Abstract
Objective:
To identify patient characteristics associated with improvements in speech recognition scores (SRS) and Cochlear Implant Quality of Life (CIQOL-35) scores following cochlear implantation.
Study design:
Multi-institutional prospective cohort.
Setting:
Tertiary medical centers.
Patients:
Two hundred thirty-five adult CI users with bilateral hearing loss.
Main outcome measures:
Pre-CI and 12-month post-CI CIQOL-35, CNC word (CNC), and AzBio quiet (AzBio) scores were obtained. On the basis of improvement beyond established minimally detectable change values for each CIQOL domain and 95% CIs of pre-CI SRS as compared with post-CI, the cohort was divided into 4 groups for each CIQOL domain/SRS pair: (A) CIQOL and SRS improvement, (B) CIQOL improvement only, (C) SRS improvement only, and (D) no CIQOL or SRS improvement.
Results:
Correlations between CIQOL and SRS improvements were weak (r = 0.02–0.17). Grouped by CIQOL-Global/AzBio after 12 months post-CI, 51% of patients were classified as Group A, 4% as Group B, 39% as Group C, and 7% as Group D; percentages were similar for CIQOL-Global/CNC outcomes. Patients without CIQOL improvement had higher pre-CI CIQOL scores than patients who improved (d = 0.58–2.19), and patients without SRS improvement had higher pre-CI SRS scores than patients who improved (CNC: d = 1.35–2.89, AzBio: d = 1.09–2.78). Patients in Group D for the Entertainment domain were older than patients in Group A. Other patient factors were not significantly associated with the odds of improvement.
Conclusions:
Patients with higher baseline scores for a given outcome measure are less likely to improve following cochlear implantation. SRS and CIQOL score improvements were weakly correlated. The vast majority of patients (93%) improved in one or both outcome measures.
Keywords: Adult, AzBio, CIQOL- 35, CNC, Cochlear implant, Cochlear Implantation, Prospective studies, Quality of Life, Speech recognition
Introduction
Cochlear implantation is a safe and effective surgery with ~80%–90% of adults with postlingual hearing loss demonstrating improvement compared with their preimplantation speech recognition ability[1–3]. Most unilateral cochlear implant (CI) recipients with bilateral hearing loss also report improved hearing-related and nonhearing-related quality of life (QOL)[4,5] as well as satisfaction with their CI[6]. Despite the effectiveness of cochlear implantation, some patients report no improvement in self-reported functional abilities. Approximately 20% of patients reported no improvement in communication and over 40% reported no improvement in functional abilities related to entertainment, listening effort, emotional wellbeing, and social interaction[5].
When weighing cochlear implantation against alternative options for patients who meet CI candidacy criteria, it is crucial to improve our understanding of which patients would most likely benefit from a CI. With the expansion of CI candidacy criteria in recent years, cochlear implantation is becoming more accessible to patients with a wider range of baseline abilities[7]. While a majority of patients implanted under broader candidacy criteria have demonstrated improved speech recognition performance and certain QOL outcomes[7,8], preoperative metrics or patient characteristics to guide decision-making are needed to reduce the risk of implanting patients who are unlikely to benefit or be satisfied with their implants.
Speech recognition scores (SRS) obtained from word and sentence recognition tests, such as CNC words and AzBio sentences in quiet or in noise, have traditionally served as the primary measures of CI success[9]. In addition to SRS, patient-reported outcome measures (PROMs) have become more commonly used to comprehensively assess the self-reported, real-world functional abilities of CI users. Due to its rigorous development that included stakeholder engagement and robust psychometric analyses, the Cochlear Implant Quality of Life (CIQOL) instruments have become some of the most commonly used PROMs to measure CI outcomes and are now included in the Minimum Speech Test Battery, Version 3 (MSTB-3)[9–12]. The CIQOL instruments, which include the CIQOL-35 Profile and CIQOL-10 Global, are validated tools for assessing functional abilities of CI recipients and are more psychometrically sound compared with legacy instruments, such as the Health Utilities Index-3 (HUI-3) and the Nijmegen Cochlear Implant Questionnaire (NCIQ)[13].
