Digit-in-Noise Test as a Hearing Screening Test for Individuals With Intellectual Disability

Diagnosis of intellectual disability (ID) may overshadow, or co-occur with, hearing impairment, but screening is frequently inaccessible due to various factors that prevent successful test execution. There is a pressing need for easily, locally administered hearing tests. This study aimed to assess the efficacy of the digit-in-noise (DIN) test, as well as three variations of it, as a hearing screening for individuals with mild to moderate ID. Additionally, we explored correlations between participant characteristics and cognitive-linguistic abilities, with DIN test performance.

Forty participants with ID aged 21-40 were recruited from two supported employment centres, 31 of whom met full inclusion criteria. Controls were 20 typically developed (TD) participants, aged 21-40. The original DIN test (DIN(3)) was administered, and those unable to recall the three digits were administered a version with two digits (DIN(2)). Participants unable to successfully complete DIN(3) or DIN(2) were administered versions with added visual and verbal performance feedback.

A significant difference in speech receptive threshold in noise (SRTn) between DIN(2) and DIN(3) was only present for the ID group. A moderate negative relationship between DIN(2) SRTn and vocabulary and a positive relationship with age was found for the ID group; no correlation was found with digit span or matrices. The DIN(2) SRTn was correlated with the average hearing level of pure tones measured by audiometry.

Our findings highlight the DIN(2) as the most effective version, as its signal-to-noise ratio (SRTn) threshold was closest to the typically developed (TD) control group. This study is the first step towards developing a hearing screening test for individuals with ID who are at elevated risk of impairment and who have insufficient evaluation access. Our findings suggest that adults with mild to moderate ID can sufficiently perform the adapted DIN(2) as a hearing screening test.