Dr. Frank Lin, M.D., Ph.D., an assistant professor at the Johns Hopkins University School of Medicine and the university's Bloomberg School of Public Health, has spent several years researching how loss of hearing affects cognitive functioning. In the early 1990's, he and his colleagues began a study that tracked hundreds of people, both men and women, for a number of years. At the outset of the study, approximately 25% of the participants had hearing loss of some degree, but none had dementia. By 2008, 9% of the participants had dementia. The researchers determined that the participants who had some degree of hearing loss from the beginning of the study were much more prone to develop dementia. Study participants with mild, moderate, and severe hearing loss had twofold, threefold and fivefold, respectively, the risk of developing dementia over the course of time as did participants without hearing loss.
In a subsequent study, hearing impaired participants took repeated cognition tests over a six year period. The cognitive abilities of these hearing impaired participants declined approximately thirty to forty per cent more rapidly than non hearing impaired participants. The researchers concluded that the significance of the loss of brain function was directly correlated to the proportion of hearing loss.
Additional research indicates that shrinkage of the brain, which is a normal part of the aging process, seems to be accelerated in older adults with hearing impairment. The researchers suggest that the most effective way to deal with hearing loss is to treat it early. If, in fact, hearing impairment does contribute to these structural changes in the brain, it is best practice to treat the hearing loss before the structural changes occur.