Nearly 3 in 4 former NFL players had chronic traumatic encephalopathy (CTE) at the time of their death, according to a new study published Wednesday in the Journal of the American Medical Association.

The study also estimated that about 1 in 4 former NFL players had dementia during their lifetime.

"More than 20 million men alive today in the US have played football, so understanding how many of them have CTE is an important public health question" Yorghos Tripodis, a professor of biostatistics at Boston University and an author of the paper, told ABC News.