A Remote Digital Memory Composite to Detect Cognitive Impairment in Memory Clinic Samples in Unsupervised Settings using Mobile Devices

INTRODUCTION: Mobile app-based unsupervised monitoring of cognition holds the promise to facilitate case-finding in clinical care and the individual detection of cognitive impairment in clinical and research settings. In the context of Alzheimer9s disease, this is particularly relevant for patients who seek medical advice due to memory complaints. OBJECTIVE: We developed a Remote Digital Memory Composite score from an unsupervised remote and mobile cognitive assessment battery focused on episodic memory and long-term recall and assessed its construct validity using a neuropsychological composite score for early cognitive impairment in Alzheimer9s disease, the Preclinical Alzheimer9s Cognitive Composite (PACC5). We also assessed the test-retest reliability of the Remote Digital Memory Composite score across two independent test sessions. Finally, we assessed the diagnostic accuracy of the remote and unsupervised cognitive assessment battery when predicting PACC5-based cognitive impairment in a memory clinic sample and healthy controls. SETTING: This was an add-on study of the DZNE-Longitudinal Cognitive Impairment and Dementia Study (DELCODE) which was also performed in a separate memory clinic-based sample. PARTICIPANTS A total of 102 study participants were included as healthy controls (HC; n=25), cognitively unimpaired first-degree relatives of AD patients (REL; n=7), individuals with subjective cognitive decline (SCD; n= 48) or patients with mild cognitive impairment (MCI; n=22). MEASUREMENTS: We analyzed results from the objects-in-rooms recall (ORR) test, the mnemonic discrimination for objects and scenes (MDT-OS) test and the complex scene recognition (CSR) test implemented on the neotiv digital platform to derive a Remote Digital Memory Composite. Participants used the neotiv mobile app to complete one unsupervised test session every two weeks on their own mobile device in an environment of their choice. We assessed the relationships of the Remote Digital Memory Composite acquired through the mobile app and in-clinic measures of the PACC5 conducted by trained neuropsychologists in the memory clinics participating in the DELCODE study. RESULTS: 102 participants provided technically complete data for at least one single session of each of the three test paradigms, of which 87 participants provided data from at least two test sessions of each task. The derived Remote Digital Memory Composite score was highly correlated with the PACC5 score across all participants (r=.75, p<0.001), and also in those without complaints (HC and REL, r=.51, p=0.003) and those with complaints separately (SCD and MCI, r=.76, p<0.001). Good test-retest reliability for the Remote Digital Memory Composite score was observed in those with at least two assessments of the three tests. (r=.74; p<.0001). Diagnostic accuracy for discriminating PACC5-based memory impairment from no impairment was high (AUC = 0.9) with a sensitivity of 0.83 and a specificity of 0.74. CONCLUSION: Our results indicate that unsupervised mobile cognitive assessments in a memory clinic setting using the implementation in the neotiv digital platform has high construct validity and results in a good discrimination between cognitively impaired and unimpaired individuals based on the PACC5 score. Thus, it is feasible to complement neuropsychological assessment of episodic memory with unsupervised, remote assessments on mobile devices. This contributes to recent efforts for implementing remotely performed episodic memory assessment for case-finding and monitoring in large research trials and clinical care.