Cochlear implantation is internationally recognized as the standard of care for patients with severe-to-profound hearing loss [4,28], with bilateral implantation regarded as the gold standard.
However, despite a well-established body of research highlighting the cost-effectiveness of bilateral cochlear implantation and improved quality of life outcomes, it is believed that just 4.2% of people who are eligible for cochlear implants have access to them . In many developing nations, this figure is expected to be significantly lower.
Outcomes Compared: Unilateral & Bilateral Implantation
A recent MED-EL survey identified that 18% of unilateral users said their country provides financial support for unilateral implantation only, and that 22% of current bilateral recipients surveyed had to actively pursue a second implant where funding was available . This is despite hearing experts and an ever-growing body of medical research reaching broad consensus that bilateral implantation offers clear advantages over unilateral implantation.
Studies have shown that access to binaural cues, thus enabling binaural hearing, can deliver the following benefits [1,10,19,20,29]:
- Improved speech recognition in quiet and background noise
- Enhanced sound localization
- Reduced listening effort and related fatigue
- Enriched quality of life
- Reduced head shadow effect for improved signal-to-noise ratio
- Binaural summation benefit
- Health-related quality of life
- Improved language development for children and positive impact on phonological processing skills
Parents also report their child’s responsiveness in groups, reaction time, and language acquisition to be significantly improved following bilateral implantation .
Subjective expectations of unilateral cochlear implant users also identify improved quality of life, reduced exhaustion, and better hearing in noise as the perceived potential benefits of bilateral cochlear implant use over-and-above their current listening experience .
Inter-Implant Intervals & Sequential Implantation
Robust evidence spanning decades details the long-term socio-economic and audiological outcomes that support simultaneous bilateral implantation as the recommended and safe treatment option for children .
However, the question of whether to sequentially implant existing unilateral patients is too often still discussed, with factors such as inter-implant interval, pre- or post-lingual duration of hearing loss, and unilateral performance among the core discussion topics.
“…bilateral cochlear implants (BiCI) are better than unilateral cochlear implant,
and simultaneous BiCI is preferred than the sequential cochlear implant even after
escaping the early stage of language development.” 
Importantly, research suggests that minimizing the time delay between the first and second implant is important to maximize patient outcomes [12,29]. That said, auditory deprivation is not a contraindication to cochlear implantation , and “…even after a long period of deafness and despite a prolonged inter-stage interval, sequential bilateral cochlear implantation should be considered” .
Multiple studies support this, suggesting pediatric bilateral benefits are achieved irrespective of the inter-implant interval, age, and duration of use of the second CI, with patients showing functional binaural benefit, sound localization, and improved speech perception in quiet and noise [1,16,17].
In post-lingually deafened adults, a growing body of evidence continues to highlight subjective and objective sequential benefits including speech intelligibility in quiet and noise, as well as quality of life regardless of age at implantation and inter-implant intervals [26,34].
Quality of Life Indicators Support Bilateral Cochlear Implantation
Compared to other chronic diseases such as diabetes, hypertension, angina, and heart failure, studies have shown that hearing loss has a greater impact on a person’s quality of life [14,33]. Extensive research cites social isolation, depression, cognitive decline, low self-confidence, and related health issues among the scenarios that those living with untreated hearing loss often face [27,32]. Thus, untreated hearing loss places additional hidden burdens on healthcare systems .
When evaluating Quality of Life outcomes against generic population or intervention metrices, or disease-specific measures, several studies have shown statistically significant increases in quality of life following bilateral cochlear implantation in both adults and children [5,15,22,31]. A global survey of bilateral cochlear implant users and parents also found that 99% of participants identified an improvement in their quality of life as one of the most important benefits of their bilateral implant .
Such improvements in adults have been reported across all ages, including a prospective cohort analysis of older adults ages 80+ years . In large adult study groups, statistically significant health utility gains were recorded with HUI-3 and NCIQ when comparing bilateral implantation versus unilateral implantation. When considering bilateral versus no-intervention with or without hearing aids, the health utility gain further increases. In addition, these outcomes are consistent across sequentially and simultaneously implanted patients [5,7,13,15,21,24].
Similar results are available in pediatric cohort studies, with clinicians recording statistically significant health utility gains using HUI-3 when comparing bilateral to unilateral implantation and when considering bilateral versus no treatment, with or without hearing aids [2,6,22,31].
Cost-Effectiveness of Bilateral Implantation
In children living with bilateral sensorineural hearing loss, the cost-effectiveness of bilateral intervention is clear when compared to both hearing aids and unilateral cochlear implantation [15,25]. The same has been shown for adults as a growing body of evidence indicates that bilateral cochlear implantation is cost-effective compared to no treatment, hearing aids, or unilateral implantation [11,35,36].
