- Difficulty understanding speech amidst background noise is associated with accelerated thinning in brain networks dedicated to speech processing.
- These neural associations remained significant even after controlling for hearing thresholds and the use of hearing aids.
- Impairments in speech-in-noise comprehension may serve as an early indicator of neural vulnerability prior to the onset of visible cognitive decline.
A new study involving older adults suggests that difficulty understanding speech in noisy environments is linked to structural changes in speech-processing brain networks. These findings indicate that speech-in-noise deficits may act as an early behavioral marker for neural vulnerability before clinical cognitive decline becomes apparent.
Research led by Julien Zanin, PhD, of the University of Melbourne, and his colleagues found that poor baseline performance in speech-in-noise tasks was associated with faster cortical thinning over a three-year period. Specifically, thinning was observed in the inferior parietal (β = -0.002), precuneus (β = -0.001), middle temporal cortex (β = −0.001), and superior temporal sulcus (β = -0.001) regions.
Writing in JAMA Otolaryngology — Head and Neck Surgery, the researchers noted that these associations persisted after adjusting for hearing thresholds and hearing aid usage.
“We discovered that speech-in-noise impairment is more closely linked to structural brain changes than hearing thresholds alone,” Zanin explained. “Older adults struggling to understand speech in noisy settings exhibited faster cortical thinning in brain regions responsible for speech processing, attention, and higher-order cognitive functions.”
Zanin further told MedPage Today that because these links remained significant after accounting for peripheral hearing loss, speech-in-noise ability may provide insight into broader neural health.
“While we did not observe measurable global cognitive decline within the study cohort during the follow-up period, poorer speech-in-noise performance correlated with lower overall cognitive performance,” Zanin added. “This suggests that these neurological changes may emerge before decline is detectable via standard cognitive screening tools.”
The Lancet Commission on dementia prevention has identified hearing loss as a major modifiable risk factor for dementia. However, Zanin and his team noted that the neurobiological connections between auditory deficits, cortical integrity, and cognitive decline are not yet fully understood.
While numerous studies have connected hearing loss to dementia, most rely on pure-tone audiometry. Emerging evidence suggests that central auditory deficits might be a more sensitive indicator of neurocognitive health, as speech-in-noise performance can better differentiate between individuals with normal cognition, mild cognitive impairment, and Alzheimer’s disease than traditional pure-tone thresholds.
Previous research, including an analysis of 82,000 participants from the U.K. Biobank, has linked speech-in-noise impairment—often referred to as the “cocktail party effect”—with the incidence of dementia.
“The cocktail party effect involves the ability to use auditory information from both ears to filter out competing background noise and focus on a single speaker,” Zanin said. “Our study’s test probes this ability, specifically how effectively individuals use spatial and vocal cues to isolate target speech from competing voices.”
The study analyzed 312 adults from the Aspirin in Reducing Events in the Elderly (ASPREE) trial cohort in Australia. The participants, who had a mean age of 73.5 years and were cognitively normal at the start of the study, underwent baseline and 3-year follow-up assessments. The cohort was 54% female.
Researchers utilized T1-weighted MRI to assess longitudinal changes in cortical thickness and regional brain volumes, focusing on auditory and Alzheimer’s-vulnerable regions. Global cognitive function was measured using the Modified Mini-Mental State Examination (3MS). Peripheral hearing loss was measured via 4-frequency average thresholds in the better ear, while central auditory processing was evaluated using the Listening in Spatialized Noise-Sentences (LiSN-S) test.
Participants were categorized into groups based on audiometry and self-reported hearing aid use: normal hearing, unaided hearing loss, or hearing aid users.
At baseline, the hearing loss groups showed diminished hearing and speech-in-noise abilities despite having comparable global cognitive function. Over the three-year follow-up, while widespread age-related cortical atrophy occurred, only central auditory processing impairment—rather than peripheral hearing loss or hearing aid use—was associated with accelerated cortical thinning in speech-processing networks.
The authors acknowledged several limitations, including a potentially small sample size and a relatively short follow-up period. They also noted that global cognitive screening tools like the 3MS may lack the sensitivity required to detect the subtle cognitive disruptions associated with central auditory decline and the executive-attentional demands of auditory comprehension.