Reliability and Validity of Cognitive Workload in Older Adults

Cognitive workload or mental effort is a measure of attention allocation to a task, which can be administered through self-report or physiological measures. Cognitive workload is increasingly recognized as an important determinant of performance in cognitive tests and daily life activities. However, the reliability and validity of these measures have not been established in older adults with a wide range of cognitive ability. The aim of this study was to establish the test-retest reliability of the NASA-Task Load Index (NASA-TLX) and Index of Cognitive Activity (ICA), extracted from pupillary size. The convergent validity of these measures against event-related potentials (ERPs) was also investigated. A total of 38 individuals with scores on the Montreal Cognitive Assessment ranging between 17 and 30 completed a working memory test (n-back) with three levels of difficulty at baseline and two-week follow-up. Intraclass correlation coefficients (ICC) values of the NASA-TLX ranged between 0.71 and 0.81, demonstrating good to excellent reliability. Mean ICA scores showed fair to good reliability, with ICCs ranging between 0.56 and 0.73. Mean ICA and NASA-TLX scores showed significant and moderate correlations with Pearson r ranging between 0.30 and 0.33 with P3 ERP at the midline channels. We conclude that ICC and NASA-TLX are reliable measures of cognitive workload in older adults. Further research is needed in dissecting the subjective and objective constructs of cognitive workload.