Brain Changes Linked With Speech-in-Noise Impairment

Difficulty understanding speech in background noise was tied to brain changes in speech-processing networks and may be an early behavioral marker of neural vulnerability before cognitive decline, a study of older adults suggested.

Over 3 years, poorer baseline speech-in-noise performance was associated with faster cortical thinning in the inferior parietal (β = -0.002), precuneus (β = -0.001), middle temporal cortex (β = −0.001), and superior temporal sulcus regions (β = -0.001), reported Julien Zanin, PhD, of the University of Melbourne in Australia, and co-authors.

These associations remained significant after adjusting for hearing thresholds and hearing aid use, the researchers wrote in JAMA Otolaryngology — Head and Neck Surgery.

“We found that speech-in-noise impairment was more closely related to structural brain change than hearing thresholds alone,” Zanin said. “Older adults who had more difficulty understanding speech in noise showed faster cortical thinning in regions involved in speech processing, attention, and higher-order cognitive function,” he pointed out.

“These associations remained after accounting for peripheral hearing loss, suggesting speech-in-noise ability may capture broader neural vulnerability,” Zanin told MedPage Today.

“We did not see measurable global cognitive decline over the follow-up period in the study cohort, but poorer speech-in-noise performance was associated with lower overall cognitive performance, suggesting these brain changes may emerge before decline is detected on standard cognitive screening assessments,” he added.

Hearing loss is a major modifiable risk factor for dementia, according to the Lancet Commission on dementia prevention. “Despite this, the neurobiological mechanisms linking auditory deficits, cortical neural integrity, and cognitive decline remain incompletely understood,” Zanin and colleagues noted.

Several studies have linked hearing loss with dementia, but these largely have been based on pure-tone audiometry data. Some evidence suggests that central auditory deficits are a more sensitive marker of neurocognitive status, with speech-in-noise ability differentiating people with normal cognition, mild cognitive impairment, and Alzheimer’s disease better than traditional pure-tone thresholds.

Earlier research, including a study of 82,000 U.K. Biobank participants, has tied speech-in-noise hearing impairment — sometimes called the “cocktail party effect” — with incident dementia.

“The cocktail party effect is closely related to speech-in-noise ability: it refers to how someone can use the auditory information arriving at both ears to filter out competing background noise and focus on a single speaker,” Zanin said. “The test we used in this study probes aspects of the cocktail party effect, particularly the ability to use spatial and vocal cues to separate out the target speech from competing talkers.”

Zanin and colleagues studied 312 adults from the Aspirin in Reducing Events in the Elderly (ASPREE) trial cohort in Australia with baseline and 3-year follow-up assessments. Participants were cognitively normal at baseline and had a mean age of 73.5 years; 54% were women.

Longitudinal changes in cortical thickness and regional brain volumes were assessed with T1-weighted MRI, with a focus on auditory and Alzheimer’s disease-vulnerable regions. Global cognitive function was evaluated with the Modified Mini-Mental State Examination (3MS).

Peripheral hearing loss was measured using better-ear 4-frequency average thresholds. Central auditory processing was evaluated using binaural speech-in-noise performance, which was assessed with the Listening in Spatialized Noise-Sentences (LiSN-S) test.

The researchers stratified participants into normal hearing, unaided hearing loss, or hearing aid user groups based on audiometry and self-reported hearing aid use.

At baseline, the hearing loss groups demonstrated poorer hearing and speech-in-noise abilities despite comparable global cognitive function. Over 3 years of follow-up, widespread age-related cortical atrophy was evident. Only central auditory processing impairment — not peripheral hearing loss or hearing aid use — was associated with accelerated cortical thinning in speech-processing networks.

The study had several limitations, Zanin and co-authors acknowledged. The sample size may have been too small and the follow-up period may have been too short. Global cognitive screening measures like the 3MS are relatively insensitive to the executive-attentional demands of auditory comprehension and may not detect subtle cognitive disruptions associated with central auditory decline, they added.