Development of a dual task interference assessment tool: evaluating test-retest reliability and concurrent validity...

This study aimed to develop and evaluate the reliability and concurrent validity of the Dual Task Interference Assessment Tool (DTIT) in community-dwelling older adults. A total of 93 participants (42 with cognitive decline and 51 without) were assessed using the DTIT, which evaluates dual-task abilities across four domains: upper extremity, lower extremity, balance, and functional mobility. Motor tasks included cup stacking, tandem gait, step block, and the Timed Up and Go (TUG) test, while cognitive tasks involved serial subtraction, word generation, counting backward by months, and Reciting Alternate Letters (RAL). Motor (mDTE) and cognitive (cogDTE) dual-task interference were calculated for each task. Significant group differences were observed in all DTIT subscales, except for the mDTE of DTIT_Lower Extremity (p = 0.308). Test-retest analyses demonstrated excellent reliability for all DTIT subscales, with no significant learning effect between sessions (p > 0.05). Strong concurrent validity was confirmed by significant correlations between DTIT_Upper Extremity and NHPT, DTIT_Balance and the Functional Reach Test, and DTIT_Lower Extremity/Functional Mobility and walking speed (p < 0.05). The DTIT is the first instrument to comprehensively assess dual-task interference in older adults, with and without cognitive decline. Thanks to its robust psychometric properties, it can be used as a practical clinical and research tool to identify dual-task difficulties and monitor rehabilitation outcomes.