Causes, Treatments, and Community Perspectives on Hearing Loss

Introduction

When people experience hearing loss, they have either a complete or partial inability to hear (Robinson & Sutton, 1979). There are many reasons why this can occur, and several treatments that can be used to allow them to hear again. Whether full hearing can be restored is an important consideration, but sometimes even restoring partial hearing is significant enough to help a person resume a more normal life (Kral & O'Donoghue, 2010). The level of impairment is measured in decibels using a specialized machine that presents tones for the patient to identify. What the patient indicates he or she can hear provides the technician with information on the severity of the impairment (Kral & O'Donoghue, 2010).

Another important consideration involves the strong opinions held within the deaf community regarding interventions and whether they are always in a person's best interest. Not everyone believes that those who are born deaf should be made to hear, particularly if that requires risky surgery or other invasive methods (Oishi & Schacht, 2011).

The methods used to help people hear have met with limited success. Hearing aids do not restore completely normal hearing, and they can be cumbersome and expensive. Other methods exist, but they are not suitable for everyone (Lieu, 2004). Additionally, some hearing loss cannot be reversed or halted (Lieu, 2004). Outcomes depend on the reason for the loss and the types of treatment to which the individual responds. When hearing cannot be restored, that is an unfortunate reality. However, many people who are born deaf or who lose all or part of their hearing later in life are able to live normal lives with a few modifications (Lieu, 2004). While new advances can be explored for those who wish to hear again, not everyone is eager to attempt to regain their hearing.

Causes of Hearing Loss

Age is one of the primary causes of hearing loss. As people age, they are less likely to hear well because of cumulative damage sustained over their lifetimes (Kral & O'Donoghue, 2010). High frequencies are often what these individuals lose first, although some experience difficulty with lower tones instead (Robinson & Sutton, 1979). The loss of high-frequency hearing is called presbycusis, and it actually begins early in adulthood (Lieu, 2004). Generally, people with this condition do not notice it until much later in life, because it takes until older age for them to realize they can no longer hear conversations properly (Robinson & Sutton, 1979). By the time they reach that point, they may assume the loss is simply due to "old age," when in fact the groundwork for the impairment was laid much earlier. While presbycusis is common, it varies based on genetics and is not related to noise, disease, or toxins (Lieu, 2004).

Nearly half of all cases of hearing loss are attributable to noise, and five percent of people across the globe have some degree of hearing difficulty from noise-related factors (Oishi & Schacht, 2011). Fortunately, noise is one variable that can be avoided to some degree by most of the population. People who live near airports and freeways are exposed to high levels of noise quite frequently (Lieu, 2004). These individuals are at greater risk of hearing loss due to their daily exposure, although noise affects everyone differently (Oishi & Schacht, 2011). Not everyone who lives with significant noise in their environment will sustain hearing damage; they are simply at higher risk of impairment over time (Lieu, 2004). Both the decibel level of the noise and the duration of exposure are important factors when calculating risk.

Diseases can cause hearing loss, especially in children and infants (Kral & O'Donoghue, 2010). Measles, chlamydia, mumps, and meningitis all place people at risk, as does fetal alcohol syndrome in newborns (Lieu, 2004). People living with HIV/AIDS frequently experience hearing difficulties, and being born prematurely, having syphilis, undergoing chemotherapy, or having a brain tumor can also affect a person's hearing (Lieu, 2004). While it is logical that disease could affect many parts of the body including the ears, many people do not think of illness when they consider hearing loss — tending instead to focus on genetics, noise, or old age. However, the range of illnesses that can cause hearing impairment makes it an important etiological factor to consider when pursuing proper treatment (Kral & O'Donoghue, 2010; Lieu, 2004).

Nearly 75 to 80% of genetic hearing loss cases are inherited through recessive genes (Oishi & Schacht, 2011). Another 20 to 25% arise through dominant genes, and the remaining genetic cases of hearing loss involve mitochondrial inheritance or X-linked patterns (Oishi & Schacht, 2011). There are two distinct forms of genetic deafness: syndromic and nonsyndromic (Lieu, 2004). The syndromic form occurs when genetic markers for hearing impairment are coupled with other medical conditions, while the nonsyndromic form involves hearing impairment alone, absent other medical problems (Lieu, 2004). Gene mapping is helping researchers learn more about both forms of deafness, although it is still not possible to determine the precise cause in every case.

