Cochlear implant (CI) care has traditionally been provided face-to-face, often in centralized specialist locations via a fixed schedule of appointments with little opportunity for personalization. Over the last 5 years there has been an increase in digital technology options to deliver hearing services, including CI services (Kim et al., 2021; Muñoz et al., 2021). CI service options include synchronous telehealth options, including intraoperative CI telemetry, implant programming, assessment of speech recognition and electrode-specific measures (Bush et al., 2016), and asynchronous technology to support CI users with regard to management and review (Bush et al., 2016; Philips et al., 2018; Maruthurkkara et al., 2022). The use of telehealth for CI service provision has the potential to significantly improve the ability for CI services to provide efficient, effective, and equitable services to CI users in a personalized manner. However, despite its potential, the use of telehealth to provide CI services remains limited (Ravi et al., 2018; Fletcher et al., 2019; Bennett et al., 2023a; Chong-White et al., 2023).

The move of telehealth services from research to routine practice is often hampered by limited ability to integrate current clinical practices with telehealth provision, both in terms of clinical practice and funding (Morgan et al., 2022). As part of the translation to clinical practice, it is essential to demonstrate that remote service provision provides equivalent, if not superior, CI service compared to the current standard of face-to-face clinical care (D'Onofrio and Zeng, 2021). This is necessary both for regulatory purposes, as well as to ensure that CI service providers and users have sufficient trust and confidence in the outcomes of the telehealth service to consider using it (Bennett et al., 2024). The use of sensitive and clinically relevant outcome measures to evaluate CI service provision and CI performance delivered via remote technologies is vital to facilitate the provision of evidence-based health care services, allowing stakeholders to make informed decisions about how to best care for their patients (Woods and Burgess, 2021).

Within audiology, there are large numbers of outcome measures used to assess the effectiveness of CIs and hearing aids (Granberg et al., 2014; Akeroyd et al., 2015; Boisvert et al., 2020; Neal et al., 2022). For example, a recent review reported 6,714 discrete assessment measures for hearing ability alone, of which 139 were self-report measures (Neal et al., 2022). Yet there is little consensus among research and clinical professionals on which outcome domains should be assessed, let alone which measures should be used (PriceWaterhouseCoopers, 2017; Schaefer et al., 2017; Woods and Burgess, 2021; Allen et al., 2022). This non-standardized approach makes it difficult to compare results across different studies and services, for example in systematic reviews with meta-analyses.

Over the last decade there has been increasing development and use of core outcome sets (COSs; Clarke and Williamson, 2016). A COS is an agreed standardized set of outcome that should be measured and reported as a minimum dataset for a specific condition, ideally with input from end-users including patients, clinicians, and industry (COMET, 2022). There are several benefits of using a COS in addition to standardizing outcomes for systematic review, which include reducing outcome reporting bias, enhancing transparency and accountability in research, and in clinical decision-making including the development of national or international guidelines. Although a core outcome domain set (CODS) has been defined for hearing aids, which was developed with significant input from clients and consumers (Allen et al., 2022) and based on best practice guidelines (Hall et al., 2015), there is nothing similar for CIs.

The overall aim of this research was to develop a COS to evaluate remote technologies delivered within CI services. This was informed by a systematic approach used in the “roadmap” described by Hall et al. (2015), and successfully used by Allen et al. (2022) to develop a CODS for hearing aids. An important first step in this process is to synthesize the current evidence-base. Here, we present a systematic review for remote digital technologies and the associated outcome measures for both CI and hearing aid clients and services. Hearing aid studies were also included within this systematic review to ensure that all key outcome domains used within remote hearing rehabilitation were captured and considered. It was also deemed important to identify and understand any differences in outcome domains between hearing aid and cochlear implant remote technology.

This systematic review goes beyond the CODS developed by Allen et al. (2022) by also including outcome measures. Therefore, the aim of this systematic review is to identify the outcome measures that have been used to evaluate remote technologies for both cochlear implant and hearing aid users, as well as service outcomes for remote technologies.

This systematic review was prospectively registered with The International Prospective Register of Systematic Reviews (PROSPERO; ID: CRD42022370171). The method was guided by The Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) statement 2020 (Page et al., 2021). See Supplementary material 1.

This systematic review reported the range and type of outcome domains of remote digital technology for CI and hearing aid users. The findings presented here contribute toward a larger project to develop a COS for remote technologies for CI users. The extensive outcome measures from the 49 studies were consistent with other reviews reporting large outcome diversity (Boisvert et al., 2020; Neal et al., 2022). Outcomes were classified using the COMET taxonomy (Dodd et al., 2018) into core areas, outcome domains, and outcome sub-domains. The proportion of studies in each outcome domain were compared to understand the differences between assessment in remote technology for CI and hearing aid users. Even though CI remote technology is the focus of the ongoing larger COS project, it was important to also gather information about hearing aid outcomes to understand any gaps in outcome assessment in this relatively new area of technology. This ensures that all potential outcome domains have been considered for the future COS development.

