Health satisfaction, happiness, mental health, and social relationships are among things that matter most to people and their well-being (Balestra et al. 2017; Office for National Statistics 2019). Population-based studies suggest significant associations between hearing impairment and negative health, well-being, and hearing-related outcomes (Davis 1989; Wilson et al. 1999; Agrawal et al. 2008; Dawes et al. 2014b; Golub et al. 2018). Hearing loss is associated with communication difficulties in noisy situations, listening effort, and fatigue (Gatehouse & Noble 2004; Alhanbali et al. 2017), which can contribute to social isolation, anxiety, and depression (Arlinger 2003; Heffernan et al. 2016). A Lancet commission has also identified hearing loss as the mid-life factor associated with the highest population attributable risk for all-cause dementia (Livingston et al. 2017). Therefore, successful clinical management of hearing loss may improve both physical and mental health, which are important predictors of adult well-being (Layard et al. 2014).
There is limited evidence from population-based studies about the impact of unilateral or single-sided deafness (SSD) characterized by audiometrically normal hearing in one ear and severe or profound deafness in the other ear (Baguley et al. 2006; Lin et al. 2011a; Golub et al. 2018). Findings from small-scale studies suggest difficulties following conversations in noise with unilateral hearing impairment even when the speech perception in the healthy ear is “normal,” which may be due to reduced ability to localize and separate talkers of interest from background noise (Newton 1983; Bess et al. 1986b; Slattery & Middlebrooks 1994; Douglas et al. 2007; Rothpletz et al. 2012; Vannson et al. 2015; Firszt et al. 2017; Vannson et al. 2017). These adverse hearing-related outcomes may in turn lead to social isolation and depressive symptoms (Giolas & Wark 1967; Wie et al. 2010; Sano et al. 2013; Lucas et al. 2018) and affect educational attainment and emotional well-being in children (Bess & Tharpe 1986; Bess et al. 1986a; Lieu 2004). Unilateral hearing impairment can lead to poor quality of life (Arlinger 2003; Wie et al. 2010), which can be further adversely affected by a sudden and unexplained onset as in SSD (Baguley et al. 2006; Carlsson et al. 2011).
While current evidence suggests negative impact of unilateral hearing impairment on well-being, the risks associated with having access to normal speech perception in only one ear for hearing and well-being outcomes have not yet been evaluated in population-based studies. Moreover, available evidence does not allow an evaluation of the relative impact of unilateral hearing impairment with respect to other health-related problems such as cardiovascular disease that may be comorbid and associated with hearing loss (Cruickshanks et al. 1998; Dawes et al. 2014a). As these factors may also have an adverse effect on well-being, their inclusion could provide wider context for the implications of unilateral hearing impairment and related clinical practice.
The aim of the present study was to evaluate the risks of adverse hearing and well-being outcomes in a group of 40- to 69-year-old UK Biobank participants who reported being able to hear in only one ear indicative of unilateral deafness, and having speech reception thresholds (SRTs) in noise indicative of normal hearing in their better ear (SRTN/−). The study compared the outcomes in the SRTN/− group with those from the UK Biobank participants whose speech perception was indicative of either normal (SRTN/N) or impaired hearing (SRTI/I) in both ears. The importance of having only one functionally normal ear was assessed in the context of different demographic, hearing, and health-related factors.
MATERIALS AND METHODS
UK Biobank Resource
UK Biobank is a resource of health data from >500,000 people aged 40–69 years (Allen et al. 2014). The UK Biobank participants were identified via the UK National Health Service patient registries and invited to attend one of the 22 UK Biobank Assessment Centres in the proximity of the participant’s place of residence. The baseline assessment conducted between 2007 and 2010 included a registration and consenting process, collection of health-related data using a touchscreen questionnaire and tests of hearing and cognitive function, as well as physical measures and biological samples (e.g., weight and blood samples). The consenting process and data collection were carried out by or under the supervision of trained clerical, nursing, and healthcare technician staff (UK Biobank 2007). The present study included baseline data from 113,804 participants who completed a touchscreen questionnaire and a short test of speech perception in noise. The UK Biobank has ethical approval from the North West Multi-centre Research Ethics Committee (MREC). Associated research using the resource within the United Kingdom is monitored and licensed by the UK Biobank Ethics and Governance Council.
