Hearing Aid Use by Unilaterally Impaired Individuals: Outcome of the Tinnitus Handicap Inventory

THI: Tinnitus Handicap Inventory; VAS: Visual Analog Scale; PTA: Pure-tone Average

Tinnitus (the perception of sound in the absence of external stimuli) is a highly prevalent condition and is a common feature of injuries or diseases that result in significant unilateral hearing deprivation [1]. Some identified etiologies of unilateral sensorineural hearing impairments include Meniere‘s disease, sudden hearing loss ear trauma from noise or head injury and retro-cochlear lesions [2-6]. Unilateral hearing loss can negatively impact sound localization, word understanding in noise and difficulties in hearing in everyday life [7]. The perception of tinnitus often occurs with hearing loss and has been shown to be influenced by audiometric configuration of the hearing loss [8,9]. Evidence suggests that the tonal quality of the perceived tinnitus’sound‘ is either determined by the area of maximal hearing loss or it is perceived at the edge of the hearing loss slope i.e.,’ringing‘ tinnitus is associated with high frequency impairments and’roaring‘ tinnitus is associated with mid or low frequency impairments [10,11]. Though it is well established in the literature that use of hearing aids can lessen the negative impact of tinnitus in individuals with hearing impairments, it has not been clearly established whether individuals with strictly unilateral sensorineural impairments and .tinnitus, whether unilateral or bilateral, can receive the same benefit [12-14]. Research is needed in this regard as conditions that result in unilateral sensorineural hearing impairments and tinnitus may have differing pathogenisis, such as with Meniere‘s disease or sudden hearing loss, and may be differently affected by the use of a hearing aid .

For individuals who are poor candidates for amplification, the use of noise generators or other devices that utilize broad band noise or music have been shown to provide relief from tinnitus [15-17]. Similar to hearing aid studies, application of this approach has not been solely demonstrated in individuals with unilateral sensorineural impairments. The suspected mechanism of how amplification or use of noise generators can provide tinnitus relief lies in the possibility that tinnitus is coded by spontaneous neural activity in the auditory cortex and is the result of over-representation of some frequency-tuned neurons. It is arguable that use of amplification or broadband noise, as a therapeutic intervention, alters this cortical overrepresentation of the tinnitus [18].

The clinical significance of tinnitus is the extent that an individual suffers from it. Annoyance from tinnitus is subjective and may depend on factors other than just the perceived pitch or loudness of the’sound.‘ Suffering from tinnitus may be linked to the extent that it inhibits physical and mental activities, causes emotional distress, or the extent that it is concurrent with other otologic conditions, such as with hearing loss [19-22]. The clinical assessment of the handicapping effects of tinnitus is generally accomplished by patient self-report questionnaires. One such questionnaire, the Tinnitus Handicap Inventory, was developed as a 25 item self-report questionnaire designed to assess the handicap experienced as a result of tinnitus. It was validated for patients with either primary complaints of tinnitus or hearing loss with tinnitus. The THI was not designed to assess non-tinnitus otologic conditions, which have been shown to contribute to perceived tinnitus handicap; however, the THI does assess aspects of the emotional (e.g., anger, frustration, and depression; 9 questions) and functional (e.g., concentration, sleep, and hearing; 11 questions) impact of tinnitus on an individual. Also, the THI probes the extent to which an individual feels incapacitated or that they have a terrible disease (catastrophic sub-scale; 5 questions). The THI has established validity, is well represented in the literature, has excellent test-retest reliability, and has been recommended as a tool of choice for research related tinnitus measurements [23-24].

Data presented in this report are from a larger study, a multidimensional assessment of outcome with use of a hearing aid by individuals with unilateral sensor neural hearing loss. For the larger study, data were collected on a group of individuals who had a qualifying hearing impairment and voluntarily used a hearing aid for at least three months. Pre and post assessments included hearing and tinnitus handicap questionnaires, word recognition, and performance on a test of speech perception in noise. Not all participants in the larger study reported tinnitus; however, for this report, data are given for a sub-set of 16 participants who did report tinnitus. These data characterize the prevelence of data within this population and the outcome of the THI sub-scale and total scores, as well as the visual analog scale, in pre and post-hearing aid fitting conditions. We hypothesize that these findings will provide further support for use of amplification as a treatment for tinnitus in individuals with hearing loss, despite etiology and the presence of normal hearing in one ear.

