Study Shows Earlier is Better for Cochlear Implants
Apr. 23, 2010
Receiving a cochlear implant before 18 months of age dramatically improves a deaf child’s ability to hear, understand and eventually speak, according to a multicenter study that included the UT Dallas Callier Center for Communication Disorders.
The study, titled “Spoken Language Development in Children Following Cochlear Implantation,” was published in the April 21 issue of The Journal of the American Medical Association (JAMA).
“Parents are very interested in learning how language develops in children with cochlear implants,” said Dr. Emily Tobey, co-investigator of the study and professor and Nelle C. Johnston Chair in the School of Behavioral and Brain Sciences. “This is the first nationwide study conducted in the United States to look at how children begin to acquire language when they get a cochlear implant at very young ages.”
The Childhood Development after Cochlear Implantation (CDaCI) research team, led by Dr. John K. Niparko at Johns Hopkins University School of Medicine, followed 188 children, ages 6 months to 5 years, with profound hearing loss for three years after receiving cochlear implants at six U.S. hospitals. The researchers tracked the children’s newly emerging ability to recognize speech after the implant and compared their levels of language development to those of 97 same-age children with normal hearing.
While speech and language skills improved in all children regardless of age after they received a cochlear implant, age emerged as a powerful predictor in just how much improvement was seen. Therefore, the researchers conclude, delaying implantation deprives children of essential exposure to sounds and speech during the formative phases of development when the brain starts to interpret the meaning of sounds and speech.
The researchers say that each year of delay of receiving a cochlear implant – for children whose hearing qualifies them for an implant – can put a child a year behind in language development. Therefore, all young infants with suspected severe-to-profound hearing loss and those with a family history of such loss, should be monitored vigilantly and referred for treatment as soon as possible.
“We identified a clear pattern where implantation before 18 months of age conferred a much greater benefit than later implantation, allowing children to catch up fast, sometimes to nearly normal levels,” says Niparko. “Delaying intervention until a child loses every last bit of hearing deprives the brain of much-needed sound and speech stimulation that is needed to develop language.”
Although many of the children in the study never reached the language levels of their hearing counterparts, those who received cochlear implants developed better abilities to understand and speak than they would have without the device. Children who received a cochlear implant before age 18 months nearly caught up with their normal-hearing counterparts over the subsequent three years, and children who received implants after age 3 had language gaps that corresponded directly to the length of delay before receiving the implant.
Another important factor in language development was how soon and how much the parents interacted with a child, the study found.
“Language development in children with cochlear implants is greatly aided when parents are actively engaged in communication activities with their child, whether the child has normal hearing or some degree of hearing loss,” says Tobey.
The CDaCI research team will continue to follow and measure communication in these children as they move into kindergarten and elementary school.
Co-investigators on the study include Donna Thal, PhD, University of California, San Diego; Laurie Eisenberg, PhD, House Ear Institute; Nae-Yuh Wang, PhD, Johns Hopkins University; Alexandra Quittner, PhD, University of Miami; and Nancy Fink, MPH, Johns Hopkins University.
Data for the study was collected by the clinical teams associated with Johns Hopkins University, UT Dallas, University of Miami Medical Center, University of North Carolina, University of Michigan and the House Ear Institute.
The research was funded by the National Institute on Deafness and Other Communication Disorders, the CityBridge Foundation and the Sidgmore Family Foundation.
The Callier Center is a member of the Dallas Cochlear Implant Program, which is a collaborative enterprise between The University of Texas at Dallas, The University of Texas Southwestern Medical Center and Children’s Medical Center Dallas.