Genetic Susceptibility to Noise-Induced Hearing Loss

An international team of neuroscientists from the University of Southern California have authored a new genome-wide association study that suggests some people may be more genetically predisposed to noise-induced hearing loss than others. The study examined the biological processes that can affect a vulnerability towards hearing loss caused by noise exposure, and identified a gene that could be the key. This is not the first study on the link between noise-related hearing loss and genetics, but this is the first large study that successfully replicated their results and published their findings.

Researchers used mice as test subjects and identified the Nox3 gene, which is expressed almost entirely in the inner ear, as the link to hearing loss vulnerability. While more research is necessary before any there are any clinical implications, this gene could be very important in the future. People could be tested for genetic susceptibilities, and take more precautions against excessive noise in order to protect their hearing.

Cognitive Shifts Due to Hearing Loss

A group of researchers at the University of Colorado have found that hearing loss may cause dramatic brain shifts in both children and adults. Using electroencephalographic (EEG) recordings of subjects with deafness and hearing loss, the group at the Department of Speech Language and Hearing Science was able to measure brain activity in response to auditory stimulation.

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Researchers discovered that the areas of the brain that process vision or touch can take over the areas that would normally process hearing, but receive very little stimulation when a person is deaf or hard of hearing. This change is termed cross- modal cortical reorganization and reveals how adaptable the brain is, in response to its environmental changes. The study showed that this cortical reorganization was apparent in even patients with only mild hearing loss. Researchers concluded that this adaptation can decrease the brain’s propensity for processing sound, which can in turn affect a deaf patient’s ability to understand speech with cochlear implants. The group also suggested that the brain’s compensations for hearing loss can increase the overall workload on the brains of aging people, which could significantly correlate with dementia. Researchers demonstrated that examining cortical reorganization can be a valuable tool to create therapies and rehabilitation strategies for those with cochlear implants.

Hearing Loss in the Latino Community

A recent study funded by the National Institute of Health took an in-depth look into the hearing of Latinos in America, aged 18-74. Researchers discovered that 1 in 7 Latinos suffer from hearing loss in at least one ear, which is about the same rate as the national average. The study also examined sub-categories of Latino subjects, analyzing data from self-identified Central American, Cuban, Dominican, Mexican, Puerto Rican, and South American patients.

Interestingly, the data showed that Puerto Ricans were most likely to be affected by hearing loss, with 21 percent of subjects having hearing loss in one ear, and 12 percent having hearing loss in both ears. Chicanos (Mexican-Americans) were the least likely, with 11 percent having hearing loss in one ear and 6 percent with hearing loss in both ears.

Unsurprisingly, researchers found that age was the biggest factor in hearing loss: 45-65 year olds were five times more likely to have some level of hearing loss than the 18-44 year olds. The study concluded that hearing loss in Latino communities is a common problem, and can be associated with socioeconomic factors, exposure to excessive noise, and abnormal glucose metabolism. Researchers found that men were 66 percent more likely than women to suffer from hearing loss, and lower income levels correlated with a higher percent of hearing loss. The study set out to identify potential risk factors for hearing loss in Latinos, and researchers aim to follow it up with long-term studies to determine whether these risk factors can predict the development of hearing loss in the future.

By: Elena McPhillips