Between September 2011 and August 2012, 30 participants with unilateral sensorineural hearing loss were recruited. For the purpose of this study, unilateral sensorineural hearing loss was defined as normal hearing in one ear (pure-tone average (PTA) of 500Hz, 1000Hz, and 2000Hz ≤ 25 dB HL) and a moderate or greater sensorineural hearing loss (PTA of 500Hz, 1000Hz, and 2000Hz ≥ 40 dB HL) in the contralateral ear, with an air-bone gap no greater than 10 dB HL for any test frequency. Each participant received an audiologic exam that confirmed healthy function of the external and middle ear. Nine participants were not able to complete the entire study protocol. Of the 21 participants who actually completed the study, 5 of these individuals did not report tinnitus. Therefore, analysis of data from the Tinnitus Handicap Inventory (THI), in pre- and post-hearing aid fitting conditions, is given for the 16 remaining individuals who reported tinnitus, met inclusion criteria, and completed the field trial. All individuals who participated in this study reviewed and signed an informed consent document that described benefits and risks of participation. The experimental design, test protocol and informed consent materials were reviewed and approved by the University of Mississippi Medical Center Institutional Review Board.

All audiologic assessments were performed by licensed clinicianinvestigators in an outpatient clinic that is outfitted with commercially available test rooms that meet ANSI specifications for permissible ambient noise [25]. Otoscopic inspection of the external ear canals was performed to verify the absence of occluding debris or active infection in the canal or middle ear space. Assessment of middle ear compliance and pressure were assessed with a conventional tympanometer (Tympstar; Grason-Stadler, Eden Prairie, MN), which also met ANSI specifications [26]. Speech reception thresholds (SRT) were obtained using pre-recorded spondee world lists and were followed by a diagnostic pure-tone assessment of auditory thresholds. Puretone audiometry and SRT testing was performed in accordance with procedures recommended by the American Speech-Language-Hearing Association [28]. An average of air-conducted pure-tone thresholds (PTA) at 500, 1000 and 2000 Hz was used to determine severity of impairment, such as mild (30 dB HL to < 40 dB HL), moderate (40 dB HL to < 60 dB HL), moderately-severe (60 dB HL to < 70 dB HL), severe (70 dB HL to <90 dB HL) or profound (≥ 90 dB HL). For use in this report, individuals were categorized by audiometric configuration, such as “normal/mild sloping to moderate high frequency hearing loss,” “flat moderate/moderately severe hearing loss,” “moderate to severe hearing loss,” or “severe to profound hearing loss.”

Participants completed the Tinnitus Handicap Inventory both before and after being fit with a hearing aid [23]. Completion before fitting will be called’unaided‘ and completion after fitting and the associated field trial will be called’aided.‘ The field trial was three months in length, during which participants completed a minimum of two follow-up visits. The THI is a 25-item questionnaire that was selfadministered by participants after receiving verbal instructions on its use. By design, this instrument probes three distinct aspects of tinnitus handicap, the self-perceived emotional (e.g., impact on feelings of anxiety, and depression; 9 questions), functional (e.g., impact on concentration, sleep, and hearing; 11 questions), and catastrophic (e.g., impact on feelings of desperation and coping; 5 questions) aspects. Responses are forced-choice and given values similar to a traditional Likert scale. Each item includes three possible answers, YES (value of 4), SOMETIMES (value of 2), and NO (value of 0). Generally, the sub-scale questions are analyzed individually, whereas the sum of all questions (THI total score) can be used as an estimate of overall tinnitus handicap. The handicapping scale of the THI total score is based on a range of values, such that:’no handicap‘=0-16,’mild handicap‘=18-36,’moderate handicap‘=38-56 and’severe handicap‘=58-100. Included with the THI is a visual analog scale (VAS) of self-perceived tinnitus severity. The VAS is a single question psychometric response scale. This measurement is selectively used in conjunction with the THI and has been shown to correlate strongly with the THI total score [28]. Respondents specify their level of agreement by indicating a position along a continuous line between two end-points, from 0 (’no tinnitus‘) to 10 (’severe tinnitus‘). All responses on this scale were rounded to the nearest whole number for analysis.

