J Am Acad Audiol 2020; 31(09): 646-655
DOI: 10.1055/s-0040-1718700
Research Article

“The Dichotic Digit Test” as an Index Indicator for Hearing Problem in Dementia: Systematic Review and Meta-Analysis

Nattawan Utoomprurkporn
1  UCL Ear Institute, Faculty of Brain Science, University College London, London, United Kingdom
2  Department of Otolaryngology, Faculty of Medicine, Chulalongkorn University, Pathumwan, Bangkok, Thailand
,
Chris J.D. Hardy
3  Dementia Research Centre, Faculty of Brain Science, University College London, London, United Kingdom
,
Joshua Stott
4  Division of Psychology and Language Science, Faculty of Brain Sciences, University College London, Gower Street, United Kingdom
,
Sergi G. Costafreda
5  Division of Psychiatry, Faculty of Brain Sciences, University College London, Gower Street, United Kingdom
,
Jason Warren
3  Dementia Research Centre, Faculty of Brain Science, University College London, London, United Kingdom
,
Doris Eva Bamiou
1  UCL Ear Institute, Faculty of Brain Science, University College London, London, United Kingdom
6  NIHR Biomedical Research Centre Hearing and Deafness, London, United Kingdom
› Author Affiliations

Abstract

Background Patients with dementia commonly have problems processing speech in the presence of competing background speech or noise. This difficulty can be present from the very early stages of dementia, and may be a preclinical feature of Alzheimer's disease.

Purpose This study investigates whether people with dementia perform worse on the dichotic digit test (DDT), an experimental probe of speech processing in the presence of competing speech, and whether test performance may predict dementia onset.

Research Design Systematic review and meta-analysis.

Data Collection and Analysis A literature search was conducted in Medline, Embase, Scopus, and Psycinfo. We included (1) studies that included people with a diagnosis of dementia and a healthy control group with no cognitive impairment; (2) studies that reported results from a DDT in a free-recall response task; and (3) studies that had the dichotic digit mean correct percentage score or right-ear advantage, as outcome measurements.

Results People with dementia had a lower DDT total score, with a pooled mean difference of 18.6% (95% confidence interval [CI]: 21.2–15.9). Patients with dementia had an increased right-ear advantage relative to controls with a pooled difference of 24.4% (95% CI: 21.8–27.0).

Conclusion The DDT total scores are lower and the right-ear advantage increased in cognitively impaired versus normal control participants. The findings also suggest that the reduction of dichotic digit total score and increase of right-ear advantage progress as cognitive impairment increases. Whether abnormalities in dichotic digit scores could predict subsequent dementia onset should be examined in further longitudinal studies.

Author Contributions

N.U. is the main author of this paper. N.U. conducted the literature search. N.U. and D.E.B. conducted the systematic review. C.J.D.H., J.S.D., S.G.C., and J.W. contributed to the manuscript write-up. All authors read and approved the final manuscript.


Financial Disclosure

No specific funding was granted for the conduct of this research.


N.U. is supported by a King Chulalongkorn Memorial Hospital (Thai Red Cross organization; Teaching hospital for Faculty of medicine, Chulalongkorn university) fellowship. C.J.D.H. is supported by an Action on Hearing Loss-Dunhill Medical Trust Pauline Ashley fellowship. J.W. receives research funding support from the Alzheimer's Society, Alzheimer's Research UK and the NIHR UCLH Biomedical Research Centre.


Supplementary Material



Publication History

Received: 26 September 2019

Accepted: 18 February 2020

Publication Date:
09 December 2020 (online)

© 2020. American Academy of Audiology. This article is published by Thieme.

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