It has long been held true that people born with sickle cell trait – possessing a single copy of the sickle cell gene variant – have a higher risk of dying early. Now, a new study funded by the US National Heart, Lung and Blood Institute in partnership with the Uniformed Services University of the Health Sciences, is challenging this theory.
Those who have the sickle cell gene variant don’t actually have sickle cell disease, a blood disorder that cuts lifespans and causes sudden, severe pain. Sickle cell happens when a person carries two copies of the gene, inheriting one from each parent.
In a large scale study, the first of its kind, researchers tracked over 48,000 black American soldiers serving active duty in the US Army over a period of four years. All participants had undergone tests for the genetic trait, US News reports.
Lianne Kurina, co-author on the study and associate professor of medicine at Stanford University School of Medicine, says, “What we can say with confidence is that there’s no evidence that it increases mortality in this Army population, and that’s incredibly reassuring.”
Previous studies have associated sickle cell trait with a higher mortality risk among black soldiers and black football players on National Collegiate Athletic Association (NCAA) Division 1 teams. These bodies of research tracked some of the deaths to heat stroke, heat stress and “exertional rhabdomyolysis,” or muscle breakdown due to extreme physical activity.
The belief that sickle cell trait increases mortality risks has led to obligatory screening by US organizations, including the US Navy, US Air Force and the NCAA, the study authors say.
Dr. Alexis Thompson, vice president of The American Society of Hematology, says he believes there is a lack of evidence supporting the assumption that mandatory screening will save more lives.
Thompson, a pediatric hematologist at Ann & Robert H. Lurie Children’s Hospital of Chicago, says, referring to this new study,
These findings suggest that sickle cell trait alone does not increase an individual’s risk of sudden death.
Some experts beg to differ, though, saying that the Army’s “universal precautions,” which include requiring active duty soldiers to drinks lots of fluids, undergo strenuous exercise and rest during hot weather, has made a difference.
Thompson added that this research only supports the benefits these precautions can have for everyone, not just those with sickle cell trait.
The US Centers for Disease Control and Prevention says that sickle cell trait rarely causes sickle cell disease symptoms. The prevailing concern over sickle cell trait is that it might cause muscle deterioration due to intense exercise, often in extremely hot temperatures.
Exertional rhabdomyolysis is rare, but it can be fatal, Kurina says, which is why the researchers focused on that result. While there was no significant difference in mortality risks, the study found that black soldiers with sickle cell trait were 54% more likely to suffer from this muscle condition compared to those who did not have sickle cell trait.
This risk level is similar to higher risks linked to tobacco use and obesity, the researchers note. The absolute risk was small, however. Just over 1% of black soldiers with sickle cell trait actually developed exertional rhabdomyolysis, compared to 0.8% of those who did not have sickle cell trait, Kurina says.
The study identified 391 cases of exertional rhabdomyolysis during its investigation. Risk ofr the condition increased with age, but was significantly lower for women than for men. Only one death caused by exertional rhabdomyolysis was recorded during the study period, and it was a soldier who did not have sickle cell trait.
The study was published in The New England Journal of Medicine.