Seven outcome variables were selected from responses to the UK Biobank touchscreen questionnaire questions that corresponded to concerns reported by people with SSD (Giolas & Wark 1967; Wie et al. 2010; Lucas et al. 2018). Two questions from the “hearing” category of the questionnaire described “functional” domains of hearing loss: whether participants experienced difficulties following conversations in the presence of background noise or had tinnitus (see Table ST1 in Supplemental Digital Content, http://links.lww.com/EANDH/A746) Five further questions from the “psychosocial factors” and “general health” categories of the questionnaire were selected as relevant domains of well-being and included self-reports on depression, health rating, satisfaction with health, happiness and loneliness. These measures were framed in a general context without reference to hearing and were always asked before any questions about hearing. Responses were recoded as binary variables, indicating the presence or absence of a negative outcome on well-being or hearing (Table 1).
TABLE 1. -
Definitions of outcomes
||UK Biobank Question
||Over the past 2 weeks, how often have you felt down, depressed, or hopeless*
||(a) Not at all
||(b) Several days
||(c) More than half the days
||(d) Nearly every day
|In poor health
||In general how would you rate your overall health*
|Dissatisfied with health
||In general how satisfied are you with your health*
||(a) Extremely happy
||(b) Very happy
||(c) Moderately happy
||(d) Moderately unhappy
||(e) Very unhappy
||(f) Extremely unhappy
||Do you often feel lonely*
||In general how happy are you*
| As “Dissatisfied with health”
||Response options as in “Dissatisfied with health”
|Has difficulty following conversations in noise
||Do you find it difficult to follow a conversation if there is background noise (such as TV, radio, children playing)*
| As “Lonely”
||Response options as in “Lonely”
||Do you get or have you had noises (such as ringing or buzzing) in your head or in one or both ears that lasts for more than 5 min at a time*
||(a) Yes, now most or all of the time
||(b) Yes, now a lot of the time
||(c) Yes, now some of the time
||(d) Yes, but not now, but have in the past
||(e) No, never
*Included options “Do not know” and “Prefer not to answer” treated as missing data.
Data on participants’ sex and age banded into 5-year age groups were extracted as demographic factors known to be associated with both general health and hearing (Dawes et al. 2014b). The national quintiles for the Townsend deprivation index score were used as a demographic measure quantifying an increase in material deprivation status of the population (Norman 2010; Dawes et al. 2014b). A subset of data from the questionnaire and physical measures conducted as part of the UK Biobank baseline assessments were also selected to determine 13 additional factors that may have influenced the outcomes due to their known associations with general health, well-being, or hearing (Dawes et al. 2014a). These data included self-reports about the participant’s ethnic background, physical activity levels, illnesses or specific medication use as evidence of hypertension, high cholesterol, cardiovascular disease or diabetes, as well as information about tobacco and alcohol consumption, the use of ototoxic medication, and exposure to loud noise or music. The data also included physical measurements of body mass index (BMI), pulse wave arterial stiffness index (PWASI), and blood pressure as supporting evidence of hypertension (see Table ST1 in Supplemental Digital Content, http://links.lww.com/EANDH/A746). The confounding factors were either recoded using responses on the self-report measures or used as continuous variables for physical measures (BMI, PWASI) similar to our previous studies (Dawes et al. 2014a).
Speech in Noise Perception Assessment
Participants who did not indicate being completely deaf or a cochlear implant user in the touchscreen questionnaire were asked to complete the Digit Triplets Test (DTT)—a short test of speech perception in noise (Smits et al. 2004; Dawes et al. 2014b; UK Biobank 2012). The DTT was completed at 10 UK Biobank assessment centers by 164,770 UK Biobank participants (Dawes et al. 2014b). Participants who wore hearing aids were asked to remove them for the DTT. Each ear was assessed separately using circumaural headphones (Sennheiser D25). A participant’s ear was not assessed if they selected “I can only hear on the right/left side” response option at the beginning of the test, indicating potential unilateral deafness.
