Effects of Hearing Impairment and Hearing Aid Amplification on Listening Effort: A Systematic Review

OBJECTIVES:To undertake a systematic review of available evidence on the effect of hearing impairment and hearing aid amplification on listening effort. Two research questions were addressedQ1) does hearing impairment affect listening effort? and Q2) can hearing aid amplification affect listening effort during speech comprehension? DESIGN:English language articles were identified through systematic searches in PubMed, EMBASE, Cinahl, the Cochrane Library, and PsycINFO from inception to August 2014. References of eligible studies were checked. The Population, Intervention, Control, Outcomes, and Study design strategy was used to create inclusion criteria for relevance. It was not feasible to apply a meta-analysis of the results from comparable studies. For the articles identified as relevant, a quality rating, based on the 2011 Grading of Recommendations Assessment, Development, and Evaluation Working Group guidelines, was carried out to judge the reliability and confidence of the estimated effects. RESULTS:The primary search produced 7017 unique hits using the keywordshearing aids OR hearing impairment AND listening effort OR perceptual effort OR ease of listening. Of these, 41 articles fulfilled the Population, Intervention, Control, Outcomes, and Study design selection criteria ofexperimental work on hearing impairment OR hearing aid technologies AND listening effort OR fatigue during speech perception. The methods applied in those articles were categorized into subjective, behavioral, and physiological assessment of listening effort. For each study, the statistical analysis addressing research question Q1 and/or Q2 was extracted. In seven articles more than one measure of listening effort was provided. Evidence relating to Q1 was provided by 21 articles that reported 41 relevant findings. Evidence relating to Q2 was provided by 27 articles that reported 56 relevant findings. The quality of evidence on both research questions (Q1 and Q2) was very low, according to the Grading of Recommendations Assessment, Development, and Evaluation Working Group guidelines. We tested the statistical evidence across studies with nonparametric tests. The testing revealed only one consistent effect across studies, namely that listening effort was higher for hearing-impaired listeners compared with normal-hearing listeners (Q1) as measured by electroencephalographic measures. For all other studies, the evidence across studies failed to reveal consistent effects on listenin