Abstract
Mild cognitive impairment (MCI) and hearing loss (HL) have been separately associated with increased dementia risk. These highly co-occurring dementia risk factors are associated with aberrant functional brain connectivity. In individuals with HL aberrant functional connectivity has been associated with cognitive impairment. In individuals with MCI, aberrant brain connectivity has been associated with severity of cognitive impairment and conversion to dementia. Despite the high prevalence of HL in individuals with MCI, the relationship between the two is understudied, especially in the context of functional connectivity.
Participants
include 94 older adults with MCI. Hearing measures include pure-tone hearing thresholds and speech-reception thresholds. In analyses with pure-tone hearing loss, participants were classified as having normal hearing (n = 60) or hearing loss (n = 34) based on a pure-tone screening protocol. We used independent component analyses on resting-state functional magnetic resonance imaging data to identify the default-mode network (DMN). Analysis of variance with covariate control was used to investigate DMN connectivity differences between the normally hearing individuals with MCI and individuals with MCI and pure-tone HL. A linear regression was used to investigate the relationship between speech-reception threshold and DMN connectivity in the whole sample.
Compared to those with MCI and normal hearing, those with MCI and pure-tone HL had decreased connectivity between the DMN and the caudate and thalamus. There was no difference in DMN connectivity as a function of speech-reception threshold.
Our findings indicate that in individuals with MCI, HL is associated with decreased connectivity between the DMN and regions important for sensory and cognitive processing. This suggests that the increased risk for cognitive decline and dementia in individuals with HL may be due to decreased DMN connectivity in individuals with HL.
Plain language summary
Individuals with mild-cognitive impairment are at increased risk for developing Alzheimer’s disease. Individuals with hearing-loss are also at increased risk for developing Alzheimer’s disease. Hearing loss is common in mild cognitive impairment and connected to it. Individuals with hearing loss and individuals with mild cognitive impairment often have changes in the connections inside their brain. These changes are likely related to the cognitive decline that individuals with mild cognitive impairment and hearing loss HL often experience. The relationship between hearing loss, mild cognitive impairment, and brain connectivity has never been studied.
We looked at a brain network that changes in individuals with mild cognitive impairment and in individuals with Alzheimer’s disease. We compared this network in people with mild cognitive impairment and normal hearing to people with mild cognitive impairment and hearing loss. Compared to those with mild cognitive impairment and normal hearing, those with mild cognitive impairment and hearing loss had decreased connectivity between the default-mode network and regions responsible for sensory and cognitive processing (caudate and thalamus). This suggests that the increased risk for cognitive decline and dementia in individuals with hearing loss may be due to altered connectivity between and within brain regions responsible for sensory and cognitive processing. In other words, the results suggest that hearing loss leads to having less brain connections important for cognition.