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Wideband absorbance in young infants (0-6 months): a cross-sectional study.

BACKGROUND
Wideband acoustic immittance (WAI) studies on infants have shown changes in WAI measures with age. These changes are attributed, at least in part, to developmental effects. However, developmental effects in young infants (0-6 mo) on WAI have not been systematically investigated.


PURPOSE
The objective of this study was to compare wideband absorbance (WBA) in healthy neonates and infants aged 1, 2, 4, and 6 mo.


RESEARCH DESIGN
This was a prospective cross-sectional study. All participants were assessed by using 1-kHz tympanometry, distortion product otoacoustic emission (DPOAE) tests, and WBA tests.


STUDY SAMPLE
Participants included 35 newborns (35 ears), 16 infants aged 1 mo (29 ears), 16 infants aged 2 mo (29 ears), 15 infants aged 4 mo (28 ears), and 14 infants aged 6 mo (27 ears). For each participant, the ears that passed both high-frequency (1-kHz) tympanometry and DPOAE tests were included for analysis.


DATA COLLECTION AND ANALYSIS
WBA was recorded at ambient pressure conditions, and the response consisted of 16 data points at 1/3-octave frequencies from 0.25 to 8 kHz. A mixed-model analysis of variance (ANOVA) was applied to the data in each age group to evaluate the effects of sex, ear, and frequency on WBA. WBA was compared between various age groups. In addition, a separate mixed-model ANOVA was applied to WBA data, and post hoc analyses with the Bonferroni correction were performed at each of the 16 data points at 1/3-octave frequencies across age groups to examine the effect of age on WBA.


RESULTS
For all age groups, WBA was highest between 1.5 and 5 kHz and lowest at frequencies of less than 1.5 kHz and greater than 5 kHz. A developmental trend was evident, with both the 0- and 6-mo-old infants being significantly different from other age groups at most frequencies. The WBA results exhibited a multipeaked pattern for infants aged 0 to 2 mo, whereas a single broad peaked pattern for 4- and 6-mo-old infants was observed. The difference in WBA between 0- and 6-mo-old infants was statistically significant across most frequencies. In contrast, the WBA results for 1- and 2-mo-old infants were comparable. There were no significant sex or ear effects on WBA for all age groups.


CONCLUSIONS
Developmental effects of WBA were evident for infants during the first 6 mo of life. The WBA data can be used as a reference for detecting disorders in the sound-conductive pathways (outer and middle ear) in young infants. Further development of age-specific normative WBA data in young infants is warranted.