Introduction
A hearing impairment is not only a disability (a communication dysfunction) but can also be perceived by an individual as a handicap with its psychosocial effects. Patients often encounter confusion, stigmatization or even mockery. The extent of the handicap, however, cannot be predicted from the audiometric profile itself. It has been argued that behavioral and affective variables have to be considered to provide successful management of the disease. Consequently, new tools are being introduced to clinical practice measuring health-related quality of life (HRQoL) in patients, including its core element, mental health, along specific psychological tools to assess psychopathology (mental distress). Still, however, it remains extremely challenging to capture the non-tangible psychosocial aspects of hearing loss and thereby predict communication and adjustment hardships of patients, as well as their potential benefit from treatment and rehabilitation with e.g. cochlear implantation [
1‐
5].
Whereas patients with a postlingual onset of deafness grow up with a hearing identity to suddenly or progressively be devoid of the auditory sense, those born with a hearing impairment are never exposed to a non-degraded acoustic and speech surrounding. Some authors suggest that underdeveloped communication skills at an early age can deteriorate emotional and social development (and potentially also neurological), with others arguing that an altered identity from hearing to deaf in a later-onset deafness can actually be more detrimental to mental health (see Ohre and colleagues for a review [
4]).
Several large- and medium-population studies have indicated increased mental distress among patients with an acquired postlingual hearing impairment (with an onset after developing language skills), as compared to the general population. Depressive/anxiety symptoms and social isolation were found most distinctive [
1‐
8]. Findings concerning the correlation between audiological measures, such as pure-tone audiometry, and mental health have been contradictory, probably since numerous factors can contribute to the development of a mental distress and a sensory impairment can be one of those [
4]. Thomas and colleagues reported a four times larger scoring above cut-off for significant anxiety/depression symptoms among patients with a hearing impairment than in the general population, with the proportion twice as large for a deficit of 70 dB and above [
8]. At the same time, two example studies revealed no clear association between the objectively measured hearing-loss severity (acquired, moderate to profound) and the frequency of depressive symptoms [
1,
2]. It was rather the individual attitude towards the disability, as well as their coping strategies that were indicated as major predictors of the psychological well-being [
2]. In addition, these and other trials provided evidence of annoying tinnitus as a factor increasing the depressive mood in patients [
1,
2,
9,
10]. Lower energy levels, greater distress and social isolation were also found in the patient population using HRQoL tools, with again none of the objective audiological measures consistently indicative of the individual quality of life [
7]. Hallam and colleagues suggested that mental health in the hearing impaired was affected by the self-assessed level of communication skills, self-esteem and acceptance of the disability, as well as coexisting medical conditions [
3; cf.
7]. Both trials, furthermore, showed lower HRQoL in women, with contradictory findings reported as to the predictive value of satisfaction with hearing devices [
3,
7].
Increased mental distress, and especially elevated anxiety, depression and interpersonal sensitivity have also been detected in the profoundly deaf population using sign language [
3,
11,
12]. These trials required specifically designed assessment tools adapted to sign language [
13]. In a study by Hallam and colleagues there were no specific effects demonstrated of audiological variables on psychopathology levels, except for a comorbid medical condition in patients with prelingual severe to profound deafness. Furthermore, in terms of the health-related quality of life, neither presence of tinnitus nor satisfaction with hearing devices was found a predictive factor. As was the case of the co-studied population of patients with postlingual hearing deficits, the scores in signing patients deteriorated with poorer acceptance of the disability, as well as among women [
3]. The sex effect on HRQoL was further confirmed by Fellinger and colleagues (in this study women were also reported to have more significant depressive symptoms) [
11]. Tinnitus was either found to have no effect on the quality of life of patients with a prelingual hearing loss or this comorbidity was an uncontrolled variable [
3,
11,
12].
Partial deafness is a special type of sensorineural hearing loss, with a severe to profound impairment at frequencies above 1–2 kHz and normal to moderately deteriorated hearing acuity at lower frequency bands [
14,
15]. With preservation of relatively good audio-oral communication and support from lip-reading, noisy and multi-talker situations still remain very challenging for this population. Therefore, one suggested and successful treatment option for partial deafness is cochlear implantation (CI), including a combination of a cochlear implant and a hearing aid in one ear (electroacoustic system, EAS) [
15,
16]. The Institute of Physiology and Pathology of Hearing (Warsaw, Poland) has a long tradition of providing pre- and postoperative medical and psychological services to patients with various subtypes of hearing deficits, including cochlear implantation in partial deafness [
14,
17]. This is a preliminary study investigating health-related quality of life, as well as the prevalence of psychopathological symptoms in patients with residual hearing on low frequencies. All patients will participate in a follow-up visit involving an identical diagnostic assessment after at least 6 months of cochlear implant use. The authors seek to explore various relationships between audiological, demographic and psychological measures which might in the future be investigated as predictors for CI-outcomes. Pre- and post-implantation outcomes will be compared to appraise, among others, the improvement of HRQoL after the intervention [
5,
18‐
20].