The stimuli were presented at a comfortable level set by the participant. The speech material comprised 15 monosyllabic digit triplets (e.g., 1-3-9). The triplets were presented in a spectrally shaped noise that was matched to the complete set of nine digits (0–9, excluding the disyllabic 7 and with “0” spoken as “oh”). The noise level varied adaptively between the presentation trials but was limited such that the signal to noise ratios (SNRs) did not exceed the minimum of –12 dB and maximum of +8 dB. The mean SNR from the last eight triplets defined the SRT in noise and was used as a measure of the participant’s hearing function. The SRT scores indicate the SNR at which the participant can report all three successively presented digits accurately against a noise background on 50% of presentation trials. A more negative SRT score corresponds to an ability to identify digit triplets in higher levels of background noise, and thus to better hearing.
Several studies have shown that DTT SRTs correlate well with the average pure-tone thresholds and have high specificity and sensitivity (about 0.9) for distinguishing individuals with normal and impaired hearing (Smits et al. 2004; Jansen et al. 2013; Vlaming et al. 2014). The above characteristics of the DTT, better ecological validity due to the assessment of speech perception in noise as the most commonly reported complaint with hearing impairment (Action on Hearing Loss 2011; Smits et al. 2013) and ease of administration compared to pure-tone audiometry (Jansen et al. 2013), enabled a quantifiable assessment of hearing function in a large cohort of the UK Biobank participants. The high specificity and sensitivity of the DTT is typically achieved by an appropriate choice of cutoff values for differentiating between individuals with normal and impaired hearing based on the normative DTT SRT data obtained in these populations (Smits & Houtgast 2005; Vlaming et al. 2011). In a similar way, the normative data obtained from a sample of 20 young adults with clinically normal hearing (audiometric thresholds ≤25 dB HL from 0.25 to 8 kHz) who performed the UK Biobank DTT were used to assess the SRT variability and cutoffs to develop performance categories on the UK Biobank DTT (Dawes 2013; Dawes et al. 2014b). The normative data suggested a better ear mean SRT of −8 dB SNR (SD, 1.24) and categories “normal” (SRT < −5.5 dB SNR), “insufficient” (SRT ≥ −5.5 and ≤ −3.5 dB SNR), and “poor” (SRT > −3.5 dB SNR), which can be used as indicators of hearing impairment in the UK Biobank participants (Dawes et al. 2014a,2014b; Moore et al. 2014; Rönnberg et al. 2014; Dawes et al. 2015; Pierzycki et al. 2016; Rudner et al. 2016).
The study group and two comparator groups were selected based on their hearing function and the performance categories developed for the UK Biobank DTT (Figure 1). To avoid the inclusion of any cases where the DTT results could have been attributable to noncompliance or equipment failure, 849 participants with the poorest possible SRT score of +8 dB SNR in either ear were excluded (Pierzycki et al. 2016). The study group was selected from participants whose overall results suggested unilateral hearing impairment similar to SSD (self-reported ability to hear in only one ear and SRT in noise for that ear indicative of normal hearing; <−5.5 dB SNR). As the DTT was not performed in the contralateral ear, the group was referred to as SRTN/−.
The outcomes reported in the SRTN/− group were compared with those reported in a group of participants with SRTs indicative of bilaterally normal hearing, SRTN/N (i.e., <−5.5 dB SNR in both ears). To further increase the specificity in the SRTN/N group, participants in that group who reported using hearing aids were excluded. A second comparison group, SRTI/I, comprised people with SRTs indicative of bilaterally symmetric hearing impairment (i.e., ≥−5.5 dB SNR in both ears). The SRTI/I group only included participants who had abnormal SRTs that differed by <4.6 dB SNR between the ears to avoid the inclusion of participants with potentially extreme forms of asymmetry in hearing function. An SRT difference ≥4.6 dB SNR was considered atypical as it fell more than 2 SDs away from the average SRT difference between the ears in the sample of UK Biobank participants whose SRTs indicated bilateral hearing impairment.