Importantly, simultaneous bilateral cochlear implantation is shown to be more cost-effective compared to sequential bilateral implantation in both adults and children [35,39]. In developing countries, evidence also notes the cost-effectiveness of bilateral implantation [38,41].
Achieving Universal Access to Bilateral Cochlear Implants
The decades of research outlined above provide strong evidence to support bilateral cochlear implantation. However, despite the evidence, access to bilateral cochlear implantation remains out of reach for families unable to shoulder the financial burden of private treatment in many developed and developing nations across the globe.
We encourage policymakers to engage with national and international experts, including the HEARRING Group or the Hearing Health Forum EU, to facilitate the reimbursement of bilateral cochlear implants for both children and adults.
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] Almeida, G. F. L., Martins, M. F., Costa, L. B. A. D., Costa, O. A. D., & Martinho De Carvalho, A. C. (2019). Sequential bilateral cochlear implant: results in children and adolescents. Brazilian Journal of Otorhinolaryngology
(6), 774–779. https://doi.org/10.1016/j.bjorl.2018.07.008
 Barton, G. R., Stacey, P. C., Fortnum, H. M., & Summerfield, A. Q. (2006). Hearing-impaired children in the United Kingdom, IV: cost-effectiveness of pediatric cochlear implantation. Ear Hear
(5), 575-588. https://doi.org/10.1097/01.aud.0000233967.11072.24
 Bianchin, G., Tribi, L., Formigoni, P., Russo, C., & Polizzi, V. (2017). Sequential pediatric bilateral cochlear implantation: The effect of time interval between implants. International Journal of Pediatric Otorhinolaryngology
, 10–14. https://doi.org/10.1016/j.ijporl.2017.08.025
 Buchman, C. A., Gifford, R. H., Haynes, D. S., Lenarz, T., O’Donoghue, G., Adunka, O., Biever, A., Briggs, R. J., Carlson, M. L., Dai, P., Driscoll, C. L., Francis, H. W., Gantz, B. J., Gurgel, R. K., Hansen, M. R., Holcomb, M., Karltorp, E., Kirtane, M., Larky, J., Mylanus, E. A. M., Roland, J. T., Jr., Saeed, S. R., Skarzynski, H., Skarzynski, P. H., Syms, M., Teagle, H., Van de Heyning, P. H., Vincent, C., Wu, H., Yamasoba, T., & Zwolan, T. (2020). Unilateral Cochlear Implants for Severe, Profound, or Moderate Sloping to Profound Bilateral Sensorineural Hearing Loss: A Systematic Review and Consensus Statements. JAMA Otolaryngol Head Neck Surg
 Chen, J. M., Amoodi, H., & Mittmann, N. (2014). Cost-utility analysis of bilateral cochlear implantation in adults: a health economic assessment from the perspective of a publicly funded program. Laryngoscope
(6), 1452-1458. https://doi.org/10.1002/lary.24537
 Cheng, L. J., Soon, S. S., Wu, D. B., Ju, H., & Ng, K. (2019). Cost-effectiveness analysis of bilateral cochlear implants for children with severe-to-profound sensorineural hearing loss in both ears in Singapore. PLoS One
(8), e0220439. https://doi.org/10.1371/journal.pone.0220439
 Crowson, M. G., Semenov, Y. R., Tucci, D. L., & Niparko, J. K. (2017). Quality of Life and Cost-Effectiveness of Cochlear Implants: A Narrative Review. Audiol Neurootol
(4-5), 236-258. https://doi.org/10.1159/000481767
 D’Haese, P. S. C., Van Rompaey, V., De Bodt, M., & Van de Heyning, P. (2019). Severe Hearing Loss in the Aging Population Poses a Global Public Health Challenge. How Can We Better Realize the Benefits of Cochlear Implantation to Mitigate This Crisis? Front Public Health
