The Short Physical Performance Battery does not correlate with daily life gait quality and quantity in community-dwelling older adults

BackgroundBoth the Short Physical Performance Battery (SPPB) and daily life gait quality and quantity values obtained from wearable sensors are used to measure functional status. It is generally assumed that they are interrelated and exchangeable, but this has not yet been established. Interchangeability of these measures would pave the way for remote monitoring of functional status.Research questionAre the SPPB score and daily life gait quality and quantity values correlated in community-dwelling older adults? MethodsThe SPPB and gait quality and quantity data of 229 community-dwelling adults of 65 years or older were collected. The SPPB is a combined score of the Three Stage Balance test, Four Meter Walk test, and Five Times Sit to Stand test and ranges from 0 to 12. Participants wore a tri-axial inertial sensor for one week to assess gait quality (e.g. gait stability and smoothness) and quantity (e.g. number of strides). Correlation coefficients between SPPB scores and gait quality and quantity values were assessed using Spearman’s correlation.ResultsThe median age of the study population was 76.2 years (IQR 72.6-81.0), and 76% were women (n=175). The median SPPB score was 10 (IQR 8-11). Spearman's correlation coefficients between the SPPB and gait quality and quantity values were all below 0.3.SignificanceA possible explanation for the observed weak correlations is that the SPPB reflects the maximal capacity, while the gait quality and quantity values reflect the submaximal performance in daily life. The SPPB and gait quality and quantity values seem distinct constructs with complementary value, rather than being interchangeable. A more comprehensive understanding of functional status might be achieved by combining the SPPB assessment of standardized activities with the evaluation of inertial sensor measurements obtained during daily life activities.