Increased intra-individual variability in stride length and reaction time in recurrent older fallers

Aims: To study and compare both mean performance measures as well as intra-individual variability measures of stride length and reaction time in vulnerable recurrent and non-recurrent older fallers. Methods: Stride length during walking and walking while dual-tasking (GAITRite (R)) and choice reaction time (CANTAB (R)) were assessed in geriatric outpatients and their informal caregivers (n=60, >= 60yrs). Logistic regression and Receiver Operating Characteristic (ROC) analysis were used to generate models with mean performance measures and intra-individual variability measures (coefficients of variation; CV=[sd/mean]x100)), as risk factors for recurrent falls. Results: Reaction-time CV was higher in recurrent fallers than in non-recurrent fallers: 21.3%[9.3-47.7] vs 15.8% [8.3-34.9] (p=0.04). Also, stride-length CV was higher in recurrent fallers during performance of the verbal fluency dual-task: 4.5% [1.2-31.4] vs 3.5% [0.9-9.7] (p=0.017). The model with CVs provided an explained variance of 23.7%, and an area under the curve (AUC) of 0.73, which was higher than that of the model including mean performance measures (8.6% and 0.65 respectively). Conclusions: Older recurrent fallers are characterized by increased within-task variability in reaction time and stride length while dual-tasking. In addition, variability in performance is a more sensitive measure in discrimination of recurrent falls than mean performance itself, suggesting deterioration in neurocognitive regulation mechanisms as part of the causal pathway for recurrent falls. (Aging Clin Exp Res 2011; 23: 393-399) (C)2011, Editrice Kurtis