Research Roundup updates HR readers on some of the latest research and clinical findings related to hearing health care. Where appropriate, sources and original citations are provided, and readers are encouraged to refer to the primary literature for more detailed information. Additionally, related articles can be found and keywords can be searched in the HR Online Archives

Hearing Loss Is Twice as Common in People with Diabetes

Hearing loss is about twice as common in adults with diabetes compared to those who do not have the disease, according to a new study funded by the National Institutes of Health (NIH).

“Hearing loss may be an under-recognized complication of diabetes. As diabetes becomes more common, the disease may become a more significant contributor to hearing loss,” says senior author Catherine Cowie, PhD, of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), who suggested that people with diabetes should consider having their hearing tested. “Our study found a strong and consistent link between hearing impairment and diabetes using a number of different outcomes.”

The researchers discovered the higher rate of hearing loss in those with diabetes after analyzing the results of hearing tests given to a nationally representative sample of adults in the United States. The test measured participants’ ability to hear low, middle, and high frequency sounds in both ears. The link between diabetes and hearing loss was evident across all frequencies, with a stronger association in the high frequency range. Mild or greater hearing impairment of low- or mid-frequency sounds in the worse ear was about 21% in 399 adults with diabetes compared to about 9% in 4,741 adults without diabetes. For high frequency sounds, mild or greater hearing impairment in the worse ear was 54% in those with diabetes compared to 32% in those who did not have the disease.

Adults with pre-diabetes, whose blood glucose is higher than normal but not high enough for a diabetes diagnosis, had a 30% higher rate of hearing loss compared to those with normal blood sugar tested after an overnight fast.

The study, published early online June 17, 2008, in the Annals of Internal Medicine, was conducted by researchers from the NIDDK, the National Institute on Deafness and Other Communication Disorders (NIDCD), components of the NIH, and Social & Scientific Systems Inc, which provides support on public health topics to NIH and other government agencies.

The researchers analyzed data from hearing tests administered from 1999 to 2004 to participants in the National Health and Nutrition Examination Survey (NHANES) conducted by the National Center for Health Statistics, part of the Centers for Disease Control and Prevention (CDC). Half of the 11,405 survey participants aged 20 to 69 were randomly assigned to have their hearing tested via puretone audiometry, and nearly 90% of them completed the hearing exam and the diabetes questionnaire.

“Using the data from the hearing tests, we measured hearing impairment in eight different ways,” says Cowie. “Also, participants responded to questions about hearing loss in the questionnaire, which asked whether they had a little trouble hearing, a lot of trouble hearing, or were deaf without a hearing aid.” In addition, 2,259 of the participants who received hearing tests were randomly assigned to have their blood glucose tested after an overnight fast.

Earlier US studies that examined diabetes and hearing loss found a weaker association or no association, but these studies were based on smaller samples of older adults, and they were not nationally representative, according to co-author Howard Hoffman, an epidemiologist at NIDCD. “This is the first study of a nationally representative sample of working age adults, 20 to 69 years old, and we found an association between diabetes and hearing impairment evident as early as ages 30 to 40.”

“The link between diabetes and hearing loss has been debated since the 1960s or before, and our results show that a relationship exists even when we account for the major factors known to affect hearing, such as age, race, ethnicity, income level, noise exposure, and the use of certain medications,” noted Kathleen Bainbridge, PhD, of Social & Scientific Systems Inc.

Diabetes may lead to hearing loss by damaging the nerves and blood vessels of the inner ear, the researchers suggest. Autopsy studies of diabetes patients have shown evidence of such damage.

Diabetes is a group of diseases marked by high levels of blood glucose resulting from defects in insulin production, insulin action, or both. Afflicting nearly 21 million people in the United States, it is a major cause of heart disease and stroke and the most common cause of blindness, kidney failure, and lower limb amputations in adults. Pre-diabetes, which causes no symptoms, affects about 54 million adults in the United States, many of whom will develop type 2 diabetes in the next 10 years. Pre-diabetes raises the risk of a heart attack or stroke even if diabetes does not develop. People with pre-diabetes can often prevent or delay diabetes if they lose a modest amount of weight by cutting calories and increasing physical activity. People with diabetes also benefit from diet and exercise, as well as medications that control blood glucose, blood pressure, and cholesterol.

  • New Study Looks at Link Between Diabetes and Hearing Loss. October 19, 2006 HR Insider.

Most NHANES participants with diabetes had type 2 diabetes, which accounts for up to 95% of diabetes cases in the United States. Type 2 diabetes usually appears after age 40, and is more common in overweight, inactive people and in those with a family history of diabetes.

Hearing loss is a common problem caused by aging, disease, heredity, and noise. About 17% of American adults—36 million people—report some degree of hearing loss. There is a strong relationship between age and reported hearing loss: 8% of American adults 18 to 44 years old, 19% of adults 45 to 64 years old, and 30% of adults 65 to 74 years old report trouble with hearing. Source: NIDCD.

Original Citation

Bainbridge KE, Hoffman HJ, Cowie CC. Diabetes and hearing impairment in the United States: audiometric evidence from the National Health and Nutrition Examination Survey, 1999 to 2004. Ann Intern Med. 2008;149(1):1-10.


