Study Of Different Illumination Effects On Stability Of Elderly People During Stair Descent

Objective : The number of diseases and the incidence of disability and mortality among the Chinese elderly, which bring a heavy burden to the country, have significantly increased as the aging population and the life extension trend continue to surge. While the elderly fall has been one of the most important public health problem been recognized. Previous research showed that, Falls are the leading cause of fractures, trauma-related hospital admissions, loss of independence, and death due to injury among older adults. The visual system of an individual significantly changes as he/she grows older. Therefore, may affect stair safety. According to literatures, there were few papers in biomechanical of domestic level to analysis the fall factors during stair descent, and studies on the effects of light on the elderly daily life still belongs to the blank. This study aims to determine indexes of the stability to find the effect on elderly during stair during stair descent under different illumination(3 lx, 75 lx, 300 lx), to provide some advice for the elderly in living, working, public place.Methods : Thirty healthy elderly who are aged between 65 years and 70 years were recruited for this study. Subjects with musculoskeletal or neurological impairments were excluded from the sample. The subjects were subsequently asked to complete five stair descent trials under illumination of 3 lx, 75 lx and 300 lx. Two force plates were used to collect plantar pressure data, eight Vicon cameras were placed around the stairs to record the movements of each subject at the same time. One-way repeated ANOVA with mixed design was used to compare the differences between the different illuminations. A Type 1 error rate of 0.05 will be used to indicate statistical significance.Results :1. Vertical ground reaction forces: With the illumination increased, the first peak pressure of vertical ground reaction force was decreased, under the 3 lx illumination, the first peak pressure of vertical ground reaction force was higher than others, but there were no difference between 75 lx and 300 lx, the second peak pressure of vertical ground reaction force was also decreased under three illumination, but change was not obvious.2. Antero-Posterior force: There were not regular change of the first peak pressure of antero-posterior force under different illumination. the first peak pressure of antero-posterior force got the minimum under the 300 lx illumination, the difference was statistically significant. compare with 75 lx. There were no statistically significant among 75 lx and 300 lx. the second peak pressure of antero-posterior force was increased with the illumination increased, but there were no statistically significant difference between them. 3. Medial-Lateral forces: the medial-lateral forces pressure showed a decreasing trend with the illumination decreased, the first and the second peak of the medial-lateral forces pressure under 300 lx illumination showed the statistically significant difference compare with the 3 lx. 4. COP displacement: The COP displacement showed an increasing trend with the illumination increased, the COP displacement didn’t have any statistically significant difference, when illumination change from 3 lx to 75 lx, there were statistically significant difference, when illumination got the 300 lx. 5. Head inclination angle: The maximum of head inclination angle got down, with the illumination increased, the change was statistically difference, the minimum of head inclination angle also changed down, but there were no difference of the variation range under three illuminations. 6. Trunk inclination angle: The trunk inclination angle increased with the illumination increased, the change was statistically difference, there were no significant among 3 lx and 75 lx, when illumination got the 300 lx, the minimum level decreased, the variation of trunk inclination angle turn down under the 300 lx compare with 3 lx, the average of trunk inclination angle begin to turn down under 75 lx. 7. Gait cycle: The gait cycle increased with the illumination increased during stair descent, the gait cycle increased significant under 3 lx illumination compare with 75 lx and 300 lx, but there were no significant difference, under 75 lx and 300 lx.Conclusion :1. The first peak pressure of vertical ground reaction force, medial-lateral forces pressurecurve increased with the illumination decreased during stair descent, it’s means the illumination changed would effect the stability of the elderly during stair descent. The head and trunk inclination angle would increase with the illumination decreased, it increased the risk of elderly during stair descent. 2. Many of indexes didn’t have any significant difference among 75 lx and 300 lx, it means 75 lx illumination could satisfied the elderly requirement in their daily life, but the 3 lx couldn’t satisfied the elderly during their daily life.