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T A B L E O F C O N T E N T S
A B S T R A C TThis is the protocol for a review and there is no abstract. The objectives are as follows:To evaluate the effectiveness of hearing aids for mild to moderate hearing loss in adults who have been prescribed at least one hearing aid.
B A C K G R O U N D Description of the conditionHearing loss is the most prevalent sensory deficit (Mathers 2000); it represents a major public health issue with substantial economical and societal costs. Untreated, adult hearing loss results in communication difficulties that can lead to social isolation and withdrawal, depression and reduced quality of life (Davis 2007). Hearing loss is also associated with an increased risk of dementia (Lin 2011). According to the World Health Organization hearing loss is the 13th most common global disease burden and the third leading cause of years living with disease (WHO 2008). Disabling hearing loss is estimated to affect 360 million persons globally (5.3% of the world's population) (WHO 2012a). The prevalence of hearing loss increases with age (Akeroyd 2014), and given the ageing society it is predicted that by 2030 adult-onset hearing loss will be the seventh largest disease burden, above diabetes and human immunodeficiency virus (HIV) (WHO 2008). Epidemiological data suggest that the majority of cases of hearing loss in adults are sensorineural (92%) and bilateral (94.8%) (Cruickshanks 1998). There are numerous definitions of hearing loss across different countries and organisations (Timmer 2015). In this review, hearing loss is defined according to pure-tone thresholds averaged across 0.5 kHz, 1.0 kHz, 2.0 kHz and 4.0 kHz in the better-hearing ear, consistent with the World Health Organization grades of hearing impairment (Mathers 2000). The majority of hearing losses (92%) are those that are defined as mild or moderate (AoHL 2015). Mild (or slight) hearing loss is indicated as 26 to 40 dB hearing level (HL) and described as the ability to hear and repeat words spoken in a normal voice at one metre. Moderate hearing loss is indicated as 41 to 60 dB HL and described as the ability to hear and repeat words using a raised voice at one metre (Mathers 2000). In addition to a loss of hearing sensitivity, there may be additional sensory deficits of temporal and spectral pro-