Can You Hear Me Now?
Hearing difficulty (HD) and tinnitus in the presence of normal audiometric thresholds represent a clinical challenge. So-called, hidden hearing loss (HHL) has captured significant interest from clinicians and researchers in attempts to understand factors that contribute to this phenomenon. Etiologies ranging from cochlear synaptopathy to central auditory processing deficits have been suggested. Most audiologists have come across these patients with complaints of hearing problems (particularly in noise) but normal hearing. Though anecdotally common, it is unclear what the prevalence of HD and tinnitus are in persons with normal hearing.
Recently, Spankovich et al (2017) examined data from the National Health and Nutrition Examination Survey to answer the question. Over 2,000 participants were included in the sample that allows generalization to the U.S. non-institutionalized population. They found that the prevalence of HD and tinnitus among the “normal hearing” was dependent on how normal hearing was defined. The two primary definitions of “normal hearing" were a pure-tone average (PTA) of 500, 1000, 2000, and 4000 Hz >= 25 dBHL for each ear and frequency-specific thresholds at 500, 1000, 2000, 4000, 6000, and 8000 Hz <= 25dBHL for each ear.
Applying the more stringent definition of “normal hearing” (i.e., thresholds <= 25 dBHL at every frequency), the prevalence of HD was 10.4 percent, and persistent tinnitus was reported by 7.9 percent. As the definition of “normal hearing” was shifted to PTA, the prevalence of HD increased to 15 percent, and persistent tinnitus to 10.6 percent.
Factors related to HD and tinnitus included reported balance issues, noise exposure, vision deficits, arthritis, peripheral neural symptom complaints, and physical/mental/emotional issues. Age, sex, and race/ethnicity were not significant when using the more restrictive definition. The authors suggested that approximately 10 percent of HD may be explained by tinnitus percept, as there was significant overlap between those reporting HD and persistent tinnitus.
Spankovich C, Gonzalez VB, Su D, Bishop CE. (2017) Self-reported hearing difficulty, tinnitus, and normal audiometric thresholds, the NHANES, 1999-2002. Hearing Research December 7.