When teenagers use the excuse that they didn't hear you, they could be telling the truth.  More than 6 million teens in the United States have some hearing loss.

New research of national health data on adolescents finds that one in five teens has some hearing loss, an astonishing jump of 31% in the last decade.  The obvious culprit would appear to be MP3 and other personal music players, used with ear buds inserted inside the ear. However, researchers aren't ready yet to put the blame solely on these devices yet.

Dr. Josef Shargorodsky, Ear, Nose and Throat Specialist, Channing Laboratory at Brigham and Women's Hospital and Massachusetts General Hospital along with a team, studied cross-sectional analyses of US representative demographic and audiometric data from the 1988 - 1994 and 2005 - 2006 time periods collected by the government's National Health and Nutrition Examination Survey (NHANES).

There are many contributing factors associated with the type of damage researchers found.  After adjusting data for age, race andexposure to infections that can impair hearing by damaging auditory nerves, researchers could not place full responsibility on one particular cause.

Some audiologists believe the causes may be related to an increase in certain genetic disorders, or the fact that premature babies, who are often more susceptible to hearing loss as they get older, have better survival rates than ever before.

Excessive volume, no matter what the cause, street noise, tools, yard/garden equipment, live music or earphones, as well as diet and nutrition, and exposure to toxins have been linked to damaging delicate auditory nerves resulting in hearing loss. 

Children in lower-income families may not get adequate nutrition to support proper development of the auditory system.

In most states across the US, infants have their hearing tested at birth and some pediatricians inquire about and informally check a child's hearing at regularly scheduled 'well visits.'   Considering that some insurance companies do not cover 'well visits', a lot of children only see a physician when they are sick which could in itself alter an informal hearing check due to stuffiness, ear ache or general grumpiness associated with being sick.

Most elementary schools perform hearing screenings as well, but from that point on, it is up to the child to report hearing problems, or parents, teachers or doctors to recognize that something is wrong if a child's schoolwork is suffering, they show no response when their name is called or can't seem to keep up with conversations in a noisy environment.

The inability to hear very soft sounds or certain consonants is consider to be 'slight' hearing loss.  Of the participants, 5.3%  suffered 'mild' hearing loss, missing entire words spoken at a normal volume.

Classrooms are often a noisy, chaotic environment, and audiologists estimate there to be one or two students in each class with significant hearing loss.  These students would likely not be able to participate in classroom discussions or follow lectures.

"If they're not hearing everything that's being said, they might not be able to fill in the blanks," said Dr. Jody Winzelberg, Audiologist and Director of Rehabilitation Services, Packard Children's Hospital. "Classrooms do not have the best signal-to-noise ratio. A hearing loss is going to add to that difficulty to hear and learn."

Partipants in the study didn't report having more exposure to loud noises over time, although  teenagers are notoriously inaccurate in determining what's "loud", especially in relation to music. 

"I'm sure they do not readily recognize the symptoms of noise exposure - the ringing in their ears, or feeling like your hearing is deadened or numbed down," Winzelberg said. "We're really working on educating children as to the dangerous side effects of being exposed to noise."

One of the best things parents can do to protect their children's hearing is to be mindful of the volume level when they are listening with earphones (if you can hear it from three feet away, it's too loud).  Encourage listening breaks, such as no earphones at the dinner table or during other set times.  Let them know that protecting hearing is important for both you and them by example; wearing ear protection while mowing the lawn or using power tools. 

The American Speech-Language-Hearing Association (ASLHA) has a wealth of information regarding hearing loss in children and the effect it has long term. 

 "It is well recognized that hearing is critical to speech and language development, communication, and learning. Children with listening difficulties due to hearing loss or auditory processing problems continue to be an underidentified and underserved population."

"The earlier hearing loss occurs in a child's life, the more serious the effects on the child's development. Similarly, the earlier the problem is identified and intervention begun, the less serious the ultimate impact."

There are four major ways in which hearing loss affects children--

       1. It causes delay in the development of receptive and expressive communication skills
      2. The language deficit causes learning problems resulting in reduced academic achievement.
       3. Communication difficulties often lead to social isolation and poor self-concept.
       4. It may have an impact on vocational choices.

Specific Effects:

Vocabulary

    * Vocabulary develops more slowly in children who have hearing loss.
    * Children with hearing loss learn concrete words like cat, jump, five, and red more easily than abstract words like before, after, equal to, and jealous. They also have difficulty with function words like the, an, are, and a.
    * The gap between the vocabulary of children with normal hearing and those with hearing loss widens with age. Children with hearing loss do not catch up without intervention.
    * Children with hearing loss have difficulty understanding words with multiple meanings. For example, the word bank can mean the edge of a stream or a place where we put money.

Sentence Structure

    * Children with hearing loss comprehend and produce shorter and simpler sentences than children with normal hearing.
    * Children with hearing loss often have difficulty understanding and writing complex sentences, such as those with relative clauses ("The teacher whom I have for math was sick today.") or passive voice ("The ball was thrown by Mary.")
    * Children with hearing loss often cannot hear word endings such as -s or -ed. This leads to misunderstandings and misuse of verb tense, pluralization, nonagreement of subject and verb, and possessives.

Speaking

    * Children with hearing loss often cannot hear quiet speech sounds such as "s," "sh," "f," "t," and "k" and therefore do not include them in their speech. Thus, speech may be difficult to understand.
    * Children with hearing loss may not hear their own voices when they speak. They may speak too loudly or not loud enough. They may have a speaking pitch that is too high. They may sound like they are mumbling because of poor stress, poor inflection, or poor rate of speaking.

Academic Achievement

    * Children with hearing loss have difficulty with all areas of academic achievement, especially reading and mathematical concepts.
    * Children with mild to moderate hearing losses, on average, achieve one to four grade levels lower than their peers with normal hearing, unless appropriate management occurs.
    * Children with severe to profound hearing loss usually achieve skills no higher than the third- or fourth-grade level, unless appropriate educational intervention occurs early.
    * The gap in academic achievement between children with normal hearing and those with hearing loss usually widens as they progress through school.
    * The level of achievement is related to parental involvement and the quantity, quality, and timing of the support services children receive.

Social Functioning

    * Children with severe to profound hearing losses often report feeling isolated, without friends, and unhappy in school, particularly when their socialization with other children with hearing loss is limited.
    * These social problems appear to be more frequent in children with a mild or moderate hearing losses than in those with a severe to profound loss.

What You Can Do

Recent research indicates that children identified with a hearing loss who begin services early may be able to develop language (spoken and/or signed) on a par with their hearing peers. If a hearing loss is detected in your child, early family-centered intervention is recommended to promote language (speech and/or signed depending on family choices) and cognitive development. An audiologist, as part of an interdisciplinary team of professionals, will evaluate your child and suggest the most appropriate audiologic intervention program.

To find an audiologist in your area, contact the American Speech-Language-Hearing Association (ASHA) by calling 800-638-8255 or use the  Find a Professional service on ASHA's Web site (www.asha.org).

Laura Lamp King