Cochlear Implantation and Cognitive Function in Adults: A Systematic Review and Meta-analysis

OBJECTIVE: To assess for changes in cognitive function in the first year following cochlear implantation in adult implant recipients. DATABASE REVIEWED: MEDLINE, Embase, Cochrane CENTRAL, Web of Science, PsycINFO, and CINAHL. METHODS: A comprehensive literature search was conducted to identify studies that assessed cognition in adult cochlear implant recipients. Included studies were English-language publications reporting objective cognitive testing scores both before and a minimum of 6 months after cochlear implantation in adults with postlingual hearing loss. Interventional studies, cohorts, case-controls, and case series with more than 5 patients were eligible. Two reviewers independently screened studies and extracted data. Study quality and risk of bias were evaluated using Newcastle-Ottawa Scale. Within-subjects random-effects meta-analyses were performed using the DerSimonian-Laird method. Pooled mean differences in cognitive test scores pre- versus postcochlear implantation were calculated for cognitive tests reported by more than 3 studies. Pooled standardized mean differences were calculated, including all reported cognitive tests across all studies. RESULTS: Twenty eligible studies were identified, including a total of 798 cochlear implant recipients. Fifteen separate cognitive tests or testing batteries were applied at a median of 12 months postoperatively (range, 6 to 48 mo). The Mini-Mental Status Exam (MMSE) was the most frequently applied test (6 studies), followed by the MoCA (4 studies). Meta-analysis of mean differences showed no significant effect of cochlear implantation on MMSE score (pooled mean difference, 0.63 [95% CI: -1.02-2.28]), and a small but significant effect of cochlear implantation on MoCA score (pooled mean difference, 1.38 [95% CI: 0.33-2.42]). Considering all cognitive tests, there was a small but significant improvement in cognitive testing scores following cochlear implantation (pooled standardized mean difference 0.32 [95% CI: 0.19-0.44]). CONCLUSIONS: Cochlear implantation in adults is associated with small but significant improvements in cognitive testing scores on at least some tests. Further research is needed to assess whether these findings translate to a reduction in dementia risk.