Objectives: To maintain optimal understanding, persons with sensorineural hearing loss (SNHL) often report a need for increased attention, concentration, and "listening effort" compared with persons without hearing loss. It is generally assumed that this increased effort is related to subjective reports of mental fatigue in persons with hearing loss. Although the benefits of hearing aids for improving intelligibility are well documented, their impact on listening effort and mental fatigue are less clear. This study used subjective and objective measures to examine the effects of hearing aid use and advanced hearing aid features on listening effort and mental fatigue in adults with SNHL.
Design: Sixteen adults (aged 47-69 years) with mild to severe sloping SNHL participated. A dual-task paradigm assessed word recognition, word recall, and visual reaction times (RTs) to objectively quantify listening effort and fatigue. Mental fatigue was operationally defined as a decrement in performance over the duration of the experiment (approximately 1 hr). Participants were fitted with study hearing aids and tested unaided and in two aided conditions (omnidirectional and with directional processing and digital noise reduction active). Subjective ratings of listening effort experienced during the day and ratings of fatigue and attentiveness immediately before and after the dual-task were also obtained.
Results: Word recall was better and dual-task RTs were significantly faster in the aided compared with unaided conditions, suggesting a decrease in listening effort when listening aided. Word recognition and recall in unaided and aided conditions remained relatively stable over the duration of the dual-task, suggesting these processes were resistant to mental fatigue. In contrast, dual-task RTs systematically increased over the duration of the speech task when listening unaided, consistent with development of mental fatigue. However, dual-task RTs remained stable over time in both aided conditions suggesting that hearing aid use reduced susceptibility to mental fatigue. Subjective ratings of fatigue and attentiveness also increased significantly after completion of the dual-task; however, no differences between unaided and aided subjective ratings were observed. Correlation analyses between subjective and objective measures of listening effort and mental fatigue showed no strong or consistent relationship. Likewise, subject variables such as age and degree of hearing loss showed no strong or consistent relationship to either subjective or objective measures of listening effort or mental fatigue.
Conclusions: Results from subjective and select objective measures suggest sustained speech-processing demands can lead to mental fatigue in persons with hearing loss. It is important to note that the use of clinically fit hearing aids may reduce listening effort and susceptibility to mental fatigue associated with sustained speech-processing demands. The present study design did not reveal additional benefits, in terms of reduced listening effort or fatigue, from use of directional processing and digital noise-reduction algorithms. However, experimental design limitations suggest further work in this area is needed. Finally, subjective and objective measures of listening effort and mental fatigue due to sustained speech-processing demands, were not strongly associated, suggesting that these measures may assess different aspects of listening effort and mental fatigue.