Following Gifford's death, a team of pathologists diagnosed him with Chronic Traumatic Encephalopathy, his family said. Prior to his death, Gifford's family said they were suspicious he was "suffering from the debilitating effects of head trauma."
"We decided to disclose our loved one's condition to honor Frank's legacy of promoting player safety dating back to his involvement in the formation of the NFL Players Association in the 1950s," the statement read. "His entire adult life Frank was a champion for others, but especially for those without the means or platform to have their voices heard. He was a man who loved the National Football League until the day he passed, and one who recognized that it was -- and will continue to be -- the players who elevated this sport to its singular statue in American society."
Gifford's family also wrote that they would "continue to support the National Football League and its recent on-field rule changes and procedures to make the game Frank loved so clearly -- and the players he advocated so tirelessly for -- as safe as possible."
Over the last decade, the NFL has instituted nearly 40 rules changes aimed at reducing injuries, especially to the head and neck. Among the changes, teams are limited to 14 days of full-contact practice over the course of the season -- an average of less than one full-contact session a week.
In addition to changes on the field, the NFL has been an active advocate in pushing for further medical research on brain injuries. In September 2012, the league announced a $30 million unrestricted grant to the Foundation of the National Institutes of Health (FNIH) to help spur further research into head injuries. The grant was the single-largest donation the NFL has ever given to any organization.
"We are working now to improve the safety of our game," NFL Commissioner Roger Goodell said in a statement Wednesday. "The NFL has made numerous rules changes to the game, all to enhance player health and safety at all levels of football."
Gifford, the NFL's Most Valuable Player in 1956, was the centerpiece of the New York Giants' offense in the 1950s and early '60s. In addition to running back, he also played receiver and defensive back during his 12 seasons with the team.
The Giants released a statement regarding Gifford's CTE diagnosis: "We have great respect and sympathy for the Gifford family. We all miss Frank dearly. We support the family's decision to contribute to the discussion and research of an issue we take very seriously."
After retiring, Gifford worked as an announcer and later as an analyst for ABC's "Monday Night Football" broadcasts.