, 227. https://doi.org/10.3389/fpubh.2019.00227
 Elrashidy, R., Khater, A. M., Shabana, M., Khashaba, A., & Tharwat, A. (2020). Bilateral cochlear implantation: simultaneous versus sequential. The Egyptian Journal of Otolaryngology
(1), 16-16. https://doi.org/10.1186/s43163-020-00015-3
 Eskridge, H. R., Park, L. R., & Brown, K. D. (2021). The impact of unilateral, simultaneous, or sequential cochlear implantation on pediatric language outcomes. Cochlear Implants Int
, 1-8. https://doi.org/10.1080/14670100.2020.1871267
 Foteff, C., Kennedy, S., Milton, A. H., Deger, M., Payk, F., & Sanderson, G. (2016). Cost-Utility Analysis of Cochlear Implantation in Australian Adults. Otol Neurotol
(5), 454-461. https://doi.org/10.1097/mao.0000000000000999
 Grieco-Calub, T. M., & Litovsky, R. Y. (2010). Sound localization skills in children who use bilateral cochlear implants and in children with normal acoustic hearing. Ear Hear
(5), 645-656. https://doi.org/10.1097/AUD.0b013e3181e50a1d
 Harkonen, K., Kivekas, I., Rautiainen, M., Kotti, V., Sivonen, V., & Vasama, J. P. (2015). Sequential bilateral cochlear implantation improves working performance, quality of life, and quality of hearing. Acta Otolaryngol
(5), 440-446. https://doi.org/10.3109/00016489.2014.990056
 Hawkins, K., Bottone, F. G., Jr., Ozminkowski, R. J., Musich, S., Bai, M., Migliori, R. J., & Yeh, C. S. (2012). The prevalence of hearing impairment and its burden on the quality of life among adults with Medicare Supplement Insurance. Qual Life Res
(7), 1135-1147. https://doi.org/10.1007/s11136-011-0028-z
 Health Quality Ontario. (2018). Bilateral Cochlear Implantation: A Health Technology Assessment. Ont Health Technol Assess Ser
 Jang, J. H., Roh, J.-M., Choo, O. S., Kim, Y.-J., Kim, H., Park, H. Y., & Choung, Y.-H. (2019). Critical Factors for Binaural Hearing in Children with Bilateral Sequential Cochlear Implantation: First Implant Performance and Inter-Implant Interval [https://doi.org/10.1159/000500700
]. Audiology & neuro-otology
 Killan, C. F., Killan, E. C., & Raine, C. H. (2015). Changes in children’s speech discrimination and spatial release from masking between 2 and 4 years after sequential cochlear implantation [https://doi.org/10.1179/1754762815Y.0000000001
]. Cochlear Implants Int
 Knopke, S., Grabel, S., Forster-Ruhrmann, U., Mazurek, B., Szczepek, A. J., & Olze, H. (2016). Impact of cochlear implantation on quality of life and mental comorbidity in patients aged 80 years. Laryngoscope
(12), 2811-2816. https://doi.org/10.1002/lary.25993
 Laske, R. D., Veraguth, D., Dillier, N., Binkert, A., Holzmann, D., & Huber, A. M. (2009). Subjective and objective results after bilateral cochlear implantation in adults [https://doi.org/10.1097/MAO.0b013e31819bd7e6
]. Otol Neurotol
 Lee, Y. (2021). Benefit of Bilateral Cochlear Implantation on Phonological Processing Skills in Deaf Children. Otology & Neurotology
, Publish Ahead of Print
 Litovsky, R., Parkinson, A., Arcaroli, J., & Sammeth, C. (2006). Simultaneous bilateral cochlear implantation in adults: a multicenter clinical study. Ear Hear
(6), 714-731. https://doi.org/10.1097/01.aud.0000246816.50820.42
 Lovett, R. E., Kitterick, P. T., Hewitt, C. E., & Summerfield, A. Q. (2010). Bilateral or unilateral cochlear implantation for deaf children: an observational study. Arch Dis Child
(2), 107-112. https://doi.org/10.1136/adc.2009.160325
 MED-EL. (2020). Bilateral Cochlear Implant Survey. Data on File.
