CHICAGO - (AP) - A new study has found a stunning increase in therate of hearing loss among American teenagers. The report saysnearly one in five teenagers has at least slight hearing loss.

The cause is a mystery. But some experts are urging teenagers toprotect their hearing by turning down the volume on their digitalmusic players. They warn that slight hearing loss can causeproblems in school.

The reseachers compared hearing loss rates from the late 1980sand early 1990s with rates in 2005 and 2006.

They found hearing loss increased from about 15 percent toalmost 20 percent of teens. That means about 6.5 million teenagershave at least slight hearing loss.

The study appears in Wednesday's Journal of the American MedicalAssociation.