Yet, prior studies have consistently demonstrated an absent-to-low correlation between SRS and PROMs[7,14–20]. In addition, CI satisfaction has a stronger association with improvements in QOL than with improvements in SRS[6,21,22]. Many of these studies, however, have been cross-sectional rather than longitudinal, limiting the ability to evaluate associations between pre-CI to post-CI changes in SRS and PROMs. Specifically, there is a need to determine how meaningful changes in SRS are associated with meaningful changes in PROMs over time. It is also highly relevant to identify patient factors associated with these changes, as these outcome measures are important for CI patient selection and counseling.
To address these gaps, the current study examines SRS and CIQOL longitudinal improvement patterns among patients implanted at 2 institutions: one in Canada and one in the United States. The purpose of this study is to (1) investigate the associations between improvement in SRS and CIQOL, (2) determine the proportions of patients with different improvement patterns (improved in both, in CIQOL only, in SRS only, or in neither), and (3) identify patient factors associated with these improvement patterns.
Materials and methods
Patients and data collection
This multi-institutional prospective cohort study was approved by both institutional review boards. Patients were retrospectively identified from prospectively maintained databases from 2 tertiary medical centers. Inclusion criteria were CI users aged 18 years or older with bilateral hearing loss, history of postlingual deafness, completed pre-CI and 12-month post-CI CIQOL-35 Profile, and completed pre-CI and 12-month post-CI CNC word (CNC) or AzBio sentences in quiet (AzBio) scores. Exclusion criteria were patients with single-sided deafness, retrocochlear pathology, or undergoing CI revision.
A total of 235 adult CI users met the inclusion criteria and were included for analysis. Of these 235 patients, 123 were implanted at Medical University of South Carolina (MUSC) and 112 were implanted at Sunnybrook Health Sciences Centre (SHSC). Of the 235 patients, there were 6 without complete CNC data, who were included only in AzBio analyses, and 28 without complete AzBio data, who were included only in CNC analyses. Race and ethnicity data were available for patients implanted at MUSC only.
Improvements in CIQOL-35 Profile scores and CNC or AzBio scores from pre-CI to 12-month post-CI were assessed. CIQOL-Global scores were assessed in addition to scores of the 6 CIQOL domains: Communication, Emotional, Entertainment, Environment, Listening Effort, and Social.
Clinically important outcome values were used to determine improvements in SRS and CIQOL scores. Improvements in CNC and AzBio were defined as improving from pre-CI to 12-month post-CI SRS beyond previously established 95% CIs for pre-CI scores in the ear to be implanted[23,24]. Improvements in CIQOL-35 scores were determined based on previously established conditional minimal detectable change (cMDC) values[5]. Using these values, patients with CIQOL and CNC scores (n = 229) or AzBio scores (n = 207) were divided into 4 groups: CIQOL and SRS improvement (Group A), CIQOL improvement only (Group B), SRS improvement only (Group C), and no CIQOL or SRS improvement (Group D).
The following patient factors were then compared across groups: age at implantation, sex, race/ethnicity (MUSC only), duration of hearing loss before implantation, pre-CI hearing aid use, and contralateral listening modality. Pre-CI audiological factors [pure-tone average (PTA), CNC scores, and AzBio quiet scores] of the implanted and contralateral ears were also compared across groups. PTAs were determined by averaging unaided air conduction hearing thresholds at the frequencies of 500 Hz, 1000 Hz, and 2000 Hz. Prior hearing aid use refers to using a hearing aid before their CI surgery.
Statistical analysis
Pearson correlation coefficients were calculated to determine the strength of the association between CIQOL and SRS improvement. A correlation coefficient of 0.0–0.09 is considered negligible, 0.1–0.39 weak, 0.4–0.69 moderate, 0.7–0.89 strong, and 0.9–1.0 very strong[25].
