Use of time-to-boundary to assess postural instability and predict functional mobility in people with diabetes mellitus and peripheral neuropathy

Background People with diabetes mellitus and peripheral neuropathy (DMPN) often have balance and mobility deficits. Time-to-boundary (TTB) is a parameter of postural control that combines position and velocity center of pressure data. While not previously investigated, assessment of TTB may provide new insight regarding postural control in people with DMPN. Research question Is TTB reduced and related to a measure of mobility in people with DMPN? Methods Thirteen people with DMPN without fall history and 13 healthy matched controls participated in this case-control study. Participants stood in double-limb stance on a force plate. The anterior-posterior and medial-lateral center of pressure position and velocity relative to the boundaries of the base of support were used to calculate TTB (s). Lower values indicate less postural control. Time-to-failure during single-limb stance was a secondary measure of postural control. Time to complete the Timed Up and Go (TUG) was our measure of mobility. Longer TUG times correspond to decreased mobility, strength, and balance. Independent t-tests or Mann-Whitney U tests were conducted to assess group differences. Bivariate correlations between task outcomes were conducted. Results Anterior-posterior TTB and single-limb stance times were shorter in people with DMPN (p ≤ 0.04). TUG times were longer in the DMPN group (p = 0.04). In the DMPN group, inverse relationships were observed between TTB and TUG (anterior-posterior R2 = .34; medial-lateral R2 = .49; both p = 0.01), but not between single-limb stance times and TTB or TUG. Significance TTB was a sensitive measure of postural control in people with DMPN. The detected relationship between TTB and TUG newly establishes TTB as a clinically meaningful indicator of balance and function. Study findings may serve to further guide balance screening and rehabilitation efforts in people with DMPN.