The National Institute on Deafness and other Communication Disorders estimates that there are 37.5 million (15%) adults in the United States with hearing loss (NIDCD). Hearing loss affects various segments of the population at different rates, degrees, and types of damage. No two people have identical hearing losses, nor do they always respond similarly to the same treatment. Furthermore, there are remarkable differences in the causation of hearing loss to include aging, genetics, health status, injury from accidents, medications, noise exposure, and environment.
Two to three out of every 1000 children born in the United States are hard of hearing or totally deaf. Ninety percent of the children are born to normal hearing parents. Premature birth, genetics, birth defects, and infection are primary causes of infantile hearing loss.
As we age, 25% of those over the age of 65 and about half of those over the age of 75 and older develop some degree of loss. Adult causation include noise exposure, drug reactions, genetic factors, heart disease, diabetes, thyroid dysfunction, and a host of others. Of the U.S. population with hearing loss, 2- 3% of children and adults have severe to profound losses. Fortunately, for humanity, hearing loss rarely reaches total deafness and almost all patients can be helped with surgical treatment, a cochlear implant, or with hearing aids.
There are varieties of diseases and traumas that cause hearing loss. Some of theseoriginate at the ear while others develop in the brain. Hearing loss caused by medical problems of the ear canal, eardrum, and middle ear prevents sound from being transferred to the deeper structures of the inner ear or cochlea (coke-lee-uh) where nerve impulses are generated to be sent to the brain. Problems in the outer and middle ear are similar to having difficulty focusing with the lens of the eye and needing glasses. The pinna, ear canal, eardrum, and middle ear are actually magnifying system to enhance hearing. Although the most common cause of decreased hearing is wax in the ear canal, the most common ear disease is the middle ear infection
Almost all hearing loss caused by diseases of the outer and middle ear including swimmers ear, chronic middle ear fluid, Otosclerosis, and perforated eardrums are curable or accessible to hearing aids.
Conditions that are more challenging are those that can produce permanent nerve damage inside the cochlea or growths on auditory nerve. This is because changes in the nerves of the inner ear or the acoustic nerve frequently leave some permanent hearing loss. These permanent changes are primarily due to decreased blood circulation, noise exposure, genetic factors, and to a lesser degree, aging. Other well-known causes include inner ear infections, ear trauma, syndromes, premature birth, tumors, viral and/or bacterial, and medication or toxic substance reactions. An example of a disease that causes reduced blood circulation is Microangiopathy. This process gradually restricts blood flow by building up plaque on the blood vessel walls resulting in hearing loss. A common medical disease that associated with Microangiopathy is diabetes.
Noise exposure, especially when combined with aging is a primary cause of permanent hearing loss. There are nearly 26 million people in the U.S. that have high frequency hearing loss from industrial noise, gunfire and motorcycles, and loud music that are known to cause “noise induced hearing loss.” Additionally, home power tools and recreational toys can create hearing loss and should be controlled by using earplugs or non- electronic/electronic muffs. For firearms, ear plugs and 30 dB NRR (Noise Reduction Rating) muffs is the best defense. However, this is not a guarantee of protection against a 170 dB peak for some firearms. Signs of over exposure are ringing in the ears and dull or muffled hearing. Although these may appear to be temporary, the damage is already done in small increments with some even occurring more rapidly.
Outside influences, such as taking aspirin or being exposed to toxic fumes (such as gasoline) at the same time as being exposed to noise, can promote hearing loss. Multiple exposures over time accumulate into a high frequency hearing loss requiring hearing aids. Most noise-induced hearing loss does not exceed a severe degree of damage, however, when coupled with aging or other diseases the results can be significantly worse. The cure for noise induced hearing loss is ear protection when in noise and to avoid loud sound or explosive noise, whenever possible.
Although there are reasonable treatments and solutions for many ear diseases, there are limited treatments for genetic hearing loss as there are approximately 400 genes that may cause hearing loss. One in every eight people carries a recessive gene for hearing loss. A recessive gene is one that when matched in both parents produces hearing loss in some of the offspring. Sometimes the loss is at birth, but in many cases genetic changes occur into adulthood. In rare cases, dominant genes (always causes hearing loss) produce families that have similar hearing losses or are susceptible to acquiring hearing loss. Some individuals can acquire hearing loss at levels far below the government OSHA standards. For these reasons, it is not unusual to find that hearing loss from noise exposure runs in families, more often in the male population.
One of the least recognized problems that cause hearing loss is damage to inner ear nerve cells because of toxicity or an allergic reaction to medication. Some powerful antibiotics taken in large quantities, usually by iv to combat infection can actually cause severe hearing loss. Additionally, diuretics, aspirin in large quantities, chemotherapy, and exposure to toxic waste are other examples of known substances that cause hearing loss. In fact, there are hundreds of substances and medications that cause hearing or balance disturbance. In some cases, the hearing loss may be only temporary if the medication or exposure is discontinued. However, medication reaction in the inner ear frequently causes permanent damage. The hallmark of a reaction to a drug or toxic material is the observation of ringing or other sounds in the head or ears. This is known as tinnitus. Should tinnitus occur at the onset of any medication or exposure to chemicals, it is best to consult an ENT physician and Audiologist, immediately.
Auditory Brain Processing
(two-sided hearing)In addition to problems at the ear, hearing areas deeper in the brain can also be affected resulting in very poor word understanding even with hearing aids. This is because information is not routed correctly, auditory functions no longer work, or critical cues are missing. The four primary areas of processing include dichotic listening , temporal processing (timing), low redundancy speech (hearing in noise), and binaural interaction (combining/separating signals from each ear). These changes are called auditory processing disorders (APD) and occur from a variety of causes including head trauma, neurological disorders such as Parkinson’s and Alzheimer’s diseases, the aging brain, vascular abnormalities, tumors, and a host of others.
What makes APD problems so important to identify is the need for specialized equipment and counseling that help to preserve a more acceptable hearing performance and quality of life. This is because; an APD hearing loss is more closely related to memory loss than it is to pure hearing loss. The functions are similar, but remarkably different. Unfortunately, some patients develop both a hearing loss and an APD and need specialized care.
In children, the earliest identification of hearing loss is the primary objective. Appropriate treatment at the correct time of development is strategic. Guidelines suggest that ideally, hearing loss should be identified by six months of age or earlier and a cochlear implant or hearing aids be fitted as soon as possible. Leaving a child in deafness without care is not a cultural choice. The purpose of each treatment is to provide access to sound and promote the development of the hearing system, speech and language, and social skills. Hearing loss prevents communication and age appropriate learning. Reducing these delays, in all cases, can be accomplished by early intervention.
Fortunately, early intervention is available throughout the United States and the solutions to improve communication and foster development are available for all children thru state and federal funding.
Aging Hearing Loss