Certain medications commonly cause irreversible damage to the ear, such as cisplatin and similar chemotherapy drugs (Lieu, 2004). For this reason, they are used only when necessary, in order to limit permanent hearing damage. Other medications can affect hearing, but their effects tend to be more reversible; these include aspirin, NSAIDs, and diuretics (Lieu, 2004). Women must be particularly cautious about taking NSAIDs and related medications, as they face a greater risk of hearing loss than men (Lieu, 2004). Medications used for erectile dysfunction can also cause hearing loss, which may be permanent (Kral & O'Donoghue, 2010). However, both over-the-counter and prescription medications are not the only concern for those seeking to protect their hearing.

Chemical exposure is also problematic. Solvents, lead, gasoline, crude oil, automobile exhaust, asphyxiants, and heavy metals are all potential causes of hearing loss (Lieu, 2004). When a person begins losing hearing due to chemical exposure, it starts with higher frequencies and is not reversible (Robinson & Sutton, 1979). Lesions damage the cochlea, and central portions of the auditory system are degraded (Lieu, 2004). Ototoxic chemicals such as styrene are particularly hazardous, creating an elevated risk of hearing loss — especially when combined with high noise levels, as in many factory environments (Lieu, 2004).

Trauma can affect hearing in two distinct ways: through direct physical damage to the ear itself, and through brain damage that affects how auditory signals are processed (Kral & O'Donoghue, 2010). Any type of head injury places a person at significant risk of hearing loss, which may be permanent or temporary (Lieu, 2004). Auditory cortex lesions can be a serious source of hearing impairment and may result in deafness or other difficulties (Lieu, 2004). Importantly, hearing impairment does not always mean an inability to hear at all. It can also mean that sounds are perceived as garbled, or that ringing or other intrusive noise in the ears makes hearing difficult (Lieu, 2004). Many auditory lesions produce these kinds of partial impairments rather than complete deafness, as total deafness would require the lesion to be in a precise location and of a particular size.

There are neurobiological reasons for deafness and other hearing impairments. Either there is something wrong with the mechanical workings of the ear itself, or there is something wrong with the brain's ability to process the signals it receives from the ear (Kral & O'Donoghue, 2010; Lieu, 2004). Sound travels from the ear to the brain through a delicate and complex process. The more complex the process, the more opportunities exist for something to go wrong. Issues can arise anywhere along the pathway from sound entering the ear to the point at which it is processed in the brain (Lieu, 2004). Because each step depends on the one before it, a disruption at any point may prevent the sound from reaching the area of the brain responsible for hearing — meaning the person may not hear the sound correctly, or at all (Oishi & Schacht, 2011).

Conclusion

Overall, deafness is considered a serious impairment by many people and not seen as being that serious by others. It just depends on the person who is asked the question — and often whether that person is deaf. People who were born deaf have no experience of hearing, and may not perceive the absence of hearing as a significant loss. Since they cannot experience what they are purportedly "missing," they are likely not missing it in any meaningful sense. Those who have had hearing in the past and have lost it, either partially or completely, may feel very strongly that they are missing something important. They can remember what they once experienced through hearing, and it is logical that they would miss some of that ability.

For those who can be helped through hearing aids or other means, it is entirely understandable that they would want something done to restore or at least improve their hearing so they can resume what they have known as a normal life. It is equally understandable that older individuals would seek hearing aids in order to maintain independent living. Losing one's hearing after a lifetime of being accustomed to it can make daily functioning extremely difficult, which means hearing aids and other assistive devices are critically important for quality of life in older populations. Given the wide range of factors that can cause hearing loss, it is essential that hearing aids remain accessible and that advances in technology continue to progress so that more people can receive effective help.

Kral, A., & O'Donoghue, G. M. (2010). Profound deafness in childhood. New England Journal of Medicine, 363, 1438–1450.

Lieu, J. E. (2004). Speech-language and educational consequences of unilateral hearing loss in children. Archives of Otolaryngological Head & Neck Surgery, 130(5), 524–530.

Oishi, N., & Schacht, J. (2011). Emerging treatments for noise-induced hearing loss. Expert Opinion on Emerging Drugs, 16(2), 235–245.

Robinson, D. W., & Sutton, G. J. (1979). Age effect in hearing — a comparative analysis of published threshold data. Audiology: Official Organ of the International Society of Audiology, 18(4), 320–334.