When subjecting hearing loss to the nature vs. nurture debate, we are left with the staggering reality that hearing loss may occur to anyone, at any age, regardless of genetics. Years of exposure to damaging volumes, beginning at a young age with earbuds blasting loud music to occupationally hazardous sounds, whether you are a dentist or a construction worker, to the decline of hearing that occurs as we get older (presbycusis), hearing loss is a common physical condition affecting 20% of the US population.
Understanding environmental factors
We must first acknowledge the many environmental factors that lead to hearing loss. Loud music, earbuds, rock concerts, do-it-yourself home improvement projects with power tools, riding a motorcycle – these are sounds of our daily life that are potentially damaging in their decibel levels. In terms of employment, there are many occupations that expose us to dangerous levels of sound – from construction to dentistry to airfield operation to teaching preschool.
Sixty percent of veterans returning from combat report some degree of hearing loss. Noise-related hearing loss affects the hair cells of the inner ear, which translate sound wave vibrations into neural signals that the brain registers as sound. Presbycusis, age-related hearing loss, is also linked to the irreparable damage of inner ear hair cells.
Genetics and hearing loss
Even so, there are genetic factors at play. The American Hearing Research Foundation reports: “While acquired deafness associated with age or noise exposure is more common than genetic deafness by roughly two orders of magnitude, congenital deafness occurs in 1 out of every 1,000 to 2,000 births. Autosomal recessive inheritance is the most common form, account for more than 75% of congenital deafness.”
Certain congenital conditions increase the chance of a person losing their hearing: abnormalities of the ear structures, for example, may lead to conductive hearing loss. Additionally, ear diseases such as Meniere’s disease or otosclerosis heighten the risk for hearing loss, as they affect bones and structures of the ear which process sound.
In other cases, inherited syndromes, such as Alport or Branchio-Oto-Renal, affect the kidneys, eyes, and ears; or mitochondrial disorders, such as Kearns-Sayre, MELAS, and MERFF, which cause mutations in mitochondrial DNA, may increase the risk of hearing loss.
Dr. Stephanie Moody, a hearing specialist, writes on genetic sensorineural hearing loss: “New genetic mutations are linked to hearing loss every year. More than 100 loci have been identified involving genes that code for proteins involved in the structure and function of hair cells, supporting cells, spiral ligament, stria vascularis, basilar membrane, spiral ganglion cells, auditory nerve, and virtually every structural element of the inner ear.”
Predisposition meets environmental factors
If we are already exposed on a daily basis to damaging volumes of sound, certainly individuals who are genetically predisposed to sensorineural hearing loss are at greater risk of developing hearing loss as they age, compounded with environmental factors. At the same time, genetics may affect structures of the ear, which complicate and hinder the auditory process. With advancements in molecular biology and genetics research, screenings tests are available for certain notable genes, such as the GJB2 (a recessive genetic disorder known to cause deafness), which may inform us of potential hearing issues, as well as the potential to genetically pass this on to our offspring.
The American Academy of Otolaryngology (Head and Neck Surgery) notes that “although exact data is not available, it is likely that genetics plays an important role in hearing loss in the elderly” and that “inherited genetic defects are just one factor that can lead to hearing loss and deafness, both of which may occur at any stage of a person’s life span.”
To schedule a consultation with Dr. David Dekriek, call (562) 926-6066.
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