Hearing loss

New Zealand researchers agree: hearing loss is probably a dementia risk factor

By Daniel Fink, MD, Chair, The Quiet Coalition

Many people don’t understand the process of medical and scientific research and how different hypotheses are developed and tested, using different methods in different human populations with animal studies when possible, until a consensus is reached. This was how researchers–including doctors, epidemiologists, researchers using animal models, and scientists doing basic research at the cellular, molecular, and genetic levels–figured out that cigarette smoke causes cancer and many other diseases, and how it does this. Despite the broad scientific and public health consensus, there are still skeptics, such as those at the conservative Heartland Institute, who say there is still doubt about whether smoking causes lung cancer. There is also a Flat Earth Society. Many Americans think that evolution is an unproven theory despite more than a century of research and strong evidence supporting evolution.

For the rest of us who believe in evidence-based science and evidence-based social and economic policies, our understanding of reality is always evolving based on the evidence. Sometimes something long thought to be true is found not to be correct after all. In medicine, one of the best examples may be ulcers in the stomach and small intestine, which for decades were thought to be caused by too much stomach acid but were found to be caused by bacteria. Australians Barry Marshall and J. Robin Warren won the Nobel Prize in 2005 for making this discovery. But most of the time an early hypothesis is confirmed by one study, and then another, and then by studies in animal models, and then by basic science research, until a broad consensus is reached.

This is what is happening with the hypothesis that hearing loss is associated, probably causally, with dementia. Dr. Frank Lin at Johns Hopkins University may be the best-known researcher in this field but other researchers in other countries are studying the same question. This report from New Zealand discusses what is being done there. And this report from the UK discusses research presented there.

It’s always good to have confirmation of research by different researchers using different techniques in different populations. Such confirmation helps validate initial findings in one population and help move our understanding forward. We know that noise exposure causes hearing loss. If hearing loss is shown to be causally associated with the development of dementia, then preventing hearing loss should help to also prevent dementia. One theory is that they brain needs input to maintain function, and without auditory input and/or social connections, brain function declines. Another theory is that whatever degenerative process causes hearing loss also causes loss of mental function. Ongoing studies, providing hearing aids to those with hearing loss but not to others and then measuring intellectual function over time, may elucidate the cause-effect relationship. Regardless, we don’t need to wait for more evidence for the link. Preserving one’s hearing should be enough reason to avoid loud noise or to wear ear plugs if you can’t.

Dr. Daniel Fink is a leading noise activist based in the Los Angeles area. He serves on the board of the American Tinnitus Association, is the interim chair of Quiet Communities’s Health Advisory Council, and is the founding chair of The Quiet Coalition, an organization of science, health, and legal professionals concerned about the impacts of noise on health, environment, learning, productivity, and quality of life in America.

New drug may prevent hearing loss after noise exposure

By Daniel Fink, MD, Chair, The Quiet Coalition

For many years, a body of research has shown that chemicals with antioxidant properties might prevent or reduce hearing loss after noise exposure. In animals, noise exposure reduces levels of a chemical called glutathione peroxidase 1 (a naturally occurring enzyme). A recent report in the British journal The Lancet looks at how a similar chemical, ebselen, works in helping to reduce “both temporary and permanent noise-induced hearing loss in preclinical studies.”

It appears to work quite well.

Of course, we at The Quiet Coalition think it’s better just to avoid loud noise exposure, which is 100% safe and effective at preventing hearing loss. That said, the experimental protocol raises interesting questions about research ethics. Namely, the study tested the efficacy of different doses of ebselen after the subjects, healthy adults aged 18–31 years, were exposed to loud sound. The measure of ebselen’s success was the prevention of a phenomenon called temporary threshold shift (TTS), more completely noise-induced temporary threshold shift (NITTS). This audiometric measure has been used for decades to measure the impact of noise on humans.

Unfortunately, recent research, beginning with a 2009 report and updated last year describes a phenomenon called “hidden hearing loss,” a synaptopathy (injury to the synapses in the cochlea) caused by noise exposure. Hidden hearing loss is called that because it is not detected by standard audiometric techniques. Hidden hearing loss is the likely cause of being unable to follow one conversation among many in a noisy environment, or having a normal or near-normal audiogram but still having difficulty understanding speech.

Many experts think that there is no temporary auditory damage. That is, TTS is a real phenomenon but the use of the word “temporary” is misleading because if TTS occurs then it is likely that permanent auditory damage has also occurred.

In this study, healthy young adults were exposed to noise levels loud enough and long enough to cause TTS, likely indicating permanent auditory damage. Some of the subjects were given large enough doses of the experimental drug ebselen to prevent TTS from occurring, but whether the drug would or wouldn’t work, and at what dosage, wasn’t known when the study began. Simply put, the study exposed all subjects to the threat of auditory damage, and most likely caused auditory damage in the subjects who received the placebo or didn’t get a high enough dose of the experimental drug.

