Psychometric properties of instrumented postural sway measures recorded in community settings in independent living older adults

Background In the last few decades, research related to balance in older adults has been conducted in lab-based settings. The lack of portability and high cost that is associated with the current gold standard methods to quantify body balance limits their application to community settings such as independent living facilities. The purpose of the study was to examine the relative and absolute reliability and the convergent validity of static standing balance performance using an accelerometer device. Methods A total of 131 participants (85% female, mean age 80 +/- 8 years) were included for the validity aim, and a subsample of 38 participants were enrolled in the reliability testing (89% female, mean age 76 +/- 7 years). The root-mean-square (RMS) and normalized path length (NPL) for sway in antero-posterior (AP) and medio-lateral (ML) directions were calculated for different standing balance conditions. Test-retest reliability was assessed over two testing visits occurring 1 week apart using the intraclass correlation coefficient (ICC) for relative reliability, and the minimal detectable change (MDC) was calculated for the absolute reliability. Spearman's rank correlation coefficient was used to test convergent validity at baseline between balance measurements and related mobility measures. Results Reliability of balance performance using accelerometers was good to excellent with ICC values ranging from 0.41 to 0.83 for RMS sway and from 0.49 to 0.82 for NPL sway. However, the ICC during semi-tandem stance in A-P direction was 0.35, indicating poor reliability. The MDC of the sway measurements ranged from 2.4 to 9.4 for the RMS and 5.2 to 13.8 for the NPL. Balance measurements were correlated with mobility measurements. Conclusions Using a portable accelerometer to quantify static standing postural control provides reliable measurements in community settings.