Effects of diabetes and aging on posture and acceleration thresholds during lateral translations

Research objectives. One source of falls in the elderly may be an inability to sufficiently adjust to transient postural perturbations or slips. Identifying useful predictors of fall potential, as well as factors that affect the ability of an individual to detect a movement of the standing support surface may provide insight into postural stability and methods to increase stability in elders. To do this, acceleration thresholds to short, precise, lateral platform translations and the resultant psychophysical responses of adults with early Type 2 diabetes to age-matched controls and young adults were measured. Methods. Using an innovative SLIP-FALLS platform, short (1, 2, 4, 8,and 16mm) lateral perturbations were presented to 21 individuals—9 young adults, 6 neurologically intact elder adults, and 6 elders with diabetes using a two-alternative forced choice (2AFC) protocol. All subjects underwent lower-limb nerve conduction velocity determination, air conduction velocity testing, Semmes-Weinstein monofilament thresholds, the Mini Mental Status Exam, and reaction time tests to touch, tone and high acceleration, 4mm super-threshold perturbations. Results. All three groups had significantly different thresholds at all small (\u3c4mm) movement lengths, with the diabetic neuropathy group having a markedly higher acceleration threshold (P \u3c 0.001); the healthy elderly, which, in turn, had markedly higher thresholds than young adults. Patients with neuropathy had significantly higher reaction times to platform movements and touches to the plantar sole, but not for auditory tones. Both elderly groups had a significantly higher reaction time to superthreshold platform movement than did young adults. Sensory tests revealed slower nerve conduction velocities, higher air conduction velocities, and lower cognitive ability in the diabetic group. Conclusions. A marked decrease in perception of very small moves due to aging and diabetic neuropathy could well have a detrimental effect on postural control mechanisms. The higher prevalence of falls in the elderly and elderly diabetics may be due to decreased perceptual ability, slower nerve conduction velocities, and slowing reaction times compounded by larger amounts of imparted energy needed for detection of a slipping event

The Effect of Dual-Task Testing on Balance and Gait Performance in Adults with Type 1 or Type 2 Diabetes Mellitus: A Systematic Review

BACKGROUND: Individuals with diabetes mellitus (DM) are susceptible to balance, gait and cognitive impairments. Importantly, diabetes affects executive function, a set of cognitive processes critical to everyday cortical function and mobility. Reduced executive function is a risk factor for falls in people with DM. Dual-task testing, the completion of two tasks at once, enables the examination of the cognitive-mobility relationship. A synthesis of the literature on the effects of dual- task testing on the balance and gait of individuals with DM has not been performed. OBJECTIVE: To systematically review the literature on the effect of dual-task testing on balance and gait in people with DM. METHODS: Databases EMBASE, CINAHL, MEDLINE, PsycINFO, Scopus and Web of Science were searched (inception-April 2020). INCLUSION CRITERIA: participants were adults with a diagnosis of DM, instrumented dual-task balance and/or gait was assessed, and articles were published in English. RESULTS: Ten articles met inclusion criteria- three examined dual-task balance and seven dual-task gait. In people with DM with or without peripheral neuropathy, dual-task resulted in larger sway velocities during standing tests. Individuals with DM and peripheral neuropathy had impaired dual-- task gait; specifically, and more consistently, reduced pace and rhythm compared to controls or people with DM without peripheral neuropathy. CONCLUSION: The findings support a compromise in the cognitive-mobility relationship of people with DM, and especially in those with peripheral neuropathy. Future research should continue to examine the cognitive-mobility relationship in order to understand the increased prevalence of falls in this population

THE IMPACT OF TYPE 2 DIABETES MELLITUS ON SYMPTOM PRESENTATION AND RESPONSE TO TREATMENT IN INDIVIDUALS WITH BENIGN PAROXYSMAL POSITIONAL VERTIGO

