P1-240: Gait impairments distinguish dementia subtypes and normal ageing: A comparison of single- and dual-task gait

Background Gait impairments distinguish dementia subtypes from each other and normal ageing when assessed under single task (ST) conditions (i.e. performing gait only). Assessing gait under dual-task (DT) conditions (i.e. performing an additional cognitive task) may reveal gait impairments not obvious during ST gait, due to greater cognitive demand. Studies suggest DT gait may be useful for identifying early dementia. This study aims to investigate whether DT gait can improve distinguishing between dementia subtypes and normal ageing. Methods 107 participants were recruited; 34 AD ((mean±SD) Age:77±7; MMSE:23±4), 29 DLB (Age:76±6; MMSE:24±4), 15 PDD (Age:78±6; MMSE:24±4) and 29 controls (Age:74±9; MMSE:29±1). Dementia subtypes ranged in severity from mild cognitive impairment to moderate dementia. Gait was assessed using an instrumented walkway (GAITRite) under ST and DT conditions (performing an additional standardized digit-span task). Dual task cost (DTC) was calculated by subtracting ST performance from DT performance and described by raw scores. One-way ANOVA and non-parametric equivalents assessed group differences. Paired-samples t-tests and non-parametric equivalents assessed differences in gait performance between conditions. Results In ST, preliminary results show that all disease groups had impaired gait compared to controls (p≤.05). The PDD and DLB groups were also significantly more variable and asymmetric (p≤.05) compared to AD. However, in DT conditions, there were no between-group differences. Controls had a higher maximum digit span compared to all dementia groups (6±1 vs.5±1, respectively;p≤.05).When comparing conditions using repeated measures, gait was significantly impaired under DT conditions (p≤.05) for controls. The AD groups demonstrated greater step velocity variability (p=.048) during DT, and the DLB group had greater step velocity and length variability (p≤.001). After calculating DTC for gait, AD group demonstrated less change for gait variability (p≤.05) compared to controls. There were no other group differences for gait DTC or for digit span DTC. Conclusions This study found that ST gait distinguishes early dementia from normal ageing and differentiates subtypes. However, assessing DT gait using a cognitive task standardised to individual performance, gait impairments were indistinguishable between groups. Therefore, ST gait assessment may be more effective for supporting dementia diagnosis. However, future studies should investigate different dual-task paradigms