The cognitive correlates of gait in incident Parkinson's disease

[Poster] Objective: To examine the relationship between cognition and gait in an incident cohort of Parkinson's disease (PD) and the effect of disease severity on these relationships. Background: The link between gait and cognition is evident with decline in healthy ageing and dementia, but has not been studied extensively in incident PD. Selective features of gait are likely to correspond with different features of cognition and be sensitive to change over time. These relationships provide a basis for understanding the cognitive control of gait in PD, its evolution, and the utility of gait as a surrogate biomarker for cognitive decline in PD. Methods: ICICLE-GAIT recruited 121 people with incident PD who underwent a comprehensive gait assessment using a 7m instrumented GAITrite mat whilst walking for 2 minutes under single task conditions. Sixteen gait outcomes were extracted and reduced to robust domains based upon a previously described theoretical gait model (pace, rhythm, variability, asymmetry, and postural control). Participants also undertook a battery of cognitive tests which included outcomes from six cognitive domains (attention, fluctuating attention, executive function, memory, working memory, visuospatial function). PD participants were also sub-classified according to PIGD tertile scores from the new UPDRS scale, and relationship with cognition explored further. Step-wise regression was used to identify significant correlates, controlling for age, sex, years of education (and PIGD score for the total PD group). Results: Poorer fluctuating attention, attention and working memory were independent predictors of impaired pace (β= .251, P = .002), variability (β= .201, P = .031) and postural control (β= .242, P = .008) domains respectively. This relationship was stronger in those with moderate and severe PIGD symptoms. Significant regression models were also identified for those with moderate PIGD symptoms (2nd tertile) (fluctuating attention with pace: β= .242, P = .008; and variability: β= .242, P = .008), and most severe PIGD symptoms (3rd tertile) (attention and pace: β= .242, P = .008). Conclusions: The cognitive control of gait in incident PD is seen most strongly in attentional cognitive features, consistent with early fronto-striatal deficits. This relationship is likely to change over time given the heterogeneity of PD and variation in mechanisms that underpin different phenotypes.