When it comes to cochlear implants, outfitting deaf children with two rather than just one could help them learn significantly more words in the long run, finds a new study from the University of Melbourne.

Bilateral cochlear implants (CIs), as they’re known, would not only help children gain a stronger mastery of vocabulary and speech skills, argue the study authors, but would also have tremendous social implications, as the current system of special education runs a cost of $25,000 per child and results in a loss of productivity cost of $6.7 billion over the long term. Treating congenital hearing loss early would have a massive effect for years to come, the researchers say.

“Children in this study with bilateral CIs developed vocabulary and spoken language significantly faster than children with only one CI.  This has enormous implications for their long-term future,” said lead researcher Dr. Julia Sarant, from the Department of Audiology and Speech Pathology, in a statement.

Sarant and her colleagues tracked the language and speech capabilities of 91 kids, ages 5 or 8, over a five-year period. The team also evaluated kids’ cognitive ability, parent involvement in their child’s intervention and education programs, and each family’s reading habits. Overall, bilateral CIs predicted faster language acquisition than unilateral implants, and the earlier kids began wearing both, the greater effect the two implants had.

Other factors also played a role in regulating speech abilities, such as high parental involvement and time spent reading to kids, along with low amounts of screen time. More educated parents, and those who also suffered hearing loss conditions, tended to raise kids with better vocabularies — an effect of added experience further reflected in each older sibling performing five to 10 percent worse on measures of vocabulary than younger siblings.

Worldwide, more than 300,000 people currently make use of a cochlear implant, with most of the cases falling in developed countries, due to the high cost of the device. In the U.S., some 58,000 adults and 38,000 children use a CI. Overall, children have a much easier time adapting to the implant, which bypasses the damaged portion of the ear and reroutes incoming sound directly to the auditory nerve, than their parents do. However, because some adults may have been exposed to speech prior to the implant, they already have a frame of reference for language. Kids whose language skills are still fluid often need postimplantation therapy.

Sarant and her team believe the findings should help motivate policymakers to amend federal funding in favor of bilateral implants. Outfitting kids with two over one has enormous benefits, their study suggests, for both the individual child and the community in which he or she grows up. Recent activity in the News Zealand Health Department included a recommendation for all children under 6 who are hard-of-hearing to receive federal aid for bilateral implants.

“I was asked to consult with policy makers in NZ and I am pleased they have noted these findings and made the appropriate changes,” Sarant said. 

Source: Sarant J, Harris D, Bennet L, Bant S. Bilateral Versus Unilateral Cochlear Implants in Children: A Study of Spoken Language Outcomes. Ear and Hearing. 2014.