NEW YORK – Brain damage caused on the football field ultimately led to the suicide of former NFL defensive back Andre Waters, according to a forensic pathologist who studied Waters' brain tissue.

Bennet Omalu of the University of Pittsburgh told The New York Times that Waters' brain tissue resembled that of an 85-year-old man and that there were characteristics of early stage Alzheimer's. Omalu told the newspaper he believed the damage was related to multiple concussions Waters sustained during his 12-year NFL career with the Philadelphia Eagles and Arizona Cardinals.

Waters was 44 when he committed suicide in November.

Omalu said trauma was a significant factor in Waters' brain damage, "no matter how you look at it, distort it, bend it."

The pathologist also told the newspaper the signs of depression that family members described Waters as exhibiting in his final years probably was caused by the brain trauma. Had he lived, Omalu said, the former player would have been fully incapacitated within 10 years.

The Alzheimer's Association reports a strong link between serious head injury and future risk of Alzheimer's.

Omalu began his research at the request of Chris Nowinski, a former Harvard football player and professional wrestler whose career was ended by multiple concussions. After hearing of Waters' suicide, Nowinski called Waters' sister, Sandra Pinkney, and asked permission to do further investigation on her brother's remains.

Nowinski chose Omalu because he had examined the brains of two former Pittsburgh Steelers players who were discovered to have brain trauma after sustaining concussions – Mike Webster, who suffered brain damage and died of heart failure in 2002, and Terry Long, who killed himself in 2005.