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Logo of nihpaAbout Author manuscriptsSubmit a manuscriptHHS Public Access; Author Manuscript; Accepted for publication in peer reviewed journal;
Am Ann Deaf. Author manuscript; available in PMC 2013 July 1.
Published in final edited form as:
Am Ann Deaf. 2012 Summer; 157(3): 249–250.
PMCID: PMC3644050

Representativeness in Studies of Early Cochlear Implantation

Nae-Yuh Wang, PhD, Christine M. Carson, ScM, John K. Niparko, MD, and The CDaCI Investigative Team

We read with interest the review by Belzner and Seal (2009) on demographics in research samples of children with cochlear implants (CIs). We applaud the authors’ effort in evaluating and promoting the awareness of representativeness of research study samples in this pediatric population as reported in the peer-reviewed literature. In Belzner and Seal’s review, one of the longitudinal outcomes reports that were examined was Quittner et al. (2007), which reported on a subset (n=88) of CI recipients from the Childhood Development after Cochlear Implantation (CDaCI) Study (N=188). While the subsample of CDaCI participants demonstrated some racial diversity, the chi-square value led to the conclusion that the subsample was not representative of the national pediatric deaf population. It is surprising, however, that the authors referred to theFink et al. (2007) publication, which provided a detailed description of the CDaCI Study’s design and participants as well as nonparticipants, but they did not choose to examine the representativeness of the full CDaCI cohort.

In designing and conducting the CDaCI Study, tremendous efforts were put in place to ensure the diversity and representativeness of the children enrolled in the CDaCI Study. These efforts included enlisting multiple implant centers from diverse geographic locations across the nation and carefully documenting and comparing the participants to those who were eligible but declined participation. In response to Drs. Belzner and Seal’s comments regarding the representativeness of the CDaCI Study sample, and thus the generalizability of the CDaCI Study results to young children with sensorineural hearing loss fitted with CIs, we provide the race/ethnicity distribution for the CI cohort of the CDaCI Study (Table 1). As can be seen, the percentages for the race/ethnicity categories of the CDaCI Study are similar to, and in fact, the demographic distribution of children with CIs in the CDaCI Study does not significantly differ from, the 2000 U.S. Census data, as was reported in Drs. Belzner and Seal’s review.

Table 1
Representativeness of Children with Cochlear Implantation in the CDaCI Cohort.

We agree with Drs. Belzner and Seal that generalization of outcomes has to be done very carefully. Though the CDaCI Study was also shown by the authors to not be representative of the larger deaf population in terms of disabilities and socioeconomic status, our study design and comprehensive data collection regarding these and other important confounds have enabled us to track critical outcomes and correlates of successful CI use while controlling for these confounds with multivariable-adjustment in data analyses (Fink et al., 2007; Markman et al., 2011; Niparko et al., 2010). We believe this approach is critical in assessing real world comparative effectiveness and share Drs. Belzner and Seal's appreciation for the representativeness of the study population.


The CDaCI Study was supported by grant R01 DC004797 from the National Institute on Deafness and Other Communication Disorders, National Institutes of Health.


  • Belzner KA, Seal BC. Children with cochlear implants: A review of demographics and communication outcomes. American Annals of the Deaf. 2009;154:311–333. [PubMed]
  • Fink NF, Wang NY, Visaya J, Niparko JK, Quittner AL, Eisenberg LS, Tobey EA. the CDaCI Investigative Team. Childhood Development after Cochlear Implantation Study (CDaCI): Design and baseline characteristics. Cochlear Implants International. 2007;8:92–116. [PubMed]
  • Markman TM, Quittner AL, Eisenberg LS, Tobey EA, Thal D, Niparko JK, Wang NY. the CDaCI Investigative Team. Language development after cochlear implantation: An epigenetic model. J Neurodev Disord. 2011;3:388–404. [PMC free article] [PubMed]
  • Niparko JK, Tobey EA, Thal DJ, Eisenberg LS, Wang NY, Quittner AL, Fink NE. for the CDaCI Investigative Team. Spoken language development in children following cochlear implantation. JAMA. 2010;303:1498–1506. [PMC free article] [PubMed]
  • Quittner AL, Barker DH, Snell C, Cruz I, McDonald LG, Grimley ME, Botteri M, Marciel K. the CDaCI Investigative Team. Improvements in visual attention in deaf infants and toddlers after cochlear implantation. Audiol Med. 2007;5:242–249.