Altitude above sea level as a variable for definition of anemia.

I read with special interest the Perspective article by Drs Beutler and Waalen1 about the definition of anemia. The authors refer to some variables, such as the sex, age, and race of the individuals, that may influence their levels of hemoglobin in normal conditions. In the final part of their paper, they suggest lower normal levels of hemoglobin for adults, according to their age, sex, and race, based on the Scripps-Kaiser data,1 so that the definition of anemia can be made with more precision. In countries where cities are located in different altitudes above sea level, this variable is critical and should always be taken into account when defining anemia.2 The data presented by Beutler and Waalen may be correct for individuals living at sea level (San Diego), but they are not correct for healthy individuals living at higher altitudes. Interestingly, the data presented by Beutler and Waalen for white men living at sea level are similar to those that we found and published for Mexican mestizos living at the same altitude, but significantly lower than those for individuals living at higher altitudes, such as Mexico City or Puebla (my home town), both located 2240 m above sea level.3 For example, a hemoglobin level of 137 g/L for adult men is normal at sea level, but it is definitely low and indicative of anemia if the individual lives in Mexico City. In summary, the altitude of the residence site of healthy individuals is critical for the definition of anemia and should always be taken into account, along with the other variables addressed by Drs Beutler and Waalen.