NPR featured a piece on  “All Things Considered,” considering how to improve speech understanding in noisy environments. The segment focused on an ongoing study by Frank Russo, the director of the Science of Music, Auditory Research, and Technology Lab (SMART Lab) at Ryerson University in Toronto.

Based on work of other researchers such as Nina Kraus, Russo and colleagues are recruiting subjects to join a choir to see if musical training, even short-term, can influence speech understanding in noise. The subjects in the choir group are being compared to two control groups, one with no musical intervention and a second not singing, but listening to music in a music appreciation course. The group plan to share their findings this summer at The Neurosciences and Music-VI.

Reference

Siegel R, Hsu A. (2017 “Like Brain Boot Camp:” Using Music to Ease Hearing Loss. ) National Public Radio, May 31.

Does chronic tinnitus have an impact on listening effort? Degeest et al (2017) completed a pilot investigation where this was the primary question. Subjects included 13 individuals with both normal hearing and constant, chronic tinnitus and 13 individuals who made up a matched control group without tinnitus. Both subject groups completed a dual-task paradigm and a subjective assessment of listening effort in three real-world conditions: (1) quiet with one talker, (2) quiet with multiple talkers, and (3) in background noise.

A significant effect of group was obtained in terms of performance on the secondary task of the dual-task paradigm, which is considered a metric of effort. This suggests that the individuals with tinnitus were expending more effort. No effect of condition, however, was obtained, suggesting there was no relationship between effort and the difficulty of the listening task. No significant differences were obtained between groups on the subjective assessment of effort either. It should be noted that the subjects with tinnitus reported little to no tinnitus handicap, nor was their tinnitus handicap score correlated with their test results.

These findings suggest that chronic tinnitus, therefore, may have an impact on listening effort regardless of the difficulty of the listening condition. The authors, however, do suggest that this finding may be impacted by the study design and suggest future work in this area. 

References

Degeest S, Keppler H, Corthals P. (2017) The effect of tinnitus on listening effort in normal-hearing young adults: a preliminary study. J Speech Lang Hear Res, 60:1036–1045.

Patients with unilateral hearing loss can present with variable issues. Much is dependent on the severity of the hearing loss (threshold and speech understanding), age of onset, hearing status of contralateral ear, and presence of comorbidities (e.g., vertigo, cognitive status, central auditory processing, hyperacusis, tinnitus, disease/pathology/disorder, etc.). Adult-onset severe-to-profound unilateral sensorineural hearing loss with normal hearing sensitivity in the contralateral ear presents a unique dilemma. The most common issues described in this population include difficulty understanding speech-in-noise, sound localization, awareness of sound located on the compromised side (even in quiet), and tinnitus.

Several options exist to address adult-onset severe-profound unilateral sensorineural hearing loss with normal contralateral hearing sensitivity. One approach is traditional amplification. This will be dependent on remaining function in the affected ear and ability to achieve audibility. A second approach is rerouting of the signal to the contralateral normal hearing ear. This may be accomplished by use of a contralateral routing of signal (CROS) hearing aid or through bone conduction. Bone conduction can be achieved in two ways, either a high-powered hearing aid or a bone-anchored hearing device. A third approach is to try to restore binaural hearing with the use of a cochlear implant.  The final approach is to do nothing. So what to do?

Recently, Kitterick et al. (2016) performed a systematic review and meta-analysis to determine the nature and quality of evidence for the use of hearing instruments in adults with unilateral severe to profound sensorineural hearing loss. The criteria for study inclusion required the following:

• Hearing pure-tone average threshold ≤30 dBHL in the better hearing ear and >70 dBHL thresholds in the compromised ear
• Evidence of a sensorineural hearing loss
• Use of a hearing instrument
• Use of a hearing instrument and placebo device (or no intervention)
• Speech perception measures and/or other outcomes (e.g., localization)
• Design consistent with a controlled trial or prospective observational study

The quality of the studies was assessed based on the level of evidence, use of randomization, blinding, use of control group, identification, and control of confounds, etc. A total of 778 articles were identified, of which only 30 articles reporting on 27 separate studies met the inclusion criteria.  The majority of the studies included were pre- and post-comparisons in which the patient acted as their control. All studies were judged to be of low-moderate quality; the reduced quality was most commonly related to lack of power analysis to determine sample size, the non-matched control group, and lack of control for confounding factors. 

Evidence was then described for speech perception in quiet, speech perception in noise, sound lateralization/localization, hearing health-related quality of life and complications/adverse events. In each of these areas, there was a comparison of re-routing vs. unaided, bone-conduction device vs. air-conduction device, cochlear implant vs. unaided, and cochlear implant vs. rerouting. Brief summaries of these findings are provided. 

Speech Perception in Quiet
No overall evidence of benefit was indicated with speech presented directly in front of patients in aided vs. unaided performance. One study showed compromised speech perception accuracy in individuals with an air conduction routing device. Also, no overall evidence of benefit was indicated for bone conduction vs. air conduction device for re-routing of the signal. Cochlear implant studies only examined pre and post-perception in the implanted ear only; therefore, no evidence of benefit for improved binaural performance was demonstrated. A condition that seems to be missing in the literature is the presentation of soft speech to the compromised ear in quiet, consistent with someone talking softly on the compromised side.

Speech Perception in Noise
The benefit was indicated when the compromised ear had a more favorable signal-to-noise ratio (SNR). Conversely, deficits were reported when the compromised ear had less favorable SNR. When noise was comparable for both ears, patients performed better with a bone-conduction device compared to air-conduction re-routing. A similar dependency on SNR was reported with cochlear implant studies. Overall, the evidence suggests benefit and detriment depending on SNR at each ear.

