TasTest: moving towards a digital screening test for pre-clinical Alzheimer’s disease

Background

There is urgent need to develop population-level digital biomarkers that can detect Alzheimer’s disease (AD) across the continuum, including the preclinical phase. This would allow risk stratification for specialist tests and early recruitment to clinical trials. Motor function declines in the preclinical phase but there has been little exploration of digital motor biomarkers. We have developed ‘TasTest’, an online test that assesses multiple cognitive domains, including movement. The aim of this study was to compare performance on TasTest with subtests of the Cambridge Neuropsychological Test Battery (CANTAB), a validated digital measure of cognitive decline, and determine how performance on the TasTest items varies with age in a large community sample of older adults.

Method

The TasTest items include measures of motor control (speed and coordination of keyboard tapping), processing speed (single and choice reaction time), attention and visual perception (identification of an animal in a distorted image), and visuospatial memory (identifying features from delayed recall of a complex figure). A total of 510 adults aged over 50 years (30% male; mean 65.5 years; SD 7.36), performed TasTest and CANTAB online assessments in their homes. We compared performance on TasTest items to performance on the Paired Associates Learning (PAL) task, which has been previously validated as predictive of accelerated cognitive decline (Barnett et al. 2015, Current Topics in Behavioral Neurosciences, vol 28, Springer, Cham).

Result

All TasTest items were significantly associated with PAL scores except the total number of correct responses on the reaction time tasks (Table 1). Several TasTest items had stronger correlations with age than the PAL, these included the keyboard tapping tasks, the number of correctly identified animals on the distorted image, and both simple and choice reaction times (Figure 1).

Conclusion

Older people were able to readily complete TasTest tasks remotely from their homes, and performance on most items was significantly associated with scores on a previously validated test of cognition, and correlated with age. TasTest shows potential as a non-invasive, scalable dementia screening tool.