From left to right: a normal brain, the brain of a former NFL linebacker who suffered 8 concussions, and the brain of a boxer with dementia. The brown spots show an accumulation of the tau protein. Photo: WBUR Boston's NPR

The protein tau is extremely important in the research of concussions and chronic traumatic encephalopathy (CTE). CTE is characterized by the accumulation of tau in regions of the brain that control mood, cognition and motor function. Tau is also one of the abnormal protein deposits found in the brains of people with Alzheimer’s. Most researchers at the forefront of concussion science believe it is tau that will ultimately help in both understanding and diagnosing what happens in the brains of injured athletes.

Now, researchers at the National Institutes of Health, have found another use for tau—it could be the basis of a quick, reliable clinical lab test to identify athletes who need more recovery time than the typical 10 days after a sports-related concussion.

If you pay attention to sports, you’re likely to have noticed the discrepancies in time athletes take to recover from concussions before safely returning to play. A hockey player could take an entire season to return, while one football player can come back in 6 or 7 days, but it takes another a full 14 days to recover.

Athletes who return before they are fully recovered from a concussion put themselves at a higher risk for long-term symptoms, like headaches, dizziness and cognitive deficits—and possibly CTE, although research is still ongoing. About half of college athletes see their post-concussive symptoms resolve within 10 days, but in others, the symptoms become chronic.

This new study suggests that tau levels post-concussion could be an unbiased tool to help prevent athletes from returning to action too soon.

In the study, led by Dr. Jessica Gill, NIH Lasker Clinical Research Scholar and chief of the NINR Division of Intramural Research's Brain Injury Unit, researchers evaluated changes in tau following a sports-related concussion in male and female collegiate athletes to determine if higher levels of tau relate to longer recovery durations.

To measure tau levels, a group of 632 soccer, football, basketball, hockey and lacrosse athletes from the University of Rochester first underwent pre-season blood plasma sampling and cognitive testing to establish a baseline. They were then followed during the season for any diagnosis of a concussion, with 43 of them developing concussions during the study. For comparison, a control group of 37 teammate athletes without concussions was also included in the study, as well as a group of 21 healthy non-athletes.

Following a sports-related concussion, blood was sampled from both the concussed and control athletes at six hours, 24 hours, 72 hours, and seven days post-concussion.

Concussed athletes who needed a longer amount of recovery time before returning to play (more than 10 days), had higher tau concentrations overall at six, 24 and 72 hours post-concussion compared to athletes who were able to return to play in 10 days or less. These observed changes in tau levels occurred in both male and female athletes, as well as across the various sports studied.

The researchers said further studies will test protein biomarkers beyond tau, and examine other post-concussion outcomes.