Comparisons of categorical variables between Groups A–D were performed using χ2 or the Fisher exact tests. Continuous variables were tested for normality using the Shapiro-Wilk test. If data passed the normality test, a One-Way Analysis of Variance (ANOVA) followed by Tukey multiple pairwise comparison test and Holm-Sidak correction were performed to compare continuous variables between groups. If data failed the normality test, a Kruskal-Wallis ANOVA on ranks followed by Dunn multiple comparison test was performed. Cohen d effect sizes and 95% CIs were calculated for all analyses. An effect size of 0.2–0.49 is considered small, 0.5–0.79 medium, 0.8–1.29 large, and 1.3 or greater very large[26].
Data analyses were performed with SPSS version 29 (IBM Corp., Armonk, NY); SigmaPlot version 14.5 (SYSTAT Software); MedCalc version 22.021 (MedCalc Software Ltd); and R version 4.4.1 (R Foundation for Statistical Computing, Vienna, Austria).
Results
Patient characteristics
A total of 235 patients completed the CIQOL-35 Profile instrument before CI and at 12-months post-CI. Patient characteristics are summarized in Table 1. Median age of the total cohort was 69.5 years (IQR: 58.7–77.1 y). The cohort included 109 (46.4%) males, 126 (53.6%) females. Of 123 patients with race and ethnicity data, 108 (87.9%) self-identified as White, 14 (11.4%) self-identified as Black, and 1 (0.8%) self-identified as Hispanic. Three CI device companies, Cochlear Americas, MED-El, and Advanced Bionics, were represented in the cohort.
Table 1.
Demographics of patients with CIQOL-35 and either AzBio or CNC scores included in analysis overall and by institution
| Characteristic | Total (N = 235) | MUSC (N = 123) | SHSC (N = 112) |
|---|---|---|---|
|
| |||
| N (%) | |||
| Sex | |||
| Male | 109 (46.4) | 52 (42.3) | 57 (50.9) |
| Female | 126 (53.6) | 71 (57.7) | 55 (49.1) |
| Racea | |||
| White | — | 108 (87.9) | — |
| Black | — | 14 (11.4) | — |
| Other | — | 1 (0.8) | — |
| Ethnicitya | |||
| Hispanic | — | 1 (0.8) | — |
| Not Hispanic | — | 122 (99.2) | — |
| Pre-CI hearing aid use | |||
| Yes | 153 (65.1) | 86 (69.9) | 67 (59.8) |
| No | 82 (34.9) | 37 (30.1) | 45 (40.2) |
| Post-CI listening modality | |||
| Single CI, contralateral hearing aid | 184 (78.3) | 92 (74.8) | 92 (82.1) |
| Single CI, no contralateral hearing aid | 51 (21.7) | 31 (25.2) | 20 (17.9) |
| Mean (SD) | |||
| Age at implantation (y) | 66.7 (14.0) | 67.2 (15.4) | 66.2 (12.4) |
| Duration of hearing loss (y) | 24.4 (16.3) | 23.5 (16.2) | 25.3 (16.3) |
| Pre-CI PTA (dB HL), implanted ear | 88.6 (17.6) | 85.6 (17.5) | 91.6 (17.4) |
| Pre-CI PTA (dB HL), contralateral ear | 75.1 (19.5) | 74.3 (19.0) | 75.8 (20.0) |
Only MUSC data available. Percentages are for 123 MUSC patients.
AzBio indicates Arizona Biomedical sentence recognition in quiet; CI, cochlear implant; CIQOL-35, Cochlear Implant Quality of Life; CNC, consonant-nucleus-consonant word; PTA, pure-tone average (average of unaided air conduction hearing thresholds at 500 Hz, 1000 Hz, and 2000 Hz).