Discussion
The current study provides evidence that patients with partial deafness are a specific population that can experience psychological challenges potentially related to their disability. The cross-sectional design, however, does not permit inferring about causal relationships between the sensory loss and the mental well-being. Literature frequently reports an elevated depressed mood, assessed with depression and anxiety questionnaires in the hearing-impaired population [
1‐
4,
8,
9,
11]. In the present study the effect was also statistically significant but not spectacular, especially with respect to the maximum scores that could be obtained in tests, and suggests low- to medium-range levels of depression and anxiety in both the normal hearing and the patient population (see e.g. work by Leigh and colleagues who used BDI II to evaluate depressive symptoms in hearing deficits) [
6]. More sizable effects seen in literature might have been due the fact that the majority of the recruited patients had severe to profound deficits across all frequency ranges, as opposed to partial deafness where the low-frequency hearing loss is mild to moderate. Interestingly, Tambs and colleagues provided vast data on psychopathology in hearing-impaired patients and showed that high and middle frequency hearing abilities affected mental health only to a little extent provided that the low-frequency hearing was within normal ranges (in the current population 90 % had HL < 50 dB HL in the range 0.125–0.5 kHz) [
28]. Furthermore, the often reported affective symptoms in patients with prelingual hearing deficits involved patients unfamiliar with spoken language, which might have additionally and considerably affected their mental well-being [
3,
4,
11‐
13]. Nevertheless, during psychological consultations provided at the Institute of Physiology and Pathology of Hearing within the frames of the present study, mood and coping problems have been reported by patients with partial deafness. The authors believe that this population, despite of the preserved low-frequency hearing, might have to face social and emotional challenges that go far beyond those experienced by the normally hearing and which might require professional attention. This especially seems so, as further outcomes of the current study revealed decreased quality of life in patients related to the overall physical and psychological health. This was found despite absence of any additional serious handicaps in the tested population [cf.
3,
7]. Physical health refers to, among other aspects, the required medical care, pain experience, energy level and quality of sleep. One possible reason of lower quality of life among patients might be related to their naturally enhanced focus on health and medical issues which results from their hearing problems. At the same time, however, psychosomatic symptoms might be specifically associated with the auditory impairment which would also be reflected in some patients reporting an elevated depressive mood (with one-third of the BDI questions referring to physical aspects of well-being). The reported significantly deteriorated psychological health, including, among others, the extent of problems with self-esteem, internal coherence, mood and concentration in the patient population lends further support to the latter hypothesis. Similar outcomes were reported by Fellinger and colleagues who also used the WHOQOL-BREF tool to assess health-related quality of life in prelingual signing individuals [
11]. The authors pointed to the possible feelings of insecurity and inferiority in deafness when living in a “perfectly” hearing world.
The present trial revealed no significant relationship between the objectively measured severity of the hearing deficit, depressive/anxiety levels and HRQoL, replicating outcomes of several cohort studies [
1‐
3,
7]. The implication would be that mental well-being predominantly depends on the subjective perception of the disability, as well as appropriate medical interventions and not the degree of the impairment itself. Moreover, no effect of tinnitus was demonstrated in patients with partial deafness, which was probably due to the fact that all of them perceived this comorbidity as non-bothersome. As literature shows, it is the level of annoyance with tinnitus that might become a predictor of mental distress in hearing-impaired patients [
1‐
3,
29]. The history of hearing aid use has been recognized by some authors as improving life quality and decreasing psychopathology among patients [
7,
30]. We argue, however, that this effect is only true for patients who definitely require and are satisfied with such amplification. Almost 40 % of the patients who participated in the current trial had no benefit from hearing aids and were non-users. This was probably related to their moderate audiometric thresholds, as well as individual features of the auditory system. These patients were actually most proficient in advanced sound perception and speech production, suggesting a significant involvement of residual acoustic hearing in these functions [
5,
17]. Should their hearing impairment progress, however, these patients might be re-referred for fitting of hearing aid before a cochlear implantation (e.g. an electro-acoustic system) is considered. At the same time, there was no clear impact demonstrated of the number of hearing aids used (unilateral
vs bilateral) on any aspect of health/hearing-related quality of life. According to personal communication there were comparable levels of hearing aid satisfaction across all users. Several other studies also failed to show a clear relationship between hearing aid use and mental well-being [
2,
3].
