Step initiation characteristics in dementia patients
The early identification of balance disorders and their appropriate interpretation is crucial for dementia patients. The aim of this study was to identify postural instability in dementia patients with mild to moderate stage and control group during step initiation under different conditions. 54 dementia patients and thirty age-matched healthy controls voluntarily participated in the study. Step initiation was performed on two force plates under four conditions: unperturbed transition between platforms, obstacle clearance, step-up and step-down. The trials were repeated 3 times and lasted 35 s each. Recordings of center-of-foot pressure displacements were divided into three distinct phases: 1st phase – quiet standing before step initiation, 2nd phase – transit, and 3rd phase – quiet standing after step initiation. The following variables of COP displacement were calculated for the 1st and 3rd phases: the mean velocity of COP (vCOP) [cm/s] in an anterior-posterior (AP) and medio-lateral (ML) plane. In the 2nd phase, the following variables were also derived: TT (s)– transit time - the duration of the second phase, S1 (s) – first stability time - the time from exiting steady standing (beginning of phase 2) to the time when the leading foot was resting on the other platform, S2 (s) – second stability time - the time from raising the foot from the first platform to the end of the phase, DSP (s) – double-support period - when the trailing foot is touching the first platform and the leading foot is simultaneously touching the second platform during the step. Dementia patients were characterized by the longer step initiation time compared to control group under all conditions (p < 0.03). There were significant differences in quiet standing before step initiation between dementia patients and control group but only in unperturbed and obstacle clearance trials (p < 0.02). There were no significant differences in quiet standing after step transition between dementia patients and control group (p > 0.05). The new proposed objective method is a reliable tool for detecting differences between mild and moderate stages of dementia and healthy peers, which is crucial in clinical practice. Postural control research should focus on functional motor tasks rather than simple motor tasks such as quiet standing.
Steps to reproduce
Raw platform data were processed offline using MATLAB (Mathworks Inc., Natick, MA, USA, v. r2017b). The data were low-pass filtered (Butterworth) with a cut-off frequency of 7 Hz.