Sickle cell trait as a limiting factor for high-level performance in a semi-marathon.

Of 1506 black males participating in the first Abidjan semi-marathon, 123 subjects with sickle cell trait (SCT) were detected, i.e., 8.7%. Twenty-nine of these subjects with hemoglobin S (HbS) were ranked among the first 332 participants to finish the race, a percentage of 8.2. These percentages did not significantly differ from the prevalence of SCT observed in the general Ivory Coast population (12.0%). Only one subject with SCT was found among the 22 internationally-ranked athletes. The concentration of HbS found in this athlete (37.7%), his mean globular volume (87 fl), and his hemoglobin concentration (13.8 g/100 ml) suggest the coexistence of alpha-thalassemia with SCT. These results indicate that the percentage of SCT individuals participating in a semi-marathon is equal to the prevalence of SCT found in the local population. Furthermore, the general ranking of SCT individuals is comparable to that of non-SCT individuals. Nevertheless, at the level of internationally-ranked performance, no subject with SCT only, was ranked; the one ranked subject with SCT presented an associated alpha thalassemia. We thus hypothesize that SCT may be a limiting factor for high level performance in a semi-marathon and alpha-thalassemia, an enhancing factor for subjects with SCT to succeed in long distance races.