Modeling Cognitive Trajectories in the Long-Term After Cochlear Implantation

Hearing restoration by cochlear implantation (CI) yields benefits beyond hearing. Short-term benefits on cognition are well-known, but long-term data are limited and inconsistent. Therefore, we analyzed a large sample of CI recipients with a focus on cognitive changes in the long-term follow-up.

Seventy-five CI recipients aged older than or equal to 50 (mean age 65.4, SD 9.2) were tested in attention, immediate and delayed recall, working memory (OSPAN) and verbal fluency (VF) pre-implantation and 12, 24, 54 as well as 99 months post-CI. Three linear mixed-effects models (linear, quadratic, and time-indicator) were fitted and contrasted.

Despite different statistical assumptions, all 3 models converged on initial cognitive improvement after implantation. In the time-indicator model, significant improvements relative to baseline were observed across all 5 outcomes at 12 and 24 months (P<0.01), with effect sizes at 24 months ranging from d=0.26 (OSPAN) to d=0.93 (VF). Subsequent trajectories diverged across domains. At 99 months, only attention (M3) showed sustained improvement (P <0.001, d=0.60), with an effect size comparable to its 24-month peak. The remaining 4 outcomes did not significantly differ from baseline (P>0.05). The quadratic model confirmed inverted-U-shaped trajectories for all outcomes, with significant negative quadratic terms (all P≤0.001).

Cognitive benefits of cochlear implantation extend beyond the short-term, but long-term trajectories are domain-specific. Considering the multifactorial nature of cognitive aging, multicenter studies with larger sample sizes and extended follow-up visits are needed to clarify the mechanisms behind the impact of CI on cognition.