Wednesday, July 31, 2002

Common causes of nerve hearing loss

Although hearing loss can occur at any age, it is one of the most common problems in the over-50 population, affecting about 15 percent of the 45-64 year-old group. Only arthritis and hypertension are more common.

Men are more likely to have hearing loss (although women are more likely to get help for their hearing). One university study suggests that hearing loss is the most common untreated problem in men and women over 50 years of age.

The following are the most common causes of sensorineural ("nerve") hearing loss:

Presbycusis. The aging process is the most common cause of hearing loss. The typical loss is a bilateral, sensorineural hearing loss that develops so slowly that the individual often doesn't notice the change in hearing. Generally, hearing for higher frequencies is affected more, leading to a decline in speech understanding ("I can hear but I can't understand"). Ironically, the loss may be accompanied by an increased sensitivity to loud sounds.

Noise. Exposure to moderate levels of noise over a long period of time, or to brief high-intensity sounds, can lead to sensorineural hearing loss. As with presbycusis, the loss usually develops very gradually, although instantaneous loss can occur from sudden high-impact sounds, such as an explosion. The loss is often accompanied by tinnitus (ringing, hissing or other noises in the ear). Sources of toxic noise levels include hunting, lawnmowers, motorcycles and personal stereo headsets. Music, whether Bach or rap, is also a common cause of noise-induced hearing loss and professional musicians have a higher incidence of hearing loss than the general population.

Genetics. Inherited sensorineural hearing loss can occur at any age, from birth to adulthood. The genetic cause can be either recessive or dominant. In cases of recessive hereditary hearing loss, both parents may be carriers of the gene, but not have hearing loss themselves. The loss may be progressive, but often stabilizes at a certain level.

Sensorineural hearing loss is one of the easiest to correct with hearing aids. About 95 percent of people who get help for their hearing loss have nerve damage or sensorineural hearing loss.

Andrew Waits

Clinical audiologist