Predictable Factors of People with Asymmetrical Hearing Loss Wearing a Hearing Aid in the Worse Ear Only

{"Background": "Bilateral hearing aids are the standard for bilateral hearing loss, but in asymmetrical hearing loss (AHL), fitting strategies are less clear. Many patients can only afford one hearing aid, creating a clinical dilemma about which ear to amplify. The 60 dB HL rule (fitting the ear with four-frequency PTA closer to 60 dB HL) is commonly used but may underestimate binaural advantages. This study hypothesized that empirical prescription of a hearing aid to the worse ear in AHL could reduce interaural differences and improve satisfaction. The secondary objective was to identify predictable factors influencing hearing aid outcomes.", "Methods": "This retrospective study included 102 Korean adults (37 men, 65 women; mean age 63\u00b114 years) with AHL who purchased a hearing aid at one secondary-referral university-based hospital. Inclusion criteria: age \u226519 years, asymmetrical hearing loss (interaural difference \u226515 dB HL in PTA4), sensorineural or mixed-type HL, ear anatomy compatible with conventional hearing aid, and hearing aid fitted to the worse ear. Exclusion criteria: conductive hearing loss, fluctuating hearing loss, neurological/psychiatric disorders, inadequate cognitive competence, or self-reported physical/mental health unsuitable for hearing aid use. AHL was classified into three subgroups: unilateral hearing loss (UHL; n=48), AHL type 1 (AHL1; n=26), and AHL type 2 (AHL2; n=28), based on poorer ear PTA4 of 70 dB HL and better ear PTA4 of 30 dB HL. Hearing aid fitting was performed using the NAL formula at 1, 2, 3, 6, and 12 months post-purchase. At 12 months, outcomes were evaluated and patients classified as successful users (wearing hearing aid >4 hours/day for \u226512 months, >2% improvement in HINT, improved sound localization, IOI-HA score \u226521), intermittent users (did not meet all success criteria but continued use), or failed users (stopped use within 12 months). Statistical analyses included Kruskal-Wallis test, Mann-Whitney U test, chi-squared test, and discriminant analysis.", "Key Results": "Of 102 patients, 44 were successful users (43.1%), 25 intermittent users (24.5%), and 33 failed users (32.4%). The overall usage rate (successful + intermittent) was 67.6% (69/102). Among all cases, successful users were significantly younger than intermittent users (59\u00b113 vs. 67\u00b112 years; p=0.041). Retrocochlear/neural etiology was more frequent among successful users (p=0.008 for three outcomes; p=0.037 for two outcomes). Sudden hearing loss specifically was more common in successful users (p=0.006). In the UHL subgroup (n=48), the 1 kHz hearing threshold of the better ear was significantly lower in successful users (13\u00b16 dB HL) than intermittent users (19\u00b17 dB HL; p=0.046). Retrocochlear/neural etiology was more frequent in successful UHL users (p=0.021). In the AHL1 subgroup (n=26), retrocochlear/neural etiology (p=0.040) and sudden hearing loss specifically (p=0.040) were more frequent in successful users. In the AHL2 subgroup (n=28), successful users were significantly younger (63\u00b111 years) than intermittent (76\u00b14 years) and failed users (73\u00b18 years; p=0.007). Discriminant analysis for all cases (three outcomes) identified etiology as the sole predictor (discriminating power 47.1%). For UHL, etiology had 45.8% discriminating power. For AHL2, age had 53.6% discriminating power. Subgroup success rates: UHL 50.0% (usage 70.8%), AHL1 42.3% (usage 73.1%), AHL2 32.1% (usage 57.1%). Among 27 patients with sudden hearing loss etiology, 19 were successful users, 3 intermittent, and 5 failed.", "Clinical Implications": "This study demonstrates that fitting a hearing aid to the worse ear in AHL yields success and usage rates (43.1% and 67.6%) substantially higher than previously reported South Korean national data (12.6% for bilateral moderate-to-profound loss; 0.86% for unilateral loss). The findings identify three clinically useful predictors: (1) better 1 kHz threshold in the better ear predicts success in UHL, suggesting the better ear's residual hearing plays a crucial supplementary role; (2) younger age predicts better outcomes in AHL2, possibly due to better binaural central processing and neural plasticity; (3) sudden hearing loss etiology is associated with better outcomes across AHL subgroups, possibly reflecting distinct neural processing compared to gradual hearing loss. These factors can guide clinicians when only one hearing aid is feasible. However, the study's retrospective design, lack of comparison with better-ear amplification, and inability to account for cognitive function, social status, and listening environments are limitations. No definitive fitting rule emerged, suggesting that trial fitting with adaptation time remains necessary. The results support worse-ear amplification as a viable strategy in AHL and provide evidence-based factors to inform patient counseling and expectation management."}