Can vitamins and minerals prevent hearing loss?

Noise is an enemy of hearing, and it really doesn't take a lot of noise to damage hearing. About 10 million people in the United States alone —from troops returning from war to students with music blasting through headphones— are suffering from impairing noise-induced hearing loss.

The rising trend is something that researchers and physicians at the University of Michigan Kresge Hearing Research Institute are hoping to reverse, with a cocktail of vitamins and the mineral magnesium that has shown promise as a possible way to prevent hearing loss caused by loud noises. The nutrients were successful in laboratory tests, and now researchers are testing whether humans will benefit as well.

"The prevention of noise induced hearing loss is key," says Glenn E. Green, M.D., assistant professor of otolaryngology at the U-M Health System and director of the U-M Children's Hearing Laboratory.

"When we can't prevent noise-induced hearing loss through screening programs and use of hearing protection, then we really need to come up with some way of protecting people who are still going to have noise exposure. My hope is that this medication will give people a richer, fuller life."

The combination of vitamins A, C and E, plus magnesium, is given in pill form to patients who are participating in the research. Developed at the U-M Kresge Hearing Research Institute, the medication, called AuraQuell, is designed to be taken before a person is exposed to loud noises. In earlier testing at U-M on guinea pigs, the combination of the four micronutrients blocked about 80 percent of the noise-induced hearing impairment. This is the first NIH-funded clinical trial involving the prevention of noise-induced hearing loss."

If we can even see 50 percent of the effectiveness in humans that we saw in our animal trials, we will have an effective treatment that will very significantly reduce noise-induced hearing impairment in humans. That would be a remarkable dream," says co-lead researcher Josef M. Miller, Ph.D., the Lynn and Ruth Townsend Professor of Communication Disorders and director of the Center for Hearing Disorders at the U-M Department of Otolaryngology's Kresge Hearing Research Institute. Miller is leading the research along with colleagues at Karolinska Institute, where Miller also has an appointment; the University of Florida; and the University Castille de La Mancha.

Info at ScienceDaily

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Researchers Urge Caution When Buying Noisy Toys

From Science Daily

While Road Rippers Lightning Rods, Let's Rock Elmo and the I Am T-Pain musical microphone might be sought-after gifts this holiday season, parents should ensure that their children don't risk permanent hearing damage by misusing them.

Researchers from UC Irvine's Department of Otolaryngology measured the noise levels of two dozen popular toys in stores and purchased the 10 loudest for precise gauging in a soundproof booth at UC Irvine Medical Center. They found that all exceeded 90 decibels and several reached 100 or more, equivalent to the noise of a chain saw, subway train or power mower.

"Generally, toys are safe if used properly," said Dr. Hamid Djalilian, associate professor of otolaryngology and director of neurotology and skull base surgery. "We tested the sound levels at the speaker and again at 12 inches, which is about the length of a toddler's arm."

But problems can arise if a noisy toy is held too close to the ears, he said: "Children are very sensitive to loud and high-pitched sounds. Unfortunately, hearing loss from noise damage is permanent and not currently curable."

According to the American Academy of Otolaryngology, unprotected exposure to sounds above 85 decibels for a prolonged period can lead to hearing impairment. Two factors contribute to this, Djalilian noted: loudness and duration. The louder a sound is, the less time it takes to cause hearing loss.

He suggested that someone buying a noisy toy for a child pay attention to the speaker's location -- under the item is often better than on top. Djalilian also recommended that an adult hold the toy as a youngster would and listen to its sound. "If it hurts your ears," he said, "then it's probably too loud for a child."

Toys tested / Decibel level at the speaker / Decibel level 12 inches from the speaker:

• Road Rippers Lightning Rods / 108 / 68
• I Am T-Pain microphone / 101 / 64
• Tonka Mighty Motorized Fire Truck / 100 / 69
• Marvel Super Shield Captain America / 98 / 69
• Whac-A-Mole game / 95 / 69
• Tapz electronic reflex game / 95 / 65
• Sesame Street Let's Rock Elmo / 95 / 74
• VTech Magical Learning Wand / 94 / 69
• Toy Story Buzz Lightyear Cosmic Blaster / 93 / 60
• Green Lantern Colossal Cannon / 92 / 67

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Exposure to Secondhand Smoke Associated With Hearing Loss in Adolescents

Exposure to secondhand smoke (SHS) is associated with increased risk of hearing loss among adolescents, according to a report in the July issue of Archives of Otolaryngology-Head and Neck Surgery, one of the JAMA/Archives journals.

Among U.S. children, approximately 60 percent are exposed to SHS, according to background information in the article. Studies have associated exposure to secondhand smoke prenatally or during childhood with various health conditions, from low birth weight and respiratory infections to behavioral problems and otitis media. Children exposed to SHS are more likely to develop recurrent otitis media, the authors note. "Secondhand smoke may also have the potential to have an impact on auditory development, leading to sensorineural hearing loss (SNHL)," they add.

