A hearing aid is a rehabilitative device that amplifies sound frequencies for those with hearing impairment. Not all people with hearing loss will require or benefit from a hearing aid. Appropriateness of hearing aid use for an individual is dependent on the type (conductive or sensorineural; Table 1)17 and severity18 (mild to profound; Table 2) of hearing loss.19 Hearing aids support improvement for varying degrees of hearing loss from mild to severe sensorineural hearing loss, which is caused by damage to the small sensory cells in the inner ear.
TABLE 1: HEARING LOSS BY TYPE
| HEARING LOSS TYPE | CONDUCTIVE | SENSORINEURAL | MIXED (CONDUCTIVE AND SENSORINEURAL) |
| Description | Sound is prevented from reaching the inner ear/cochlea. Can be caused by acute problems such as ear infections or ear wax, or by malformations of the outer or middle ear | Caused when the hair cells of the inner ear and/or cochlear nerve are damaged | Combination of conductive and sensorineural hearing loss |
| Treatment Protocol | Medical or surgical | May be managed using hearing technology (i.e. hearing aids) | Resolve conductive component medically and manage sensorineural component with hearing technology |
TABLE 2: HEARING LOSS BY SEVERITY
| SEVERITY OF HEARING LOSS | MILD | MODERATE | SEVERE | PROFOUND |
| Hearing Loss Threshold (can hear sounds louder than) | 40d.B. | 60d.B. | 80d.B. | N./A. |
| Relative distribution (%, million people) | / | 77% (359 million) | 20% (93 million) | 3% (14 million) |
| Description | Difficulty hearing soft speech, speech from distance or against a background noise | Difficulty hearing regular speech, even at close distances | May only hear very loud speech or sounds (e.g, sirens), but no conversational speech | May perceive loud sounds only as vibrations |
| Use of hearing aids appropriate? | Yes, in some cases, and depending on the type | Yes, depending on the type | Yes, but some cases may require cochlear implants | |
W.H.O. estimates that more than 72 million people worldwide would benefit from the use of hearing aids, but only 10% of those that need it have it, with coverage at less than 3% in L.M.I.C.s.20 This estimate is based on limited data and is considered by many experts to be an underestimate. The forthcoming World Hearing Report, which is expected to be published in 2020 by the W.H.O., will provide updated estimates of need.
Not all individuals with severe to profound sensorineural hearing loss will benefit from a hearing aid. When hearing aids are insufficient or do not provide expected benefit and in select circumstances, cochlear implants may be recommended. A cochlear implant is a medical device that consists of an external portion that sits behind the ear and an internal portion that consists of an electrode array and receiver/stimulator that must be surgically implanted. A cochlear implant bypasses the damaged portions of the ear to deliver sound signals directly to the auditory nerve. Hearing via a cochlear implant takes time to learn or relearn. While an important assistive technology, cochlear implants will not be a focus of this product narrative as they only benefit a tiny fraction of the population (less than 50,000 cochlear implants are sold globally each year) and are currently prohibitively expensive for L.M.I.C.s with costs for the device and surgery ranging from $40,000 to $100,000 per implant, require complex surgical and audiological care that is often not available in L.M.I.C.s yet..
For people with conductive hearing loss, for which hearing aids are not appropriate, medical treatments, such as antibiotic therapy or earwax removal performed by primary care healthcare workers or primary care physicians, or surgical treatments performed by Ear, Nose and Throat (E.N.T.) surgeons, may help resolve hearing issues. For example, W.H.O. estimates that 330 million of the 466 million people with disabling hearing loss suffer from chronic ear infections or chronic otitis media,21 which can be resolved medically. Once the conductive hearing loss has been resolved, patients may require a hearing aid in case of sustained damage to the ear.