December 1, 2013 Departments

From the Journals: December 2013

Catch up on the latest findings by researchers in communication sciences and disorders in this roundup of study results.

Yes on Hearing Conservation for Marching Bands

College marching band members showed no evidence of standard threshold shift or persistent notched audiograms—either of which may indicate noise-induced hearing loss—in a three-year study of rehearsal sound levels and students' hearing test results. The study, published in the June 2013 issue of the American Journal of Audiology, still recommends hearing conservation programs for college musicians, given the high sound-level exposure typical of their lengthy rehearsals.

Researchers led by Su-Hyun Jin at the University of Texas–Austin sought to examine the risk for noise-induced hearing loss in university marching band members, and to outline a hearing conservation program for marching bands. To do so, researchers recorded sound levels during band rehearsals and measured 350 musicians' audiometric hearing thresholds and transient otoacoustic emission over a three-year period. They also provided musician's earplugs and hearing loss information to the students. They tested the hearing thresholds of 348 other college students as a partial control.

The study found no significant differences in hearing thresholds between the two groups. During initial testing, more marching band members than control students showed apparent high-frequency notches. But in follow-up hearing tests for band members in a subsequent year, almost all the notches disappeared. The authors noted the band members had no persistent standard threshold shift across tests.

Because accepted hearing measurement procedures were not always precise enough to reliably detect early NIHL in marching band members, the study authors recommend that signs of NIHL be sought in repeated measurements compared to baseline audiograms rather than in a single measure.

Dual-Language Support Benefits Bilingual Children With Hearing Loss

Parents and clinicians can support both languages of bilingual children with hearing loss without adverse effects on the children's language development, according to a study published in the July 2013 issue of Language, Speech, and Hearing Services in Schools. Moreover, supporting both languages in bilingual children with hearing loss may have numerous positive effects.

A team led by Ferenc Bunta at the University of Houston investigated the effects of supporting both English and Spanish on language outcomes in bilingual children with hearing loss who used listening devices—cochlear implants and hearing aids. Researchers compared the English language skills of 20 bilingual children with hearing loss to those of 20 monolingual English-speaking peers with hearing loss. They also compared the bilingual participants' Spanish and English language skills.

The authors collected auditory comprehension, expressive communication and total language scores using the Preschool Language Scale (4th ed.). On all three measures, the bilingual participants' English language skills were commensurate with those of their monolingual English-speaking peers. The bilingual group's Spanish and English total language scores were also comparable and highly correlated.

Tinnitus Has Variable Effect on Otoacoustic Emissions

A study designed to measure the effect of tinnitus on distortion product otoacoustic emissions, while accounting for the effects of hearing loss and aging, found that DPOAE levels were diminished in adults with hearing loss and tinnitus. The study, published in the June 2013 issue of the American Journal of Audiology, also found that DPOAE levels in participants with normal hearing and tinnitus were enhanced, relative to DPOAE levels in the controls.

DPOAEs are used to index outer hair cell function, which has a complex association with tinnitus. This association implies DPOAEs might be used as a tool to test for tinnitus and to create a model of the neural mechanisms underlying tinnitus.

Fatima T. Husain of the University of Illinois at Urbana–Champaign measured DPOAEs twice in both ears in five participant groups: 11 young adults (ages 20–26) with normal hearing, 20 middle-age adults (ages 36–63) with normal hearing, 23 adults (ages 37–71) with high-frequency sensorineural hearing loss, 23 age-matched adults (ages 42–69) with similar hearing loss and tinnitus, and nine adults (ages 33–50) with normal hearing and chronic tinnitus.

A multivariate analysis revealed a main effect of hearing loss and age—but no effect of tinnitus—across all five groups. Separate tests revealed significant effects of age and tinnitus in the normal-hearing groups, and hearing loss in adults with or without tinnitus, but no effect of tinnitus in those with hearing loss.

Researchers Pinpoint Source of Dizziness

Researchers have isolated a site in a highly developed area of the human brain that plays an important role in the subconscious recognition of which way is straight up and which way is down, according to a study published in the journal Cerebral Cortex. The finding may help explain some causes of spatial disorientation and dizziness, and offers targets for treating the feelings of unsteadiness and "floating" people experience when the brain fails to properly integrate input from the body's senses.

Disabling dizziness can be a symptom of damage to the inner ear or other senses such as vision. A team led by Amir Kheradmand, a neurology instructor at the Johns Hopkins University School of Medicine, recruited eight healthy participants (five male and three female, ages 22–72) for the study, placed each person in a dark room, and showed them lines illuminated on a screen. The researchers asked the subjects to report the orientation of the lines by rotating a dial to the right, left or straight.

Participants then received trans-cranial magnetic stimulation, which painlessly and noninvasively delivered 600 electromagnetic pulses—that can temporarily disrupt the function of the targeted area—over the course of 40 seconds to precise locations in the brain. After each 40-second session, the subjects were again asked to report the orientation of lines on the screen. Ultimately, the researchers found that each subject reported that his or her sense of being upright was skewed in the same way after transcranial magnetic stimulation in the same spot in the parietal cortex: the supramarginal gyrus.

Kheradmand says the study's results raise the possibility that this technology could be used to treat chronic dizziness, theorizing that if magnetic stimulation can disrupt upright perception in healthy people, it might also fix dysfunction in the same location in people with dizziness and spatial disorientation.

Sibling Comparisons Reveal Consequences of Preterm Births

An unprecedented study suggests that only some of the problems previously associated with preterm birth are actually caused by preterm birth itself. The study, published Sept. 25 in JAMA Psychiatry confirms the strong link between preterm birth and the risk of infant and young adult death, autism and ADHD. But it also suggests that other threats that have been closely tied to the issue—such as severe mental illness, learning problems, suicide and economic woes—may, instead, be more closely related to other conditions in a family.

In what is thought to be the largest population-based study of preterm births to date, Indiana University-Bloomington researchers, led by Brian D'Onofrio, looked at records of 3.3 million children born in Sweden between 1973 and 2008. Using a sibling-comparison approach and considering a broad continuum of premature gestational ages, the study examined the associations between preterm birth and mortality, psychological health, educational outcomes and social functioning.

The results are somewhat consistent with previous studies that compare preterm infants to unrelated non-preterm infants. Unlike those efforts, however, the current study also compared preterm infants to their non-preterm siblings and cousins—an approach that made it possible to control for and hold constant everything those siblings share: mothers and fathers, socioeconomic status, and some genetic factors.

When the researchers looked at infant and young adult mortality, as well as autism and ADHD, the results were the same when comparing siblings as when they compared preterm infants to unrelated non-preterm individuals.

In other areas, however, the results are strikingly different from previous findings. The association between preterm birth and severe mental illness, such as schizophrenia or bipolar disorder, was greatly reduced when comparing siblings. Both siblings had higher chances of severe mental illness than the general population. For suicide, the findings are even more dramatic. Although individuals born preterm are more likely to attempt suicide than unrelated individuals who were not born preterm, no distinction exists between siblings.

"The study confirms the degree to which preterm birth is a major public health concern and strongly supports the need for social services that reduce the incidence of preterm birth," D'Onofrio said. "Yet, the findings also suggest the need to extend services to all siblings in families with an offspring born preterm. In terms of policy, it means that the entire family, including all of the siblings, is at risk."


  

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