alpha-Thalassemia among sickle cell anemia patients in various African populations.

We have studied the incidence of alpha-thalassemia in normal and SS individuals from Senegal, Benin, Upper Volta, and Central Republican Africa. The alpha thal gene frequency is not significantly different in the controls from the various populations and in the SS patients from Senegal. In contrast it is compatible with increased survival of SS patients in Benin, Upper Volta. The data suggest epistatic effects of other factors in the Senegalese population.