Changes in speech recognition scores after 12 months
Pre-CI and 12-month post-CI SRS and CIQOL-35 scores are shown in Table 2 for patients by institution and combined. Mean AzBio score was 16.6% ( ± 20.6) before CI and 69.6% ( ± 23.8) at 12 months, increasing by 53.0 percentage points ( ± 2.2). Mean CNC score was 14.0% ( ± 15.8) before CI and 54.1% ( ± 19.6) at 12 months, increasing by 40.1 percentage points ( ± 1.7). These values were similar across the 2 institutions.
Table 2.
CNC, AzBio, and CIQOL-35 scores from pre-CI to 12-month post-CI visits overall and for each institution
| Characteristic | Total (N = 235) | MUSC (N = 123) | SHSC (N = 112) | ||||||
|---|---|---|---|---|---|---|---|---|---|
|
|
|
|
|||||||
| Mean (SD) | |||||||||
| Speech recognition scores | Pre-CI | 12-mo Post-CI | Δ | Pre-CI | 12-mo Post-CI | Δ | Pre-CI | 12-mo Post-CI | Δ |
| CNC (%), implanted ear | 14.0 (15.8) | 54.1 (19.6) | 40.1 (25.2) | 13.4 (14.7) | 56.0 (21.0) | 42.6 (25.6) | 14.8 (16.9) | 52.1 (17.7) | 37.3 (24.5) |
| CNC (%), contralateral ear | 32.9 (25.4) | — | — | 31.9 (24.8) | — | — | 34.1 (26.1) | — | — |
| AzBio (%), implanted ear | 16.6 (20.6) | 69.6 (23.8) | 52.9 (31.5) | 15.7 (19.5) | 70.1 (23.8) | 54.4 (30.8) | 17.7 (21.9) | 69.0 (24.0) | 51.2 (32.5) |
| AzBio (%), contralateral ear | 42.2 (30.5) | — | — | 39.2 (30.2) | — | — | 45.9 (30.6) | — | — |
| CIQOL-35 scores | Pre-CI | 12-mo Post-CI | Δ | Pre-CI | 12-mo Post-CI | Δ | Pre-CI | 12-mo Post-CI | Δ |
| Communication | 28.8 (11.9) | 44.8 (12.4) | 16.0 (15.5) | 29.2 (12.8) | 46.3 (12.3) | 17.1 (17.1) | 28.3 (10.9) | 43.1 (12.4) | 14.8 (14.1) |
| Emotional | 42.9 (14.4) | 57.5 (17.4) | 14.6 (17.4) | 43.5 (15.3) | 60.1 (17.5) | 16.7 (23.3) | 42.3 (13.4) | 54.6 (16.8) | 12.4 (14.7) |
| Entertainment | 34.3 (17.4) | 48.8 (22.1) | 14.5 (22.8) | 34.0 (16.6) | 52.8 (23.5) | 18.8 (28.8) | 34.7 (18.3) | 44.5 (19.7) | 9.8 (21.3) |
| Environment | 34.4 (17.8) | 54.9 (18.3) | 20.5 (22.8) | 32.5 (17.1) | 54.3 (18.3) | 21.8 (25.1) | 36.4 (18.4) | 55.6 (18.3) | 19.1 (23.7) |
| Listening effort | 20.0 (13.8) | 35.5 (14.7) | 15.5 (17.8) | 21.4 (15.1) | 37.6 (14.3) | 16.2 (20.8) | 18.4 (12.2) | 33.1 (14.7) | 14.7 (16.1) |
| Social | 47.3 (16.4) | 62.3 (20.5) | 15.1 (20.4) | 47.0 (17.6) | 62.7 (19.9) | 15.7 (26.6) | 47.5 (15.1) | 61.9 (21.3) | 14.5 (19.9) |
| Global | 35.4 (8.5) | 48.1 (11.5) | 12.7 (12.5) | 36.0 (9.1) | 49.7 (11.9) | 13.7 (15.0) | 34.7 (7.9) | 46.4 (10.8) | 11.7 (11.0) |
AzBio indicates Arizona Biomedical sentence recognition in quiet; CI, cochlear implant; CIQOL-35, Cochlear Implant Quality of Life; CNC, consonant-nucleus-consonant word.