All research protocols in the U.S. must pass review by an Institutional Review Board (IRB) which must make certain that steps are taken to prevent harm to research subjects.. Under the Helsinki Declaration of the World Medical Association, and in the United States under what is called the federal “Common Rule” (45 CFR §46 et seq.), human subjects must be protected. If there is a risk of permanent auditory damage when the phenomenon of TTS is observed–and Drs. Liberman and colleagues certainly think that temporary auditory changes denote permanent auditory damage–we think the IRB should have done more to protect the subjects from any possibility of harm.

How could a study that exposes young people to noise levels loud and long enough to cause TTS pass IRB review? We hope the federal Office for Human Research Protections will let us know.

Dr. Daniel Fink is a leading noise activist based in the Los Angeles area. He serves on the board of the American Tinnitus Association, is the interim chair of Quiet Communities’s Health Advisory Council, and is the founding chair of The Quiet Coalition, an organization of science, health, and legal professionals concerned about the impacts of noise on health, environment, learning, productivity, and quality of life in America.

Judge denies NYPD’s motion to dismiss sound cannon lawsuit

Photo credit: Peter Bergin licensed under CC BY-SA 2.5

Mark Chiusano, AMNewYork, writes about the New York Police Department’s use of long range acoustic devices on people who were protesting against “the non-indictment of Daniel Pantaleo, the police officer involved in the death of Eric Garner on Staten Island.” One protester, Anika Edrei, ran after hearing a crash that sounded like a bottle shattering near the crowd, but then Edrei heard “a different sound,” one which sounded like a very loud car alarm. How loud? “Another listener described it as the loudest noise he’d ever heard.”

Edrei saw two police officers carrying “a bulky appliance,” which was a long range acoustic device (LRAD). LRADS can be used as a loudspeaker, but they also generate “sharper, high decibel “alert” or “deterrent” tones intended to control a crowd.” Chiusano reports that the police’s use of the sharper, high decibel tone on the crowd was “one of the first times the police reportedly used the tone.” Edrei and others claim that they suffered injuries due to the exposure to that tone.

LRADs are military devices that were developed after the 2000 bombing of the U.S.S. Cole in Yemen, but Chiusano writes that the devices “made their way to some police departments, too.” The NYPD purchased two LRADs before the 2004 Republican National Convention.

Edrei and others at the protest have sued the NYPD for injuries they claimed to have sustained from exposure to the LRADs, asserting that after exposure they developed migraines, sinus pain, dizziness, facial pressure, and ringing in their ears. Chiusano notes that:

[I]nternal NYPD documents available so far appear to lend weight to the plaintiffs’ claims. A 2010 document from the department’s Disorder Control Unit says the device’s alternate function can emit sounds at higher levels “than are considered safe to human ears. In this dangerous range (above 120 decibels), the device can cause damage to someone’s hearing and may be painful.

Chiusano reports that the judge “appeared convinced of the possibility of danger, finding a ‘cognizable claim’… that use of the LRAD had constituted excessive force.” As a result, the federal lawsuit will continue, while “the conclusion of a separate lawsuit in June requires the police, in part, to release certain documents about current LRAD training and usage procedures.”

It is disgraceful that a U.S. police department would use a device that can permanently injure its victims on citizens engaging in their First Amendment right to protest.

“Baby Driver” highlights the problems of tinnitus

Photo credit: leadfoot licensed under CC BY 2.0

Daniel Fink, MD, Chair, The Quiet Coalition

I am not a moviegoer although my wife would say I am a movie critic, but I can’t comment on the new movie “Baby Driver” because I haven’t seen it. What I can say, based on movie reviews and this online article, is that the lead character has tinnitus from head trauma in a motor vehicle crash, and he plays music constantly to mask it.

Although there are many causes of tinnitus, the most common cause is noise, with a strong correlation between noise-induced hearing loss and tinnitus. Most people with tinnitus have at least some hearing loss, and half of people with hearing loss have tinnitus.

So, movie conventions aside, what’s the best way to avoid developing tinnitus? It’s simple–avoid loud noise and wear hearing protection if you can’t.

Dr. Daniel Fink is a leading noise activist based in the Los Angeles area. He serves on the board of the American Tinnitus Association, is the interim chair of Quiet Communities’s Health Advisory Council, and is the founding chair of The Quiet Coalition, an organization of science, health, and legal professionals concerned about the impacts of noise on health, environment, learning, productivity, and quality of life in America.

 

Hearing Restoration: A Step Closer?

