The Scripps Research Institute (TSRI) undertakes basic biomedical research, primarily in laboratory settings, to learn how the human body operates on all levels. Our discoveries are often licensed to biotechnology or pharmaceutical firms for further development toward a drug or treatment. As a nonprofit biomedical research institute, we do not see patients and rarely conduct clinical trials; for the latest information on clinical trials throughout the United States, visit www.clinicaltrials.gov. For information on specific diseases, search for associations or organizations dedicated to the disease, for example, the American Speech-Language-Hearing Association and the National Association of the Deaf.
Hearing loss may result from damage or disruption to any part of the hearing system from simple wax blocking the ear canals, through to age-related changes to the sensory cells of the cochlea, to damage to the brain.
Hearing loss can be mild, moderate, severe, or profound. People with mild hearing loss may find it hard to follow speech, particularly in noisy situations. Those with moderate deafness have difficulty following speech without a hearing aid. The severely deaf rely primarily on lip-reading, even with a hearing aid. Profoundly deaf people may communicate by lip-reading, and Sign Language may be their first or preferred language.
Hearing loss occurs primarily when the inner ear or auditory nerve is damaged or when sound waves cannot reach the inner ear. Untreated, hearing problems can get worse. Possible treatments include hearing aids, cochlear implants, special training, certain medicines, and surgery. According to the World Health Organization, half of all cases of deafness and hearing impairment are avoidable through prevention, early diagnoses, and management.
According to the National Institute on Deafness and Other Communication Disorders (NIDCD), common causes of deafness in adults include:
In addition, certain diseases can lead to hearing loss, including:
Common causes of deafness in children include:
Presbycusis, the loss of hearing that gradually occurs in most individuals as they grow older, is usually greater for high-pitched sounds. For example, it may be difficult for someone to hear the nearby chirping of a bird or the ringing of a telephone. However, the same person may hear clearly the low-pitched sound of a truck rumbling down the street. Presbycusis most often occurs in both ears, affecting them equally. Because the process of loss is gradual, people who have presbycusis may not realize that their hearing is diminishing.
Another common hearing impairment, tinnitus, is commonly described as a ringing in the ears, but it also can sound like roaring, clicking, hissing, or buzzing. The sound may be soft or loud, high-pitched or low-pitched and heard in either one ear or both. Tinnitus is a symptom that something is wrong in the auditory system, which includes the ear, the auditory nerve that connects the inner ear to the brain, and the parts of the brain that process sound. Tinnitus is sometimes the first sign of hearing loss in older people. It also can be a side effect of medications. In 2010, according to NDICD, experts estimated 22.7 million adult Americans experienced tinnitus for more than three months, roughly 10 percent of the U.S. adult population.
The Hearing Loss Association of America estimates one in three people older than 60 and half of those older than 85 have hearing loss.
According to the NIDCD, two to thee children out of every 1,000 in the United States are born deaf or hard-of-hearing; nine out of every 10 children born deaf are born to parents who can hear, and approximately 15 percent of Americans (26 million) between the ages of 20 and 69 have high frequency hearing loss due to exposure to loud sounds or noise at work or in leisure activities.