Stability of daily home-based measures of postural control over an 8-week period in highly functioning older adults

The focus of this study was to monitor daily objective measures of standing postural control over an 8-week period, recorded in a person's home, in a population of healthy older adults. Establishing natural patterns of variation in the day-to-day signal, occurring in the relative absence of functional decline or disease, would enable us to determine thresholds for changes in postural control from baseline that could be considered clinically important.

Eighteen community-dwelling older adults (3 M, 15 F, 72 ± 6 years) participated in a home-based trial where each day they were asked to complete a technology-enabled routine consisting of a short questionnaire, as well as a quiet standing balance trial. Centre of pressure (COP) excursions were calculated over the course of each daily balance trial to generate variables such as postural sway length and mean sway frequency.

The data demonstrated large differences between subjects in centre of pressure measures (coefficients of variation ranging 37-107 %, depending on the variable). Each participant also exhibited variations in their day-to-day trials (e.g. coefficients of variation across 8 weeks ranging ~17-56 %, within person for mean COP distance). Inter- and intra-subject differences were not strongly related to functional tests, suggesting that these variations were not necessarily aberrant movement patterns, but are seemingly representative of natural movement variability.

The idea of applying a group-focused approach at an individual level may result in misclassifying important changes for a particular individual. Early detection of deterioration can only be achieved through the creation of individual trajectories for each person, that are inherently self referential.