Bilateral versus unilateral hearing aids for bilateral hearing impairment in adults

Background Acquired hearing loss is common and its incidence increases markedly with age. In most people, 'age‐related' hearing loss is sensorineural (due to the loss of cochlear hair cells) and bilateral, affecting both ears to the same degree. Hearing loss categorised as mild, moderate or severe is primarily managed with hearing aids. People with bilateral hearing loss may be offered one aid, fitted to one specific ear, or two aids fitted to both ears. There is uncertainty about the relative benefits to people with hearing loss of these different strategies. Objectives To assess the effects of bilateral versus unilateral hearing aids in adults with a bilateral hearing impairment. Search methods The Cochrane ENT Information Specialist searched the ENT Trials Register; Cochrane Register of Studies Online; PubMed; Ovid Embase; CINAHL; Web of Science; ClinicalTrials.gov; ICTRP and additional sources for published and unpublished trials. The date of the search was 8 June 2017. Selection criteria Randomised controlled trials (RCTs) comparing the fitting of two versus one ear‐level acoustic hearing aids in adults (over 18 years) with a bilateral hearing impairment, both ears being eligible for hearing aids. Data collection and analysis We used the standard methodological procedures expected by Cochrane. Our primary outcomes were patient preference for bilateral or unilateral aids, hearing‐specific health‐related quality of life and adverse effects (pain or discomfort in the ear, initiation or exacerbation of middle or outer ear infection). Secondary outcomes included: usage of hearing aids (as measured by, for example, data logging or battery consumption), generic health‐related quality of life, listening ability and audiometric benefit measured as binaural loudness summation. We used GRADE to assess the quality of the evidence for each outcome; this is indicated in italics. Main results We included four cross‐over RCTs with a total of 209 participants, ranging in age from 23 to 85 and with a preponderance of men. All the studies allowed the use of hearing aids for a total period of at least eight weeks before questions on preference were asked. All studies recruited patients with bilateral hearing loss but there was considerable variation in the types and degree of sensorineural hearing loss that the participants were experiencing. Three of the studies were published before the mid‐1990s whereas the fourth study was published in 2011. Therefore, only the most