Photo credit: Ronna Hertzano et al. licensed under CC BY 2.5

By Daniel Fink, MD, Chair, The Quiet Coalition

A recent report that scientists in Boston have caused human hair cells to regrow in the laboratory is exciting news, holding out the promise of hearing restoration in the future.

But it is important to remember two facts:

1. Development and then approval of this technology for human use are likely to be years if not decades in the future, and the technology will most likely be very expensive.

2. Noise-induced hearing loss is 100% preventable and prevention is either free or inexpensive: avoid loud noise exposure and use hearing protection (ear plugs or ear muffs) if one can’t.

Dr. Daniel Fink is a leading noise activist based in the Los Angeles area. He serves on the board of the American Tinnitus Association, is the interim chair of Quiet Communities’s Health Advisory Council, and is the founding chair of The Quiet Coalition, an organization of science, health, and legal professionals concerned about the impacts of noise on health, environment, learning, productivity, and quality of life in America.

 

Is eating out bad for your ears?

By Daniel Fink, MD, Chair, The Quiet Coalition

We all know from personal experience that restaurants are too loud. In this piece in The Washington Post, Gail Richard, the president of the American Speech-Language-Hearing Association, writes that noise levels in restaurants are loud enough to damage one’s hearing. Specifically, Richard states that “[c]onsistently listening to noise levels above 70 decibels can cause hearing loss over time,” noting that “it is not unusual for restaurant reviewers who regularly list restaurant noise in their reviews to find levels above 70 and even 80 decibels.”

The Quiet Coalition has covered a number of reports about restaurant noise so this information is nothing new, but this opinion piece is a nice summary.

The only thing I disagree with is Richard’s suggestion that restaurants could provide quiet zones for customers with hearing loss or those who prefer less noisy spaces. The idea of “separate but equal” spaces embodied in quiet zones, quiet rooms, or even a request for a quiet table runs counter to the legal requirements of the Americans with Disabilities Act (ADA), which requires that places of public accommodation offer those with disabilities full and equal enjoyment. Someone with complete hearing loss in one ear would appear to meet the ADA definition of having a disability.

Simply put, we shouldn’t have to ask for a quiet table or a quiet room. All restaurants should be quiet enough to allow all customers to converse.

Dr. Daniel Fink is a leading noise activist based in the Los Angeles area. He serves on the board of the American Tinnitus Association, is the interim chair of Quiet Communities’s Health Advisory Council, and is the founding chair of The Quiet Coalition, an organization of science, health, and legal professionals concerned about the impacts of noise on health, environment, learning, productivity, and quality of life in America.

Why do humans suffer hearing loss from noise?

Image is in the public domain in the U.S.

By Daniel Fink, MD, Chair, The Quiet Coalition

Why do humans suffer hearing loss from noise? The cellular, sub-cellular, and even molecular reasons for how noise damages the auditory system are known, but why?

In a fascinating article in The Hearing Journal, evolutionary biologist William Shofner, PhD, notes that humans and our animal forebears evolved in a largely quiet environment. Exquisitely acute hearing was important for finding prey or avoiding threats, but resistance to noise damage in the auditory system conferred no selective advantage.

Our world only started getting noisy as cities evolved, and especially since the Industrial Revolution. That is, our ears haven’t evolved to handle the noise, hence the epidemic of noise-induced hearing loss reported by Centers for Disease Control and Prevention.

Shofner’s last paragraph says it all:

Why didn’t evolution make the ear more noise-resistant? Again, evolution does not proceed with purpose. Simply stated, the human ear did not evolve under conditions of high sound levels. Any genetic mutation that might have led to a noise-resistant ear was likely not selected because it did not provide any benefit for survival and reproductive success in the pre-historic acoustic environment of early mammals. Natural selection is an exceedingly slow process that occurs over many generations, and the susceptibility of the human ear to noise-induced damage shows how natural selection is unable to keep up with rapid changes in an organism’s environment (Evol Applications. 2008). Technology has produced an acoustic environment that has changed much faster than the sluggish pace of human evolution. This evolutionary explanation of why the human ear is so susceptible to damage at highly intense noise levels provides a valuable perspective that audiologists can offer patients to prevent NIHL.

Dr. Daniel Fink is a leading noise activist based in the Los Angeles area. He serves on the board of the American Tinnitus Association, is the interim chair of Quiet Communities’s Health Advisory Council, and is the founding chair of The Quiet Coalition, an organization of science, health, and legal professionals concerned about the impacts of noise on health, environment, learning, productivity, and quality of life in America.

