Although most sudden death in sports is related to cardiac issues, Sickle Cell Trait (SCT) has been recognized recently as a potential risk factor. SCT had historically been considered a benign condition.
Approximately 2.5 million Americans and 8-10 percent of African Americans carry the trait. SCT has also been found in those of Mediterranean, Central/South American, Caribbean and Indian descent.
Sickle cell anemia is a commonly known inherited disease for which we routinely screen all newborns across the United States. Having SCT alone means a person carries only one of the two hemoglobin genes necessary to cause the disease. Carrying the trait is not associated with the classic signs or symptoms of sickle cell disease, such as intermittent crises of severe pain in the extremities or chest, fatigue and shortness of breath.
Sickle cell anemia causes red blood cells to change from a disclike shape to an abnormal crescent shape (sickle shaped). The abnormal cells may become lodged in vessels impairing oxygen delivery. Although the definitive underlying mechanisms of the adverse outcomes due to SCT is not known, it has been shown that those with SCT have higher blood viscosity, reduced RBC deformability, increased RBC fragility, increased inflammatory marker levels, and may sickle in extreme exertion or altitude. Exertional sickling increases risk for developing rhabdomyolysis, which is 200 times more likely in those with SCT compared to those without.
Signs of exertional SCT-related illness include significant fatigue, muscle pain and weakness. It only takes two to three minutes of sprinting or other sustained effort activities for problems to manifest. This is different from heat illness, which usually occurs later in exercise and causes painful muscle cramping. Some individuals with SCT have a decreased ability to concentrate urine to conserve water, putting them at higher risk for dehydration, thus increased risk for rhabdomyolysis.
Altitude greater than 5,000 feet can also predispose those with SCT to an adverse outcome. Strenuous physical activity without altitude acclimatization can result in splenic infarct. Athletes often present with sudden, acute pain in the lower ribs, left upper quadrant pain, lower chest pain, weakness and nausea. Symptoms may mimic pleurisy, a pneumothorax, “a side stitch” or renal colic.
The most feared adverse outcome of SCT is exercise-associated collapse and/or death. The link between SCT and sudden death was first noted in 1970 among military recruits. Subsequent autopsies revealed a disproportionate number of recruits with a fatal collapse were SCT positive. In college athletes, deaths associated with SCT have occurred almost exclusively in football. Football student- athletes with SCT have collapsed and died more often than players with any other condition.
Risk factors for adverse event occurrence in those with SCT include poor exercise fitness, inadequate hydration and sleep, incomplete heat acclimatization, environmental heat stress, use of heat-retaining clothing, and delays in the recognition and treatment of exertional heat illness.
In collegiate athletics, all student-athletes at Division I and Division II schools are required to have SCT testing completed, to sign a waiver declining testing, or to provide documentation of prior testing. Division III schools voted in January 2013 and now require confirmation of SCT status for all student-athletes no later the 2014-15 academic year.
Athletes with SCT are not prohibited from sports participation; however, specific exercise guidelines have been established. Coaching staffs should be aware of the SCT status of their athletes so that steps can be taken to minimize the chances of adverse outcomes. Student-athletes should know their status so that they are aware of the implications for their general health, athletic participation and future family planning.
Proper hydration is paramount, especially in hot and humid conditions. This includes avoidance of high caffeine energy drinks or other supplements that may cause dehydration. Exercise during acute illness or fever should be avoided.
Care should be taken to ensure complete acclimatization to altitude, heat and humidity. This can be achieved through a slow build-up of intensity at the start of the season, preceded by a gradual pre-season conditioning program. Student-athletes should set their own pace and be sure to achieve adequate rest and recovery.
Coaches should not push student-athletes with SCT beyond the point of fatigue through abnormal muscle weakness, ischemic pain or breathlessness as this may lead to adverse outcomes. Activity should be stopped immediately if symptoms occur and a planned emergency response should be initiated.
SCT is an important concern in the athletic population and only becomes a threat in certain situations. Simple precautions and screening will prevent deaths and help athletes with SCT enjoy successful and healthy athletic careers.
Yvette Rooks, M.D., CAQ, FAAFP, is the chief medical officer for RWJBarnabas Health for Sports Medicine and the Head Team Physician for Rutgers University Athletics in New Jersey. She is a current member of the NFHS Sports Medicine Advisory Committee.