The Four Square Step Test in individuals with Parkinson's disease: Association with executive function and comparison with older adults

BACKGROUND: In Parkinson's disease (PD), motor and cognitive impairments interact to affect functional performance adversely. A valid mobility test, the Four Square Step Test (FSST) involves multidirectional stepping over obstacles. FSST performance may also be associated with cognitive performance. OBJECTIVES: This study determined the feasibility and reliability of an obstacle-based FSST in older individuals with versus without PD, and evaluated the association of PD performance of FSST with tests of cognition. METHODS: Thirty-one individuals with mild-moderate PD, evaluated while ON medications, completed the obstacle-based FSST, other mobility and cognitive measures. FSST performance was compared between a PD participant sub-set (n = 24) and 24 age-matched older adults. Data were analyzed with independent t-tests, correlations, and linear regression. RESULTS: Obstacle-based FSST was feasible and reliable within sessions in those with PD. Median best FSST time among individuals with PD was 11.72 s (9.99, 13.98) and FSST had concurrent validity with tests of mobility, and cognitive dual-tasking. Among cognitive tests, Trails Making Test B, which evaluates executive function, emerged as a sole contributor (49%) of variance. FSST performance did not differ between those with PD and older adults. CONCLUSION: The obstacle-based FSST is feasible and reliable in those with PD. The relationship between cognitive status and performance on the FSST did not appear to be strongly disease-stage dependent. Using FSST in the clinic may help assess the health status of a motor-cognitive interaction in individuals with PD.