Participant characteristics were summarized using descriptive statistics. Prevalence estimates were standardized by age-band and sex to the whole UK Biobank cohort (n = 500,097). Associations were analyzed using logistic generalized linear models using statistical software R version 3.5.0. Questionnaire responses “Prefer not to answer” or “Do not know” were treated as missing data. These responses could not be assumed missing completely at random due to the use of the “Prefer not to answer” response option (see Supplemental Digital Content, http://links.lww.com/EANDH/A746). Therefore, missing data in all outcome and predictor variables used in the models were accounted for by 100 multiple imputations by chained equations using the package “mice” in R with predictive mean matching method and five iterations (Sterne et al. 2009; van Buuren & Groothuis-Oudshoorn 2011).
Separate binomial logistic models were used to calculate the odds of reporting each outcome in the SRTN/– or SRTI/I groups compared with the SRTN/N group, and SRTN/– compared with the SRTI/I group (see full model results in Supplemental Digital Content, http://links.lww.com/EANDH/A746). The models controlled for sex, age-band, interaction between sex and age-band, material deprivation score as demographic factors, and the 13 factors related to general health, well-being, or hearing described above. Results were considered statistically significant if p < 0.05. Results were presented as odds ratios derived from regression models, which were subsequently converted to absolute and relative risks. The odds ratio is a measure of the effect size defined as the ratio between the odds of a specific outcome occurring in a diseased group compared with the odds of that outcome occurring in a comparator group (Grant 2014). By definition, the odds ratio >1 indicates a higher likelihood of the outcome occurring in the diseased group. The absolute risk describes the probability of developing a specific outcome in a given group, while the relative risk describes the ratio of the risk (probability) of the outcome in the diseased group and a comparator group. Therefore, a relative risk >1 would denote a greater risk (probability) of the outcome occurring in the diseased than in the comparator group.
A distribution of absolute risks across sex, age-bands, and material deprivation quintiles was derived for each of the hearing and well-being outcomes using the raw data (without imputations) to reflect the risks observed directly in the population. Point estimates for absolute risks were obtained using marginal standardization with corresponding 95% confidence intervals based on the distribution of standardized risks (Grant 2014; Muller & MacLehose 2014). Standardized relative risks with “robust” 95% confidence intervals were calculated using marginal structural binomial regression modeling to avoid potential instability of estimation due to stratification by a large number of confounders included in the regression models (Richardson et al. 2015).
Table 2 shows the characteristics of participants. When considering the prevalence compared with the total UK Biobank sample standardized for age-band and sex, SRTN/–, indicating unilateral hearing impairment, was found in 0.5% and SRTI/I, indicating a symmetric bilateral hearing impairment, in 1.04% of the UK Biobank’s participants. The mean SRT score in the SRTN/N group was −8.08 dB (SD = 0.96) for the better ear and −7.01 dB (SD = 0.81) for the worse ear. The mean SRT scores in the SRTI/I group were −4.61 dB (SD = 1.36) and −3.39 dB (SD = 1.81) in the better and worse ears, respectively. The mean SRT score for the only tested ear of participants in the SRTN/– group was −7.00 dB (SD = 0.90). There was a higher prevalence of older adults in the SRTN/– and SRTI/I groups with approximately double the proportion of 65- to 69-year-olds compared with the SRTN/N group. This difference may have led to higher SRT scores for the normally functioning ears in the SRTN/– compared with the SRTN/N group (Table 2). The distribution of material deprivation scores was similar across all groups and age-bands.
TABLE 2. -
Characteristics of participants
|Total participants, % (N)
|Male sex, % (N)
|Age band, % (N)
|Material deprivation, % (N)
| Quintile 1
| Quintile 2
| Quintile 3
| Quintile 4
| Quintile 5
|Better ear SRT in dB, mean (SD)
|Worse ear SRT in dB*, mean (SD)
Data are percentages (counts) unless stated otherwise (% excluding missing data).
*Worse ear SRTs were not available if only one ear was tested (SRTN/– group).
“I”, impaired; “N”, normal; SD, standard deviation; SRT, speech reception threshold.
Associations With Hearing and Well-Being Outcomes
Table 3 shows the odds ratios with 95% confidence intervals for the self-reported outcomes in the SRTN/– and SRTI/I groups compared with the SRTN/N group, and for the SRTN/– compared with the SRTI/I group. Well-being outcomes showed a moderate effect of hearing impairment, and participants in the SRTN/– group were significantly more likely to report being in poor health, dissatisfied with health, and lonely compared with those in the SRTN/N group. The likelihood of reporting adverse well-being outcomes was similar in the SRTN/– and SRTI/I groups. However, adverse hearing-related outcomes were more likely to be reported in the SRTN/– compared with both the SRTN/N and SRTI/I groups. Difficulties following conversations in noise were almost 10 times more likely with the SRTN/– compared with SRTN/N and five times more likely compared with SRTI/I. Participants with SRTN/– were also significantly more likely to report tinnitus than those in both SRTN/N and SRTI/I groups.
