Preliminary validation of a dual‐task gait assessment in early Alzheimer’s Disease

Abstract

AbstractBackgroundEarly stages of Alzheimer’s disease (eAD) are marked by changes in gait characteristics that may be measured using simple smartphone‐based gait tasks. Here we present an assessment of cognitive‐motor‐interference where participants walk for 30 seconds with a smartphone placed in a running belt while counting backwards, called the 30‐Second Walk Test Dual Task (30sWTDT). We report the preliminary reliability and validation of the 30sWTDT in a cohort of healthy individuals (HC), individuals with subjective cognitive decline amyloid‐PET negative and positive (SCDn and SCDp, respectively) and eAD.Method123 participants (32 HC, 31 SCDn, 30 SCDp and 30 eAD) were recruited as a part of a Proof‐of‐Concept study of the Alzheimer’s Disease Digital Assessment Suite (AD‐DAS) (https://www.isrctn.com/ISRCTN17035495). Participants performed 9 sessions of 30sWTDT over 28 days on provisioned smartphones. Feasibility was evaluated as the proportion of completed 30sWTDT relative to the total number of expected sessions. Two gait characteristic metrics were estimated: variability in step frequency (VSF) and the 25th percentile in step power (25SP). Intraclass correlation coefficients (ICC) tested the metrics’ reliability. Convergent validity was established as partial correlation between VSF/25SP and adjusted mean duration in Timed 25 foot Walk Test (T25WT). Clinical validity was evaluated using a proportional odds logistic regression model to differentiate between groups.ResultAmong the 97.5% of participants who completed the study (i.e., n = 120), participants completed 88.9% of all assigned 30sWTDT tasks, with no group difference in adherence. VSF and 25SP metrics showed moderate (ICC = 0.74) and good (ICC = 0.79) reliability, respectively. Both metrics significantly distinguished between HC and all other study groups (odds ratio = [0.012,0.029]), and were associated with T25WT adjusted mean duration (adjusted r2 = [0.09,0.069]).ConclusionPreliminary findings demonstrate that a smartphone‐based 30sWTDT can be successfully self‐administered by cognitively healthy participants and individuals on the eAD continuum. Participants show high adherence in an ecologically valid environment. 30sWTDT differentiated HC from all other groups with subjective or objective cognitive problems, indicating a lack of specificity of gait characteristics to differentiate between increasing levels of cognitive impairment. These findings require replication in larger independent datasets.