New explanation for why older people can’t hear in noisy environments

Photo credit: Filipe Fortes licensed under CC BY-SA 2.0

By Daniel Fink, MD, Chair, The Quiet Coalition

There are already several explanations about why middle-aged and older people can’t understand speech in noisy environments. One may just be high-frequency hearing loss caused by noise, which makes it hard to hear the higher-pitched consonant sounds (F, S, SH, T, V) that allow us to differentiate similar sounding words (Fear, Sear, Shear, Tear, Veer). (See the graph in this CDC Vital Signs Issue.) Another reason may be a phenomenon called “hidden hearing loss,” which is caused by noise damage to nerve junctions (synapses) in the inner ear.

And now a new report indicates that there may also be a brain or central processing problem. A study conducted at the Max Planck Institute in Germany, “analyzed what happens in the brain when older adults have trouble listening in loud environments.”  The researchers “monitored the brains of 20 younger adults ages 18 to 31, and 20 older adults in their 60s and 70s, during a listening task” in which constant background noise was played while participants were told to focus on certain targeted sounds.

What the researchers found was that “the younger adults were able to zero in on the target signals while filtering out the irrelevant noise,” but the older participants had “a harder time tuning out the background noise.” What remained unclear was whether the “degradation of the ear’s ability to hear actually leads to a decline in the brain’s ability to filter out noise and hear a single sound,” or whether “the brain’s listening ability erodes independently of any changes going on in the ear.”

As for why older people have a difficult time understanding speech in noisy environments, it most likely is that all three factors occur to varying degrees in various individuals. But one thing is certain, preventing hearing loss is simple: avoid loud noise. And improving the ability of people young and old to follow conversations is also simple: turn down the volume in indoor places.

Link via the UK Noise Association.

Dr. Daniel Fink is a leading noise activist based in the Los Angeles area. He serves on the board of the American Tinnitus Association, is the interim chair of Quiet Communities’s Health Advisory Council, and is the founding chair of The Quiet Coalition, an organization of science, health, and legal professionals concerned about the impacts of noise on health, environment, learning, productivity, and quality of life in America.

 

Can fireworks hurt babies’ ears?

Cat Bowen, Romper, looks at whether fireworks can hurt babies’ ears. Bowen, who is deaf, has a daughter who is hard of hearing, so she is particularly concerned about the impact of noisy fireworks, writing “that what little hearing we have, we want to protect at all costs.”

Bowen points to a Boys Town National Research Hospital report which states that “fireworks register at over 140 decibels of sound” and recommends safe distances for adults and children. Bowen writes that adults “need to be about 65 feet away from the fireworks to be considered safe,” but it’s more than double that for a child.

But what about babies? Bowen says that “it’s different with babies,” because there is no hearing protection gear made for infants under six months. So “[c]an fireworks hurt your baby’s ears?” “Absolutely,” says Bowen, who recommends that you limit your baby’s exposure, try using protective headphones, and “keep you and your baby as far from the fireworks as you can while still enjoying the view.”

A lowly fly may offer hope to hearing loss sufferers

Photo credit: Jpaur licensed under CC BY-SA 3.0

And Michelle Pucci, TVO, tells us how in her article, “How a tiny fly on a treadmill could lead to better hearing aids.” Pucci introduces us to the research team studying the ormia ochracea, a small fly that is drawn to “crickets’ singing, but no one quite knows how it manages to pick out that sound amid the cacophony of the natural world and locate it so precisely.” Why is this important?  Because if researchers can determine how the fly “pinpoints individual sounds in a noisy setting,” writes Pucci, “it could help solve the so-called cocktail party problem — the one that makes it tough for your grandmother to hear what you’re saying at family functions (and causes her to shout at you), because her hearing aid picks up too much background noise.”

Andrew Mason, a biologist at the University of Toronto explains that the fly’s “eardrums work like a scale, and incoming noises tip the balance.” Unlike humans, the fly’s “eardrums are connected — which Mason says could explain why the fly tries to interpret the different levels of sound it receives in both ears.”  Humans, on the other hand, can “locate and isolate the sounds they want to listen to, even in noisy environments, if the sources are far enough away from one another.”

The problem hearing aid wearers experience is that “it’s impossible to focus on a single conversation in a noisy room…because hearing aids trick the ear into thinking all those sounds are the same distance away.” That is, the hearing aid amplifies everything, making the task of concentrating on one conversation among many impossible. As researchers learn more about the ormia ochracea’s excellent sound-location abilities, engineers have used that knowledge.  Today, mics in some hearing aid design “mimic the fly’s ear structure,” and “research groups around the world are working on hearing aids that would allow the wearer to home in on different frequencies.”

So why do ormia ochracea search for crickets?  The answer is pretty grim:

[T]he female deposits its spawn inside the crickets, who sing when looking for a mate. Black-striped larvae then hatch inside the doomed cricket and scrape at its innards for 10 days…before “bursting out of the side like in Alien.”