TABLE 3. -
Odds ratios for the association between self-reported hearing and well-being
||SRTI/I vs. SRTN/N
||SRTN/– vs. SRTN/N
||SRTN/– vs. SRTI/I
|OR (95% CI)
||OR (95% CI)
||OR (95% CI)
| In poor health
| Dissatisfied with health
| Has difficulty following conversations in noise
| Has tinnitus
The models adjusted for all confounders used in the regression models.
CI, confidence interval; “I”, impaired; “N”, normal; OR, odds ratio; SRT, speech reception threshold.
Figure 2 illustrates the relative effects (odds ratios and 95% confidence intervals) of SRTN/– and other demographic, health, and lifestyle predictors of self-reported poor health (see model outputs in Supplemental Digital Content for other outcomes, http://links.lww.com/EANDH/A746). Females, older age and white ethnic groups, current drinkers, and those reporting moderate exercise levels were less likely to report being in poor health. Higher levels of material deprivation and the presence of all other health and lifestyle factors were associated with higher likelihood of reporting poor health.
Table 4 shows estimated standardized relative risks associated with hearing impairment for the SRTI/I and SRTN/– groups. Compared to the absolute risk in those with SRTN/N, there was a significant increase in the risk of self-reported loneliness and poor health in those with SRTN/–. The risk of difficulties following conversations in noise associated with SRTN/– increased by about 161% and 64% compared to the absolute risk of this outcome occurring in the SRTN/N and SRTI/I groups, respectively. The risk of reporting tinnitus with SRTN/– increased even more compared with the SRTN/N (182%) and the SRTI/I group (84%).
TABLE 4. -
Absolute and standardized risks associated with normal and impaired hearing
||Relative risk with impaired hearing†
|SRTN/N (95% CI)
||SRTI/I (95% CI)
||SRTN/– (95% CI)
||SRTI/I (95% CI)
||SRTN/– (95% CI)
| In poor health
| Dissatisfied with health
| Has difficulty following conversations in noise
| Has tinnitus
*Point estimates and 95% CIs for absolute risks adjusted for age and sex using UK Biobank population data.
†Relative risks and “robust” 95% CIs adjusted for all confounders used in the regression models.
CI, confidence interval; “I”, impaired; “N”, normal; SRT, speech reception threshold.
The UK Biobank data suggests that hearing function indicative of unilateral hearing impairment is associated with significant increase in the likelihood of reporting adverse hearing-related outcomes. The large increase in the risk of difficulties following conversations in noise and tinnitus presence was observed when compared with both those with hearing function indicating normal or symmetrically impaired hearing in both ears. The risks of reporting adverse well-being outcomes were similar in those with unilateral and with bilateral symmetric hearing impairment. However, the risks of self-reported loneliness and poor health were somewhat larger with unilateral than with bilateral hearing impairment when compared with absolute risks of those outcomes occurring with bilaterally normal hearing.
Hearing Outcomes With Unilateral Hearing Impairment
The significant increases in the likelihood of reporting difficulties following conversations in noise associated with unilateral hearing impairment were most likely connected with the loss of binaural hearing. Difficulty localizing sound sources has been associated with asymmetric hearing loss (Noble & Gatehouse 2004) and could have contributed to these increases as their daily-life impact on a person’s hearing ability can be disproportionate to the degree of hearing loss (Gatehouse & Noble 2004). Localization difficulties could be particularly acute when hearing in one ear is lost completely as with SSD (Wie et al. 2010). However, there is also contrary evidence of good monoaural sound localization in people with unilateral impairment (Slattery & Middlebrooks 1994; Agterberg et al. 2014; Firszt et al. 2015).