Anil K. Lalwani, M.D., and colleagues from NYU Langone Medical Center in New York City examined the risk factors for SNHL, including SHS, among adolescents, stratified by demographic groups. They included 1,533 individuals from 12 years to 19 years of age who participated in the National Health and Nutrition Examination Survey from 2005 to 2006. Participants were interviewed about their health status and family medical history, exposure to SHS, and self-recognition of hearing impairment. In addition, they underwent a physical examination, including blood testing for cotinine (a by-product of nicotine exposure), and hearing tests.

Compared with teens who had no SHS exposure, those who were exposed to secondhand smoke exhibited higher rates of low- and high-frequency hearing loss. The rate of hearing loss appeared to be cumulative, increasing with the level of cotinine detected by blood tests. The results also demonstrated that more than 80 percent of participants with hearing loss did not realize they had impairment.

As hearing loss early in life can cause problems with development and functioning, the authors suggest that these results have "significant implications for public health." They note that most adolescents do not receive screening for hearing loss in the absence of risk factors; if further studies replicate these results, they state, SHS could be considered one such risk factor. "Adolescents who are exposed to SHS may need to be more closely monitored for hearing loss," the researchers conclude. "In addition, they should be educated about risk factors for hearing loss, such as recreational or occupational noise exposure and SHS."

Info at Science Daily

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Gene Therapy for Hearing Loss Moves a Step Closer

Boston — Researchers have found long-sought genes in the sensory hair cells of the inner ear that, when mutated, prevent sound waves from being converted to electric signals, a fundamental first step in hearing. The researchers then restored these electrical signals in the sensory cells of deaf mice by introducing normal genes.

The study paves the way for a test of gene therapy to reverse a type of deafness, to be conducted by US and Swiss collaborators. Findings appear in the November 21, 2011 online issue of the Journal of Clinical Investigation.

Sound waves produce the sensation of hearing by jiggling protruding hair-like structures on sensory hair cells in the inner ear. Scientists have long believed that the hair cells carry a protein that converts this mechanical motion into electrical signals. While similar proteins have been identified for other senses, taste, smell, sight, researchers had been unable to find the critical protein required for hearing, in part because of the difficulty of getting enough cells from the inner ear to study.

The research team is co-led by Jeffrey Holt, PhD, Department of Otolaryngology at Children's Hospital Boston, and Andrew Griffith, MD, PhD, of the NIH's National Institute on Deafness and Other Communication Disorders (NIDCD).

"People have been looking for more than 30 years," says Holt, also a member of the F.M. Kirby Neurobiology Center at Children's Hospital Boston. "Five or six possibilities have come up, but didn't pan out."

Holt, Griffith, and colleagues found that two related proteins, TMC1 and TMC2, are essential for hearing. They make up gateways known as ion channels, which sit atop the stereocilia and let electrically charged molecules (ions) move into the cell, generating an electrical signal that ultimately travels to the brain.

The gene for TMC1 was previously shown by Griffith and NIDCD-funded collaborators to be mutated in both mice and humans with hereditary deafness. TMC2, the new study found, seems to have a redundant function and may compensate if TMC1 is defective.

The study also found that the same defects affect sensory hair cells in the vestibular system, which underlies the sense of balance. Although TMC1 mutations cause only hearing loss, not balance problems, in humans, mice with defects in both TMC1 and TMC2 are deaf and fail balance tests requiring them to navigate a rotating rod.

The investigators then engineered an adenovirus to carry normal copies of TMC1 or TMC2 into the inner-ear hair cells of mice that had mutations in both genes. Using special techniques developed in Holt's lab, they recorded electrical responses to noise in the sensory hair cells when either TMC1 or TMC2 was added back, where before there had been none. "This is the first time anything like this has been done," says Holt.

But does restoring the electrical response translate into restoration of hearing? Holt and collaborators at the Ecole Polytechnique Federale de Lausanne (EPFL) in Switzerland recently received a $600,000 grant for a gene-therapy trial in mice. The researchers will deliver genes to the inner ear and measure whether electrical signals can be detected in the 8th cranial nerve and whether the animals respond to sound. EPFL will supply newer, safer gene-delivery vectors for testing that could potentially be developed for human trials.

According to the NIDCD, about one in 300 to 500 newborns are born deaf or hard-of-hearing, and it's believed that about half of cases have genetic causes. About 60 genes, including TMC1, are known to be associated with human deafness.

Yoshiyuki Kawashima, Gwenaelle S.G. Geleoc and Kiyoto Kurima were co-first authors. Holt, formerly at the University of Virginia, and Griffith were co-senior authors.

Source: Hearing Review

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