Association Between Anthropometric Factors and Falls in Community‐Dwelling Older Adults During a Simulated Slip While Walking

This is the authors' abstract. We don't add key points for this paper.

To the Editor: Slip-related falls are a major public health problem facing older adults worldwide. Approximately 25% to 39% of community-dwelling people aged 65 and older experience at least one fall per year, and approximately half of them may have two or more falls.1-3 The primary purpose of this study was to determine whether and to what extent anthropometric factors such as body mass, height, and foot size could predispose older adults to falls after a sudden and unrehearsed slip induced in walking. Community-dwelling older adults (N = 187, 129 female; aged 72 ± 5; height 166 ± 9 cm; mass 76 ± 14 kg) participated in the gait-slip experiment. All subjects experienced an unannounced slip while walking on a suddenly unlocked low-friction section of a 7-m walkway under the protection of safety harness. Fall and recovery were the two outcomes of the slip trial.4 Characteristics of the outcome groups were compared using independent t-tests for continuous variables and chi-square tests for categorical variables. For body height and foot size, a distribution analysis was performed to determine the cutoff point for classifying older adults into high risk and low risk of falls groups. Univariate and multivariate logistic regression analyses were used to examine the risk factors for falls. Variables that demonstrated P < .15 in the univariate analysis were included in the subsequent multivariate regression model. Details of the experimental design, data collection, and protocol can be found elsewhere.4, 5 Ninety-eight participants (52.4%) fell during the trial, while 89 recovered from the slip. Subjects in the fall group were more likely to be female (79% vs 58%, P = .006), obese (39% vs 20%, P = .008), and on average, shorter (163.9 vs 168.8 cm, P < .001) and to have smaller feet (27.75 vs 28.85 cm, P < .001). Body height, foot size, weight, and sex were all significant predictors of falls. Women were approximately 2.6 times as likely to fall as men, and obese subjects were approximately 2.5 times as likely as those who were not obese. In the distribution analysis for height and foot size, subjects who were 165 cm tall or shorter and those with a foot size of 28.5 cm or less were at significantly greater risk of falls. Overall, the fall risk was approximately 2.9 times as great in subjects whose height were 165 cm or shorter and 2.8 times as great in subjects with a foot size of 28.5 cm or less (Table 1) than in their counterparts. In the multivariate analysis, obesity (odds ratio (OR) = 2.38, 95% confidence interval (CI) = 1.17–4.84, P = .02), female sex (OR = 3.32, 95% CI 1.37–8.01, P = .008), and being shorter (OR = 11.1, 95% CI = 2.04–60.7, P = .005) remained significant risk factors for falls. There was also a significant interaction between sex and height (P = .02). Older adults with a body mass index (BMI) of 30.0 kg/m2 or greater were 2.5 times as likely to fall as those with a BMI less than 30.0 kg/m2 (P < 0.01). Body mass itself did not increase a person's risk of falls, but shorter stature did(Table 1). This contradicts the static stability concept in which shorter stature, which is associated with a lower center of mass, will be more stable than taller stature. It was also found that body height and foot size were correlated (coefficient of determination = 0.49, P < .001). Individuals who fell had smaller feet than those who recovered; model simulation work has demonstrated that foot size is an important factor in the control of dynamic stability,6 and the finding of this study supports the theoretical prediction that a longer foot with a larger margin of stability could lower the risk of falling. The results revealed that women and individuals who were shorter (≤ 165 cm), obese (BMI > 30.0 kg/m2), had smaller feet (≤ 28.5 cm) were at significantly greater risk of falling. Although women were more prone to falling, there was also significant interaction between sex and height. Older men who were 165 cm or shorter were more likely to fall than older women of the same height. Although it is unclear whether height or foot size is the dominant factor, the taller males bear less risk of falls likely due to their longer foot size in comparison with the taller females. The fact that the relationship between height and foot size is more sensitive and stronger in men than in women could explain this. Such findings could provide guidance in developing intervention strategies to reduce falls in older adults. This work was supported by National Institutes of Health Grants 2R01-AG16727 and R01-AG029616 (YCP). Conflict of Interest: The editor in chief has reviewed the conflict of interest checklist provided by the authors and has determined that the authors have no financial or any other kind of personal conflicts with this paper. Author Contributions: Study concept and design: Zhang, Yang, Pai. Acquisition of subjects and data: Zhang, Yang. Analysis and interpretation of data: Zhang, Yang, Wang, Pai. Preparation of manuscript: Zhang, Yang, Wang, Pai. Sponsor's Role: The sponsor had no direct role in the design, methods, data collection or preparation of the paper.