BACKGROUND In a secondary analysis of data taken from a publicly available database, we examined cognitive performance, postural sway, and relations between them for four groups: younger and older individuals with versus without a recent history of falls. Our objective was to compare linear versus nonlinear measures of postural activity as post-hoc predictors of cognitive performance and falling. METHODS We evaluated standing body sway in 147 participants (18 to 85 years-old) over 60 seconds, separately with eyes-open and with eyes-closed. We evaluated cognitive performance using portions of the Trail Making Test. We evaluated postural activity in terms of standard deviation, velocity, and amplitude of the CoP. Separately, we used detrended fluctuation analysis (DFA) to examine the complexity of CoP displacements. Using analysis of variance, we conducted separate analyses of cognitive performance and postural activity comparing Younger and Older Adults and Non-fallers and Fallers, taking into account Vision (eyes-closed vs. open) and the direction of postural movements (AP vs. ML) while also controlling for participants' characteristics. We used moderation analyses to evaluate whether relationships between Trail Making Test scores and the linear and nonlinear outcomes were moderated by Age group or Fall status. RESULTS For postural activity, only DFA differed between Non-fallers and Fallers. Older adults exhibited increased complexity associated with better processing speed function, while fallers show an opposite association, relying on processing speed to increase postural rigidity instead of facilitating adaptive control of balance. CONCLUSIONS We conclude that DFA can provide information regarding postural activity and cognitive performance that cannot be obtained from more traditional, linear measures of postural activity, and that DFA may be a valuable tool for assessing fall risk.

中文翻译：

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安静站立时压力中心位置的复杂性及其与认知、衰老和跌倒的关系

背景 在对从公开数据库中获取的数据进行二次分析时，我们检查了四组的认知表现、姿势摇摆以及它们之间的关系：最近有跌倒史的年轻人和老年人。我们的目标是比较姿势活动的线性与非线性测量作为认知表现和跌倒的事后预测因素。方法 我们对 147 名参与者（18 至 85 岁）在 60 秒内分别在睁眼和闭眼时的站立身体摇摆进行了评估。我们使用越野测试的一部分来评估认知表现。我们根据 CoP 的标准差、速度和幅度来评估姿势活动。另外，我们使用去趋势波动分析 (DFA) 来检查 CoP 位移的复杂性。使用方差分析，我们对年轻人和老年人以及非跌倒者和跌倒者的认知表现和姿势活动进行了单独分析，同时考虑了视力（闭眼与睁开）和姿势运动方向（AP 与 ML） ），同时还控制参与者的特征。我们使用调节分析来评估越野测试分数与线性和非线性结果之间的关系是否受到年龄组或跌倒状态的调节。结果 对于姿势活动，非跌倒者和跌倒者之间只有 DFA 不同。老年人表现出与更好的处理速度功能相关的复杂性增加，而跌倒者则表现出相反的关联，依靠处理速度来增加姿势刚度，而不是促进平衡的自适应控制。结论 我们的结论是，DFA 可以提供有关姿势活动和认知表现的信息，而这些信息无法从更传统的、线性的姿势活动测量中获得，并且 DFA 可能是评估跌倒风险的有价值的工具。