Drinking Can Lead to Hearing Loss

Alcohol damages auditory pathways in the brain

MONDAY, March 15, 2004 (HealthDayNews) -- A new German study suggests drinking can cause some hearing loss, in a finding that's sure to fuel the debate on the health risks and benefits of alcohol.

While studies have shown moderate drinking can lower your risk for heart disease, excess alcohol can damage your liver and brain and increase your risk for certain cancers.

The new study finds that even moderate drinking can cause some degree of hearing loss by increasing the time it takes to process sound in the auditory brainstem. This nerve damage is caused by the long-term, cumulative effect of drinking, the researchers say.

"High, life-long alcohol consumption leads to damage in the central auditory cortex of the brain," says lead researcher Dr. Elisabeth Stephanie Smith, from the Ear, Nose and Throat Clinic at the University of Ulm.

The study appears in the March issue of Alcoholism: Clinical and Experimental Research.

In their study, the investigators looked at electrical currents in the brain called brainstem auditory evoked potentials (BAEPs), which are a measure of the brain's response to sound.

Smith's team measured BAEPs in 38 men -- 19 were head and neck tumor patients who were heavy drinkers, and 19 were plastic surgery patients who were moderate drinkers.

The men were asked to fill out a questionnaire on how much they drank and smoked. They also had blood and hearing tests before their BAEPs were measured.

While the researchers didn't administer subsequent hearing tests, they did find it took, on average, 2 to 4 milliseconds longer than normal for the brain to process sounds for all 38 men.

Kathleen C. M. Campbell, director of audiology research at Southern Illinois University, says it's not known what specific hearing difficulties these drinkers would notice.

However, she suspects they would have difficulty accurately hearing people who were speaking quickly. They might also have problems distinguishing one voice or sound from another in a setting where there was a lot of background noise, such as a party or sporting event.

Smith says, "Chronic alcohol consumption leads to defects of the central auditory brainstem, which cause delay in neurotransmission time." This finding "can be explained by the loss of white matter in the brain and delay in neurotransmission through the loss of neurotransmitters," she adds.

But because the damage to the auditory nerves adds up, even moderate drinkers can end up with as much nerve damage and hearing loss as heavy drinkers, Smith says.

Smith notes this type of hearing loss can also result from exposure to solvents such as toluol and benzene, and diseases such as multiple sclerosis or cerebellar angle tumors.

The importance of the new study is that "even an amount of alcohol consumption which is normally accepted by society can lead to a negative effect on the central auditory system," Smith says.

Dr. Jeffrey Harris, a professor and chief of otolaryngology at the University of California, San Diego, says "this is a very interesting article and adds additional credence to the accepted concept that alcohol is toxic to the central nervous system."

However, he adds, the patients with head and neck tumors may have caused the study's findings to be skewed because "treatments with radiotherapy and chemotherapy may have resulted in irreversible changes to the BAEPs."

"Nevertheless, it is well recognized that balance is greatly affected by long-term consumption of alcohol as well. So it would be expected that BAEPs would similarly have the same sensitivity to alcohol, even though it is in another site in the brain," Harris says.

More information

The National Institute on Deafness and Other Communication Disorders has more information on hearing loss. The National Institute on Alcohol Abuse and Alcoholism can tell you more about alcoholism.

SOURCES: Elisabeth Stephanie Smith, M.D., Ear, Nose and Throat Clinic, University of Ulm, Germany; Kathleen C. M. Campbell, Ph.D., director, audiology research, Southern Illinois University, Springfield; Jeffrey Harris, M.D., Ph.D., professor and chief, otolaryngology, University of California, San Diego; March 15, 2004, Alcoholism: Clinical and Experimental Research
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