Sickle cell trait means you carry one copy of the gene that causes sickle disease. Most people with sickle cell trait don’t experience symptoms, but they can pass the affected gene on to future generations.

Sickle cell disease (SCD) is a group of inherited blood disorders. People with SCD have two copies of a gene that affects hemoglobin, an essential component of red blood cells. People with only one copy of the gene have sickle cell trait (SCT).

SCT affects 1 to 3 million Americans, according to the American Society of Hematology (ASH). It’s especially common among Black people and African Americans.

Because a person with SCT has only one copy of the gene, they’ll never develop SCD. Instead, they’re a carrier for the disease, meaning they can pass the gene on to their children.

Having SCT isn’t the same as having SCD. But in rare cases, people who carry the trait can experience some of the same severe symptoms of SCD.

Sickle cell disease

SCD affects the form and function of your red blood cells. People with SCD have hemoglobin, the oxygen-carrying component of red blood cells, that does not function properly.

This impaired hemoglobin causes red blood cells, which are typically flattened disks, to become crescent-shaped. The cells look like a sickle, a tool used in farming.

These red blood cells can’t live as long as healthy red blood cells and can block your blood vessels. This causes serious health problems such as:

Sickle cell trait

On the other hand, SCT rarely leads to deformed red blood cells, and only under certain conditions. People with SCT typically have enough regular hemoglobin to prevent the cells from becoming sickle-shaped. Without sickling, red blood cells function as they should, transporting oxygen-rich blood to your tissues and organs.

SCT can be passed on from parent to child. If both parents have SCT, they may have a child with SCD.

If both parents have SCT, there is:

  • a 50% chance that their child will have the trait
  • a 25% chance their child will have SCD
  • a 25% chance their child will have neither the trait nor the disease

If only one parent has sickle cell trait, there is:

  • a 50% chance that their child will have the trait
  • a 50% chance that their child will not have it

Since SCD symptoms can start as early as 5 months old and early diagnosis is critical, it is routine in the United States to test all newborns.

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How people inherit sickle cell disease or sickle cell trait
Medical Illustration by Bailey Mariner

Most people with SCT don’t have any symptoms. But in certain stressful conditions, healthy red blood cells in people with SCT can become sickle-shaped, causing symptoms linked to SCD. Such conditions include:

Some of the severe symptoms and complications linked to SCT include:

Athletes with SCT need to take precautions when performing. Staying hydrated is extremely important.

Sickle cell trait in athletes

After a 19-year-old college athlete suddenly died during intense football training, the National Collegiate Athletic Association (NCAA) implemented a screening policy for SCT to prevent future deaths.

Athletes and others with SCT who exert themselves physically, such as people in the military, may have a greater risk of more severe symptoms. If you’re in this group and have SCT, you’re more likely to experience heat stroke and muscle breakdown during bouts of intense exercise. Your risk is highest under extreme temperatures and severe conditions.

According to researchers, people with SCT have a 54% higher rate of muscle breakdown during physical exertion than those without the trait. But research has also shown that you can minimize this risk through proper hydration and temperature regulation.

People with SCT participating in athletics need to be mindful during training and competition. To prevent serious complications linked to SCT:

  • Drink lots of water before, during, and after training and competition.
  • Get immediate medical treatment when you feel ill.
  • Keep a cool body temperature when exercising in hot and humid conditions. Mist your body with water or move to an air-conditioned space during breaks or rest periods.
  • Set your own pace for physical activities and build intensity slowly.
  • Rest in the shade between drills and sets.
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SCT is a lifelong genetic trait. People with SCT prone to medical complications should avoid situations that will put their bodies under additional stress, including:

  • dehydration or drinking too little water
  • exposure to increased atmospheric pressure, such as when scuba diving
  • high altitudes, such as air travel, visiting a high-altitude place, or mountain climbing
  • low oxygen levels in the air, such as when mountain climbing, training for athletic competition, or completing military boot camp
  • extreme exercise
  • sudden temperature changes

When mild symptoms of SCT arise, many people can manage them at home. Some people find the following actions can help ease symptoms:

  • Apply a warm towel or wrapped heating pad to the affected part of your body.
  • Distract yourself with a movie or book.
  • Drink plenty of water.
  • Take over-the-counter pain relievers, such as ibuprofen.

If you have a case with severe symptoms, contact a medical professional right away.

SCT and SCD are most common among populations with ancestors from parts of the world where malaria is or was common. That’s because SCT may have evolved as a protective response against malaria. According to the Centers for Disease Control and Prevention (CDC), these regions include:

  • sub-Saharan Africa
  • South America, the Caribbean, and Central America
  • Saudi Arabia
  • India
  • Mediterranean countries such as Turkey, Greece, and Italy

In the United States, SCT appears most often in the African American population, affecting 8–10%, according to ASH. The CDC notes that about 1 in 13 Black or African American babies is born with SCT. That’s compared to:

  • 1 in 145 Hispanic births
  • 1 in 333 white births
  • 1 in 455 Asian or Pacific Islander births

Doctors or healthcare professionals can diagnose SCT with a simple blood test. You may want a doctor to test you for SCT if you have one or more family members who carry the trait or have SCD. If you learn that you or a loved one has SCT, schedule an appointment with a healthcare professional.

You may also want to visit a genetic counselor to learn more about the diagnosis and how it can affect you and your family.

How common is sickle cell trait?

About 300 million people globally have SCT. It’s most common among people of African or Caribbean ancestry.

Do people with sickle cell trait have a lower life expectancy?

According to experts, people with SCT tend to have a similar life expectancy to people without the trait. But they’re at higher risk of serious complications that may significantly decrease a person’s life span.

Does sickle cell trait increase my risk of serious COVID-19 infection?

According to researchers, people with SCD and SCT have risk factors that make them more likely to experience severe COVID-19 infection and death compared to other people. Early evidence suggests that people with SCT may be more likely to be hospitalized or die from COVID-19, particularly African American people assigned male at birth.

More long-term research on SCT and COVID-19 is needed to understand the full range of effects.

SCT is a genetic trait in which you have one copy of the gene that causes SCD. In the United States, it’s most common among Black people. Because you can pass on the trait and because it can cause symptoms in extreme conditions, it’s important to talk with a doctor about being tested and monitored for the condition.

Rare but severe risks include pregnancy complications, muscle breakdown, and even sudden death. In more mild cases, you can manage symptoms at home.

The best way to prevent complications of SCT is to avoid situations that may trigger severe symptoms, such as strenuous exercise, scuba diving, or mountain climbing. Athletes with SCT must be cautious about exerting themselves and ensure they stay cool, rested, and hydrated.

It’s possible to live a fulfilling, healthy life with SCT. Knowing how to avoid serious complications can help you live life to the fullest with little to no symptoms.