Each participant underwent audiometric assessment and was given the THI before receiving a hearing aid (’unaided‘ condition). The hearing aids used in this study were multi-channel, digital, behind-the-ear devices (S Series 11, Starkey Hearing Technologies). Ear mold venting and acoustic modifications were done based on the audiometric configuration of the hearing loss, and were modified to control feedback or to relieve occlusion. Hearing aid programming was done in a conventional manner. Participants were seen for a hearing aid fitting appointment that involved probe-microphone verification of device settings. Gains were prescribed to targets generated by NALNL1 with minor modifications made to ensure participant compliance. On follow up visits, the hearing aid datalog was reviewed. In cases where the hearing aids were worn less than 6 hours per day, the participant was counseled and encouraged to increase use. Hearing aid signal processing features were left active for the duration of the study; directional microphones functioned automatically, switching between omni-directional and directional configurations when noise levels reached appropriate limits. The noise reduction algorithms were adjusted to the maximum allowable limit of the hearing aid. No specific counseling was performed regarding tinnitus habituation and participants were not informed whether a hearing aid may or may not improve their THI scores.

THI sub-scale item, total and VAS scores were analyzed for both’unaided‘ and’aided‘ conditions for all participants in this study (N=16). Results were analyzed respective to level of measurement. Number and percent values, as well as THI total scores in both test conditions were assessed for participant sub-group characteristics, such as gender, age, audiometric configuration, tinnitus description, etiology of hearing loss, and study outcome. Group responses to individual THI sub-scale items were summed and results were given for both test conditions. Differences between the’aided‘ and’unaided‘ values for each sub-scale item were ranked. A paired differences t-test in means between THI total test scores in’unaided‘ and’aided‘ conditions was performed. Level of significance was set at 95%, alpha = 0.05. This statistical test was used since the THI total score lends itself to parametric statistical analysis and this data set satisfies the Shapiro-Wilks test of normality [29]. The VAS is a single item question and comparison of means between’unaided‘ and’aided‘ conditions requires a non-parametric approach, such as with the Wilcoxon Signed Ranks Test. Spearman rank correlations were used to compare the THI total score with the VAS in both test conditions and was performed as a check of THI total score internal validity. All statistical procedures were conducted on SPSS 19.0 (IBM, Inc.). In Table 1, frequencies (n/%) of each participant characteristic and means for the THI total score for’unaided‘ and’aided‘ conditions, are given.

The study sample was comprised of 16 individuals who met inclusion criteria for unilateral sensorineural hearing loss with tinnitus. The sample was comprised of more females (62.5%) than males (37.5%), and there was a near equal distribution of participants across a wide range of age- groups, with 37.5% in the 20-49 yr age- group, 12.5% in the 50-59 yr age- group, 31.25% in the 60-69 yr age- group and 18.75% in the older 70-79 yr age- group. For all participants, hearing in one ear was normal (PTA ≤ 25 dB HL). In the affected ear, most participants presented with a flat moderate or flat moderately- severe sensorineural hearing loss (56.25%). Also seen were a number of hearing losses with a sloping normal to moderate (25%), or a sloping moderate to severe sensorineural hearing loss (18.75%). Several different tinnitus descriptions were noted, with many participants reporting a “ringing” (31.25%), or “roaring” (18.75%) sensation. The majority of participants reported tinnitus that is complex (43.75%), which is a combination of “ringing” at different identifiable pitches, as well as other sensations identified as either “roaring” or “waterfall.” Hearing loss etiology was most often reported as sudden/idiopathic (68.75%), with a few participants having a suspected etiology of cardiovascular disease (18.75%), noise trauma (6.25%), or Meniere‘s (6.25%). In total, 7 participants (43.75%) elected to continue using a hearing aid after the study and another 9 (56.25%) elected to discontinue use. For all participant sub-groups there was an observed decrease in THI total score (reduced tinnitus handicap) from the’unaided‘ to the’aided‘ condition, which included the group of participants who elected to discontinue use of a hearing aid after the study.

