The classical backward digit span task detects changes in working memory but is unsuitable for classifying the severity of dementia

Abstract

Dementia is characterized by the deterioration of working memory (WM). The backward digit span (DS) task and reading span test (RST) are measures of WM. DS task and RST have not been directly compared in assessing dementia. This study aimed to compare the performance of individuals with dementia in forward and backward DS tasks to that in RST. We investigated the ability of forward/backward DS tasks to discriminate dementia severity. Forward/backward DS tasks and RST were performed in 15 elderly Japanese individuals with dementia. Twenty-six and 20 elderly individuals for the DS task and RST, respectively, were included as controls. Clinical Dementia Rating scale (CDR) was used to evaluate dementia severity. DS task scores were significantly correlated with RST scores. Both types of DS tasks correlated with RST, only the RST distinguished dementia severity based on CDR. Our findings indicate that the backward DS task may detect WM decline in dementia, but the RST is more suitable for assessing dementia severity. The backward DS task may be an effective screening measure for dementia signs in the elderly and may be used to identify patients requiring further assessments such as the RST to evaluate dementia severity based on WM performance.

Keywords:

• Backward digit span
• dementia
• forward digit span
• short-term memory
• working memory

Acknowledgments

We would like to thank Editage (www.editage.com) for English language editing.

Ethical approval and informed consent

This study was approved by the Ethics Committee of Kyoto Gakuen University (No. 14, 111, 116) (former name of Kyoto University of Advanced Science). All procedures were conducted according to the principles of the Declaration of Helsinki 1964 and its later amendments. All participants provided written as well as verbal informed consent prior to the commencement of the study.

Disclosure statement

No potential competing interest was reported by the author(s).

Data availability statement

The data used to support the findings of this study are available from the corresponding author upon request.

Additional information

Funding

This work was supported in part by JSPS KAKEN HI under Grant JP [15K00214] and Health Labor Sciences Research under Grant [201916012 A].