Physical activity is important for glycemic control and disease management in people with diabetes mellitus (DM). Balance impairment is a barrier to physical activity and elevates fall risk in people with DM, and is particularly frequent in those with DM and peripheral neuropathy (DMPN). Additionally, adequate vestibular function is important for adequate balance. Unfortunately, DM can result in peripheral vestibular dysfunction and is also more likely to be present in people with DMPN. However, further characterization of vestibular function is needed, and it is unknown if anticipated vestibular dysfunction is related to imbalance in people with DMPN. Therefore, the purpose of this study is to evaluate vestibular function in Veterans with DMPN (Aim 1), and determine the degree to which vestibular function is related to balance (Aim 2). People with DMPN (n=25) and age, gender, and body mass index matched controls without DM (n=25) will participate in this case-control study. Otolith function will be measured with cervical (saccule pathway) and ocular (utricle pathway) vestibular evoked myogenic potential testing (VEMP). Inter-amplitude and latency will be the primary VEMP testing outcomes. Horizontal semicircular canal function will be measured with sinusoidal harmonic acceleration and step velocity rotational chair testing protocols. Vestibulo-ocular reflex (VOR) gain, phase, time constant, and a novel metric, GainTC, which combines data from both rotational chair protocols to give a single metric related to remaining vestibular function, will be the primary rotational chair testing outcomes. Dynamic balance will be assessed with valid and responsive clinical tests: the Timed Up and Go (TUG) and the Functional Gait Assessment (FGA). Secondary outcomes include measures of global health, self-efficacy, physical activity, and fall history. Between- group comparisons in vestibular outcomes will be made with mixed ANOVAs and/or t-tests (Aim 1). GainTC values will be regressed on balance measures (TUG and FGA separately) to determine if vestibular deficits correlate with imbalance in people with DMPN to a greater degree than controls (Aim 2). Covariates such as age, duration of DM, and cognition scores (Montreal Cognitive Assessment) will be considered. Evaluation of relationships between vestibular function and secondary outcomes will also be conducted to fully explore the potential ramifications of anticipated vestibular dysfunction. It is suspected that objectively measured vestibular function is worse and related to imbalance in those with DMPN in comparison control participants. If this is true, study findings will substantiate future work to prospectively evaluate the interplay of DM, vestibular dysfunction, balance, fall risk and physical activity, as well as substantiate the development of exercises to target detected vestibular deficits and evaluate the effect of these exercises on balance in people with DMPN.

Diabetes mellitus (DM) is a pandemic. However, the prevalence of DM in the Veteran population (25%) is more than 2.5 times greater than worldwide estimates. DM results in multi-system impairments which elevate medical care costs, dramatically reduce quality of life, and often results in premature death. Sensory system impairment is a rampant and catastrophic consequence of DM. The prevalence of vision impairment and peripheral neuropathy (reduced foot sensation) can exceed 70%, and are linked to imbalance and elevated fall risk. Accordingly, an estimated 1.5 million Veterans are up to 17 times more likely to fall than people of the same age, and falls themselves are associated with elevated morbidity, mortality, and medical cost. Since inner ear function, another important sensory system for balance, can be reduced in up to 85% of people with DM, it is important to examine inner ear function and its influence on balance in Veterans with DM; with the ultimate goal of designing new intervention strategies to improve balance, fall risk, quality of life, and medical care costs.