Objective: To explore the use of within-subject variation in the Cognitive Timed Up and Go test (Cognitive TUGWSV) as an explanatory variable in fall risk in the Parkinson's disease population.
Design: Cross-sectional study.
Methods: Fifty-three patients with Parkinson's disease completed 3 trials of the Cognitive TUGWSV. Within-subject variation was calculated using the standard deviation of an individual's repeated measurements, and compared on the basis of the fall history reported in the previous 6 months. Participants who reported < 2 falls were classified as "non-recurrent fallers" (n = 31) and those who reported ≥ 2 falls were classified as "recurrent fallers" (n = 22). Univariate and a multivariate logistic regression were used to investigate the statistical impact of the Cognitive TUGWSV as an explanatory variable in fall risk. Discriminative ability and cut-off score were determined based on receiver operating characteristic analysis.
Results: There was a significant difference between groups in the Cognitive TUGWSV (p = 0.002). Univariate logistic regression indicated a significant association between Cognitive TUGWSV and fall risk (χ2=12.365, p < 0.001), with an odds ratio of 2.5 (95% confidence interval (95% CI) = 1.34-4.65). Multivariate logistic regression showed that body mass index (BMI), Falls Efficacy Scale-International (FES-I), Cognitive TUGWSV, and the mean velocity of the centre of foot pressure under closed eyes condition (Velocity COP (CE)) were significant explanatory variables in fall risk. Cognitive TUGWSV was the most important independent variable. Receiver operating characteristic analysis revealed an acceptable discriminative power (area under the curve (AUC) = 0.757, 95% CI = 0.619-0.864, p < 0.001) and a cut-off point of 1.53 s.
Conclusion: A higher Cognitive TUGWSV correlated significantly with higher fall risk. Thus, diagnostic tests and exercise programmes could consider Cognitive TUGWSV when assessing fall risk in the Parkinson's disease population.