Notably, there were several differences in the types of outcomes that were assessed for users of these hearing devices. Within the auditory functioning domain, 95% of studies assessing remote CI technology reported speech perception outcome measures, compared to only 20% of hearing aid remote technology studies. However, when auditory functioning was assessed via self-reported outcome measures, there were a greater number of hearing aid studies assessing these outcomes compared to CI studies (73% and 19%, respectively). This is not particularly surprising as traditionally, CI outcomes have focused on the domains of speech perception. However, there is growing evidence that self-report measures offer a more functional real-world outcome, tapping into different mechanisms of benefit to speech perception outcomes (Dietz et al., 2022).

Whilst auditory functioning outcomes were present in all studies of remote technology for CI users, there was a marked reduction of outcomes across emotional functioning and wellbeing (9.5%) and cognitive functioning (4.8%) with no studies in the social functioning domain. These results are consistent with a scoping review of CI outcomes in adults (Boisvert et al., 2020) in which self-reported measures were dominated by measures of auditory ability. Studies have demonstrated the importance of social, emotional, and cognitive functioning in hearing loss and rehabilitation in general (Kricos, 2000; Knudsen et al., 2010; Barnett et al., 2017) so it is important that these psychosocial and cognitive factors are considered going forward. There was only one study (Cullington et al., 2018) that reported adverse event outcomes for CI remote technology, and none in studies of remote hearing aid technology. This may be due to an absence of adverse events occurring, however, there is a dearth of reporting adverse events in the hearing aid literature, identified in Cochrane reviews where both primary and secondary adverse events are required outcome domains (Barker et al., 2016; Ferguson et al., 2017). Adverse event reporting is more prominent in CI research (Crowson et al., 2020; Jinka et al., 2023), therefore it was surprising that this was not reported more frequently in the studies of remote technologies. Therefore, it is not possible to comment on the safety of a remote technology service delivery, and this may act as a barrier to implementation.

Given the nature of remote technology and services, there may be a need to focus on outcomes that are of specific importance in remote delivery. For example, empowerment has recently emerged as feature of remote technologies, given the additional demands on client technological literacy and self-management (Maidment et al., 2019, 2020; Gomez et al., 2022). As with all new emerging concepts, these outcomes also need to be developed and measured. For example, empowerment for hearing health has been recently conceptualized (Gotowiec et al., 2022). This has led to a new patient reported outcome measure on empowerment (EmpAQ), developed according to best practice COSMIN principles (Prinsen et al., 2018) with hearing aid users (Bennett et al., 2023b). As remote technology becomes more prevalent, there may be other outcomes, such as empowerment, that are revealed to be crucial in understanding the benefits of remote CI services. Therefore, the outcomes and outcome domains presented in this review are limited to those that have been measured to date.

Furthermore, there are other considerations specific to the service delivery of remote technologies that are of particular importance during a time when remote technology and service uptake remain low (D'Onofrio and Zeng, 2021). Service outcomes, collated in the delivery of care domain, can give providers assurance of remote technology efficacy, accuracy, and reliability, and may demonstrate benefits to both clients and services, such as reduced time, convenience, and costs. Some recent studies indicate that audiologists are largely positive toward remote technology within service provision for hearing aids, and that the low uptake is a result of system barriers such as infrastructure, funding, and privacy regulations (D'Onofrio and Zeng, 2021; Bennett et al., 2023a). This positivity from audiologists is not reflected in CI clinics, where there is more ambivalence, although there are similar barriers regarding infrastructure (Ferguson et al., 2023). These barriers sit within the resource use domain, which was one of the few outcome domains that had similar representation in both groups, albeit in only around a third of studies of both CI and hearing aid remote technology (31 and 38%, respectively). It is likely then that there may be a need to continue to assess resource use outcomes until more is known about infrastructure and funding requirements to support remote technologies.

Grouping outcomes using the COMET taxonomy (Dodd et al., 2018) allowed for an initial understanding of what type of client and service information is being assessed for remote technology. A strength of using this taxonomy is the ability to compare outcomes across audiology and wider health fields. A weakness of this method, and of domain classification more widely, is that many outcomes measures do not assess isolated domains. For example, the International Outcome Inventory for Hearing Aids (IOI-HA; Cox and Alexander, 2002) was categorized within the physical (auditory) functioning domain in this systematic review. However, there are items within this measure that are also applicable to the delivery of care domain, perceived health status domain and emotional functioning domain. It is important to therefore consider these domain classifications as “best fit” rather than strict categorizations.

In conclusion, there are a wide variety of outcomes that have been identified for digital technologies and services for CI and hearing aid users. These outcomes sit within the physiological and clinical domain, functioning (auditory, cognitive, emotional, and social) domain, perceived health status domain, delivery of care domain, resource use domain, and adverse events domain. There are differences in the way outcomes are measured in studies of CI and hearing aid remote technology and services. Finally, the results from this study will inform next steps in the development of a COS for remote technology and services for CI users.

The original contributions presented in the study are included in the article/Supplementary material, further inquiries can be directed to the corresponding author.

EL: Data curation, Formal analysis, Investigation, Methodology, Validation, Writing – original draft, Writing – review & editing, Visualization. CS: Conceptualization, Funding acquisition, Methodology, Validation, Writing – review & editing. KN: Data curation, Formal analysis, Investigation, Methodology, Validation, Writing – review & editing. MF: Conceptualization, Funding acquisition, Methodology, Project administration, Resources, Supervision, Validation, Writing – review & editing.