DETROIT – Former Detroit Lions running back Mel Farr, who died in 2015, had Stage 3 chronic traumatic encephalopathy (CTE) at the time of his death, according to ESPN.

Farr died suddenly in 2015 of a massive heart attack due to undiagnosed hypertension.

Farr's family donated his brain and spinal cord to Boston University School of Medicine, where researchers have been testing the brains of deceased athletes since 2008.

CTE is a progressive degenerative brain disease associated with repeated blows to the head.

"Mr. Farr had Stage 3 CTE, which is consistent with other football players of similar age and exposure," said Dr. Ann McKee, the director of Boston University's CTE Center. "At Stage 3, the disease is widespread, but most severe in the frontal lobes as well as the medial temporal lobes, specifically the hippocampus, which plays a critical role in forming new memories, and the amygdala, which governs emotion.

"Mr. Farr had symptoms consistent with other Stage 3 cases, including memory problems, significant personality change, and behavioral symptoms," added Dr. McKee, who is also a professor of neurology and pathology at the Boston University School of Medicine and the Chief of Neuropathology for the VA Boston Healthcare System. "His family noted that Mr. Farr was aware of, and frustrated by, his decline."

Farr spent his entire NFL career with Detroit, from 1967-73. He was named NFL Offensive Rookie of the Year in 1967, when he ran for 860 yards in 13 games.

He ran for 717 yards in 1970, helping the Lions go 10-4 in the regular season. They reached the playoffs that season for the first time since 1957. Farr finished his pro career with 3,072 yards on 739 carries.

Following his football career, Farr opened a metro Detroit Ford dealership in 1975. During the 1980s he and Jesse Jackson joined to battle against what they deemed "racist" attitudes toward minority dealers by Ford. Farr also partnered with Donald Trump on a failed bid for one of Detroit's three casino licenses.

His dealer empire grew in the 1980s and 1990s, eventually adding a Hyundai/Kia dealership and a used car dealership in metro Detroit as well as interests in out-of-state dealerships.

However, his "superstar" image was tarnished in 1999-2000 when he was sued for allegedly violating consumer credit rules and overcharging customers. A device installed in his leased vehicles designed to prevent the car from starting was alleged to have shut off some cars while driving.

Facing outstanding liens from the automaker, Farr was forced to close his Ford franchises in 2002.