Who is affected by hearing loss?
Hearing loss is the most common physical disability in the whole wide world. In the United States alone, about 28 million people have some level of hearing impairment that interferes with their ability to understand normal speech and participate in conversations. Another 2 million cannot hear at all. Age is the most common factor in increasing hearing loss. About 30 percent of people between 65 and 74 experience some difficulty in hearing. That percentage and the severity of the loss increase with age. Younger people can develop hearing loss as well. Fourteen percent of people between the ages of 45 and 65, and another 8 million people between 18 and 44, suffer from some form of hearing impairment. A nationwide study that tested 6,166 children ages 6 to 19 estimated that 7 million children have some degree of hearing loss. What are the major types of hearing loss?
There are two major types of hearing loss:
Conductive is related to how the ear gathers sound.
Sensorineural is related to how the nervous system transmits that sound to the brain. Conductive
The outer ear gathers sound waves from the environment and funnels them into the ear canal. At the end of the canal, the waves hit the eardrum, causing it to vibrate. Three tiny bones in the middle ear conduct the vibrations from the eardrum to the cochlea (a spiral-shaped chamber that looks a bit like a snail) in the inner ear. If anything interferes with the transfer of sound waves up to this point, the resulting type of hearing loss is called conductive.Conductive hearing loss may be temporary or permanent. It can be caused by something as simple as a buildup of earwax or an ear infection. Sensorineural
Problems ahead of this point lead to sensorineural hearing loss, also known as nerve deafness. Normally, the vibrations from the middle ear create waves in the fluid inside the cochlea. The waves in turn stimulate thousands of delicate hair cells that line the cochlea. Their movement makes nerve impulses in the auditory nerve, which lies just beyond the cochlea and carries the impulses to the brain. Ultimately, the brain interprets and makes sense of sound, distinguishing and giving meaning to words, music and everything else we hear. Anything that damages the hair cells or blocks the transmission of the nerve impulses can lead to sensorineural hearing loss. Sensorineural hearing loss, which is almost always permanent and far more common than conductive, is most often caused by presbycusis, a form of age-related hearing loss that destroys hair cells. Prognosis
Surgical procedures and medications can normally treat conductive hearing loss, but only rarely can they help people with sensorineural hearing loss. Even so, most people with hearing loss can be helped by hearing aids. Causes
Presbycusis: age-related hearing loss
The most common cause of sensorineural hearing loss (also known as nerve deafness) is age-related and called presbycusis. It typically begins in the 40s and gradually grows worse. Normal wear and tear that comes with age destroys the tiny hair cells that line the cochlea. This route interrupts the transportation of sound waves to the inner ear and auditory nerve. Presbycusis is more common in men than women; it first affects a person's ability to hear high-frequency sounds. If we start noticing that it is increasingly difficult to tell the difference between certain sounds such as "th" and "sh" or understand women and children, who tend to have higher pitched voices, we may be showing the first signs of presbycusis. Having trouble hearing conversations on the telephone is also common. Researchers have determined the condition has a genetic or hereditary link. If one or both of the parents suffer from it, chances are higher that the child will, too. Noise
Long exposures to loud noise also can destroy the sensitive hair cells of the cochlea. High-pitched noises are the worst. Otitis media and other infections...
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