Sound Lateralization/Localization
No overall evidence was indicated for sound lateralization/localization. Some studies reported no effect, some improvement, and others deficits.

Hearing Health-Related Quality of Life
Overall, evidence suggested perceived benefit on hearing health and reduced listening difficulty for re-routing signal. However, limited evidence exists for the quality of life or hearing health for application of cochlear implants to unilateral loss. Also, there was no description of the control for general inclusion/placebo effect.

The most common complaints of individuals with individuals with an adult-onset severe-to-profound sensorineural hearing loss with normal contralateral hearing function include difficulty with speech in noise and localization/lateralization. Overall, the evidence suggests benefit under specific noise conditions and detriment in other noise conditions. Also, no evidence is proposed for localization. Despite limited evidence for common complaints, in general, patients report perceived benefit. This may be in particular in situations with minimal background noise, and the speaker of interest is positioned on their compromised side. However, this situation, or condition, was either not reported or discussed in the studies reviewed. Furthermore, there was a minimal discussion of fatigue and listening effort during signal rerouting, where now the patient needs to deal with bilateral input with one functioning side. Finally, none of these studies report on having the patient simply turn their head. 

Reference

Kitterick PT, Smith SN, Lucas L (2016). Hearing Instruments for Unilateral Severe-Profound Sensorineural Hearing Loss in Adults: A Systematic Review and Meta-Analysis, Ear and Hearing 37(5):495–507.

Murman (2015) reviews cognitive changes associated with normal aging.  He states that “there is emerging evidence that healthy lifestyles may decrease the rate of cognitive decline….” Murman notes that in 1910 the average lifespan for a male was 48 years and for female it was 52. In 2010, the lifespan averages are 76 years for men and 81 years for women. Murman divides cognitive ability into multiple domains—attention, memory, executive cognitive function, language and visuo-spatial ability. Each domain “has measureable declines with age…” and of note, “speech comprehension in the setting of background noise and ambiguous speech content declines with age….”

With regard to age-related changes in brain structure and function, he reports that gray matter loss is most prominent in the pre-frontal cortex and the temporal lobes also show moderate declines in gray matter with aging. Of significance, he notes that neuronal synapses can now be measured quite accurately through immunohistochemistry. It has been suggested that when there is a loss of 40 percent or more of cortical synapses, symptomatic dementia may occur.

Murman reports that “Terry and Katzman predicted that dementia due to aging (senility) would occur at approximately age 130 without requiring the development of a disease state such as Alzheimer’s Disease (AD)…” and AD would be expected to accelerate the rate of synaptic loss. Murman states that when “synaptic density declines to 60 percent of maximal density symptoms of dementia would be expected…” and “someone with normal (cognitive) reserve and normal rate of synaptic loss with age (i.e., normal aging) would cross the dementia threshold line around age 130….” However, if one starts with lesser synaptic density, say perhaps 30 percent less than normal at age 25 years, that individual would potentially reach the dementia threshold by age 62 years.

For More Information, References, and Recommendations

Beck DL (2015) The State of the Art: Hearing Impairment, Cognitive Decline, and Amplification. Hearing Review.

Beck DL, Clark JL. (2009) Audition Matters More as Cognition Declines, and Cognition Matters More as Audition Declines. www.audiology.org (March).

Murman DL. (2015) The Impact of Age on Cognition. Seminars in Hearing 36(3).

Kobosko et al (2015) report that when post-lingually deafened adults acquire a cochlear implant, the benefits extend beyond hearing. That is, quality of life improves, as does psychological well-being and social interactions. The authors studied the relationship between cochlear implant (CI) satisfaction and level of psychological distress, stress coping strategies, and global self-esteem. The authors report that CI satisfaction “…reflects the overall feeling of benefit…attributed to their CI, including quality of life and general psychological well-being.”

Ninety eight adult patients ( aged 19 to 85 years) with unilateral CIs participated in the mail-based, multiple-questionnaire study. Kobosko et al state that, “CI satisfaction was not related to speech perception scores, duration of deafness, length of CI use, or other socio-demographic factors.”  For the younger adults, CI satisfaction was more highly correlated with “lower severity of depressive symptoms,” and for the older adults, CI satisfaction was more highly correlated with “less severe social dysfunction symptoms.”

Kobosko et al report that average levels of satisfaction of CI users (in their study) was determined to be 82 percent. Of note, 31 percent of their subjects reported a satisfaction rate of 100 percent and 47 percent reported satisfaction above 90 percent. Further, speech perception in quiet averaged 66 percent and of interest, the authors report “no statistically significant differences between younger and older subjects or between those with shorter and longer experience….” They added that “satisfaction with CIs showed no connection with speech perception in quiet and noise,” thereby underscoring the important finding that non-audiological factors are very important with respect to CI satisfaction. Indeed, they state that higher levels of self-esteem correlate with higher levels of CI satisfaction, humor is often an advantage to satisfied CI users, and “satisfaction with a CI appears to be a phenomenon linked most strongly to the human psyche and how it deals psychologically with hearing loss….” Likewise, factors that work against CI satisfaction include depression and denial.

For More Information, References, and Recommendations

Kobosko J, Jedrzejczak WW, Pilka E, Pankowska A, Skarzynski H. (2015) Satisfaction With Cochlear Implants in Post-Lingually Deaf Adults and Its Nonaudiological Predictors: Psychological Distress, Coping Strategies, and Self-Esteem. Ear & Hearing 36(5):605-618.