http://www.timesnews.net/communityArticle.dna?_StoryID=3606543

Tumor growth related to exposure to noise

Thursday, March 02, 2006

By DANIELLE TOUSINAU

Columnist

The eighth cranial nerve has two branches, one that is responsible for

balance and one that is responsible for hearing sensitivity.

An acoustic neuroma is a non-cancerous tumor that grows on the eighth

cranial nerve. The tumor typically grows very slowly and affects only one

ear.

Symptoms are not generally noticed until the tumor is large enough to puts

pressure on nerves, causing the symptoms, including hearing loss, tinnitus,

and facial weakness or numbness on the affected side, as well as dizziness

or balance problems.

Acoustic neuromas that are large enough to cause symptoms occur in 1 to 20

people out of 100,000 people each year. Most acoustic neuromas are diagnosed

in people between 30 and 60 years old. Acoustic neuromas are fairly rare,

accounting for 8 percent of all tumors that develop inside the skull.

Most people are aware that exposure to loud noise can cause hearing loss and

tinnitus. A new study shows that years of repeated exposure to loud noise

can also increase the risk of developing acoustic neuromas.

On average people who were routinely exposed to loud noise were one and a

half times more likely to develop this type of tumor compared to people who

were not exposed to noise on a regular basis.

These findings are based on a four-year retrospective review of a Swedish

study. Participants in the study ranged in age from 20 to 69. All

participants were asked if they were regularly exposed to occupational or

non-occupational loud noise. Noise was defined as a sound level of 80

decibels, which is the approximate sound level of city traffic.

If participants were exposed to loud noise, they were asked to categorize

the type of noise source. They were also asked to indicate the duration of

noise exposure in years and whether or not hearing protection devices were

ever utilized.

Noise sources were defined by the following four categories: exposure to

machines, power tools, or construction noise; exposure to motors, including

airplanes; exposure to loud music, including employment in the music

industry; and exposure to screaming children, sports events, or

restaurants/bars.

The degree of risk of developing an acoustic neuroma depended on the type of

noise source involved. According to the study, exposure to music created a

2.25 increase in the risk of developing an acoustic neuroma; exposure to

machines/power tools/construction created a 1.8 increase in the risk;

exposure to children/sports events/bars created a 1.4 increase; and exposure

to motors created a 1.3 increase in the risk of developing an acoustic

neuroma.

The number of years that a person was exposed to any category of loud noise

also contributed to the risk of development of an acoustic neuroma. The

greater the number of years that a person was exposed to loud noise the

greater the person's risk of developing a neuroma.

Five years of regular exposure to loud noise increased the chance that a

person would develop an acoustic neuroma by one and a half times.

The study also showed that it is important to wear hearing protection when

exposed to loud noise. People who reported that they used hearing protection

when they were exposed to loud noise had about the same risk of developing

acoustic neuroma as people who were not exposed to loud noise.

While this study does have limitations, the importance of utilizing hearing

protection when exposed to loud noise is once again emphasized.