Abstract
Hearing loss is one of the most prevalent chronic health conditions in older adults. Growing evidence suggests that hearing loss is associated with reduced cognitive functioning and incident dementia. In this mini-review, we briefly examine literature on anatomical and functional alterations in the brains of adults with acquired age-associated hearing loss, which may underlie the cognitive consequences observed in this population, focusing on studies that have used structural and functional magnetic resonance imaging, diffusion tensor imaging, and event-related electroencephalography. We discuss structural and functional alterations observed in the temporal and frontal cortices and the limbic system. These neural alterations are discussed in the context of common cause, information-degradation, and sensory-deprivation hypotheses, and we suggest possible rehabilitation strategies. Although, we are beginning to learn more about changes in neural architecture and functionality related to age-associated hearing loss, much work remains to be done. Understanding the neural alterations will provide objective markers for early identification of neural consequences of age-associated hearing loss and for evaluating benefits of intervention approaches.
Highlights
Hearing loss is the third most prevalent chronic condition affecting older adults (Cruickshanks et al, 1998) and is one of the leading causes of years lived with disability worldwide (Mathers et al, 2003)
Estimates suggest that 35.6 million people lived with dementia worldwide in 2010 (Prince et al., 2013)
If not preventing, onset of cognitive decline in individuals with ageassociated hearing loss may have a significant impact on dementia prevention
Summary
Hearing loss is the third most prevalent chronic condition affecting older adults (Cruickshanks et al, 1998) and is one of the leading causes of years lived with disability worldwide (Mathers et al, 2003). The researchers found declines in gray matter volume in the right anterior cingulate and bilateral medial frontal gyrus via whole-brain analysis and in the superior temporal cortex in a region-of-interest analysis in the hearing loss group compared to the controls These results suggest that gray matter reductions observed in the brains of older adults with hearing loss are not related to age alone, supporting the findings of the other VBM studies discussed. Lin et al (2014) measured changes in brain volume in older adults with hearing loss (speech-frequency pure tone average >25 dB) as compared to normal hearing controls over a 6-year follow-up period They observed that individuals with hearing loss showed accelerated decline in whole brain volume and regional decline in the right temporal lobe. Functional alterations observed in the non-auditory regions lend support to information degradation and sensory deprivation theories, indicating that these frameworks combined might provide a better explanation of age-associated hearing loss (Wayne and Johnsrude, 2015)
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