A new affordance perception test to explain falls occurrence: Preliminary results of stepping-forward task.

Abstract

Background Falls cause injury, dependence, and death. Identify the subjects that are potential fallers is essential for a successful prevention. Re- searchers developed several models and tests in order to diagnose individual’s risk of falling [1, 2]. Risk factors such as environmental hazards, strength, balance or dual tasks are commonly tested. How- ever, their discriminative power is limited, indicating a gap which these tests do not address. The assessment on the perception of affordances for individual’s ability to perceive the critical boundary action [3, 4], may fill this gap. Objective To analyse the appropriateness of a new stepping-forward test to ex- plain fall occurrence in community-dwelling adults, that assess per- ception and action boundary.Methods Participants were 266 women and 81 men aged 73.0 ± 6.4 years. They were assessed for fall occurrence (yes vs. no), and for stepping-forward and perception boundaries. Participants judged their maximum stepping-forward distance prior to the performance of the estimated task. Absolute Error (AE) [|estimated – real|] (cm) and Absolute Percent Error (APE) (%) were computed, and the Error Tendency (ET) was classified (underestimation vs. overestimation) [5, 6]. Results Univariate binary regression analysis showed that all the described vari- ables explain significantly fall occurrence (p < 0.05). Data showed that, for each additional cm estimated in the stepping-forward test, the likeli- hood of falling decreased on 2.9%, OR: 0.971 (95%CI: 0.957-0.986), and for each additional cm performed in the test, this likelihood decreased on 4.0%, OR: 0.960 (95%CI: 0.945-0.975). Furthermore, data showed that for each additional cm computed as AE, the likelihood of falling de- creased on 3.6%, OR: 0.964 (95%CI: 0.933-0.996), and for each additional 1% computed as APE this likelihood decreased on 0.9%, OR: 0.991 (95%CI: 0.969-1.013). Finally, data showed that subjects reporting an ET of underestimation were less 47.7% likely for falling, OR: 0.523 (95%CI: 0.315-0.867), than subjects showing an ET of overestimation. Conclusions The new stepping-forward affordance perception test evidenced to be useful to determine the risk of fall occurrence. A higher estimation of maximum distance achieved or a higher real performance on the test were associated with a lower risk of falling. Further, a higher AE and an underestimation tendency showed to be associated with a decreased risk of falling. This suggests that is the marge of security provided by the higher performance ability, in contrast with a lower perception of affordance, which is protective and avoids falls.