title: Effects of hearing loss on heart rate variability and skin conductance measured during sentence recognition in noise.
abstract: OBJECTIVE
  The purpose of the study was to determine the effects of hearing loss and noise on (1) two autonomic nervous system measures associated with stress (skin conductance and heart rate variability) and on (2) subjective ratings of workload/stress. The authors hypothesized that hearing loss would increase psychophysiological and subjective reactivity to noise during speech recognition tasks. Both psychophysiological and subjective indicators of workload/stress were expected to increase with a reduction in signal-to-noise ratio.
  
  
  METHODS
  Sentence recognition in the presence of babble noise was assessed in 15 adults with clinically normal hearing and 18 adults with sensorineural hearing loss. Mean sentence recognition was equalized for the two groups using an adaptive procedure to estimate 80% recognition of words in sentences. Sentences were then presented in quiet and at four fixed signal-to-noise ratios: -6, -3, 0, and +3 dB relative to the individually determined signal-to-noise thresholds. Electrocardiography and skin conductance recordings were obtained during each listening condition. The high-frequency spectral component of heart rate variability was extracted from the electrocardiographic recordings as a measure of parasympathetic nervous system activity. Subjective ratings of effort, mental demand, stress, and perceived performance were obtained after each listening condition using the National Aeronautics and Space Administration Task Load Index.
  
  
  RESULTS
  Recognition scores referenced to the adaptive threshold were similar for the two groups. Participants with hearing loss showed a decrease in high-frequency heart rate variability at lower signal-to-noise ratios, whereas those with normal hearing did not. Skin conductance levels were not sensitive to changes in signal-to-noise ratio. However, overall skin conductance reactivity to noise (relative to quiet) was higher for those with hearing loss than for those with normal hearing. In contrast to the psychophysiological findings, there were no significant differences between subjective ratings for the two groups.
  
  
  CONCLUSIONS
  Listeners with hearing loss show greater autonomic nervous system reactivity to babble noise during speech recognition than do listeners with normal hearing, when recognition performance is equal. The findings are consistent with the conclusion that listeners with hearing loss experience increased effort and/or stress during speech recognition in noise.
authors.affiliation: School of Speech, Language and Hearing Sciences and Joint SDSU/UCSD AuD Program, San Diego State University, San Diego, California, USA.
authors.forename: Carol L
authors.initials: CL
authors.lastname: Mackersie
authors.forename: Imola X
authors.initials: IX
authors.lastname: MacPhee
authors.forename: Emily W
authors.initials: EW
authors.lastname: Heldt
mesh_terms: D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D005260:Female; D005712:Galvanic Skin Response / Q000502:physiology*; D006319:Hearing Loss, Sensorineural / Q000503:physiopathology* / Q000523:psychology; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009622:Noise; D059629:Signal-To-Noise Ratio; D013067:Speech Perception / Q000502:physiology*; D013315:Stress, Psychological / Q000503:physiopathology* / Q000523:psychology; D055815:Young Adult