Los Angeles (CNN) -- Seventy-five former professional football players are suing the National Football League, saying the league knew as early as the 1920s of the harmful effects of concussions on players' brains but concealed the information from players, coaches, trainers and others until June 2010. The players "did not know the long-term effects of concussions" and relied on the NFL to protect them, the suit says. The lawsuit also names as a defendant the football equipment maker Riddell Inc., which has been the official NFL helmet brand since 1989. "For decades, defendants have known that multiple blows to the head can lead to long-term brain injury, including memory loss, dementia, depression and (chronic traumatic encephalopathy) and its related symptoms," says the 86-page lawsuit, filed in Los Angeles County Superior Court on Tuesday.
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NEW: Ex-player Duerson, who killed himself, would approve of the suit, his widow says
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NFL's failure to act has led to the deaths and brain injuries of former players, a lawsuit says
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The lawsuit filed by 75 former NFL players asks for a jury trial and damages
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An NFL spokesman says the league will "vigorously contest" such claims
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