Longitudinal Development of Distortion Product Otoacoustic Emissions in Infants With Normal Hearing

Objectives: The purpose of this study was to describe normal characteristics of distortion product otoacoustic emission (DPOAE) signal and noise level in a group of newborns and infants with normal hearing followed longitudinally from birth to 15 months of age. Design: This is a prospective, longitudinal study of 231 infants who passed newborn hearing screening and were verified to have normal hearing. Infants were enrolled from a well-baby nursery and two neonatal intensive care units (NICUs) in Cincinnati, OH. Normal hearing was confirmed with threshold auditory brainstem response and visual reinforcement audiometry. DPOAEs were measured in up to four study visits over the first year after birth. Stimulus frequencies f1 and f2 were used with f2/f1 = 1.22, and the DPOAE was recorded at frequency 2f1–f2. A longitudinal repeated-measure linear mixed model design was used to study changes in DPOAE level and noise level as related to age, middle ear transfer, race, and NICU history. Results: Significant changes in the DPOAE and noise levels occurred from birth to 12 months of age. DPOAE levels were the highest at 1 month of age. The largest decrease in DPOAE level occurred between 1 and 5 months of age in the mid to high frequencies (2 to 8 kHz) with minimal changes occurring between 6, 9, and 12 months of age. The decrease in DPOAE level was significantly related to a decrease in wideband absorbance at the same f2 frequencies. DPOAE noise level increased only slightly with age over the first year with the highest noise levels in the 12-month-old age range. Minor, nonsystematic effects for NICU history, race, and gestational age at birth were found, thus these results were generalizable to commonly seen clinical populations. Conclusions: DPOAE levels were related to wideband middle ear absorbance changes in this large sample of infants confirmed to have normal hearing at auditory brainstem response and visual reinforcement audiometry testing. This normative database can be used to evaluate clinical results from birth to 1 year of age. The distributions of DPOAE level and signal to noise ratio data reported herein across frequency and age in normal-hearing infants who were healthy or had NICU histories may be helpful to detect the presence of hearing loss in infants. ACKNOWLEDGMENTS: The efforts of Alaaelddin Elsayed, MD, AuD, Leigh Shaid, AuD, several research coordinators, and the families who participated are gratefully acknowledged. We are appreciative of three anonymous reviewers who substantially improved the article. This research was supported by the National Institute of Deafness and other Communication Disorders of the National Institutes of Health under Award Number R01 DC010202 and an American Recovery and Reinvestment Act of 2009 (ARRA) supplement (DC010202-01S1). Coauthor D.H.K. is involved in commercializing devices to assess middle ear function in infants. L.L.H. designed and performed the experiments, cowrote the article, and provided interpretive analysis and critical revision to the article. C.M.B. performed the experiments, analyzed the data, and cowrote the article. D.H.K. designed the experiments; provided interpretative analysis and critical revision to the article; and involved in commercializing devices to assess middle ear function. M.P.F. designed the experiments and provided interpretative analysis and critical revision to the article. D.K.B helped to design and perform the experiments and helped in data collection while employed at Cincinnati Children’s Hospital Medical Center. A.M. assisted in enrollment and data analysis as part of her AuD capstone. D.F.F. designed the experiments and provided interpretative analysis and critical revision to the article. L.L. provided statistical analysis and critical revision to the article. All authors discussed the results and implications and commented on the article at all stages. Portions of this study were presented as poster presentations at the American Academy of Audiology (Orlando, FL, March, 2014) and at the American Auditory Society (Scottsdale, AZ, March, 2016). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institute of Health. The content of this article does not represent the views of the Department of Veterans Affairs or of the U.S. Government. The authors have no conflicts of interest to disclose. Address for correspondence: Lisa L. Hunter, Communication Sciences Research Center, Cincinnati Children’s Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH 45229, USA. E-mail: lisa.hunter@cchmc.org Received February 6, 2017; accepted November 5, 2017. Copyright © 2018 Wolters Kluwer Health, Inc. All rights reserved.

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