Harvard researchers found that adolescents had one-third more hearing loss in 2005-6 than in 1988-1994. The finding was unexpected. It was postulated that the introduction of vaccines against pneumococcus and haemophilus and the greater awareness of music-induced hearing loss would reduce the incidence of hearing loss. The reason for the increase is not proven, but the increased use of headphones and listening devices is the likely culprit. Be careful with the latest technology!
See JAMA(click here-subscription required), August 18, 2010, pp. 772-777.