Table 2 shows THI questions organized by sub-scale (emotional, functional and catastrophic), with the sum of the group scores presented for each individual item and for the entire sub-scale. Sum values were calculated in order to accurately reflect the ordinal, non-parametric, nature of the data and to facilitate visual comparisons between the test conditions. The sum of the scores for individual items in the’aided‘ condition were subtracted from the sum of the scores for individual items in the’unaided‘ condition, and the differences were ranked, with a possible range of 1 to 14. Each sub-scale had a notable mixture of high and low ranked differences.

The questions that were ranked the highest, i.e., those that had the greatest difference from ‘unaided’ to ‘aided’ conditions, irrespective of starting value (‘unaided’ score), were F2 Does the loudness of your tinnitus make it difficult for you to hear people? (Ranked 1st), C19 Do you feel that you have no control over your tinnitus? (Ranked 2nd), C8 Do you feel as though you cannot escape your tinnitus? (Ranked 3rd), and F18 Do you find it difficult to focus your attention away from your tinnitus and on other things? (Ranked 4th). The questions that were ranked the lowest, i.e., those that had the least difference from ‘unaided’ to ‘aided’ conditions irrespective of starting value (‘unaided’ score), were F9 Does your tinnitus interfere with your ability to enjoy social activities? (Ranked 14th), E25 Does your tinnitus make you feel insecure? (Ranked 13th), F7 Because of your tinnitus, do you have trouble falling asleep at night? (also Ranked 13th), and C11 Because of your tinnitus, do you feel that you have a terrible disease? (Ranked 12th).

For the questions with a large starting value, i.e., ‘unaided’ score of 38 or greater, question F2 Does the loudness of your tinnitus make it difficult for you to hear people?, again, saw the greatest improvement in the’ aided’ condition. Other questions that had a large starting value, i.e., ‘unaided’ score of 38 or greater, and saw the greatest reduction in the THI group sums, included: C19 Do you feel that you have no control over your tinnitus?, C8 Do you feel as though you cannot escape your tinnitus?, and F18 Do you find it difficult to focus your attention away from your tinnitus and on other things?

The THI total score (the sum of all the sub-scale item scores) was calculated for each participant in both ‘unaided’ and ‘aided’ conditions. Given that the total score is a sum of scores from all 25 items on the THI, it was treated as parametric data [29]. Paired differences t-test for the THI total test score group means is summarized in Table 3. Results were found to be consistent with a statistically significant (t=7.289(15), p=0.0001) reduction in THI total score group mean from the ‘unaided’ to the ‘aided’ condition. Cohen’s d for effect size was also assessed and judged strong (d=1.82). The Wilcoxon Signed Ranks test was used to assess differences between the VAS group means. Similar to the THI total score group mean difference, the VAS was significantly reduced in the ‘aided’ compared to the ‘unaided’ condition (Z=-2.937, p=0.003).

Table 1: Characteristics of Participants who Completed Hearing Aid Trial (n=16).

Table 4 shows the Spearman Correlation Coefficient (rs) for the VAS group mean with the THI total score group mean, for both ‘unaided’ and ‘aided’ conditions. Results were consistent with a strong positive correlation (rs=0.825, p=0.0001) of the VAS with the THI total score in the ‘unaided’ condition, and a moderate positive correlation (rs=0.546, p=0.029) of the VAS with the THI total score in the ‘aided’ condition. In both cases the correlation of the THI total score and the VAS were statistically significant (p<0.05). This result indicates that the observed THI total scores hold internal validity, such that how individual’s evaluated the severity of their tinnitus with the VAS correlated at least moderately strong with the THI total of responses on all 25 sub-scale items.