Therefore, another contributing factor could be associated with the difficulty to listen selectively when following conversations from multiple talkers in a noisy background as it relies on comparing information from two ears (Colburn et al. 2006). Difficulties with the effective use of selective attention for segregating competing sounds into separate auditory objects could be negatively affected by the peripheral and central consequences of hearing impairment (Shinn-Cunningham & Best 2008; Dai et al. 2018). However, access to and comparison of auditory information from two ears, plausibly even with bilaterally impaired but symmetric hearing function, could give a binaural advantage for spatial separation of competing sounds that would not be available in monoaural listening conditions (Marrone et al. 2008). Selective listening with unilateral hearing impairment could also be predicted by head shadow effects, which could negatively affect speech perception independently of individual localization ability and be particularly acute when the target and masking sounds are collocated (Rothpletz et al. 2012). Therefore, experience of poor localization and selective listening could have both influenced the large increases in the risk of self-reported difficulties following conversations in noise in the SRTN/– compared with both SRTN/N and SRTI/I groups.
The present findings could also be connected with the choice of measures used to evaluate hearing ability and define the study groups. A monoaural test of speech perception such as the UK Biobank DTT can be used to simulate the lack of auditory input in one ear in SSD (Williams et al. 2017), and suggests that UK Biobank participants had to rely mostly on monoaural cues to segregate the spoken digits from background noise. This scenario mimics the largest difficulty of separating the target from competing speech observed in monaural listening or when both signals are collocated (Marrone et al. 2008). This suggests that the DTT SRTs measured in noise were more relevant to the lived experience with unilateral hearing impairment and a better predictor of self-reported difficulty following conversations in noise in the SRTN/– group. Indeed, a significantly higher proportion of self-reported difficulties following conversations in noise was found in the SRTN/– group (83%) compared with the proportions reported by UK Biobank participants with large degrees of impairment in hearing function on the DTT (55% on average; Figure SF1 in Supplemental Digital Content, http://links.lww.com/EANDH/A746). This significant increase suggests a categorical change in the perceived impact from high levels of hearing impairment or deafness in the worse ear in the SRTN/– group and partly explains the significant increases in the risks of reporting difficulties following conversations in noise in the SRTN/– compared with the SRTI/I and SRTN/N groups.
Both the SRTN/– and SRTI/I were also associated with significantly greater risks of reporting tinnitus compared with SRTN/N, consistent with hearing loss being one of the major risk factors for developing tinnitus (Gopinath et al. 2010; Shargorodsky et al. 2010), and consequences of SSD (Lucas et al. 2018). However, tinnitus appears to be more prevalent in those with acquired SSD (Lee et al. 2017), and better hearing thresholds in the contralateral ear have been suggested as a predictive factor of acute tinnitus onset in patients with sudden idiopathic sensorineural hearing loss (Lee et al. 2015). The information about etiology of deafness was not available for the present sample. However, given that sudden onset of deafness is one of the most common causes of acquired unilateral hearing loss (Baguley et al. 2006), having one normally functioning ear in the SRTN/– group could have contributed to their larger risks of reporting tinnitus compared with the SRTI/I group.
Impact of Unilateral Hearing Impairment
The risks of loneliness and poor health were somewhat larger in the unilateral than in the bilateral hearing impairment when compared with the corresponding absolute risks with normal hearing function, but the increase in risks in both groups was generally consistent with a reduced sense of being able to cope with noisy situations and having a smaller social group with hearing loss (Kramer et al. 2002). The increased risk of reporting poor health was also compatible with the impaired health-related quality of life with SSD (Subramaniam et al. 2005; Sano et al. 2013) and bilateral hearing loss (Arlinger 2003).
