Researchers who study chronic traumatic encephalopathy, or CTE, have long wondered why some people are hit harder by the degenerative brain disease.
CTE is currently diagnosed only after death but the condition is associated with repeated hits to the head, often experienced by contact sports athletes. CTE has afflicted some of the world's popular athletes, which include football player Aaron Hernandez.
His family has accused the National Football league of failing to protect him from a brain injury that may have contributed to him committing suicide.
Researchers observed that some individuals develop more severe forms of CTE than others. Hernandez has been found to have one of the most severe cases of CTE among the dead athletes whose brains were studied by researchers from Boston University.
"We see a lot of former athletes who have similar levels of exposure. Two football players in college, who played eight to 10 years. Late in life, one of them develops severe disease, and the other might be mildly impaired," Jesse Mez, from Boston University's School of Medicine, told CNN.
"I think it's of value to understand that difference, and this finding starts to explain these types of differences."
Mez and colleagues examined the brains of 86 deceased contact-sports athletes for genetic variation in TMEM106B. The gene is believed to play a role in the brain's inflammation system.
The researchers found that among athletes with CTE, the genetic variation predicted increased CTE pathology and brain inflammation.
In a statement published by Eurekalert, study researcher Jonathan Cherry, from BUSM, said that those with the variation were also found to have 2.5 times higher risk of developing dementia, which suggests that the variant may predict increased odds for developing symptoms of CTE.
The researchers said that the findings inch toward a better understanding of the disease. They said that knowing why some individuals are more at risk of CTE may help researchers identify potential targets to develop therapies.
"By better understanding why some individuals are more at risk for CTE, we can identify novel therapeutic targets to help treat all with the disease," said study author Thor Stein, from VA Boston Healthcare System.