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Associated Press
FILE - In this Sept. 1, 2012, file photo, Arkansas quarterback Brandon Mitchell (17) runs away from Jacksonville State cornerback Jermaine Hough (2) during the second half of an NCAA college football game in Fayetteville, Ark. Arkansas, behind breakout performances from Mitchell and Chris Gragg, sure didn't look like a team that lost three receivers to the NFL in its season-opening win over Jacksonville State. (AP Photo/April L. Brown, File)

As the National Football League kicks off a new season, a study appearing in a leading medical journal underscores the long-term costs of the game on those who play it.

A study tracking 3,439 retired players with five or more seasons in the NFL found these athletes four times as likely as other men their age to die of Alzheimer's disease or amyotrophic lateral sclerosis, better known as Lou Gehrig's disease. Among the league's "speed players" — those who build up substantial speed before they make a tackle or are brought down by one — the odds of dying of those causes were even greater.

The heightened risk of death from these neurodegenerative disorders was in sharp contrast to an overall picture of remarkable health among the former players. Compared with men in the general population, the NFL veterans were about half as likely to die at any given age.

The study, published Wednesday by the journal Neurology, is the most extensive survey of former athletes since concern about the long-term consequences of repeated blows to the head has become a major safety issue among NFL players.

There is little doubt that the claims by former players have forced the NFL to change some of its rules and procedures. Players who suffer concussion-like symptoms must now be cleared by an independent neurologist before returning to either practice or a game. This process often takes several days before a player can rejoin his team.

The league also moved its kickoffs 5 yards closer to the opponent's end zone last season in the hope of having more touchbacks — the ball being downed without contact and placed at the 20-yard line — to avoid the dangers associated with runbacks, in which players often collide at full speed.

To that end, the NFL announced Wednesday a $30 million contribution to the Foundation for the National Institutes of Health to support "research on serious medical conditions prominent in athletes and relevant to the general population." It was largest philanthropic donation ever made by the NFL in its 92-year history to any single organization.

SAINTS CONFIDENT ABOUT OFFENSE: Drew Brees is confident the Saints can replicate Sean Payton's record-breaking offense to a certain extent. Yet the star quarterback also has come to terms with the fact that the mastermind of the schemes that have suited him so well won't be around, and that offensive coordinator Pete Carmichael Jr. is going to have to make his own gut decisions, and his own mid-stream adjustments. The Saints often point out that Carmichael took a leading role in shaping and calling the offense for the last 10 games of last season, after Payton's leg had been broken in a sideline collision.

COWBOYS NOW WORTH $2 BILLION: The Dallas Cowboys have become the first American sports franchise worth more than $2 billion, according to Forbes magazine. New England was second to Dallas in overall value at $1.635 billion.