Aug 3, 2017
Interpreting Results

By now, many have heard about the recent study published by the Journal of the American Medical Association that found chronic traumatic encephalopathy (CTE) in 110 of 111 brains belonging to former NFL players. Though researchers are saying the results are significant, they also admit that new conclusions about the link between CTE and football cannot yet be made.

In total, the study examined the brains of 202 deceased former football players from all levels. 177 of the brains (almost 88 percent) had CTE. Of the 14 brains belonging to those who only played football in high school, three were found to have CTE, along with 48 of 53 college players, nine of 14 semiprofessional players, and seven of eight Canadian Football League players. In the two brains of those who only played football before high school, CTE was not found.

“This is by far the largest [study] of individuals who developed CTE that has ever been described. And it only includes individuals who are exposed to head trauma by participation in football,” Ann McKee, MD, the study’s senior author, told NPR. “While we still don’t know what the incidence is in the general population or in the general population of football players, the fact that we were able to gather this many cases [in that time frame] says this disease is much more common than we previously realized.”

Yet, Dr. McKee, who is also the Chief of Neuropathology at VA Boston Healthcare System and Director of the CTE Center at the Boston University School of Medicine, said there is a need to be cautious about making sudden conclusions from the study because the brains that were examined were likely a skewed sample.

“Families don’t donate brains of their loved ones unless they’re concerned about the person,” she said. “So all the players in this study, on some level, were symptomatic. That leaves you with a very skewed population.”

The study itself is candid about its limitations. The authors explain:

“Public awareness of a possible link between repetitive head trauma and CTE may have motivated players and their families with symptoms and signs of brain trauma to participate in this research. Therefore, caution must be used in interpreting the high frequency of CTE in this sample, and estimates of prevalence cannot be concluded or implied from this sample.”

Dr. Munro Cullum, PhD, the Pam Blumenthal Distinguished Professor in Clinical Psychology with the O’Donnell Brain Institute at the University of Texas Southwestern Medical Center–who has studied concussion for nearly 30 years–believes this research is very valuable but is also quick to point out the limitations.

“[CTE] seems to be, perhaps, more common in people who play football, but we don’t know why,” he told NPR. “We actually don’t know what the causative factors are or the risk factors [for CTE]. There still are probably yet-to-be discovered genetic and environmental factors that could be contributing, as well.”

Others are even more skeptical.

“This study adds little new science,” Jeffrey Kutcher, MD, the National Director of the Sports Neurology Clinic, told Yahoo Sports. “It provides a larger number of cases and a better description of their problems during life. Other than that, there isn’t much here that we didn’t already know.”

Image by Boston University Center for the Study of Traumatic Encephalopathy

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