Black men and women with a sickle cell trait don’t see any more of an increased risk of premature death than those without the trait but who have other risk factors including obesity, older age and a history of smoking, a new study of American service members suggests. Sickle cell gene variants occur in about one in 13 black Americans, and previous studies have linked them to early death.

Two copies of the sickle cell gene variant causes sickle cell disease, which shortens individuals’ lifespan to only 40 to 60 years and leads to intermittent, intense bouts of pain. People with one copy of the gene have sickle cell trait, which previous studies have linked to a higher risk of premature death from exertional rhabdomyolysis (ER). ER occurs when muscle breakdown ends up in the kidneys, and it commonly affects football players and soldiers on active duty.

According to a news release for the new study, research published in 1987 concluded that black military recruits thought to have sickle cell trait saw a 2,800 percent increase in exertion-induced sudden deaths. However, researchers weren’t sure of each individual’s true sickle cell status.

For the study, researchers at Stanford University reviewed health records of nearly 48,000 black soldiers with known sickle statuses confirmed through blood tests, and who were on active duty between 2011 and 2014. Researchers said their study was the first-ever longitudinal cohort study of sickle cell trait.

Study author Dr. Lianne Kurina, an associate medicine professor at Stanford, found that those black soldiers with sickle cell trait saw only a 54 percent higher risk of ER compared to those soldiers without it. While higher, that increased risk is comparable to that observed among people taking some prescription drugs, as well as that of individuals with known risk factors for premature death including older age, smoking and obesity.

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In the release, Kurina noted that the decreased rates of ER may stem from a rule implemented in 2003 that began requiring soldiers who exercise regularly to drink sufficient fluids, take rests when it’s hot, and gradually work up to more strenuous exercise. Those steps are known to reduce exercise-related fatality rates, regardless of a person’s sickle cell status.

"The most important thing to come out of this study is the really reassuring news that under conditions of universal precautions against dehydration and overheating, we don't see an elevation in the risk of mortality in people with sickle cell trait," Kurina said in the release.

Researchers said their results also noted their findings suggest individuals may not need to be screened for sickle cell trait. Due to previous study findings, organizations like the Air Force, the Navy and the NCAA have integrated mandatory screenings. Some groups, like the American Society for Hematology, say these screening programs may lead to job discrimination.

The study was published Wednesday in The New England Journal of Medicine.