The findings of the most extensive case study yet conducted on the impact of football on the brain has some alarming results, particularly as it concerns the National Football League. Researchers found that 87% of the 202 brains they studied of individuals who had played football, most on the college and professional level, showed signs of chronic traumatic encephalopathy (CTE), including 99% of those who played in the NFL.

While those percentages, the researchers stressed, are not representative — as those who donated the brains were more likely to do so out of suspicion that the former player was suffering from brain damage — a researcher did conclude that the study shows "overwhelming circumstantial evidence that CTE is linked to football."

The Washington Post's Rick Maese provides a detailed summary of the findings of the study, including that out of the 202 brains examined for signs of CTE, 177, or 87%, came up positive for either mild or severe damage. Of the 111 brains belonging to former NFL players, all but one showed signs of the neurological condition and 86% of them exhibited signs of severe damage.

The 177 brains found to have CTE belonged to former players who had an average of 15 years of football experience. In addition to the NFL diagnoses, the group included three of 14 who played at the high school level, 48 of 53 who played in college, nine of 14 who competed semiprofessionally and seven of eight who played in the Canadian Football League. ...

The researchers distinguished between mild and severe cases of CTE, finding the majority of former college (56 percent), semipro (56 percent) and professional (86 percent) players to have exhibited severe pathology.

Neuropathologist Ann McKee explained that while the study doesn't purport to show the prevalence of CTE in the general population, "the fact that we’ve been able to gather this high a number of cases in such a short period of time says that this disease is not uncommon."

"In fact, I think it’s much more common than we currently realize," said McKee. "And more importantly, this is a problem in football that we need to address and we need to address now in order to bring some hope and optimism to football players." The study, said McKee, indicates "overwhelming circumstantial evidence that CTE is linked to football."

A spokesman for the NFL, which is directing $100 million toward concussion-related medical research and technological development, issued a statement responding to the new study:

The medical and scientific communities will benefit from this publication and the NFL will continue to work with a wide range of experts to improve the health of current and former NFL athletes. As noted by the authors, there are still many unanswered questions relating to the cause, incidence and prevalence of long-term effects of head trauma such as CTE. The NFL is committed to supporting scientific research into CTE and advancing progress in the prevention and treatment of head injuries.

Maese notes that while most of the research involving CTE and football has focused on the potential dangers, a recent study published by JAMA Neurology "showed not all former players suffer from cognitive impairment."

Read Maese's full report here.