans was slightly elevated compared with sea-level subjects, and was 24% higher compared with Andeans. After correction for hematorit and arterial oxygen saturation, CBF was ~20% higher in Himalayans compared with Andeans. Altered brain metabolism in Andeans, and/or increased nitric oxide availability in Himalayans may have a role to explain this difference in brain blood flow.