Distributions of pure-tone hearing threshold levels among adolescents and adults in the United States by gender, ethnicity, and age: Results from the US National Health and Nutrition Examination Survey.

Cumulative distributions of audiometric pure-tone thresholds for a non-occupationally noise-exposed population vary with demographic characteristics (e.g. gender, ethnicity, age), tested ear, and stimulus frequency. However, commonly-used audiometric databases either do not take these differences into account, or account for them using data not easily generalized to the US population. The objective of this study was to obtain distributions that are generalizable to the US population without significant history of exposure to occupational noise. Cumulative pure tone threshold distributions from the National Health and Nutrition Examination Survey (NHANES) III and the 1999-2004 data from the continuous NHANES were fitted with an asymmetric sigmoid function with reverse asymmetry, by gender, ethnicity, age, ear, and the stimulus frequency. Results indicated that conditional distributions based on these factors are warranted. Percentiles on the cumulative distribution functions can be transformed into standard normal variates (i.e. z-scores) to facilitate combination of results over time or across individuals with different demographic characteristics. However, combinations across frequency could obscure meaningful differences between the reference group and the hearing test results under analysis.