But having a single copy of the sickle-cell gene does put carriers at risk for a serious muscle condition, a study finds.
By Nathan Collins
Sickle-cell disease. (Photo: Wikimedia Commons)
If you pay attention to sports, you’ve probably heard a growing number of stories about athletes dropping dead from a condition called exertional rhabdomyolysis, which ravages muscles and damages kidneys. Now, researchers report that sickle cell trait, a genetic condition related to sickle cell anemia, increases the risk of exertional rhabdomyolysis, but doesn’t raise the risk of death, as many had previously thought.
There’s no doubt exertional rhabdomyolysis is bad news. It comes on when very strenuous exercise leads muscle cells to fall apart. The resulting debris flows into the bloodstream and clogs kidneys. In the worst cases, rhabdomyolysis ends in death, although it’s widely known to be preventable through proper training regimens, hydration, among other precautions.
But whether being a carrier of the sickle cell gene—what doctors call sickle cell trait—actually raises the risk of exertional rhabdomyolysis and death is less clear. The evidence, Stanford University researchers Alan Nelson, Lianne Kurina, and their colleagues write in the New England Journal of Medicine, is largely anecdotal or otherwise incomplete, often because researchers didn’t have adequate information on their subjects’ sickle cell status.
Sickle cell trait raised the risk of exertional rhabdomyolysis by 54 percent.
To remedy that problem, the researchers looked at the health records for 47,944 African-American soldiers on active duty in the Army between 2011 and 2014. (Although sickle cell trait and sickle cell disease are not unique to people of African descent, they are both more common in that group compared to others.) Crucially, each of those soldiers had undergone testing for sickle cell trait, as is now standard practice in the Army and other branches of the military.
After adjusting for sex, age, physical fitness, and other factors, the team found that sickle cell trait raised the risk of exertional rhabdomyolysis by 54 percent, on par with the increased risk associated with obesity and smoking, the researchers write. Meanwhile, sickle cell trait did not increase the risk of death.
“These findings are compelling because case reports dominate the relevant literature and emphasize the presence of sickle cell trait as a risk factor for adverse outcomes, including exertional rhabdomyolysis and sudden death,” the researchers write, and a large, controlled study was sorely lacking.
Still, questions remain—in particular, whether the lack of increase in the risk of death might be due to stepped-up precautions the Army took in response to concerns about exertional rhabdomyolysis.