What is Sickle Cell Trait?
Sickle cell trait is a descriptive term for a hereditary condition in which the individual has one normal gene for hemoglobin and one abnormal gene for hemoglobin.1 Hemoglobin is a protein in the red blood cells in your body responsible for oxygen transport. Approximately 99% of the oxygen transported in blood is bound to hemoglobin inside the red blood cells.2
Sickle cell trait is generally a benign condition that does not develop or change over time. In general, it is a condition that does not affect the life span of the individual. As individuals with sickle cell trait get older, they may become unable to concentrate urine normally. This is not usually an issue for high school or college age athletes.1
Sickle cell trait is not a barrier to exercise or participation in sport.3 Knowing your sickle cell trait status is vital to preventing an exertional sickling event. First, check with your parents as they may have this on record from your birth. If you cannot find the information this way, a simple blood test at your doctor’s office can tell you whether you are positive or negative for sickle cell trait.
What is Sickle Cell Anemia?
Sickle cell anemia is the hereditary condition in which the individual has two abnormal hemoglobin genes.1 Sickle cell anemia is a lifelong disease that can cause painful episodes sometimes requiring hospitalization. Sickle cell trait will not develop into sickle cell anemia at any time. Carriers of sickle cell trait usually do not have any of the clinical symptoms of sickle cell anemia; however, they may pass this onto their children.4
Complications of Sickle Cell Trait (SCT) for Athletes
Although sickle cell trait will not turn into the disease, it is possible to have clinical symptoms when exercising under extreme conditions of physical exertion and/or low oxygen levels.1
Athletes with sickle cell trait are potentially more vulnerable to gross hematuria, splenic infarction, exertional heat stroke, severe muscle breakdown (rhabdomyolysis) and potentially even sudden death when participating in strenuous exercise, often under intense environmental conditions.1,3,5
Gross Hematuria: Gross hematuria is defined as visible blood in the urine. Usually from the left kidney, gross hematuria is an occasional complication of sickle cell trait. If you experiene this, you should consult a doctor before returning to competition or exercise1.
Exertional Sickling. Exertional sickling is a potentially life-threatening condition resulting from the sickling of red blood cells during intense exercise. Sickling results in muscular ischemia and collapse, where you may experience intense muscular pain, rhabdomyolysis, and other serious metabolic problems.2 You initially will still be conscious and able to talk and may complain of muscular pain, however this is not to be confused with muscle cramping. Exertional sickling is a medical emergency and requires immediate treatment. Signs and symptoms of an exertional sickling event include intense pain, fatigue, feeling like you cannot continue exercising, muscle cramping and inability to catch your breath.6 If you are experiencing any of these symptoms, consult your team medical professional or coach immediately.
Explosive Rhabdomyolysis. Explosive rhabdomyolysis is severe muscle break down in which the result is the release of muscle contents into the bloodstream. Muscle contents such as myoglobin can cause kidney damage and ultimately kidney failure.7 Untreated explosive rhabdomyolysis can be fatal.
High Altitude Participation. Due to the lack of oxygen in high altitudes, athletes with sickle cell trait take a higher risk when participating in this environment. Splenic infarction can occur in athletes with sickle cell trait, particularly at high altitudes. Splenic infarction is tissue death in the spleen caused by a lack of oxygen to this vital organ. Vigorous exercise at altitudes higher than 5,000 feet may increase risk. Splenic infarction causes sudden and sometimes severe pain in the left side of the chest and abdomen. You may experience nausea and vomiting as well. You should consult a doctor immediately if signs and symptoms occur as well as for return to play protocol.1 Any time you are participating in activity at high altitudes, the risk of complications is increased.
Managing your Condition
The NCAA recommends that athletes with sickle cell trait be knowledgeable of their conditions and take the following precautions1,3.
- Set your own pace
- Gradual acclimatization to heat, humidity and altitude
- Use adequate rest and recovery between intense conditioning sets
- Limit “all-out” exertion of any kind to less than 2-3 minutes
- Be excused from performance tests that require extreme exertion for longer than 2-3 minutes
- Stop activity immediately if any signs or symptoms occur
- Stay well hydrated at all times, especially in hot and humid conditions
- Manage asthma appropriately
- Suspend exercise if feeling ill or while experiencing a fever
- Have access to supplemental oxygen as needed
- Seek proper medical attention when experiencing unusual distress
- DO NOT participate during acute illness, especially one involving fever
Screening and Communication
Complications from sickle cell trait are often preventable. The first key to prevention in any case is communication. If you are aware that you have this condition, you should freely communicate this with the entire health care team, coaches, and any other adults working with you on a regular basis. If you are unaware of whether or not you have sickle cell trait or whether or not you have been tested, this needs to be communicated as well.
Knowledge of sickle cell trait status is the first step in the prevention of an exertional sickling event. In order for you to compete successfully in sport without issues, the NATA has come to the following consensus for athletes with sickle cell trait as well as athletes that may need sickle cell trait screening.8 They are as follows:
- There is no contraindication to participation in sport for the athlete with sickle cell trait.
- Red blood cells can sickle during intense exertion, blocking blood vessels and posing a grave risk for athletes with sickle cell trait.
- Screening and simple precautions may prevent deaths and help athletes with sickle cell trait thrive in their sport.
- Efforts to document newborn screening results should be made during the PPE.
- In the absence of newborn screening results, institutions should carefully weigh the decision to screen based on the potential to provide key clinical information and targeted education that may save lives.
- Irrespective of screening, institutions should educate staff, coaches, and athletes on the potentially lethal nature of this condition.
- Education and precautions work best when targeted at those athletes who need it most; therefore, institutions should carefully weigh this factor in deciding whether to screen. All told, the case for screening is strong.
- NCAA Guideline 3c: The Student-Athlete with Sickle Cell Trait. 2009-2010 NCAA Handbook; June 2008.
- Powers, S., Howley, E. Exercise Physiology: Theory and Application to Fitness and Performance, 6th edition. Boston: McGraw Hill; 2007.
- Sickle Cell Trait. ACSM Current Comment. 2011. Available at: www.acsm.org. Accessed August 9, 2011.
- Sickle Cell Disease (SCD). Centers for Disease Control and Prevention. 2011. Available at: http://www.cdc.gov/ncbddd/sicklecell/traits.html. Accessed May 12, 2011.
- Sickle Cell Trait and Athletics. Sickle Cell Disease Association of America, Inc. 2011. Available at: http://www.sicklecelldisease.org. Accessed May 12, 2011.
- Casa DJ, Guskiewicz KM, Anderson SA, et al. National Athletic Trainers' Association Position Statement: Preventing Sudden Death in Sports. J Athl Train. 2012;47(1):96-118.
- Dugdale DC. Rhabdomyolysis. A.D.A.M. Encyclopedia. http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001505. Accessed March 3, 2012.
- Anderson S, Eichner ER. National Athletic Trainers’ Association Consensus Statement: Sickle cell trait and the athlete. http://www.nata.org/consensus-statements. Accessed April 23,2012.