Cognitive Functions in Adult Cochlear Implant Users, Cochlear Implant Candidates, and Normal-Hearing Listeners

Objectives Increasing evidence suggests that hearing loss may be linked to cognitive decline, and that cochlear implantation may lead to improvements in cognition. The goal of this study was to examine the effects of severe-to-profound hearing loss and cochlear implantation in post-lingually deafened adults, compared with age-matched normal-hearing (NH) peers. Participants were tested on several non-auditory measures of cognition: working memory (WM) (digit span, object span, symbol span), non-verbal reasoning (Raven's progressive matrices), information-processing speed and inhibitory control (Stroop test), speed of phonological and lexical access (Test of Word Reading Efficiency), and verbal learning and memory (California Verbal Learning Test). Demographic measures were also collected. Methods Cohort study at tertiary neurotology center. Forty-three post-lingually deafened experienced CI users, 19 post-lingually deafened CI candidates, and 40 age-matched NH controls with no cognitive impairment were enrolled. Comparisons among the groups on the cognitive measures were performed. Results Adult CI users and CI candidates demonstrated worse (or a trend towards worse) performance as compared with NH peers on non-verbal reasoning, information-processing speed, speed of lexical access, and verbal learning and memory. However, after controlling for gender, socioeconomic status (SES), and vocabulary knowledge among groups, some of these differences were no longer significant. Similarly, large differences were not found in most cognitive abilities between experienced CI users and CI candidates. Conclusions Adult CI users, CI candidates, and NH peers generally demonstrated equivalent non-auditory cognitive abilities, after controlling for gender, SES, and vocabulary knowledge. These findings provide support for a link between cognitive decline and hearing loss, but this association may be partly attributable to group differences in SES and vocabulary knowledge. Level of evidence 2b.