Changes in CIQOL scores after 12 months
Overall, CIQOL-35 domain and Global scores each increased by 12 months, as shown in Table 2. On average by 12 months, Communication scores had improved from 28.8 ( ± 11.9) to 44.8 ( ± 12.4), Emotional from 42.9 ( ± 14.4) to 57.5 ( ± 17.4), Entertainment from 34.3 ( ± 17.4) to 48.8 ( ± 22.1), Environment from 34.4 ( ± 17.8) to 54.9 ( ± 18.3), Listening Effort from 20.0 ( ± 13.8) to 35.5 ( ± 14.7), and Social from 47.3 ( ± 16.4) to 62.3 ( ± 20.5). Mean CIQOL-Global score before CI was 35.4 ( ± 8.5) and at 12 months post-CI was 48.1 ( ± 11.5), increasing by 12.7 points on average.
Changes in the 6 CIQOL-35 domains ranged from +20.5 points ( ± 22.8) in the Environment domain with the largest mean improvement to +14.5 points ( ± 22.8) in Entertainment with the smallest mean improvement. Communication had the next largest improvement (+16.0 ± 15.5), followed by Listening Effort (+15.5 ± 17.8), Social (+15.1 ± 20.4), and Emotional (+14.6 ± 17.4). As shown in Table 2, pre-CI CIQOL scores and changes in CIQOL scores are similar between MUSC and SHSC.
Associations between change in CIQOL and change in SRS
Correlations between CIQOL-35 and SRS were calculated using pre-CI to 12-month post-CI changes in CIQOL-35 score and SRS. A heat map of correlations is displayed in Figure 1. Change in each CIQOL-35 domain and Global scores were weakly correlated to change in CNC and AzBio scores. For the 6 CIQOL-35 domains, correlations with change in CNC score ranged from r = 0.02 (95% CI: −0.11 to 0.15) for Environment to r = 0.17 (95% CI: 0.04–0.29) for Communication. Correlations with change in AzBio score ranged from r = 0.06 (95% CI: −0.07 to 0.20) for Emotional to r = 0.13 (95% CI: 0.00–0.26) for Communication. Weak positive correlations existed between improvement in Global and improvement in CNC (r = 0.16; 95% CI: 0.03–0.29) scores and between improvement in Global and improvement in AzBio (r = 0.16; 95% CI: 0.02–0.29) scores. For each domain, correlations between change in CIQOL-35 domain score and change in AzBio score were similar to correlations between change in CIQOL-35 domain score and change in CNC score.
Figure 1.
Heat map of correlations between change in CIQOL-35 domain score and change in speech recognition scores. The first column shows correlations between changes in CNC score and CIQOL-35 scores. The second column shows correlations between changes in AzBio score and CIQOL-35 scores. AzBio indicates Arizona Biomedical sentence recognition in quiet; CIQOL-35, Cochlear Implant Quality of Life; CNC, consonant-nucleus-consonant word.
Improvement status groups
For each patient, each CIQOL-35 domain/Global, CNC, and AzBio score was assessed as to whether pre-CI/12-month post-CI improvement was beyond its clinically important outcome value. Then, for each pair of outcome measures (eg, Communication/AzBio, Social/CNC), patients were assigned to improvement status Groups A–D depending on whether both, one, or neither score improved. In other words, patients were categorized into Groups A–D based on Communication/AzBio improvement, then categorized into Groups A–D based on each additional CIQOL-35 domain/SRS pair (eg, Emotional/AzBio, Social/CNC). Proportions of patients in each group are shown in Figure 2 and Supplement Table 1, Supplemental Digital Content 1, http://links.lww.com/MAO/C290. Overall, the largest proportions of patients had improvement in SRS with (A) or without (C) CIQOL improvement and the smallest proportions of patients improved in CIQOL-35 scores only (B) or did not improve in either outcome measure (D). Results demonstrate that for most patients, CIQOL-35 domain improvements were observed when SRS also improved. Importantly, based on the proportion of patients in Group D, 7% of patients did not improve in either outcome measure at 12 months post-CI.