A smaller number of adverse well-being outcomes and the lack of significant associations with self-reports of feeling depressed or unhappy in unilateral compared with bilateral hearing impairment could be related to a specific interaction between the severity of the symptoms and the etiology or duration of deafness (Kurz et al. 2019). Psychosocial consequences of congenital deafness may be less severe as people adapt to their adverse hearing-related outcomes over time (Carlsson et al. 2015). The large risks associated with hearing-related outcomes found in the present study were compatible with an acute onset of SSD resulting from idiopathic sudden sensorineural hearing loss (Sano et al. 2013) or surgical removal of benign acoustic tumors (Kuhn et al. 2011). Both etiologies can lead to distinct impacts on a patient’s quality of life (Carlsson et al. 2011) and negative emotional responses such as the fear of losing hearing in the other ear (Sano et al. 2013). The information about participants’ etiology and duration of deafness or audiological interventions was not available. However, these factors may have contributed to hearing-related outcomes (Slattery & Middlebrooks 1994; Carlsson et al. 2015; Kurz et al. 2019) and be required for characterizing the risks of adverse well-being outcomes and the impact on quality of life in unilateral hearing impairment (Subramaniam et al. 2005; Carlsson et al. 2011; Kitterick et al. 2015; Vannson et al. 2015).
The large-scale UK Biobank health data allowed controlling for numerous demographic, lifestyle, hearing, health, and well-being characteristics (Wilson et al. 1999; Lin et al. 2011b; Dawes et al. 2014a,2014b), facilitating comparisons between the impact of unilateral hearing impairment and other significant confounding factors and health conditions (Fig. 2). For example, the demographic characteristics suggested a similar effect of material deprivation on poor health ratings to that of unilaterally impaired hearing, but females, those in older age, and white ethnic groups were less likely to report poor health. The protective effects of age and ethnicity contrasted the higher likelihood of reporting difficulties following conversations in noise in the present study (see Supplemental Digital Content, http://links.lww.com/EANDH/A746) and higher levels of hearing disability found in other epidemiological studies (Davis 1989; Cruickshanks et al. 1998; Dawes et al. 2014a). These effects could have been associated with the “healthy volunteer” bias in the UK Biobank sample (Fry et al. 2017) or the complex and comparative nature of self-health ratings observed when including multiple health indicators in multivariate models (Jylhä et al. 2001; Andersen et al. 2007).
Figure 2 also facilitates a comparison of the impact of unilateral hearing impairment with that of other significant health conditions. For example, the data from the UK Biobank sample suggest that the likelihood of reporting poor health with the SRTN/– can be similar to that associated with having hypertension or high cholesterol and potentially higher than other factors associated with poor health, such as high blood pressure and previous smoking. However, self-reports of poor health were less likely with unilateral hearing impairment than with being a current smoker or having medical conditions such as diabetes and cardiovascular disease that can be life-threatening (World Health Organization 2018). Therefore, the relatively higher impact of health conditions such as diabetes and cardiovascular disease may have been responsible for the moderate effects of unilateral hearing impairment on well-being.
Strengths and Limitations
The major strength of the present study was the use of large-scale UK Biobank data. Previous studies of the impacts of SSD used relatively small sample sizes or participants with SSD as their own controls (Kitterick et al. 2015). The UK Biobank resource allowed for the first time to establish the relative risks of adverse hearing and well-being outcomes in people with hearing function indicative of SSD, and a comparison to normal and symmetrically impaired hearing function in both ears. Another novel aspect was that the risks were evaluated while controlling for numerous factors associated with poor health and well-being.
However, the UK Biobank sample included only 40- to 69-year-old adults, and previous studies suggested that it is not representative of the population due to bias toward recruitment of healthy participants (Fry et al. 2017). However, as the UK Biobank demographics may be associated with fewer hearing-related problems (Dawes et al. 2014b), the present findings would rather underestimate than overestimate the risks of adverse outcomes associated with SRTN/–. The prevalence of SSD in the general population is likely to be higher than that estimated from SRTN/– in the UK Biobank sample. Baguley et al. (2006) estimated about 7500 new cases of acquired unilateral sensorineural hearing loss of different etiologies per year, corresponding to about 0.016% of the UK population. However, unknown etiology and history of deafness in the UK Biobank cohort does not allow estimation of and comparison with the incidence rates found in the previous study.
Direct comparisons with other studies are also difficult due to the use of different definitions of unilateral hearing loss or SSD. The prevalence of moderate-or-worse unilateral hearing loss, that is, audiometric thresholds ≥41 dB HL in the worse ear, was found to be about 1.5% in the National Health and Nutritional Examination Surveys cohort (Lin et al. 2011a; Golub et al. 2018). However, about a third (31%) of participants with moderate-or-worse unilateral hearing loss have also reported having difficulty hearing, which was also reported by the majority of participants in the SRTN/– group (84%). Therefore, the prevalence of unilateral hearing impairment in the US population may be lower and closer to the 0.5% prevalence found in the UK Biobank cohort when one considers both the unilaterally impaired hearing function and self-reported difficulty hearing.
