Development and validation of a Mandarin digit-in-noise test for screening hearing and cognitive function

Abstract

Early screening of hearing and cognitive functions in older adults is crucial for the timely implementation of appropriate interventions and treatments, facilitating recovery, maintaining quality of life, and alleviating related socio-economic burdens. However, cognitive screening is greatly limited by long test time, the need for trained personnel to administer the tests, and the influence of confounding factors such as education level, hearing and vision impairments on results. Because hearing loss and cognitive decline both adversely affect the ability to understand speech and there is no tool to differentiate the effects of one from the other, the current study attempted to develop an integrated digit-in-noise (iDIN) test to simultaneously screen hearing and cognitive functions. Thus, the iDIN test extends the application of the Digit Triplet Test, which is currently available in over 20 languages and has been utilized for hearing screening.

In Study 1, a 28-sentence dual-task Mandarin Reading Span Test (RST) was developed and validated to measure working memory capacity related to speech perception. Although dual-task RST is commonly used in cognitive hearing research, no Mandarin version existed. Therefore, a Mandarin RST was developed so it can be used to validate the iDIN test for hearing and cognitive screenings in the current research. The test material was developed considering psycholinguistic factors to achieve good test reliability and face validity. We confirmed the relationship between RST and speech perception in noise using validated materials. Furthermore, we found the shorter, 9-sentence version of the RST could yield similar results as the standard 28-sentence version, indicating potential clinical use when time constraint is important to consider.

In Study 2, the Mandarin iDIN Test was developed based on The International Collegium of Rehabilitative Audiology guidelines for digit test development, and validated using four digit sequences (i.e., 2-digit, 3-digit, 4-digit, and 5-digit). The test-retest reliability and psychometric function of each digit sequence were determined among young, normal-hearing adults. The criterion validity of each digit sequence was determined by comparing the performance of older adult hearing aid users with that obtained using two other well-established sentence-in-noise tests. The results suggest that while the 3-digit sequence is appropriate for clinical use for auditory perception assessment, the 2-digit sequence could also be used for hearing screening.

Study 3 investigated the application of the iDIN test for simultaneous screening of hearing and cognitive function in older adults with moderate to severe HL. The differences in speech recognition thresholds (SRT) between the 5- and 2-digit sequence (SRT5-2) and the 5- and 3-digit sequence (SRT5-3) could serve as indicators of the effects of cognitive function on speech understanding. SRT5-2 and SRT5-3 correlated highly with the Montreal Cognitive Assessment Basic and other cognitive tests, and yielded high sensitivity and specificity for distinguishing mild cognitive impairment.

In conclusion, this thesis developed and proposed the iDIN test, capable of simultaneous screening for hearing and cognitive function issues among older adults. Our findings underscore the potential application of this test for screening hearing and cognitive functions.