Hearing loss has become the 3rd most common health problem in the US. 79% have difficulty hearing or know somebody who has. 36 million Americans suffer from some kind of hearing loss, with only a
quarter of these people recognizing that they have a problem and seeking
treatment.

Link: http://www.hear-it.org/Hearing-loss-is-the-3rd-most-common-health-problem-in-the-US