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Hearing impairment negatively affects well-being and is a major contributor to years lived with disability.1,2 The World Health Organization (WHO) estimates that 466 million people were living with disabling hearing impairment in 2018 and this estimate is projected to rise to 630 million by 2030 and to over 900 million by 2050.3 However, these projections are based on a hearing impairment classification that does not fully reflect the provisions of the International classification of functioning, disability and health for assessing all forms of functional impairments.4 Here we make the case for a review of the concept of disabling hearing loss adopted by WHO after the recommendation of the Global Burden of Disease (GBD) Expert Group on Hearing Impairment in 2008.
The need for an independent classification system for all impairments and disabilities as a complement to the well-established International statistical classification of diseases and related health problems, was first suggested in 1976 by the World Health Assembly. As a result, in 1980 WHO developed the International classification of impairments, disabilities and handicaps.5 One of the key features of this system was the use of qualifiers such as mild, moderate, severe and profound to distinguish various levels of observed or measured deviations outside of the range considered for normal functioning for any health condition. This categorization has been reinforced in the subsequent revisions to the system, such as the International Classification of Functioning, Disability and Health, and accompanied with descriptions of typical problems encountered in daily activities at various levels of severity.4 The classification, notably, does not use the term disabling, as it recognizes the needs of all persons with functional impairments for appropriate intervention.
WHO's first classification for hearing impairment dates to 1986 and is based on the recommendations of an expert group established by WHO specifically for this purpose; the classification has been modified several times since then. The current one is shown in Table 1; it is based on the version published in 1991, which remarked that persons with average pure-tone audiometry of 15-20 decibels (dB) hearing level may experience hearing problems, and those with unilateral hearing losses may experience hearing problems even if the better ear was normal.6 However, currently only adults (> 15 years) with a permanent unaided hearing impairment above...