There were differences demonstrated between patients with a prelingual onset of hearing loss and those who developed partial deafness during their lifetime with respect to social activity and interactions. The prelingual group showed an advantage. The activity domain refers to the subjectively perceived limitations imposed by the hearing loss on daily professional, family and leisure activities, with social interactions assessing the quality of personal contacts with close family and friends, as well as complete strangers. Patients with prelingual partial deafness due to their residual hearing can never become members of the often stigmatized deaf culture using sign language. Furthermore, due to the lifetime experience of disability, they seem to develop efficient communication modes, as well as coping and adjustment mechanisms [
3,
4,
31]. In contrast, patients with an acquired hearing deficit tend to miss fluent audio-verbal communication which they might still recall. It may well be that these patients experience confusion and insecurity, which they yet have to cope with, when devoid of the healthy auditory sense. Consequently, patients with a later onset of hearing loss are more prone to withdraw from social participation [
2‐
4,
31]. At the same time, however, the current analysis failed to demonstrate statistically significant differences between patients with a prelingual and a postlingual onset of hearing impairment with respect to depression/anxiety symptoms, as well as health-related QoL. This finding suggests that other factors should be considered as more predictive than the age at onset of a hearing deficit, especially that both patient populations used spoken language at the time of the study, such as e.g. personal attitude towards the impairment [
3].
As to relationships between various measures applied to patients in the present study, there was a clear correlation detected between audiometric thresholds and the subjectively rated sound perception, suggesting a direct relationship between tests performed in a clinical setting and real-life situations related to hearing problems [cf.
27]. Furthermore, an interesting association was revealed for left-ear audiometric word recognition scores only with the subjectively indicated level of recognition of advanced sounds. The authors hypothesize that the effect might be due to the fact that the aspects of auditory processing, such as listening to music and prosody are mainly subserved by the right brain hemisphere, which chiefly receives the information delivered to the left ear (see a review paper by Friederici and Alter [
32]). This discussion, however, goes far beyond the scope of this report. These findings seem to confirm the relevance of the Nijmegen-Cochlear-Implant-Questionnaire, as do the significant differences revealed with this tool between patients with a postlingual and a prelingual onset of partial deafness. The instrument had received a very positive feedback from the participating patients who stated that the NCIQ tool focuses on the very basic and fundamental hardships related to their hearing deficits. Similar subdomains of the hearing loss-related quality of life seem to be affected by partial deafness, as is the case of other types of hearing losses [
19,
20,
26,
27].
In the patient group there were also several statistically significant correlations established between various audiological measures. Among other outcomes, it has been found that patients with steeper hearing losses in frequency ranges between 0.5 and 2 kHz found it easier to detect speech (lower SDT scores). This effect of hearing loss configuration on speech perception has already been described by Hornsby and colleagues who argued that patients with ski-sloping sensorineural impairments have better ability to use low-pass filtered speech, when compared to their counterparts with flat hearing loss configurations [
21]. Listening experience was indicated as one possible explanation of this effect, with another suggesting an enhancement of cortical representations of low-frequency sounds due to high-frequency cochlear dead regions [
33]. Interestingly, the correlations were also found for contralateral outcomes, clearly suggesting that listening to speech is a complex binaural phenomenon. Further large-population investigation is required to elucidate the relationship between slope and speech understanding (word recognition scores) which failed to reach statistical significance in this trial. In addition, in patients with postlingual partial deafness worse speech detection thresholds without aiding were related to a longer duration of hearing loss, as well as a younger age at the onset (first use of hearing aids, as reported by the patient). The authors hypothesize that the effect originates in a prolonged exposure to degraded speech, especially with the old-generation hearing aids, whereas some patients should have been earlier equipped with a cochlear implant. Notably, duration of hearing impairment has been suggested as one possible predictor of auditory performance with a cochlear implant [
5,
18].
To be able to extrapolate the findings of the study on the entire population of patients with partial deafness, further longitudinal investigation is required before and after cochlear implantation. In addition, considerable care should be taken to provide a precise account of patient’s self-evaluation of hearing aid use and the collateral tinnitus. The authors are aware that some bias could be introduced to the results by the fact that only patients willing to participate and probably those more extrovert decided to participate in the study and complete questionnaires that directly reflect personal attitudes and feelings.