[2] While much attention in the NFL has focused on limiting or treating concussions, the latest medical research indicates that the brain damage in CTE is caused by the cumulative impact of all collisions involving a player's head,[3][4] which confirms what was generally known nearly a century ago but was then largely forgotten.
[5] The NFL has implemented rule changes to reduce collisions to the head[6] and has sought to improve football helmet design.
[9] As more parents (including some NFL players) decide not to let their children play football,[10][11] it remains to be seen whether football will eventually face a significant decline in popularity[12] like boxing, which fell from prominence as the brain damage suffered by ex-boxers drew more public attention.
[25][26] Two former NFL Man of the Year winners suffering from CTE symptoms have committed suicide by shooting themselves in the chest, with the intent of leaving their brains intact to be studied for the damage inflicted by football.
[27][28] Heisman Trophy winner and former NFL All-Pro Bo Jackson said in a 2017 interview with USA Today that if he had known about the risks associated with CTE, he would never have played football, and he discourages his children from doing so.
[29] In late 2017, former running back Larry Johnson, who holds the NFL record for most rushing attempts in a season, reported having symptoms akin to Aaron Hernandez, including memory blanks, suicidal thoughts and thoughts of committing violent acts.
A typical diagnosis of ALS has primarily been based on the symptoms and signs the physician observes in the patient and a series of tests to rule out other diseases[148] and therefore, prior to the discovery of CTE as a phenomenon in ex-American football players, many CTE cases were diagnosed as ALS.
[150] A cohort mortality study run by the National Institute for Occupational Safety and Health (NIOSH) examined 3,349 NFL players who played at least five full seasons from 1959 to 1988.
After multiple lawsuits[223] and many years of litigation, the NFL and lawyers for around 4,500 former players (or their estates) announced a financial settlement of $765 million in 2013.