RESUMEN
BACKGROUND AND OBJECTIVES: High altitude has an effect on blood count parameters, but low altitude (especially below sea level) has not been studied. DESIGN AND SETTING: A cross-sectional study of aymptomatic subjects aged between 18 to 35 years of age who had reported to the blood bank at the King Abdullah University Hospital (KAUH)/Irbid and Ministry of Health, Jordan, during the period between January 2010 to June 2011 for blood donation. METHODS: Hematological values were compared in healthy adult blood donors living in areas 200 to 300 meters below sea level and areas 500 to 1500 meters above sea level. The study population consisted of 800 females and 666 males aged between 18 to 35 years. RESULTS: The mean values for hemoglobin level, mean corpuscular volume and leukocyte counts were significantly higher in people living above sea level than in people living below sea level (P < .0001), whereas platelet count and red cell distribution width were significantly higher in people living below sea level than in people living above sea level (P < .0001). CONCLUSION: We found a significant difference in hematological parameters in healthy adults living above and below sea level. The hematological values presented here are from a large, representative population sample and the first report of people living below sea level.