Figure 2.
Percentages (%) of patients in Groups A–D for each CIQOL-35 domain/CNC pair and for each CIQOL-35 domain/AzBio pair. AzBio indicates Arizona Biomedical sentence recognition in quiet; CIQOL-35, Cochlear Implant Quality of Life; CNC, consonant-nucleus-consonant word; SRS, speech recognition score.
Differences in patient factors and pre-CI scores among groups
When comparing patient factors between Groups A–D for each pair of outcome measures, several patterns were observed. First, pre-CI CIQOL-35 domain scores were higher for patients whose CIQOL-35 scores did not improve at 12-months post-CI than for patients with improvement. Figure 3A–B and Supplement Table 2, Supplemental Digital Content 2, http://links.lww.com/MAO/C291 show comparisons of pre-CI CIQOL-35 scores between Groups A–D for each CIQOL/SRS pair. Second, pre-CI CNC scores were higher for patients whose CNC scores did not improve at 12-months post-CI than for patients with improvement; similar patterns were observed for AzBio scores. Comparisons of pre-CI CNC scores are shown in Figure 3C and Supplement Table 3, Supplemental Digital Content 3, http://links.lww.com/MAO/C292. Comparisons of pre-CI AzBio scores are shown in Figure 3D and Supplement Table 4, Supplemental Digital Content 4, http://links.lww.com/MAO/C293.
Figure 3.
Pre-CI CIQOL-35 domain scores for Group A-D for each CIQOL/CNC pair (A) and each CIQOL/AzBio pair (B). Pre-CI CNC word scores for Groups A–D for each CIQOL/CNC pair (C). Pre-CI AzBio sentences in quiet scores for Groups A–D for each CIQOL/AzBio pair (D). AzBio indicates Arizona Biomedical sentence recognition in quiet; CI, cochlear implant; CIQOL-35, Cochlear Implant Quality of Life; CNC, consonant-nucleus-consonant word; SRS, speech recognition score.
Significant differences in age were observed for the Entertainment/AzBio pair. Specifically, patients whose AzBio and Entertainment domain scores did not improve were older than patients whose scores improved for both of these outcomes (74.0 vs. 64.4 y, d = −0.64, 95% CI: −1.18 to −0.10). No other significant differences between Groups A–D were found when assessing sex, pre-CI hearing aid use, patient-reported duration of hearing loss, and pre-CI contralateral audiological (PTA, CNC, or AzBio) data.
Discussion
To deepen our understanding of patient characteristics associated with improvement in speech recognition and quality of life following cochlear implantation, this study grouped patients according to their improvement status in 3 validated CI outcome measures: CIQOL-35 Profile, CNC word recognition score, and AzBio sentences in quiet score. Results demonstrated that SRS or both SRS and CIQOL-35 scores improve 12-months post-CI for ~90% of patients whereas 7% do not improve in either outcome measure.
