BOSTON (Reuters) - The union that represents U.S. professional football players has given Harvard University a $100 million grant for a study of the range of health problems, from brain damage to heart conditions, that affect current and former players.

Researchers with Harvard Medical School plan to spend a decade studying hundreds of former players who are members of the National Football League Players Association, university officials said on Tuesday. The aim is to develop strategies to limit the long-term damage that players suffer from years of hits on the field.

The recent suicides of a spate of former NFL players, including 12-time Pro Bowl linebacker Junior Seau, have raised concerns about the toll that blows to the head take on the brains of current and former players.

Scientists have found that years of steady, small hits can lead to a condition called chronic traumatic encephalopathy, which at its start can cause victims to have a hard time concentrating on small tasks and eventually can lead to aggression and dementia.

The worries are not limited to the pros, who are part of a $9 billion U.S. industry. Parents of players, from peewee leagues to college, have raised concerns about the game and leagues have changed rules to limit hits to the head.

Those concerns reach all the way to the White House.

"I'm a big football fan, but I have to tell you if I had a son, I'd have to think long and hard before I let him play football," President Barack Obama said in an interview with the New Republic magazine published on Sunday, a week before the Super Bowl championship will be played in New Orleans.

Harvard Medical School Dean Jeffrey Flier said the research would aim to address health concerns at all levels of play.

"Millions of kids and college athletes play football, formally and informally," Flier said in a statement on the school's website. "We cannot afford to ignore the health risks associated with this sport."

Harvard researchers plan to identify a group of at least 1,000 retired NFL players from around the country and focus their study on 100 healthy and 100 unhealthy former players.

The NFL lauded the move.

"We look forward to learning more about the Harvard study and hope that it will play an important role in advancing medical science," league spokesman Brian McCarthy said.

The league faces lawsuits from more than 2,000 former players who say NFL management concealed information about the risk of chronic brain injury to players. It has begun to change the rules of the game to lower the risks, including sharply penalizing the most dangerous helmet-on-helmet hits.

Seau's family sued the NFL this month, saying brain damage he suffered during his 20 years in the league led to his suicide. A study by independent researchers found that Seau, 43, suffered from chronic traumatic encephalopathy - the same debilitating brain disease diagnosed in at least two other former NFL players who committed suicide.

The NFL has said the findings about Seau's brain underscored "the recognized need for additional research to accelerate a fuller understanding of CTE." League teams have donated $30 million to the National Institutes of Health for research.