Hearing loss and subjective tinnitus loudness
Most patients who experience tinnitus also have some form of hearing loss, but not all patients with hearing loss have tinnitus (Nicolas-Puel et al. 2002; Tyler & Baker 1983; Mazurek et al. 2010). The strong relationship between tinnitus and hearing impairment probably explains why, in the UK, 82% of tinnitus patients are referred to Audiology departments (Gander et al. 2011). To complicate matters, some people with clinically normal hearing have tinnitus (Aazh et al. 2011) suggesting that hearing loss per se not be the dominant factor for induction of tinnitus.
A common concern expressed by patients is that although they can cope with the current level of their tinnitus, one of their fears is that if their hearing worsens it may lead to an increase in tinnitus loudness that they would not be able to cope with. Audiologists typically reassure patients by explaining that there is no direct relationship between severity of hearing loss and tinnitus loudness. There are many people with clinically normal hearing who experience very loud tinnitus and people with very severe hearing loss, but no tinnitus. A compelling counter argument is people with acute hearing impairments such as an impacted wax, ear infections, acute noise exposure or those wearing hearing protection experience an increase in tinnitus loudness. Consistent with this view is the observation that ear plugging leads to decreased loudness tolerance (Formby et al. 2003). Therefore, it is reasonable to assume that hearing loss severity is related to tinnitus loudness, an interpretation that is consistent with some central gain models of tinnitus and hyperacusis (Eggermont & Roberts 2004; Chen et al. 2015; Auerbach et al. 2014).
A recent analysis conducted by Dr. Aazh’s tinnitus team on the data for approximately 1500 patients showed that impact of tinnitus on patient’s life as measured via Tinnitus Handicap Inventory (THI) (Newman et al. 1996) is weakly but significantly correlated with average hearing thresholds across ears, correlation coefficient (r)=0.13 (p<0.001) (Figure 1). However this analysis doesn’t take into account the intervening effect of other factors. Therefore, it is not clear whether the relationship between hearing loss and tinnitus remains statistically significant, if the effects of other variables known to impact tinnitus are taken into account (e.g., depression, anxiety etc).
In a pioneering study, Dr Aazh’s tinnitus team assessed the relationship between tinnitus loudness and pure tone hearing thresholds while taking into account the effect of other factors among over 400 patients with tinnitus and hyperacusis (Aazh & Salvi 2018). This study is published in the Journal of the American Academy of Audiology.
Hearing loss and other predicting factors for tinnitus loudness
To determine the contribution of other factors in Tinnitus Loudness as measured via visual analogue scale (VAS), we performed a stepwise linear regression analysis that, in addition to PTA threshold of the better ear, included the PTA threshold of the worse ear, ULLmin, VAS of Tinnitus Annoyance, VAS of Tinnitus Life Effect, Insomnia Severity Index (ISI), THI, Hyperacusis Questionnaire (HQ), Hospital Anxiety and Depression Scale-Anxiety subscale (HADS-A), HADS-D (Depression subscale), age and gender in the linear regression model.
Nine variables did not significantly increase the proportion of variance predicted by the regression model hence were removed from the model. These were the HADS depression score (p = 0.35), PTA thresholds for the worse ear (p = 0.47), THI score (p = 0.31), HADS anxiety score (p = 0.65), ULLmin (p = 0.79), HQ score (p = 0.58), ISI score (p = 0.8), age (p = 0.08), and gender (p = 0.05).
The remaining three variables in the stepwise linear regression model that increased the proportion of variance accounted for by the model are shown in Table 1. Tinnitus Loudness was significantly associated with PTA Threshold of the better ear (t = 3.16, p<0.001, regression coefficient: 0.022). However, Tinnitus Loudness was more strongly correlated with Tinnitus Annoyance (t = 2.77, p <0.0001, regression coefficient 0.49) and Tinnitus Life Effect (t = 2.77, p<0.006, regression coefficient 0.10) than PTA threshold of the better ear. In this three-factor linear regression model, a 1-dB increase in PTA threshold of the better ear increased the Tinnitus Loudness score 0.022 units. Scores on Tinnitus Annoyance and Tinnitus Life Effect had larger effects on Tinnitus Loudness than PTA. An increase in 1 VAS unit of Tinnitus Annoyance was correlated with an increase of 0.49 VAS units of Tinnitus Loudness while an increase of 1 VAS unit of Tinnitus Life Effect was associated with an increase of 0.1 VAS unit of Tinnitus Loudness. Together, the inclusion of these three factors in the linear regression model explained 52% of the variance in Tinnitus Loudness as measured via VAS.
TABLE 1. Variables included in the final version of the stepwise linear regression model for predicting VAS tinnitus loudness together with regression coefficients, p values, and 95% CI values (n = 445).
|Regression coefficient||p value||95% CI|
|PTA of the better ear||0.022||<0.001||0.01||0.034|
|VAS of Tinnitus Annoyance||0.48||< 0.001||0.41||0.57|
|VAS of Effect of Tinnitus on Life||0.09||0.006||0.028||0.17|
Tinnitus patients often ask whether the loudness of their tinnitus will increase if their hearing gets worse. Our results suggest that tinnitus will likely get louder, but not by very much. However, further longitudinal studies in the same subjects are needed to test the hypothesis that tinnitus will get louder as hearing loss increases. Because hearing loss increases with age and ototraumatic insults, patients should be advised to avoid loud sounds in order to preserve their hearing. However, prolonged daily use of hearing protection is not recommended because it could increase the risk that the tinnitus patient might develop hyperacusis (Aazh & Allott 2016; Formby et al. 2003). On the other hand, hearing protection should be used when noise levels equal or exceed noise safety regulations. Often patients with tinnitus feel that they should protect their hearing to avoid worsening their tinnitus. Hence, some use hearing protection on a daily basis to prevent further hearing loss. These safety-seeking behaviours likely contribute to tinnitus-related anxiety (Bennett-Levy et al. 2004; McManus et al. 2012). Safety-seeking behaviours that restrict a patient’s life experience likely contribute to tinnitus annoyance making the tinnitus “sound” even louder. Although there is no cure for tinnitus, there are a wide range of rehabilitative approaches that can minimize tinnitus annoyance and its impact on patient’s life (Aazh et al. 2016; Tyler et al. 2015). Patients who are less annoyed by their tinnitus or who feel tinnitus does not negatively affect their life have lower tinnitus loudness ratings (Aazh & Moore 2016; Aazh et al. 2008).
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