Results also showed that patients who improved in SRS and CIQOL-35 outcome measures had lower pre-CI CIQOL-35, AzBio, and CNC scores than patients who did not improve. Patients whose CIQOL-35 domain scores improved after 12 months (Groups A and B) had mean pre-CI CIQOL-35 Global scores of 30 (A: 29; B: 32) whereas comparable scores for patients who did not improve were 40 (C: 39; D: 38) (Fig. 3A–B, Supplement Table 2, Supplemental Digital Content 2, http://links.lww.com/MAO/C291). Similar results were observed for pre-CI CNC scores (Fig. 3C, Supplement Table 3, Supplemental Digital Content 3, http://links.lww.com/MAO/C292) and AzBio scores (Fig. 3D, Supplement Table 4, Supplemental Digital Content 4, http://links.lww.com/MAO/C293). Patients whose CNC scores improved (Groups A and C) had mean pre-CI CNC scores of 10% (A: 11%; C: 10%), whereas comparable scores for patients who did not improve were 30% or greater (B: 32%; D: 37%). Pre-CI scores for AzBio were 13% (A: 13%; C: 13%) for patients who improved and were 40% or greater (B: 57%; D: 40%) for patients who did not improve. Overall, these patterns indicate that certain pre-CI CIQOL-35, AzBio, and CNC scores may be predictive of improvement in these outcome measures.
A prior study that created a CIQOL functional staging system based on CIQOL-35 scores applying psychometric techniques to stratify patients’ abilities into 3–5 stages per domain used stage progression to represent CIQOL improvement[12]. Comparing to the current results, this study found that patients at higher pre-CI CIQOL stages were less likely to improve, despite higher stages being achievable. Perkins et al[8]. found that CNC scores at 6-months or 12-months post-CI improved for a greater proportion (70% vs. 40%) of patients with lower pre-CI CNC scores (CNC ≤ 40%) compared with patients with higher pre-CI CNC scores (CNC > 40%). Still, 40% of patients in the higher CNC score group improved.
The expanded CI candidacy criteria offer significant advantages, such as greater inclusion and coverage of patients who could benefit from implantation. With broader criteria, however, the proportion of patients who meet criteria but who are less likely to benefit from a CI may increase. Thus, there is a need for careful selection of CI candidates to ensure that patients do not undergo a surgery that may not be effective for them. The results of our study, which reveal patient factors associated with improvement in CI outcomes following implantation, support the need for a comprehensive pre-CI evaluation that considers baseline SRS and CIQOL-35 scores. In addition, as patient expectations about their functional abilities assessed before implantation may exceed or fall below actual post-CI abilities, the baseline evaluation should also consider patient expectations using a tool like the CIQOL-Expectations instrument[27]. A more comprehensive pre-CI assessment battery may provide the evidence needed to develop better and more individualized recommendations and counseling.
Regarding the correlational analyses, improvement in CIQOL-Global (r = 0.16) and Communication (r = 0.17) demonstrated the strongest correlations with SRS improvement, though all CIQOL-35 measures had similar weakly positive correlations with SRS improvement. This weak correlation between SRS and CIQOL-35 improvement is consistent with previous research[7,20] and underscores that, while SRS are valuable for assessing certain aspects of auditory performance, they do not capture the full effect of a CI on patients’ lives. Whereas SRS are psychophysical outcome measures, CIQOL-35 scores represent patients’ perception of their real-world functional abilities[13]. Shannon et al [22]. found that CIQOL-35 improvement was associated with lower decisional regret and higher satisfaction while SRS improvement was not. The current study determined that nearly half of the patients’ SRS improve alone, whereas far fewer patients’ CIQOL-35 scores improve alone. This finding provides more evidence that the CIQOL-35 captures functional impacts of hearing loss that are not reflected in speech recognition measures. Collecting pre-CI baseline CIQOL-35 scores during pre-CI counseling and monitoring post-CI CIQOL-35 scores can bridge this gap between auditory performance measures and broader functional abilities. Regarding the patient perspective, patients have favored pre-CI and post-CI outcome counseling based on CIQOL-35 scores and the CIQOL-35 Functional Staging System, which incorporates real-world examples, rather than counseling based on SRS[12].
Age differences were found in only one improvement group, with older patients less likely to improve in both AzBio and CIQOL-Entertainment at 12 months post-CI. However, our study found no association between the improvement group and the duration of hearing loss before implantation or contralateral audiologic metrics. While prolonged duration of hearing loss was initially thought to be related to poorer speech recognition outcomes, a recent meta-analysis found that it is not correlated to post-CI SRS and accounts for < 10% of the variance in post-CI SRS[28]. Longer duration of hearing loss has also been shown to have a very small positive association with CIQOL-35 scores[19]. Inconsistent measurements of the duration of hearing loss may contribute to discrepancies across studies, hindering our ability to fully understand its association to CI outcomes.
