A new study carried out by a team of Stanford scientists showed that carrying a single copy of the sickle cell gene variant may not increase a person’s risk of premature death. Shortening of the life span is a result of the blood disorder but people with the disease carry two copies of the gene — one from each parent.

The study released Thursday in the New England Journal of Medicine is the first of its kind where researchers followed nearly 48,000 black American soldiers — all having undergone tests for the trait — on active duty in the U.S. Army for a four-year period.

“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,” said study co-author Lianne Kurina, an associate professor of medicine at Stanford University School of Medicine.

According to the Centers for Disease Control and Prevention, the sickle cell disease occurs in 1 out of every 365 black people born in the U.S. On the other hand, 1 in 13 black Americans have sickle cell trait, where they carry only one copy of said gene. In the past, a study had found that the trait may also lead to an increased risk of sudden death, a theory that the new study refutes.

However, the study found that carriers of the sickle cell trait were more likely to develop exertional rhabdomyolysis, a condition where skeletal muscle tissue breaks down, usually due to strenuous exercise. Other factors like gender, age and lifestyle also affected the exertional rhabdomyolysis cases. While women had a significantly lower rate, soldiers over the age of 36 saw a 57 percent heightened risk. The risk was significantly higher in soldiers who were obese or smoked.

The absolute risk of developing the condition was small. Compared to 0.8 percent of the soldiers without sickle cell trait who developed exertional rhabdomyolysis, just over 1 percent of black soldiers with the trait developed the condition, Kurina said.

“There are a lot of factors that should be considered,” she said. “Sickle cell trait is a non-modifiable risk factor. Some of these factors are modifiable.”

The Washington Post reported Rakhi Naik, a certified hematologist at Johns Hopkins School of Medicine, as saying that organizations like the army, navy and NCAA carrying out mandated screenings for sickle cell trait have been important. Those who test positive for the gene trait are warned against dehydration and overheating.

“The major point of this study is that it seems that the risk of death can be completely eliminated by hydration,” Naik said. This was also stated by Kurina who said that increased awareness about hydration and overheating could have contributed to no increase in mortality among soldiers with sickle cell trait.

The study was funded by the U.S. National Heart, Lung, and Blood Institute in collaboration with the Uniformed Services University of the Health Sciences.