St George Rebecca J, Fitzpatrick Richard C, Rogers Mark W, Lord Stephen R
Prince of Wales Medical Research Institute, University of New South Wales, Sydney, Australia.
J Gerontol A Biol Sci Med Sci. 2007 May;62(5):537-42. doi: 10.1093/gerona/62.5.537.
Deterioration with age of physiological components of balance control increases fall risk. Avoiding a fall can also require higher level cognitive processing to select correct motor and stepping responses. Here we investigate how a competing cognitive task and an obstacle to stepping affect the initiation and execution phases of choice stepping reaction times in young and older people.
Three groups were studied: young persons (YOUNG: 23-40 years, n = 20), older persons with a low risk of falls (OLR: 75-86 years, n = 18), and older persons with a high risk of falls (OHR: 78-88 years, n = 22). Four conditions were examined: choice stepping, choice stepping + obstacle, choice stepping + working memory task, and choice stepping + working memory task + obstacle. Step response and transfer times were measured for each condition, in addition to hesitant stepping, contacts with the obstacle and errors made in the memory test.
Older participant groups had significantly longer response and transfer times than the young group had, and the OHR group had significantly longer response and transfer times than the OLR group had. There was a significant Group x Secondary task interaction for response time (F(2,215) = 12.6, p <.001). With the memory task, response time was minimally affected in the YOUNG (7% increase, p =.11) but was slowed significantly in the OLR fallers (42% increase, p <.001) and more so in the OHR fallers (48% increase, p <.001). The obstacle had a small but significant effect on response time (9.4%) and a larger effect on transfer time (43.3%), with no differences among the groups. Errors in stepping, performing the secondary task and contacting the obstacle increased with age and fall risk.
Compared with young people, older people, and more so those at risk of falling, have an impaired ability to initiate and execute quick, accurate voluntary steps, particularly in situations where attention is divided.
平衡控制的生理成分会随着年龄增长而退化，从而增加跌倒风险。避免跌倒还可能需要更高层次的认知处理，以选择正确的运动和步行动作反应。在此，我们研究一项竞争性认知任务和一个步行动作障碍如何影响年轻人和老年人选择步行动作反应时间的启动和执行阶段。
研究了三组人群：年轻人（YOUNG：23 - 40岁，n = 20）、低跌倒风险的老年人（OLR：75 - 86岁，n = 18）和高跌倒风险的老年人（OHR：78 - 88岁，n = 22）。研究了四种情况：选择步行动作、选择步行动作 + 障碍物、选择步行动作 + 工作记忆任务以及选择步行动作 + 工作记忆任务 + 障碍物。除了犹豫步行动作、与障碍物接触以及记忆测试中的错误外，还测量了每种情况下的步行动作反应时间和转移时间。
老年参与者组的反应时间和转移时间明显长于年轻组，并且OHR组的反应时间和转移时间明显长于OLR组。对于反应时间存在显著的组×次要任务交互作用（F(2,215) = 12.6，p <.001）。在进行记忆任务时，年轻人的反应时间受影响最小（增加7%，p =.11），但在OLR跌倒者中显著减慢（增加42%，p <.001），在OHR跌倒者中更是如此（增加48%，p <.001）。障碍物对反应时间有较小但显著的影响（9.4%），对转移时间有较大影响（43.3%），各年龄组之间无差异。步行动作错误、执行次要任务时的错误以及与障碍物接触的错误随年龄和跌倒风险增加。
与年轻人相比，老年人，尤其是有跌倒风险的老年人，启动和执行快速、准确的自主步行动作的能力受损，特别是在注意力分散的情况下。
