Initial High-Frequency Amplification Accuracy Predicts Long-Term Hearing Aid Fitting Outcomes: A Real Ear Measurement-Based Study

Background: To investigate whether the accuracy of initial hearing aid amplification verified by real ear measurement (REM) predicts long-term fitting outcomes after one year, and to identify frequency-specific predictors associated with sustained fitting precision. Methods: This retrospective study included 426 ears from 269 patients who underwent initial REM during hearing aid fitting and repeat REM at 9–15 months after fitting. The primary outcome was the absolute difference between real ear insertion gain (REIG) and target gain (TG) for middle-level input sounds at one-year follow-up. Multivariable linear regression analysis was performed to evaluate demographic, audiologic, and initial REM-related predictors. Results: At initial fitting, the discrepancy between REIG and TG increased progressively toward higher frequencies, with the largest deviation observed at 6000 Hz (16.2 ± 9.5 dB). Multivariable analysis demonstrated that initial REM discrepancy at 6000 Hz was the strongest predictor of poorer fitting accuracy at one year (B = 0.129, p < 0.001). Initial discrepancies at 250 Hz and 500 Hz were also significant but showed weaker associations. Higher aided pure-tone thresholds and poorer aided word recognition scores were independently associated with less accurate long-term fitting outcomes. Conclusions: Initial amplification accuracy, particularly at high frequencies, plays a critical role in long-term hearing aid fitting stability. Achieving sufficient gain at 6000 Hz during the first fitting session may improve long-term fitting outcomes and reduce suboptimal hearing aid use.