Abstract
Impaired hearing and cognition are disabling conditions among older adults. Research has presented inconsistent conclusions regarding hearing impairment posing a risk for cognitive impairment. We aimed to assess this from published evidence via searching PubMed and Embase, from the inception of the databases indexed to December 2, 2016. For those high-quality studies retrieved, relative risk (RR) and 95% confidence intervals (CIs) were combined to estimate the risk of cognitive impairment. Eleven cohort studies were included in the present study. Pooled results found that elderly people with disabled peripheral and central hearing function had a higher risk of cognitive impairment (for moderate/severe peripheral hearing impairment: RR = 1.29, 95% CI: 1.04–1.59 during a follow-up ≤6 years. RR = 1.57, 95% CI: 1.13–2.20 during a follow-up >6 years; for severe central hearing impairment, RR = 3.21, 95% CI: 1.19–8.69) compared to those with normal hearing function. We also recorded a dose-response trend for cognitive impairment as hearing thresholds rose. No evident bias from potential confounding factors was found with one exception: the length for clinical follow-up. Although results are preliminary because qualifying studies were few, statistical findings were consistent with older people identified as having greater levels of hearing loss, having a corresponding higher risk of cognitive impairment.
Highlights
Age-related hearing loss (ARHL) may be widely associated with neurodegenerative, functional, physical, and psychosocial impairment[9]
When the hearing threshold was greater than 40 decibels hearing level for the pure-tone average (PTA) at 0.5, 1, 2, and 4 kHz, the risk of cognitive impairment in older subjects increased 29–57% compared to those with normal hearing (follow-up ≤6 years, relative risk (RR) = 1.29, 95% confidence interval (CI): 1.04–1.59; follow-up >6 years, RR = 1.57, 95% CI: 1.13–2.20, Fig. 2a)
The RR for incidence of cognitive impairment in older people was 2.42 in the moderate central auditory dysfunction (CAD) group compared with the normal function group (SSI-ICM < 80% correct, RR = 2.42, 95% CI: 1.14–5.11, Fig. 3a)
Summary
ARHL may be widely associated with neurodegenerative, functional, physical, and psychosocial impairment[9]. The first meta-analysis to explore hearing loss and cognitive function[25], without putting restrictions on age or methodology when retrieving studies, concluded that individuals with hearing loss had worse cognitive performance. By including more recent data, we appraised the hearing function-cognition relationship in older adults and its dose-response trend with more participants. We incorporated both peripheral and central hearing function as independent variables to carry out an analysis for the risk of cognitive impairment by category. Apart from the hearing function-cognition relationship, we analyzed the initial findings from these retrieved studies about the effect of hearing aid use on the incidents of cognitive impairment
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