Dependency of Postural Control Factors on Sway in Individuals with/without Diabetic Peripheral Neuropathy

Diabetic peripheral neuropathy (DPN) is one of the leading causes of decreased sensation in the feet. This consequentially deteriorates the capability of postural control and increases the potential risk of slips or falls. Various studies have investigated the effect of DPN on postural control, incidents of slips or falls, and gait changes by measuring postural sway. The dependent measurements used in the analysis of the effect of DPN on postural instability include displacement of sway path, velocity or acceleration of sway, and virtual time to contact a boundary. These measurements characterize how quickly or slowly the body sway may reach an area for postural control and not regain stability after a perturbation. In the literature, many studies have concluded that individuals with DPN tend to sway more than those without DPN, and thus may be at higher risk of slips or falls. This inference has been based on comparisons of descriptive statistics for observed sway measure between the two groups. Additionally, most of these studies applied different postural control factors, perturbation types, apparatus of measurement, and dependent variables. As a result, there are inconsistent reports regarding the effect of DPN on instability. Several studies have discussed potential causes of the inconsistency. From the perspective of sensory information processes needed, these include variability of perturbed sensory perceptual systems and different types of postural control triggers such as local-control using postural muscles or central-control using sensory cueing. Postural control requires many different neuromusculoskeletal components working at various joints. However, all studies in the literature have used the simple outcome resulted by working those components together as a dependent variable without considering a possible dependency of those components on sway in individuals with/without DPN. To date, few studies have considered DPN as a dependent variable and measure of sway as an independent variable. The objective of this study was to propose an application of mediation analysis to measure an impact of sway on determination of DPN by considering sway measure as a mediator variable between postural control factors and DPN.