Association of Hearing Aids and Cochlear Implants With Cognitive Decline and Dementia: A Systematic Review and Meta-analysis

Abstract

Importance: Hearing loss is associated with cognitive decline. However, it is unclear if hearing restorative devices may have a beneficial effect on cognition.

Objective: To evaluate the associations of hearing aids and cochlear implants with cognitive decline and dementia.

Data sources: PubMed, Embase, and Cochrane databases for studies published from inception to July 23, 2021.

Study selection: Randomized clinical trials or observational studies published as full-length articles in peer-reviewed journals relating to the effect of hearing interventions on cognitive function, cognitive decline, cognitive impairment, and dementia in patients with hearing loss.

Data extraction and synthesis: The review was conducted in accordance with Preferred Reporting Items for Systematic Review and Meta-analyses (PRISMA) reporting guidelines. Two authors independently searched the PubMed, Embase, and Cochrane databases for studies relating to the effect of hearing interventions on cognitive decline and dementia in patients with hearing loss.

Main outcomes and measures: Maximally adjusted hazard ratios (HRs) were used for dichotomous outcomes and ratio of means for continuous outcomes. Sources of heterogeneity were investigated using sensitivity and subgroup analyses, and publication bias was assessed using visual inspection, the Egger test, and trim and fill.

Results: A total of 3243 studies were screened; 31 studies (25 observational studies, 6 trials) with 137 484 participants were included, of which 19 (15 observational studies, 4 trials) were included in quantitative analyses. Meta-analysis of 8 studies, which had 126 903 participants, had a follow-up duration ranging from 2 to 25 years, and studied long-term associations between hearing aid use and cognitive decline, showed significantly lower hazards of any cognitive decline among hearing aid users compared with participants with uncorrected hearing loss (HR, 0.81; 95% CI, 0.76-0.87; I2 = 0%). Additionally, meta-analysis of 11 studies with 568 participants studying the association between hearing restoration and short-term cognitive test score changes revealed a 3% improvement in short-term cognitive test scores after the use of hearing aids (ratio of means, 1.03; 95% CI, 1.02-1.04, I2 = 0%).

Conclusions and relevance: In this meta-analysis, the usage of hearing restorative devices by participants with hearing loss was associated with a 19% decrease in hazards of long-term cognitive decline. Furthermore, usage of these devices was significantly associated with a 3% improvement in cognitive test scores that assessed general cognition in the short term. A cognitive benefit of hearing restorative devices should be further investigated in randomized trials.

Figure 1.. PRISMA Flow Diagram of the Study Selection Process

HL indicates hearing loss; PRISMA, Preferred Reporting Items for Systematic Reviews and Meta-analyses.

Figure 2.. Longitudinal Association of Hearing Aid Use and Any Cognitive Decline

The size of each box reflects the relative weight apportioned to the study; the diamond indicates the estimated pooled hazard ratio (HR) for each random-effects meta-analysis. seTE indicates standard error of treatment estimate; TE, estimated treatment effect.

Figure 3.. Pooled Ratio of Means (ROM) of Cognitive Test Scores Before and After the Use of Hearing Restorative Devices

The size of each box reflects the relative weight apportioned to each study; the diamond indicates the estimated pooled ROM for each random-effects meta-analysis.