they should be looking at people with thalessemia major and minor and sickle cell who already have oxgyen issues but not iron issues.
I would presume they have a harder time with this diseases...but..maybe not. Not counting black issues in US that could be due to high blood pressure, obesity, etc.
There is a trait in sickle cell seen in Africa but not in US..cant remember what it is called. That difference should be looked at as well.
Duffy Antigen is what I am thinking about with sickle cell