The impact of tinnitus on n-back performance in normal hearing individuals

Background: Tinnitus sufferers commonly report concentration difficulties. Despite several previous studies investigating this, the underlying cause and the role of hearing status remains unclear. Purpose: To investigate whether there are any differences between normal hearing individuals with and without tinnitus in terms of working memory capacity, and whether working memory capacity correlates with high-frequency hearing thresholds. Research Design: Participants had their hearing thresholds measured (0.125-16 kHz) and performed a visual n-back test. All participants completed the Hospital Anxiety and Depression Scale, in addition tinnitus participants filled out the Tinnitus Questionnaire. Study Sample: Sixty-two individuals participated, 31 had tinnitus (tinnitus group) and 31 did not have tinnitus (control group). Groups were age- and sex matched, and all participants had normal hearing thresholds (20 dB HL or better at 0.125-8 kHz). Data Analysis: Friedman test of differences among repeated measures was conducted on the collected data of n-back performance, and Mann-Whitney U-test was used to compare groups. Age-corrected correlations were calculated for high-frequency hearing and each n-back condition. Results: We found no significant differences between the groups in terms of n-back task performances, except for the 2-back condition where the tinnitus group performed significantly better than the controls (p = 0.007). Furthermore, we found high-frequency hearing thresholds of the best ear (10-16 kHz) to correlate with performances at more demanding n-back conditions (p = 0.029 for 1-back and p = 0.015 for 2-back). Conclusion: This suggests that presence of tinnitus might not imply poorer working memory capacity and that deteriorated high-frequency hearing thresholds.