Chapter 1 48 Discussion The aim of this study was to identify factors influencing NFR and LE in hearingimpaired employees. Four factors were shown to directly influence NFR and four factors were shown to directly influence LE. In line with the literature arguing the theoretical assumption that increased LE may cause a sense of mental fatigue (McGarrigle et al., 2014), LE was found to be the factor with the highest associationwithNFR(r =0.527) in the correlationanalysis. In contrast, nosignificant associationswereobservedbetweenthehearing test outcomes and NFR, including BHI, maximum discrimination score, and the critical SNR. While tinnitus has earlier been shown to be associated with NFR ( Juul Jensen et al., 2018), we did not find a significant association in this study. This may be explained by the dichotomous question that we used that did not allow for differentiating in degree of tinnitus. Also, because we used routinely obtained healthcare data, we may have missed hearing-related factors, such as hyperacusis. For concepts related to NFR, mixed results are presented for hearing loss (Hornsby & Kipp, 2016; Svinndal et al., 2018). Pure-tone audiometry was not significantly related to fatigue and vigor (Hornsby & Kipp, 2016), but patients with more severe hearing loss reported lower workability and higher degrees of fatigue (Svinndal et al., 2018). The lack of a significant association between SNRandNFR in the correlation analysis contrasts the results of an earlier study that found poorer SNR to be associated with higher NFR (Nachtegaal et al., 2009) In this earlier study, the SNR was derived from an adaptive digits-in-noise test performed over the internet and the subjects completed the test without hearing aids. In our study, routinely healthcare data were used, having the advantage that all hearing tests were performed instandardizedaudio cabins, but with the disadvantage that SNR data were missing in 158 patients (54%). Performing the speech reception test in noise is not obligatory in standard care. The choice to perform the speech reception test is determined by a patient’s profession and associated auditory demands.Therefore, themissing SNRdata are not missing at random, and the presence of confounding cannot be ruled out. Another explanation might be that we derived SNR’s with and without hearing aids, to resemble patients’ daily life work situation. Although we expected the SNR scores to be more strongly associated with NFR, this choice may have masked an existing association. Since BHI correlates with LE, but not with NFR, we presume that the degree of hearing
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