Audiology & Hearing Aids: Hearing Loss

Understanding hearing loss


	More than 28 million Americans have a hearing loss
	By age 65, approximately half of the U.S. population has a hearing loss
	The average delay between the onset of hearing loss and seeking a professional diagnosis is five to seven years


	Why the Delay in Diagnosis?

	People often think it is not their hearing, but others not speaking clearly. They may make excuses, or wait for their doctor to recommend a hearing test. Sometimes, if the loss occurs gradually, it may not be as obvious.


	Common Signs of Hearing Loss

	Hearing well in private settings, but not in groups
	Playing the TV or radio louder than others prefer
	Becoming sensitive to increases in volume
	Experiencing ringing in the ears
	Complaining that "people mumble"
	Missing out on conversations


	Psychological Impact of Hearing Loss

	People with hearing loss that goes untreated suffer many negative effects. Compared to those who use hearing aids, they are more likely to report...

	Isolation and Reduced Social Activity
	Avoiding things they once enjoyed - the restaurant is too noisy, they can't hear the church service, family gatherings are uncomfortable because everyone tends to talk at once.

	Worry and Anxiety
	Fearing they may miss information or safety warning signals - and these concerns are very real - a smoke alarm, a physician's instructions, a 9-1-1 operator, or an intruder in the home.

	Sadness and Depression
	Going through the stages of grief before accepting the situation and seeking help - denial, projection, anger, depression, and finally acceptance.

	Untreated hearing loss is a serious and prevalent problem. Denial is the greatest barrier to hearing aid use; most hard of hearing persons who don't wear hearing aids think they don't need them, or can get by without them. Cost considerations and vanity are also barriers for many.


	Impact on Family and Friends

	Hearing loss affects the whole family; communication is a key part of maintaining healthy relationships with people you care about. A person with hearing loss might think they are "getting by" guessing at words they miss - but these guesses are often incorrect - leading to a range of reactions from laughter, to confusion, to anger.

	If a person with hearing loss withdraws socially, ultimately the whole family misses out. Family and friends may perceive this as meaning they are not important or being avoided.

	Families should be aware of the potential consequences of untreated hearing loss, as well as the benefits of hearing aids and other options. If you suspect a relative has a hearing loss, encourage them to get an evaluation.


	Benefits of Treatment

	Individuals whose hearing loss is treated show significant improvements in the quality of their lives. With hearing aids, they enjoy improvements in their relationships at home, with children and grandchildren, and in their confidence, independence, and life outlook. They are more involved socially and in their communities, and report feeling greater security and positive mental health. Family members tend to observe all of these benefits to an even greater degree.

	Study conducted by the Seniors Research Group, an alliance between the National Council on the Aging (www.ncoa.org) and Market Strategies Inc.


	About the Ear

	Sound is vibration. Sound travels as vibrations through the air. When these vibrations reach the outer ear, this is the beginning of hearing. The ear has four main parts: the outer ear, the middle ear, the inner ear, and beyond the inner ear (retro-cochlear).

	Outer Ear
	The outer ear consists of the external ear (pinna), the ear canal (external auditory meatus) and the ear drum (tympanic membrane). The outer ear directs sound into the ear canal and carries it to the eardrum. When these sound vibrations reach the eardrum, the eardrum begins to vibrate.

	Middle Ear
	The middle ear contains the three smallest bones in the body: the malleus, incus and stapes. They conduct sound through the air-filled middle ear to the inner ear. These bones are known as the "ossicles" and are connected to form the "ossicular chain". The "handle" of the malleus is embedded in the ear drum while the other end is joined to the incus. The incus in turn is connected to the stapes which rocks in and out of the oval window of the cochlea of the inner ear. The oval window moves at the same vibration rate as the eardrum. The eustachian tube, which equalizes pressure between the ear and the environment, is also found in the middle ear.

	Inner Ear
	The inner ear, the end organ of hearing, contains both the cochlea and the vestibular system. The snail-shaped cochlea contains approximately 3,500 inner hair cells, and 9,000-12,000 outer hair cells. These hair cells connect to approximately 24,000 nerve fibers which are essential for hearing. The rocking of the stapes in the oval window moves fluid within the cochlea causing a "shearing" action or movement of the hair cells.

	The vestibular system works to keep the body balanced.

	Beyond the Inner Ear (Retro-Choclear)
	The "shearing" motion, stimulating the hair cells, sends impulses beyond the cochlea, to the auditory (VIIIth) nerve. The auditory nerve carries the information to the brain, via the brainstem, for decoding or giving meaning to the sound. There are auditory centers along the brainstem and in the brain which interpret the stimulus enabling the person to understand what is being heard. If these parts of the brain are badly damaged, a person may not be able to understand any sound even though the auditory nerve has transmitted it to the brain.


	Types of Hearing Loss

	There are four types of hearing loss: conductive, mixed, sensorineural, and retro-cochlear.

	Conductive Hearing Loss
	Conductive hearing loss is caused by a problem in the outer or middle ear, including eustachian tube malfunction or a defect in the ossicular chain. In most cases, conductive hearing loss affects the lower frequencies and makes it difficult for the ear to hear vowel sounds and interpret the slight differences among them. Since vowels contain the "power of speech" the person perceives speech and other sounds as being much "quieter" than normal. If the sound is loud enough, a person with a conductive hearing loss can hear and understand clearly, thereby making them a good hearing aid candidate. Conductive hearing loss can often be medically treated. If a conductive hearing loss is not treated, it can sometimes lead to permanent damage of the inner ear.

	Sensorieneural Hearing Loss
	Sensorineural hearing loss is the most common type of hearing loss and is caused by damage to the inner ear and/or the auditory nerve. Noise exposure, diseases, certain medications and aging can destroy parts of the inner ear and cause permanent hearing loss. Once damaged, the inner ear cannot be repaired. A "cochlear implant" is available for some who have a profound hearing loss and do not gain benefit from conventional hearing aids.

	With sensorineural hearing loss, the entire cochlea is seldom damaged. If a sound is loud enough, a person with inner ear damage may hear something. The undamaged parts of the cochlea transmit sound to the auditory nerve and on to the brain, however the sound may be distorted. Distortion occurs when the cochlea changes the sound in some way. Sensorineural hearing loss is also characterized by a lower tolerance to loud sounds. Sensorineural hearing loss usually affects the high frequencies the most, which impairs a persons ability to differentiate consonant sounds.

	Mixed Hearing Loss
	When a person has both a conductive hearing loss and a sensorineural hearing loss, it is called a mixed hearing loss. For example, if a child who has a permanent sensorineural hearing loss gets a middle ear infection, the effects of the two types of hearing loss combine to create a greater hearing loss.

	Retro-Cochlear Hearing Loss
	When a person has a sensorineural hearing loss, particularly a unilateral hearing loss, the problem may be beyond the inner ear, somewhere in the brainstem. An acoustic tumor may be involved and may lie on the auditory nerve, brainstem or in the brain. Surgical intervention is most often warranted. Retro-cochlear hearing loss is noted by inconsistencies on the audiogram, such as poorer speech recognition ability than the pure tones indicate, especially at loud presentation levels.