Researchers led by the University of South Florida's Lorena Madrigal surveyed and genetically tested more than a dozen American football players with sickle cell trait, asking them about their health and genotyping them at SNPs falling in three regions that modify fetal hemoglobin production: the intergenic region HBS1L-MYB, the BCL11A gene, and the γ gene within the β-globin gene cluster. As she and her colleagues note in their paper in the Southern Medical Journal, most players with sickle cell trait do not have clinical complaints or die, but a small portion do develop exercise collapse associated with SCT.
They found that players with particular genetic variants in the β-globin gene cluster were more likely to complain of extreme heat or thirst during or after training. This, the researchers note, suggests that variants affecting fetal hemoglobin levels may modulate sickle cell trait manifestation in adults.
Madrigal tells New Scientist that further studies may enable them to better identify athletes who may be at high risk of collapse. She and her colleagues add in their paper that they "applaud and support the efforts of medical staff who insist that players be hydrated and train slowly at the start of the season. We are complementing their work by pointing out that genetic variation also can play a role in the clinical manifestation of SCT during extreme physical exercise."