HIGH ALTITUDE MEDICINE & BIOLOGY Volume 14, Number 3, 2013 ª Mary Ann Liebert, Inc. DOI: 10.1089/ham.2013.1064
Rebuttal to Pro Statements Fabiola Leo´n-Velarde and Francisco C. Villafuerte
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igh-altitude (HA) natives show distinctive physical and functional characteristics that give them an advantage over lowlanders at HA. These advantages are not confined to the cardio-respiratory or hematological systems, as they include indeed the whole organism, and must be reflected in different regions of the brain. In this regard, the reduced cerebrovascular reactivity in HA natives reported by Yan et al., (2011a) was particularly manifested among brain regions involved in cerebral modulation of respiration. Hochachka and co-workers have shown that lower regionby-region brain glucose metabolic rates in HA Quechuas compared to lowlanders may be the result of a defense adaptation against chronic hypoxia (Hochachka et al., 1994). Also, the psychomotor slowing observed in European, Native American, and African altitude groups is proposed to be an adaptive rather than a deficient trait (Hogan et al., 2010). In addition, the very scarce studies in spatial working memory matched by age, gender ratio, educational level, and ancestral lines, show equal accuracy response in HA compared to SL groups, but with more variability in reaction time; and the same activation patterns in their neural pathways (Yan et al., 2011b). Evaluation of the effects of altitude on mood, behavior profile, and cognitive function is complicated by differences between studies, including the specific methods of measurement and type of participants, which explain why there are so few. Since most of the systematic research in these areas has been conducted in exposure to experimental acute or moderate-lasting hypoxia, the results should not be generalized to altitude settings. On the physical side, besides being able to run a complete marathon at 4300 m, superior pulmonary gas-exchange and acidbase state in HA natives was evidenced by Wagner et al. (2002) and Lundby et al. (2004), who compared lowlanders acclimatized to 5260 m with HA natives at the same altitude in Bolivia. During exercise, HA natives showed smaller alveolar-arterial Po2 difference, 40% higher O2-diffusing capacity, and greater lactic acid buffering. In addition, despite lower anaerobic capacities, HA natives were capable of calf muscle work rates equal to those of highly-trained power athletes (Matheson et al., 1991). Also, aerobic exercise capacity of chronic mountain sickness patients with significant erythrocytosis is preserved in spite of severe pulmonary hypertension and relative hypoventilation, probably by a combination of increased oxygen carrying capacity of blood and pulmonary O2-diffusion (Groepenhoff et al., 2012). Even though in his later publication (Barcroft, 1925), concluded that acclimatization to HA does not exist, generalizing this concept even to HA natives, Barcroft was very impressed
by the physical capacities of the Peruvian Andean natives, and this was certainly an accurate feeling. Author Disclosure Statement No competing financial interests exist. References Barcroft J. (1925). The respiratory functions of the blood: Lessons from high altitude. Cambridge, Cambridge University Press. Groepenhoff H, Overbeek MJ, Mule` M, et al. (2012). Exercise pathophysiology in patients with chronic mountain sickness exercise in chronic mountain sickness. Chest 142:877–884. Hochachka PW, Clark CM, Brown WD, et al. (1994). The brain at high altitude: Hypometabolism as a defense against chronic hypoxia? J Cereb Blood Flow Metab 14:671–679. Hogan AM, Virues-Ortega J, Botti AB, et al. (2010). Development of aptitude at altitude. Dev Sci 13:533–544. Lundby C, Calbet JA, van Hall G, Saltin B, Sander M. (2004). Pulmonary gas exchange at maximal exercise in Danish lowlanders during 8 wk of acclimatization to 4,100 m and in highaltitude Aymara natives. Am J Physiol Regul Integr Comp Physiol 287:R1202–1208. Matheson GO, Allen PS, Ellinger DC, et al. (1991). Skeletal muscle metabolism and work capacity: A 31P-NMR study of Andean natives and lowlanders. J Appl Physiol 70:1963–1976. Wagner PD, Araoz M, Boushel R, et al. (2002). Pulmonary gas exchange and acid-base state at 5,260 m in high-altitude Bolivians and acclimatized lowlanders. J Appl Physiol 92:1393–1400. Yan X, Zhang J, Gong Q, Weng X. (2011). Cerebrovascular reactivity among native-raised high altitude residents: An fMRI study. BMC Neurosci 26;12:94. Yan X, Zhang J, Gong Q, Weng X. (2011). Adaptive influence of long term high altitude residence on spatial working memory: An fMRI study. Brain Cogn 77:53–59.
Address correspondence to: Dr. Fabiola Leon Velarde Departamento de Ciencias Biologicas y Fisiologicas Facultad de Ciencias y Filosofia Universidad Peruana Cayetano Heredia Av. Honorio Delgado 430 Lima 31 Peru E-mail:
[email protected] Received May 28, 2013; accepted in final form May 30, 2013.
Departamentao de Ciencias Biologicas y Fisiologicas, facultad de Ciencias y Filosofia, Universidad Peruana Cayetano Heredia, Lima, Peru.
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