Any athlete suspected of getting a concussion during sports should stop play, leave the game and not return until cleared by a licensed healthcare professional, according to new US guidelines out Monday. The risk of concussion is greatest in American football and rugby, followed by hockey and soccer among male athletes, said the new standards by the American Academy of Neurology. In women, the risks are greatest in soccer and basketball.

Helmets and mouthguards can prevent serious head and facial injuries, but there is no evidence they specifically stave off concussion, top authorities in sports medicine say. Paradoxically, wearing this protection may lead to injuries because a player is tempted to take greater risks, they say. Concussion has become a big issue in contact sports such as American football, ice hockey, rugby and football. Writing in the British Journal of Sports Medicine, a panel of 28 neurologists say concussion is a complex phenomenon.

Heading the ball may increase the risk of brain damage to football players, new research has indicated. The US study, which concentrated on schoolgirl footballers, revealed evidence of mental impairment cause by repeatedly heading the ball, with scientists saying the effects suggest "mild traumatic brain injury of the frontal lobes". However, they stressed more research was required to determine whether the changes were permanent or temporary. The study featured a group of 12 teenage female footballers and a matching group of non-players.

(Adds quotes, details, background) By Dan Whitcomb LOS ANGELES, Jan 23 (Reuters) - The family of former San Diego Chargers star Junior Seau, who killed himself last year, sued the National Football League on Wednesday, saying that brain damage he suffered during his 20 years in the league led to his suicide.