Further Evaluation and Application of the Wisconsin Age-Related Hearing Impairment Classification System

Purpose: The primary purpose of this report is to further evaluate the Wisconsin Age-Related Hearing Impairment Classification System (WARHICS) scheme for the classification of audiograms obtained from older adults, ages 50-89 years. Method: This was a retrospective analysis of data from 11,729 older adults included in two population, one community, and two clinical data sets. To aid in the interpretation of the audiogram classifications, the functional significance of audiogram categories was evaluated using Hearing Handicap Inventory-Screen scores available for 10,330 of these same individuals. Results: A WARHICS level could be obtained successfully for 99.5% of the 11,729 audiograms included in these analyses. It was applied successfully to population, community, and clinical samples. WARHICS Level 8 audiograms, corresponding to a broad profound hearing impairment (pure-tone thresholds from 500 to 8000 Hz, all > 80 dB HL), were very rare (.1% prevalence). WARHICS subtypes, designed to identify those with high-frequency notched audiograms or flat audiograms, occurred only 3%-6% of the time, depending on the data set. When compared to the current hearing-impairment grading system of the World Health Organization (WHO), several WARHICS levels fell within a given WHO hearing-impairment grade suggesting a finer grained categorization by the WARHICS. The Hearing Handicap Inventory-Screen scores provided justification for the fine-grained categorization according to the WARHICS. It is also demonstrated that the WARHICS levels could be extended to the classification of audiograms from all adults, regardless of age. Finally, a WARHICS-WHO hybrid classification scheme is proposed for future evaluation. Conclusions: Although the WARHICS was developed from a population data set, it was demonstrated here to be applicable to population, community, and clinical data sets for adults aged 50-89 years. The applicability of the WARHICS or a WARHICS-WHO hybrid to population data sets that included younger adults suggests that this classification system has the potential to be applied even more broadly than just to age-related hearing loss.