SART and Individual Trial Mistake Thresholds: Predictive Model for Mobility Decline

Abstract

The Sustained Attention to Response Task (SART) has been used to measure neurocognitive functions in older adults. However, simplified average features of this complex dataset may result in loss of primary information and fail to express associations between test performance and clinically meaningful outcomes. Here, we describe a new method to visualise individual trial (raw) information obtained from the SART test, vis-à-vis age, and groups based on mobility status in a large population-based study of ageing in Ireland. A thresholding method, based on the individual trial number of mistakes, was employed to better visualise poorer SART performances, and was statistically validated with binary logistic regression models to predict mobility and cognitive decline after 4 years. Raw SART data were available for 4864 participants aged 50 years and over at baseline. The novel visualisation-derived feature bad performance, indicating the number of SART trials with at least 4 mistakes, was the most significant predictor of mobility decline expressed by the transition from Timed Up-and-Go (TUG) < 12 to TUG ≥ 12 s (OR = 1.29; 95% CI 1.14–1.46; p < 0.001), and the only significant predictor of new falls (OR = 1.11; 95% CI 1.03–1.21; p = 0.011), in models adjusted for multiple covariates. However, no SART-related variables resulted significant for the risk of cognitive decline, expressed by a decrease of ≥ 2 points in the Mini-Mental State Examination (MMSE) score. This novel multimodal visualisation could help clinicians easily develop clinical hypotheses. A threshold approach to the evaluation of SART performance in older adults may better identify subjects at higher risk of future mobility decline.

Longitudinal Study on Sustained Attention to Response Task (SART): Clustering Approach for Mobility and Cognitive Decline

“…In order to assess global cognitive status, frequently used tests are the Mini-Mental State Examination (MMSE) score as a standard measure of overall cognitive status [ 35 ], and the Montreal Cognitive Assessment (MoCA) [ 36 ], a more challenging cognitive test compared to the MMSE, which includes executive function, higher-level language, and complex visuospatial processing, and is designed to detect milder impairments. In our previous investigation, we did not find a significant association between baseline SART performance and cognitive decline at 4 years as assessed by MMSE score [ 7 ], although SART performance and MMSE score offer two different measures of the same physiological system. Therefore, it was necessary to employ a different technique, which could allow to a higher specificity and detection of a small number of participants with signs of both physical and cognitive decline.…”

“…High IIV has been shown to be strongly correlated with inefficient sustained cognitive processes. Moreover, recent studies [ 4 , 7 ] have demonstrated that the use of the entire raw dataset could help clinicians find important features and peculiar associations that are otherwise hidden in derived measures.…”

“…Our previous companion study [ 7 ] proposed a novel method to visualise the full information obtained from the SART tests performed by a large sample of older participants in a large population-based study, and a new variable, ‘bad performances’, based on a thresholding method, which could allow detection of a subset of participants considered to have a poor SART performance, and important clinical implications such as future falls and mobility decline [ 7 ]. Moreover, recent studies have underscored the importance of the longitudinal investigation of cognitive data in order to individuate possible neurodegenerative disorders as soon as possible [ 24 ], as well as functional decline in other physiological systems [ 25 ].…”

“…Furthermore, recent studies [ 26 , 27 ] have shown the presence of an integrated network of interactions and feedback mechanisms among different physiological systems, particularly between the brain and the loco-motor system. Specifically, correlations have been found between RT and mobility decline [ 7 , 25 , 28 ], and between poor mobility performance and cognitive decline [ 25 ]. Evidence of the interconnections between the cognitive and the loco-motor systems has generated great interest among researchers, and finding a clinical and biological interpretation of the complex networked interactions remains a challenge in medical research.…”

“…Recent findings have suggested that baseline quantitative gait parameters are significant predictors of cognitive decline and dementia in older adults [ 25 , 32 , 33 ]. On the other hand, recent studies have demonstrated that older participants with poorer SART performances [ 7 ] and poorer choice reaction times [ 28 ] may present an accelerated mobility decline and have a higher risk of incident falls [ 34 ].…”