Strengths and limitations
This longitudinal study was conducted using data from 2 institutions from different countries, strengthening the generalizability of our findings. When comparing outcome measures between 2 institutions, notable similarities between cohorts were observed. Mean CIQOL-35 domain scores at 12-months post-CI for each institution were consistent with findings found in a cross-sectional study reporting normative CIQOL-35 data from 30 CI centers on experienced CI users[29]. For example, Emotional and Social domain scores at pre-CI and at 12-months post-CI were relatively higher than scores in most other domains. The CIQOL-35 Profile has been validated in a multi-institutional study, and this study provides further validation[29]. An additional strength is the use of cMDC values to assess improvement in CIQOL-35 scores[5]. Available since 2023, these values allow clinicians to determine if a patient has improved in the CIQOL-35 domain and Global scores following implantation. One limitation of this study is that the analyses were based on the availability of data at both institutions. As a result, the study only assessed the SRS of the implanted ear and did not assess binaural speech recognition ability. As binaural SRS may be more representative of patients’ hearing in the real world, it is important to include binaural CNC and binaural AzBio sentences in quiet in future studies. Analysis of AzBio sentences in noise was also not included due to limited data. Correlated with AzBio in quiet, AzBio in noise testing provides a more challenging assessment of patients’ functional abilities that may be more representative of daily listening environments compared with AzBio in quiet[30]. However, no strong evidence supports correlations between AzBio in noise and CIQOL or between AzBio in quiet and CIQOL[16,20].
Other patient factors, including comorbidities and cognition, may explain individual differences in CI outcomes but could not be explored in this study due to limited data. In addition, data on race and ethnicity were only available from patients implanted at MUSC, of whom almost 90% self-identified as White, limiting our ability to compare race across Groups A-D. Future studies should assess how these factors might influence the improvement of CI outcome measures at one year.
Conclusions
In a longitudinal, multi-institutional cohort study with over 200 patients, the current study demonstrated that, while most patients (93%) improved in at least one outcome measure (CIQOL or SRS), 43% improved in one but not both. Patients with higher pre-CI scores for a given CI outcome measure are less likely to improve following cochlear implantation. This finding has substantial implications in the era of expanded CI criteria. About one-tenth of patients showed no improvement in either SRS or CIQOL-35 at 12-months post-CI, and this group of patients had higher pre-CI abilities. Pre-CI abilities—CNC word score, AzBio quiet score, and CIQOL-35 score—can serve as guides in identifying patients at risk for not improving in each outcome measure following implantation. Thus, these measures should be strongly considered as part of a comprehensive CI evaluation. Clinicians may also utilize these pre-CI measures to set realistic expectations, particularly for patients with relatively higher pre-CI abilities or who may be considered “borderline candidates.” Future studies with complete data on race and comorbidities should evaluate group differences in these patient factors using similar methodology.
Supplementary Material
Supplemental Digital Content is available for this article. Direct URL citations are provided in the HTML and PDF versions of this article on the journal's website, www.otology-neurotology.com.
Footnotes
Conflicts of interest and source of funding
T.R.M. is on the medical advisory board for Envoy Medical. K.C.S. is a paid consultant for Akouos/Eli Lilly. The remaining authors have declared no potential conflicts of interest. This study was supported by the National Institutes of Health Grant R01DC020709. The remaining authors disclose no conflicts of interest.
IRB approval: Medical University of South Carolina IRB #00126243 approved (exempt) on March 10, 2023.
The CIQOL instruments are available for download at: https://medicine.musc.edu/departments/otolaryngology/research/cochlear-implant/instruments/form.
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