New Research: Two Cochlear Implants Significantly Better Than One

A study of cochlear implant patients seen by Indiana University School of Medicine physicians is the first research to show evidence that cochlear implants in both ears significantly improve quality of life in patients with profound hearing loss and that the cost of the second implant is offset by its benefits.

The study, which appears in the May issue of the journal Otolaryngology-Head and Neck Surgery, found that improvements in factors that contribute to quality of life—including such critical abilities as hearing in noisy environments, focusing on conversations, and speaking at an appropriate volume—resulted when cochlear devices were implanted in both ears.

  • Researcher Voices Support for Binaural Cochlear Implants. May 3, 2007 HR Insider.

This study may have a significant impact for profoundly deaf individuals who hope to have their health insurance providers pay for bilateral rather than the standard single cochlear implant. The study authors found the benefits of the second implant outweighed the added cost of the second device.

“We didn’t know that cognitive skills and emotional issues would so significantly improve with the implantation of a second cochlear device,” says senior study author Richard Miyamoto, MD, Arilla Spence DeVault Professor, chairman of the IU Department of Otolaryngology–Head and Neck Surgery, and past-president of AAO-HNS. “In addition to the physiological improvements we saw in patients who had bilateral implants, we found that patients were able to function better in noisy environments and definitely felt better about themselves.”

“Profoundly deaf individuals who were born with hearing, their families, physicians, and health insurance providers now have the data they need,” says Miyamoto. “There is definite improvement after one implant and there is a significant added bump in sound and speech perception after the second implant. Emotional well-being improves. And we found a favorable cost utility analysis. Our hope is that with these findings more health insurance companies will cover the cost of bilateral implants and bring a superior quality of life to a large number of individuals.”

Approximately 1.4 million Americans are deaf in both ears and experience significant impairment in communication with the hearing world, according to the study authors. The study was funded by the IU School of Medicine’s Department of Otolaryngology-Head and Neck Surgery. Source: American Academy for the Advancement of Science.

Original Article

Bichey BG, Miyamoto RT. Outcomes in bilateral cochlear implantation. Otolarygol Head Neck Surg. 2008;138(5):655-661.


Molecular Motor Works by Detecting Minute Changes in Force

Researchers at the University of Pennsylvania School of Medicine discovered that the activity of a specific family of nanometer-sized molecular motors called myosin-I is regulated by force: the motor puts tension on cellular springs that allow vibrations to be detected within the body. This finely tuned regulation has important implications for understanding a wide variety of basic cellular processes, including hearing and balance, and glucose uptake in response to insulin. The findings appear in the July issue of Science.

“This is the first demonstration that myosin-I shows such dramatic sensitivity to tension,” says senior author E. Michael Ostap, PhD, associate director of the Pennsylvania Muscle Institute and associate professor of Physiology. “It is surprising that a molecular motor can sense such small changes in force.”

Myosin-I is a biological motor that uses the chemical energy made by cells to ferry proteins within cells and to generate force, powering the movement of molecular cargos in nearly all cells. In two specific cases, myosin-I puts tension on the specialized spring-like structures in human ears that enable hearing and maintenance of balance, and also has a role in delivering the proteins that pump glucose into cells in response to insulin. “However, why a tension-sensing molecular motor is needed for this function is unknown,” says Ostap.

In collaboration with Henry Shuman, PhD, associate professor of Physiology, the research team used optical tweezers—a combination focused laser beam and microscope, of sorts—to measure incredibly small forces and movements (on the piconewton and nanometer level) to discover that myosin-I motors are regulated by force. The motors pull on their cellular cargos until a certain tension is attained, after which they stop moving but will hold the tension. If something happens in the cell to decrease this tension, the motor will restart its activity and will restore the lost tension.

Myosins use the energy from ATP to generate force and motion. Humans have 40 myosin genes that sort into 12 myosin families. Members of the myosin family have been found in every type of cell researchers have examined. The new findings shed light on the role of myosin-I in cells, supporting the notion that this molecular motor is more important in generating and sustaining tension rather than transporting protein cargo. The research was supported by the National Institute of General Medical Sciences and the National Institute of Arthritis and Musculoskeletal and Skin Diseases. Source: Penn Medicine

Original Article

Laakso JM, Lewis JH, Shuman H, Ostap EM. Myosin I can act as a molecular force sensor. Science. 2008;321(5885):133-136.


ABRs May Be Useful in Tinnitus Workup

A research team led by Helga M. Kehrle, MD, MSc, of the Hospital de Base de Brasília examined 37 people with tinnitus and 38 without tinnitus (ages 20-45) who had puretone thresholds better than 25 dB at 500-8000 Hz. A total of 16 (43%) of the tinnitus group showed abnormalities in the 8 ABR parameters analyzed, with prolonged latencies in waves I, III, and V, as well as a significantly enlarged interpeak III-V. Although the V/I amplitude ratio found in the tinnitus group was within normal limits, a significant difference was found when the two groups were compared. The researchers conclude that “although the averages obtained in several analyzed parameters were within normal limits, the ABR results from the patients with and without tinnitus and normal hearing are different, suggesting that ABR might contribute to the workup of these patients.” The data indicates there are changes in the central pathways of the tinnitus group that suggest a need for further investigation.

