Several studies have documented the impact of untreated hearing loss. An often cited survey was commissioned by the National Council on Aging in 1999. This national survey of nearly 4,000 adults with hearing loss and their significant others, showed significantly higher rates of depression, anxiety and other psycho-social disorders in individuals with hearing loss who are not
wearing hearing aids. This survey looked at the positive benefits of amplification (hearing aids), and showed that hearing aid use positively affected the quality of life for both the hearing aid wearer and his/her family. These findings were consistent with the findings of a large randomized and controlled study that determined that hearing loss was associated with decreased psycho-emotional well-being, decreased social/emotional well-being, decreased communication and decreased cognitive function, in addition to increased depression for subjects who do not use hearing aids (as compared to those who had received hearing aids). These conditions were all improved after hearing aids were fitted. More recently, Dr. Frank Lin and his colleagues at Johns-Hopkins University found a strong link between the degree of hearing loss and the risk for developing dementia. Individuals with mild hearing loss were twice as likely to develop dementia as those with normal hearing; those with moderate hearing loss were three times more likely; and those with severe hearing loss had five times the risk. While this study could not definitively conclude that early treatment with hearing aids would reduce the risk of dementia, there was a strong positive correlation between the degree of hearing loss and the risk of dementia (Lin et.al. 2011).
Regeneration of 'hair cells' (sensory cells) in the inner ear is something that human babies and mice can only do for a short period after birth. Dr. Ksenia Gnedea and her colleagues at the A. James Hudspeth's Laboratory of Sensory Neurosciences have made some progress in activating sensory regeneration of these hair cells in mature mice. (Proceedings of the National Academy of Sciences. Oct. 2015).
Scientists at the National institue on Deafness and other Communication Disorders have recently had success in treating mice with defective inner ears with gene therapy. A particular mutated gene (whirlin) can cause defects in the inner ears of humans and mice. Although not effective in mature mice, newborn mice with the the defective whirlin gene developed normal inner ear stereocilia (hair cells) when injected with the normal whirlin gene. (Molecular Therapy. October 2015)