 Olze, H., Grabel, S., Haupt, H., Forster, U., & Mazurek, B. (2012). Extra benefit of a second cochlear implant with respect to health-related quality of life and tinnitus. Otol Neurotol
(7), 1169-1175. https://doi.org/10.1097/MAO.0b013e31825e799f
 Pérez-Martín, J., Artaso, M. A., & Díez, F. J. (2017). Cost-effectiveness of pediatric bilateral cochlear implantation in Spain. Laryngoscope
(12), 2866-2872. https://doi.org/10.1002/lary.26765
 Péus, D., Pfluger, A., Häussler, S. M., Knopke, S., Ketterer, M. C., Szczepek, A. J., Gräbel, S., & Olze, H. (2020). Single-centre experience and practical considerations of the benefit of a second cochlear implant in bilaterally deaf adults [https://doi.org/10.1007/s00405-020-06315-x
]. Eur Arch Otorhinolaryngol
 Ramakers, G. G., Smulders, Y. E., van Zon, A., Kraaijenga, V. J., Stegeman, I., Van Zanten, G. A., & Grolman, W. (2016). Agreement between health utility instruments in cochlear implantation. Clin Otolaryngol
(6), 737-743. https://doi.org/10.1111/coa.12626
 Ramsden, J. D., Gordon, K., Aschendorff, A., Borucki, L., Bunne, M., Burdo, S., Garabedian, N., Grolman, W., Irving, R., Lesinski-Schiedat, A., Loundon, N., Manrique, M., Martin, J., Raine, C., Wouters, J., & Papsin, B. C. (2012). European Bilateral Pediatric Cochlear Implant Forum consensus statement. Otol Neurotol
(4), 561-565. https://doi.org/10.1097/MAO.0b013e3182536ae2
 Reeder, R. M., Firszt, J. B., Holden, L. K., & Strube, M. J. (2014). A longitudinal study in adults with sequential bilateral cochlear implants: time course for individual ear and bilateral performance [https://doi.org/10.1044/2014_JSLHR-H-13-0087
]. Journal of speech, language, and hearing research : JSLHR
 Saunders, J. E., Francis, H. W., & Skarzynski, P. H. (2016). Measuring Success: Cost-Effectiveness and Expanding Access to Cochlear Implantation. Otol Neurotol
(2), e135-140. https://doi.org/10.1097/mao.0000000000000942
 Semenov, Y. R., Yeh, S. T., Seshamani, M., Wang, N. Y., Tobey, E. A., Eisenberg, L. S., Quittner, A. L., Frick, K. D., & Niparko, J. K. (2013). Age-dependent cost-utility of pediatric cochlear implantation. Ear Hear
(4), 402-412. https://doi.org/10.1097/AUD.0b013e3182772c66
 Shield, B. (2019). Hearing Loss – Numbers and Costs: Evaluation of the social and economic costs of hearing impairment Hear-IT AISBL
 Simpson, A. N., Simpson, K. N., & Dubno, J. R. (2015). Health-related quality of life in older adults: Effects of hearing loss and common chronic conditions. Healthy Aging Res
 Sivonen, V., Sinkkonen, S. T., Willberg, T., Lamminmäki, S., Jääskelä-Saari, H., Aarnisalo, A. A., & Dietz, A. (2021). Improvements in Hearing and in Quality of Life after Sequential Bilateral Cochlear Implantation in a Consecutive Sample of Adult Patients with Severe-to-Profound Hearing Loss. J Clin Med
 Skarzynski, P. H., Ciesla, K., Lorens, A., Wojcik, J., & Skarzynski, H. (2021). Cost-Utility Analysis of Bilateral Cochlear Implantation in Adults With Severe to Profound Sensorineural Hearing Loss in Poland. Otology & Neurotology
, Publish Ahead of Print
 Smulders, Y. E., van Zon, A., Stegeman, I., van Zanten, G. A., Rinia, A. B., Stokroos, R. J., Free, R. H., Maat, B., Frijns, J. H., Mylanus, E. A., Huinck, W. J., Topsakal, V., & Grolman, W. (2016). Cost-Utility of Bilateral Versus Unilateral Cochlear Implantation in Adults: A Randomized Controlled Trial. Otol Neurotol
(1), 38-45. https://doi.org/10.1097/mao.0000000000000901
 Sorrentino, F., Gheller, F., Lunardi, G., Brotto, D., Trevisi, P., Martini, A., Marioni, G., & Bovo, R. (2020). Cochlear implantation in adults with auditory deprivation: What do we know about it? Am J Otolaryngol
(2), 102366. https://doi.org/10.1016/j.amjoto.2019.102366
 Swami, H., Ap, A., & Shivanand, S. (2021). Cost-effectiveness of Pediatric Unilateral/Bilateral Cochlear Implant in a Developing Country. Otol Neurotol
(1), e33-e39. https://doi.org/10.1097/MAO.0000000000002862
 Trinidade, A., Page, J. C., Kennett, S. W., Cox, M. D., & Dornhoffer, J. L. (2017). Simultaneous versus sequential bilateral cochlear implants in adults: Cost analysis in a US setting. Laryngoscope
(11), 2615-2618. https://doi.org/10.1002/lary.26673
 Winkler, F., Schön, F., Peklo, L., Müller, J., Feinen, C., & Helms, J. (2002). [The Würzburg questionnaire for assessing the quality of hearing in CI-children (WH-CIK)]. Laryngorhinootologie
(3), 211-216. https://doi.org/10.1055/s-2002-25042
 World Health Organization. (2021). World Report on Hearing
. W. H. Organization.