Due to the lack of audiometric thresholds and therefore clinical diagnoses of hearing loss in the UK Biobank, deafness in one ear was inferred using self-report and normal hearing function in the better ear using cutoff criteria for SRT in noise similar to previous studies (Smits et al. 2004; Dawes 2013; Dawes et al. 2014b). Although this is a limitation of the present study, characterization of hearing using a speech in noise test, such as the DTT, increased the ecological validity of the findings compared to the use of pure-tone audiogram (Musiek et al. 2017) and related to the difficulty following conversations in noise as the most common complaint reported by patients with hearing loss (Assmann & Summerfield 2004; Action on Hearing Loss 2011; Heffernan et al. 2016). The ecological validity is further supported by the findings suggesting that difficulties understanding speech in noise may be an early symptom of dementia (Moore et al. 2014; Livingston et al. 2017).
Relevance to Clinical Practice and Future Studies
The findings suggest that one “good” ear is not enough to protect against adverse outcomes related to well-being. The results support the notion that a holistic management strategy is warranted to address both the hearing difficulties and the negative impact on well-being in unilateral hearing impairment (Gordon et al. 2015; Lucas et al. 2018). Provision of appropriate support or psychological therapies for this population is in line with the current action plans for reducing the impact of disabling hearing loss put forward by hearing charities (Action on Hearing Loss 2011) and the Department of Health in the UK (NHS England and Department of Health 2015), and globally by the World Health Organization (Curhan 2019; Olusanya et al. 2014). However, the large increases in risk of adverse hearing-related outcomes in the SRTN/– group suggest that current efforts should focus on the development and provision of effective hearing interventions for unilateral hearing impairment.
It was not possible to assess the type of hearing aid systems used by the UK Biobank participants, which may have included contralateral routing of signals (CROS) or bone-anchored hearing aid (BAHA) systems as common interventions for SSD (Gordon et al. 2015; Kitterick et al. 2016). However, a larger proportion of participants reported using “hearing aids” in the SRTN/– (19%) than in the SRTI/I group (8%; see Supplemental Digital Content, http://links.lww.com/EANDH/A746). As the risks of self-reported difficulties following conversations in noise and tinnitus were also significantly higher in the SRTN/– group, it is plausible to assume that this group would be more likely to seek interventions for their hearing problems. Indeed, despite not meeting typical eligibility criteria due to having one normally functioning ear, patients with SSD consider cochlear implantation toward restoring binaural hearing and alleviating tinnitus (Vermeire & Van de Heyning 2009).
There is an increasing body of evidence suggesting a benefit of cochlear implantation for the alleviation of tinnitus (Van de Heyning et al. 2008; Arts et al. 2015,2016; Peter et al. 2019), as well as perception of speech in noise and binaural hearing (Távora-Vieira et al. 2013; Friedmann et al. 2016; Sladen et al. 2017; Dirks et al. 2019; Litovsky et al. 2019). However, the strength of conclusions about the evidence of the comparative effectiveness of cochlear implantation, CROS and BAHA systems made by previous reviews has been limited by inconsistencies in the use and reporting of treatment outcomes (Baguley et al. 2006; Blasco & Redleaf 2014; Peters et al. 2015; Cabral Junior et al. 2016; Kitterick et al. 2016). These inconsistencies have focused recent efforts toward research identifying a core set of outcomes for use in clinical trials evaluating the effectiveness of interventions for SSD (Van de Heyning et al. 2016; Katiri et al. 2020). The significant risks of loneliness and perceptions of poor health found in the present study suggest their importance for patients and inclusion as outcomes in clinical trials of interventions for SSD in addition to those related to speech perception in noise and tinnitus.
This research has been conducted using the UK Biobank Resource under Application Number 166. This article presents independent research supported by the National Institute for Health Research (NIHR). The views expressed in this article are those of the author(s) and not necessarily those of the National Health Service (NHS), the NIHR, or the Department of Health and Social Care.
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