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Anna Rossiter, Elizabeth Brierley, Rebecca Lawton, Richard Wilkie, Mark Mon-Williams; Preventing falls in older adults: understanding postural instability under increasing visual-motor demands. Journal of Vision 2011;11(11):948. doi: 10.1167/11.11.948.
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Visual information plays an important role in maintaining posture. The role of vision changes over the lifespan with children relying more on haptic information as they mature (Wann et al., 1998). The role of vision in the maintenance of posture is not well understood in older populations but it is possible that neuromuscular degeneration increases the reliance upon vision. Our poor understanding is particularly worrying because falls have been reported as the primary cause of premature death in older persons (Sattin, 1992). Standing balance is a reasonable predictor of increased risk of falling (Jarnlo, 2003, Winter et al., 1990). Nonetheless, many falls occur when someone is engaged in a visuomotor task (e.g. putting a key in a lock) rather than simply standing upright. A high-profile study has also suggested that contemplating the past or the future can influence postural stability (Macrae et al., 2010). We explored these factors whilst measuring postural stability in young (16–26 years) and older (70–87 years) adults using a novel kinematic measuring device. First, we measured standing posture whilst participants tracked a moving target with a handheld stylus presented on a touch-screen laptop. The target moved at three speeds with stylus position recorded at 120 Hz to provide accurate performance metrics. Second, we measured posture when participants reflected on future or past events. The results for tracking showed that error increased with higher target speeds and this led to greater postural sway. The speed manipulation interacted with age so the high speed target had a particularly large impact on postural stability within the older population. In contrast, the manipulation of past versus future contemplation had no effect on posture. These findings suggest that a full evaluation of postural stability should measure the impact of visuomotor tasks when establishing the risk of falls in an older population.
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