Time-of-day influences postural balance in older adults

摘要

Background: Postural 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. Methods: Center of pressure (CoP) excursion was measured (100. Hz) by force plate analysis in 34 older adults during 30. s of narrow quiet bilateral stance. Measurements were performed around 9. a.m., 12.30. p.m. and 4. p.m. on the same day. Postural balance was quantified by velocity-moment, confidence ellipse area, total sway area and total sway length. Results: An overall significant time-of-day (between 9a.m. and 4p.m.) effect was observed for velocity-moment (mm 2/s) 57±27-65±29 (p=0.001), confidence ellipse area (mm 2) 36±16-44±19 (p0.001), total sway area (mm 2) 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. Conclusions: This 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.