Performance Phenotypes and Early Prognostic Benchmarking After Adult Cochlear Implantation

Objectives To characterize the temporal dynamics of post‐activation improvement, identify cochlear implant (CI) performance phenotypes, and establish an early prognostic benchmark following CI activation in adults. Methods Retrospective longitudinal cohort at a tertiary academic medical center. Adult CI recipients ( N = 530 patient‐ears) were analyzed across a within‐subjects improvement cohort ( n = 125, complete consonant‐nucleus‐consonant [CNC] data at 1, 3, 6, and 12 months) and a prognostic validation cohort ( n = 205, paired 1‐ and 12‐month CNC). Outcomes included CNC word recognition, improvement rates, device datalogging, and 1‐month prognostic validity. Results CNC improvement was front‐loaded. Early‐period (1 → 3 month) rates of 4.44 ± 6.95 points/month were approximately 35‐fold faster than late‐period (6 → 12 month) rates of 0.13 ± 1.84 points/month (Friedman χ 2 = 26.97, p < 0.001). k ‐means clustering identified three performance phenotypes distinguishable at 1 month ( p < 0.001). Preoperative CNC did not differ across clusters ( p = 0.25). Device usage was a stable patient‐level trait. It differed between clusters ( p < 0.001) but did not predict CNC improvement ( ρ = 0.02, p = 0.82). However, sustained or increasing engagement through 6 months was associated with higher 12‐month CNC than declining engagement ( p = 0.004). The 1‐month CNC score strongly predicted 12‐month outcomes ( ρ = 0.68, p < 0.001; R 2 = 0.45), a 15‐fold gain over preoperative CNC. A 1‐month CNC ≥ 44% predicted functional success (12‐month CNC ≥ 50%) with AUC 0.82 (95% CI: 0.76–0.88; sensitivity: 0.66, specificity: 0.89). Conclusions Adult CI recipients undergo accelerated auditory adaptation concentrated in the first 3 months post‐activation, with performance trajectories largely established by 1 month. A 1‐month CNC threshold of ≥ 44% represents a clinically actionable prognostic checkpoint, and sustained device engagement through 6 months is associated with optimal long‐term outcomes. Level of Evidence 3.