Time-of-day influences postural balance in older adults

Abstract

BackgroundPostural balance assessments are performed in both clinical and basic research settings on a daily basis. During a 24-h time span our physiology and physical performance undergo radical changes as we are influenced by the circadian rhythm. The time-of-day interaction on postural balance is unknown in older adults. The aim of this study was to investigate the time-of-day effect on postural balance in older adults. MethodsCenter of pressure (CoP) excursion was measured (100Hz) by force plate analysis in 34 older adults during 30s of narrow quiet bilateral stance. Measurements were performed around 9a.m., 12.30p.m. and 4p.m. on the same day. Postural balance was quantified by velocity-moment, confidence ellipse area, total sway area and total sway length. ResultsAn overall significant time-of-day (between 9a.m. and 4p.m.) effect was observed for velocity-moment (mm2/s) 57±27–65±29 (p=0.001), confidence ellipse area (mm2) 36±16–44±19 (p<0.001), total sway area (mm2) 548±263–627±285 (p=0.001) and total sway length (mm) 373±120–379±113 (p=0.037). The variation of postural balance was mostly pronounced from midday (12.30p.m.) toward the afternoon (4p.m.) in all sway parameters. Specifically between 12.30p.m. and 4p.m. confidence ellipse area increased by 18.5%, total sway area by 17.1%, velocity-moment by 15.8% and total sway length by 4.6%. No differences were observed between 9a.m. and 12.30p.m. in any of the sway parameters. ConclusionsThis study demonstrates that time-of-day influences postural balance in older adults. These findings have important scientific and clinical relevance, as they imply that time-of-day should be a controlled factor when assessing postural balance in older adults.