Long-term prognosis of low-frequency hearing loss and predictive factors for the 10-year outcome

Objectives: To determine the long-term prognosis of low-frequency hearing loss and predictive factors for the 10-year outcome of low-frequency hearing loss. Study Design: Case series with chart review. Setting: Tertiary referral center. Subjects and Methods: From 1979 to 1998, 466 consecutive patients with low-frequency hearing loss received initial treatment at the Hearing and Tinnitus Clinic of Keio University Hospital. Of the 49 eligible patients, pure-tone threshold data obtained over a period of 10 years after onset of low-frequency hearing loss were available for analysis. To determine the progression of hearing loss, we analyzed audiometric pattern changes. We also examined how the following factors affected 10-year prognosis: sex, age, side of hearing loss, accompanying dizziness, pre-therapeutic hearing thresholds at low frequencies, initial therapy results, and fluctuation of hearing during the first year after onset. Results: High- and pan-frequency hearing loss increased as time progressed. About half of the cases developed high- or pan-frequency hearing loss within 10 years of onset. Audiometric patterns measured at 10 years significantly correlated with those measured at one (r = 0.57), three (r = 0.73), and five years (r = 0.85). The 10-year prognosis significantly correlated with only two factors: initial therapy results (r = 0.49) and fluctuation of hearing during the first year (r = 0.43). Conclusions: About half of the cases in our study developed high- or pan-frequency hearing loss within 10 years of onset of low-frequency hearing loss. The initial therapy results and fluctuation of hearing during the first year may indicate the long-term prognosis of patients presenting with low-frequency hearing loss.