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A new study showed that play tackle football before age 12 has serious implications for the sport's stars.

The next round of NFL controversy may be about to begin, and it has nothing to do with underinflated balls.

A new study (paywall) from Boston University School of Medicine found that retired NFL players who played tackle football before age 12 were more likely to suffer cognitive impairment in retirement than peers who didn't tackle until adolescence.

"Those former NFL players who started playing before 12 years old performed 'significantly worse' on every test measure after accounting for the total number of years played and the age of the players when they took the tests. Those players recalled fewer words from a list they had learned 15 minutes earlier, and their mental flexibility was diminished," The New York Times reported.

The link between professional football and head trauma has been in the news repeatedly in recent years. In the fall of 2013, PBS released "League of Denial: The NFL's Concussion Crisis," establishing a pattern of denying the problem from league officials.

But the latest wave of the debate is taking hold with a group powerful enough to make the NFL nervous: parents.

Several articles in the past few seasons have told the stories of parents who plan to keep their young children away from tackle football. Even President Barack Obama has said he wouldn't have let a son go pro in the sport.

Just this week, a separate New York Times story offered an inside look at Moms Clinics, one of the NFL's initiatives designed to allay fears about head injuries.

"The NFL has targeted mothers, many of whom decide which sports their children play but have not competed in football themselves, to reassure them that the game can be safe," The Times reported.

As the article noted, the league relies on popular youth leagues to produce the kind of talented players who can eventually become stars.

In early January, Public Religion Research Institute polled Americans about a variety of football issues, finding that about 65 percent of people believe that football is generally more dangerous than other sports.

"At the same time, roughly three-quarters (76 percent) of Americans say that if they had a young son they would allow him to play football; only 22 percent would not allow him to play," PRRI reported.

Email: kdallas@deseretnews.com Twitter: @kelsey_dallas