Though our study was comprised of a fairly small number of participants (N=16) there was, nonetheless, representation of a wide range of ages, hearing loss configurations/etiologies and participant descriptions of tinnitus. We observed a near equal distribution of males to females and effect size for comparison of means of the THI total score was not compromised by the small sample size. Consistent with published evidence showing that hearing aids can help reduce the perceived negative impact of tinnitus on individuals with hearing impairment [12-14], our data indicate that this may also be true of individuals with strictly unilateral sensorineural impairments, regardless of etiology. As evidenced by the data presented in this report, there was an observed reduction in THI total/ sub-scale item and VAS scores from the ‘unaided’ to the ‘aided’ test conditions. These data suggest that hearing aid use by the participants in this study effectively reduced tinnitus handicap, at least as observed by THI scores.

Table 2: THI Sub-scale Item Scores and Rank of Differences (n=16).

Table 3: THI total score and VAS Paired Comparisons (n=16).

Table 4: Correlation of THI total score with VAS (n=16).

Of the individual items on the THI with a large starting value (‘unaided’ score of 38 or higher) question F2, which is related to the impact of tinnitus on hearing, saw the greatest improvement. This is not a surprising finding as this aspect of tinnitus handicap is related to auditory function and is the most likely to improve with use of a hearing aid. This is consistent with findings in the literature that suggest that individuals with tinnitus and hearing loss perceive greater relief from tinnitus with use of amplification than individuals who use sound therapy or counseling alone [30,31]. There were individual items of the THI that did not show as much improvement. The items that changed the least from the ‘unaided’ to the ‘aided’ condition involved the effect of tinnitus on sleep (F7) and feelings of having a terrible disease (C11). We explain this result by the fact that participants were not instructed during this study to use their hearing aids or a separate bedside noise generator while sleeping. Also, we postulate that item C11 did not show much improvement by the fact that it is related to catastrophic feelings not likely to improve with use of a hearing aid in the absence of adequate counseling or other medical intervention.

Despite the variability of measured improvement of individual items on the THI, the total score for the group was significantly reduced in the’aided‘ compared to the’unaided‘ condition (p< (t=7.289(15), p=0.0001). This significant difference was also seen with the VAS scores. Though this reduction in THI scores between conditions was statistically significant, it was not of sufficient magnitude to prevent nearly half of all participants in this study from electing to discontinue use of a hearing aid after the study concluded. This was not unexpected as individuals with unilateral hearing loss have demonstrated variability in satisfaction with hearing aids [32,33]. Since a large number of participants in this study were on a fixed income, we suspect that cost was a decisive barrier for many of the individuals who did not pursue the purchase of devices.

These data support the study hypothesis that hearing aid use by individuals with unilateral sensorineural hearing loss and tinnitus can lessen the negative impact of tinnitus. A distinct limitation of our study, however, is that we only used a single measure of tinnitus handicap. And, given the limited number of study participants, our results cannot be generalized to all individuals who may have tinnitus handicap with unilateral hearing loss. Also, since the THI is limited in its scope of assessment and given that it is not a validated assessment of clinical depression, changes in THI scores may not be sensitive to some aspects that determine suffering from tinnitus [23,24]. Lastly, there is the possibility that individuals overrated their tinnitus improvement as a result of the influence of their participation in the study.

The current study demonstrated that use of a hearing aid by individuals with unilateral sensorineural hearing loss and tinnitus may reduce perceived tinnitus handicap. Consistent with existing literature in the area, observed benefits were variable with some individuals reporting greater benefit than others. The reason for this variability is not clearly understood; however, the observation of significantly reduced tinnitus-related handicap with unilateral hearing aid use is not one that has been commonly reported in existing literature. This finding offers immediate clinical utility, suggesting opportunity for modification to existing treatment strategies in cases where a patient reports significant handicap as a result of unilateral hearing loss and tinnitus.