Dual tasking paradigm in clinical stages of early Alzheimer’s disease

Background In Alzheimer’s disease (AD) both motor and cognitive domains are impaired [1‐2]. However, these domains are usually assessed independently and even when performing dual‐task (DT) paradigms, the cognitive‐motor interaction (CMI) is not taken into account, which may lead to misinterpretation of the patient’s global state. To date, there are no precise markers to detect subtle signs of pre‐clinical neurodegeneration or to accurately monitor disease progression. Method We have evaluated the motor and cognitive components of a DT paradigm concurrently (Figure 1) with the aim to identify a sensitive marker of early AD. Fifty participants, aged 60 to 80 years, were included in the study and distributed across four cohorts of early AD [3]: 1) amyloid negative, cognitively healthy participants (control group), 2) amyloid positive pre‐symptomatic AD, 3) Mild Cognitive Impairment (MCI) due to AD and 4) mild AD. Two inertial gait measurement units (IMUs) (Physilog, GaitUp S.A.) were attached to each foot and a small wearable microphone (Wireless GO, RØDE) was used to record counting. Both timing [4] and gait features were extracted from raw data. Correct response rate (CRR) and gait speed were used to evaluate the CMI based on Plummer’s classification system [5]. Moreover two‐way ANOVA was carried out to evaluate the effect of cohort and cognitive load conditions on the CMI. Result Our results show that there is a significant drop in both cognitive and motor performance while performing DT and that this drop is more pronounced with increased disease severity and as we increase the cognitive load of the task (Figure 2). Moreover, CMI shows a cognitive‐priority trade‐off in all cohorts (better/stable counting performance while walking becomes slower). However, when the cognition load is increased, in particular in more severe stages of disease, this shifts towards a mutual interference effect, i.e. where both counting performance declines and walking slows down (Figure 3). Conclusion To our knowledge, this is the first feasibility study assessing the CMI at preclinical and early clinical stages of AD. Our preliminary results suggest that the DT paradigm is a sensitive method to detect early signs of neurodegeneration and monitor AD progression.