Background: Cochlear implants (CIs) can be used to address severe to profound sensorineural hearing loss, which is more prevalent in older adults. CI system reliability depends on both internal implants and external sound processors. Over time, sound processors age and may experience failure or faults and need repairing. However, spare parts for obsolete sound processors are harder to access. Upgrading sound processors could help CI users benefit from technology improvements; however, this may be prohibitively expensive for users. This study assessed the cost effectiveness of upgrading obsolete or soon-to-be obsolete sound processors compared with not upgrading them in adults aged 65 years and over with existing CIs from the Australian health system perspective, including whether and when to upgrade sound processors. In doing so, we present a novel application of individual-level microsimulation models that track not only individuals, but ears fitted with CIs.
Methods: We developed two state-transition microsimulation models reflecting adults with (i) unilateral CIs, and (ii) bilateral CIs. We applied a microsimulation approach to track CI users' age and each sound processor's age (which affects failure and fault rates, and health-related quality of life [HRQoL]) over 35 years. Two models were developed as bilateral CI users may have two sound processors of differing ages, and because sound processors beyond replacement or repair result in no access to sound in that ear-although unilateral CI users may have residual hearing in the non-implanted ear. Inputs were based on the Australian Cochlear Upgrade Sound Processor (CUSP) study (N = 200), a survey of four clinics involved in the study, the published literature and administrative sources. We reported the incremental cost-effectiveness ratio (ICER) in terms of cost per quality-adjusted life year (QALY) gained and conducted extensive threshold, univariate, scenario and probabilistic sensitivity analyses. All costs were reported in 2022 Australian dollars (AUD).
Results: For unilateral CI users, if sound processors were beyond replacement or repair at 20 (15) years then upgrading sound processors when they reach the age of around 11 years (3 years) resulted in an ICER of AUD$50,000 per QALY gained when compared with not upgrading sound processors. When the scenarios were compared incrementally to each other, upgrading sound processors when they reach the age of 20 (15) years resulted in an ICER below AUD$50,000 per QALY gained. For bilateral CI users, if sound processors were beyond replacement or repair at 15 or 20 years then upgrading sound processors when they reach the end of warranty (3 years) would result in an ICER of AUD$50,000 per QALY gained when compared with not upgrading sound processors. When the scenarios were compared incrementally to each other, then upgrading sound processors when they reach 9 years resulted in an ICER below AUD$50,000 per QALY gained. The probability that upgrading would be cost effective versus not upgrading sound processors was 49-51%, reflecting that the upgrade frequencies were determined through threshold analysis. Updating sound processors less frequently reduced the ICERs and increased the probability that upgrading would be cost effective.
Conclusions: This study estimated the frequencies at which upgrading sound processors may be considered cost effective, assuming that sound processors were eventually beyond replacement or repair. This study also demonstrated the value of microsimulation models in tracking not only individuals, but each ear when assessing the cost effectiveness of hearing interventions. Further research is needed to explore this approach in other conditions and interventions, such as other neuroprosthetics.
© 2026. The Author(s).