A neuropathologist thinks so:

The neuropathologist, Dr. Bennet Omalu of the University of Pittsburgh, a leading expert in forensic pathology, determined that Mr. Waters’s brain tissue had degenerated into that of an 85-year-old man with similar characteristics as those of early-stage Alzheimer’s victims. Dr. Omalu said he believed that the damage was either caused or drastically expedited by successive concussions Mr. Waters, 44, had sustained playing football.

In a telephone interview, Dr. Omalu said that brain trauma “is the significant contributory factor” to Mr. Waters’s brain damage, “no matter how you look at it, distort it, bend it. It’s the significant forensic factor given the global scenario.”