Original Citation

Kehrle HM, Granjeiro RC, Sampaio ALL, et al. Comparison of auditory brainstem response results in normal-hearing patients with and without tinnitus. Arch Otolaryngol Head Neck Surg. 2008;134:647-651.


Health and Hearing Loss: No Seconds, No Cigs … But You Can Have a Drink

Smoking and body mass index (BMI) are risk factors in the development of age-related hearing loss, says one of the largest-ever studies into risk factors for hearing loss—but alcohol has a protective effect. The study, which involved nine audiological centers in seven countries and a total of 4,083 people, was published online in the Journal of the Association for Research in Otolaryngology (JARO).

Researchers led by Erik Fransen in professor Guy Van Camp’s research team at the University of Antwerp found that smoking, being overweight, and occupational noise are risk factors in the most common type of hearing loss. In contrast, moderate alcohol consumption (at least one glass of alcohol per week) was seen to have a protective effect. The effect of heavy drinking was not investigated.

In view of the findings, Fransen and his colleagues conclude, “Hearing loss has always been considered an inevitable part of ageing, but more and more studies seem to indicate this is not necessarily true. Apparently a healthy lifestyle can be beneficial for hearing conservation at higher ages.” Source: American Academy for the Advancement of Science.

Original Citation

Fransen E, et al. Occupational noise, smoking, and a high body mass index are risk factors for age-related hearing impairment and moderate alcohol consumption is protective. A European population-based multicenter study. J Assoc Res Otolaryngol. 2008; (DOI 10.1007/s10162-008-0123-1).


Hospital Visits More Dangerous for Those with Communication Problems

Preventable adverse events in hospitals occur three times more often among patients with communication problems, such as deafness, blindness, psychiatric disorders, and multiple health issues or comorbidities, report researchers in a study of nearly 2,400 patient records from 20 hospitals in Quebec. The report is published in the June 3 edition of the Canadian Medical Association Journal.

Specifically, the paper states that patients with “preventable adverse events were significantly more likely than those without such events to have a communication problem (odds ratio [OR] 3.00; 95% CI 1.43–6.27),” and “patients with communication problems were more likely than patients without these problems to experience multiple preventable adverse events (46% v. 20%; p = 0.05).”

An adverse event is “an unintended injury or complication caused by the delivery of clinical care rather than by the patient’s underlying condition.” Preventable adverse events occurred more often in women than in men and in patients over age 65. The most common adverse effects were drug related or caused by inappropriate treatment, treatment delay, or failure to monitor a patient’s condition.

“Almost half of the events were associated with some level of disability or multiple hospital admissions, with one-third of the patients who experienced preventable adverse events requiring readmission to hospital,” write Bartlett and coauthors. “These results emphasize the importance of providing additional resources for these patients to improve patient safety.”

The researchers urge, “[I]t is important for future research to investigate interpersonal dynamics that may be responsible. This research will become critical as the number of adults with disabilities affecting communication increases as the elderly population increases.” Source: EurekaAlert and CMAJ.


Batman Was Right? Noise Silenced by Acoustic Cloak

Researchers in Valencia, Spain, have proven that metamaterials, materials defined by their unusual man-made cellular structure, can be designed to produce an acoustic cloak—a cloak that can make objects impervious to sound waves, literally diverting sound waves around an object. The research, “Acoustic cloaking in two dimensions: a feasible approach,” published June 13, 2008, in the New Journal of Physics (NJP), builds on recent theoretical research that has sought ways to produce materials that can hide objects from sound, sight, and x-rays.

Daniel Torrent and José Sánchez-Dehesa from the Wave Phenomena Group, Department of Electronics Engineering at the Polytechnic University of Valencia, cite theoretical work published early last year in NJP by researchers from Duke University in North Carolina as the starting point for their more practical approach. To realize the cloak physically, the Spanish research team calculated how metamaterials constructed with sonic crystals, solid cylinders in a periodic array that can scatter sound waves, could be used in a multilayered structure to divert sound completely around an object. The researchers performed multiple simulations to test their theory. They investigated the optimum number of layers required to completely divert sound and how thin the materials could be made to maintain their use but also ensure that they are easy to implement.

Results were very encouraging, showing that optimum cloaking requires approximately 200 layers of the metamaterial but that there is scope for much thinner materials to be used than technology can currently produce. So, put simply, watch this space. “We hope that this proposal will motivate future experimental work demonstrating the materials’ performance,” says co-author José Sánchez-Dehesa.

One of the first uses of the material is likely to be warships, hoping to avoid sonar radars that pick up on the noise that ships emit, but if developments continue apace, it could be used in concert halls to direct noise away from problem spots, or even as a way to deal with noisy neighbors. Source: American Academy for the Advancement of Science.

Original Article

Torrent D, Sánchez-Dehesa J. Acoustic cloaking in two dimensions: a feasible approach. New J Physics. 2008; 10 063015. Available online at: www.iop.org/EJ/abstract/1367-2630/10/6/063015.