Diabetic complications, such as retinopathy and peripheral neuropathy, have been studied extensively and are known to impair balance and increase fall risk. However, the effect of diabetes on the vestibular system is not clear. The vestibular system plays an important role in maintaining static and dynamic balance, by providing spatially orienting information. Hence, damage to the vestibular system could potentially increase imbalance and risk of falls. The primary purpose of this work was to examine the effect of diabetes on the peripheral vestibular system, and the resulting impact on symptoms, mobility and balance. In Chapter 1, we have presented a review of the literature on the pathophysiology of diabetes-related complications and their influence on balance and falls, with specific attention to emerging evidence of vestibular dysfunction due to diabetes. We have provided a perspective on the impact of vestibular complications, the need for a thorough vestibular evaluation, and recommendations for vestibular rehabilitation techniques, for people with diabetes. Chapter 2 describes the results of our pilot investigation, where we focused our attention to identify if a specific vestibular disorder may be present in higher frequency in individuals with type 2 diabetes (T2D). In this retrospective analysis of electronic health records, we examined data from 3933 individuals with nine common vestibular disorders. Of the nine vestibular disorders commonly seen in the clinic setting, the prevalence of one condition, benign paroxysmal positional vertigo (BPPV), was significantly higher in individuals with diabetes. Factors that were predictive of BPPV included age, female sex, race and presence of hypertension. Hypertension was the mediating factor that increased the prevalence of BPPV in people with diabetes. Building upon this study, we identified benign paroxysmal positional vertigo as our clinical condition of interest. We developed our specific aims to examine the direct effect of diabetes on the vestibular system using evoked potential studies, as well as the indirect effects on symptoms, mobility and balance, in people diagnosed with BPPV. Chapter 2 showed that the prevalence of BPPV was higher in people with diabetes. BPPV results when otoconia fragments dislodge from the otolith organs of the inner ear, and cause symptoms of vertigo. The effect of diabetes on the saccule and utricle of the vestibular system is not clear, and the combined effect of BPPV and diabetes on the otolith organs, has not been studied. In Chapter 3, our main purpose was to analyze otolith function using vestibular evoked myogenic potential (VEMP) tests in people with diabetes and concurrent BPPV, and to examine the relationships between VEMP variables and diabetes-related variables. For this study, we recruited people who were 40 to 65 years of age, into four groups; 20 controls, 19 individuals with T2D without vestibular dysfunction, 18 individuals with BPPV, and 14 individuals with BPPV and diabetes (BPPV+DM). Results of this study showed that the frequency of delayed and absent saccule responses was significantly higher in people with T2D, BPPV, and BPPV+DM compared to healthy controls. Delayed latency of the saccule responses were associated with higher HbA1c levels. Utricle function did not appear to be as affected by diabetes as the saccule. Although, BPPV and diabetes independently affected utricle and saccule function, they did not appear to have a distinct cumulative effect. The true impact of a disease is the resulting impairment to the affected individual, and the effect on daily activities. Chapter 3 revealed otolith dysfunction in people with T2D, BPPV and BPPV+DM. Because otolith dysfunction is associated with balance deficits and increased postural sway, in chapter 4, we examined postural sway. In this study, we compared the postural sway of people with BPPV and BPPV+DM who were between 40 to 65 years of age. We expanded the scope of our data collection to include healthy controls and people with diabetes (without vestibular dysfunction) for comparison with BPPV and BPPV+DM, as normative values for postural sway using the specific accelerometry procedures and conditions we tested is not available. Not all participants from chapter 3 were included in this study due to equipment malfunction and other issues. Ultimately, we recruited 14 controls, 14 individuals with T2D only, 13 individuals with BPPV only and 11 individuals with BPPV+DM for this study. We measured postural sway using an accelerometer positioned over the L3 spine level, in five conditions that progressively challenged the vestibular system. Results of this study showed that participants with BPPV+DM had higher postural sway measures compared to controls and the T2D group, which was particularly evident in the anteroposterior direction. Standing on foam with eyes closed and tandem stance conditions were the most challenging conditions for people with BPPV+DM. Besides causing symptoms of vertigo, BPPV is known to affect balance and functional mobility. However, BPPV can be effectively treated with canalith repositioning maneuvers. The effect of diabetes on symptom severity, mobility and balance and the response to treatment maneuvers in people with BPPV is unknown. In Chapter 5, we examined handicap due to dizziness, mobility, and balance in people between 40 to 80 years of age, in two groups, 34 individuals with BPPV and 16 with BPPV+DM, before and after treatment with the canalith repositioning maneuver. To identify these deficits, all individuals completed the Dizziness Handicap Inventory (DHI), the Functional Gait Assessment (FGA) and postural sway tests, in quiet stance with altered visual and proprioceptive feedback. We found no differences between people with BPPV and those with BPPV+DM, on the DHI or FGA scores, at baseline and after symptom resolution. Significant differences were seen in postural sway between the groups at baseline. However, after resolution of dizziness, there were no differences between the two groups on any postural sway measures. The number of treatment maneuvers required for resolution of vertigo did not differ between groups. People with BPPV with or without diabetes, made significant improvements in symptoms, mobility, and balance after their vertigo had resolved. In summary, this body of work makes significant contributions to the existing literature examining the vestibular complications due to diabetes. Our central hypothesis was that diabetes would affect the otolith organs of the vestibular system, thereby increasing symptom severity, functional deficits, and balance sway, compared to people without T2D. Our findings were that although the prevalence of BPPV was higher in people with diabetes, hypertension was the complete mediator in the relationship between BPPV and T2D. People with BPPV+DM did not have increased otolith dysfunction, compared to those with BPPV or T2D only; however, postural sway was higher in people with BPPV+DM. The higher postural sway in people with BPPV+DM may be due to the presence of diabetic peripheral neuropathy; however, we did not analyze the effect of neuropathy on mobility and balance. There was no difference in the severity of symptoms and mobility deficits of people with BPPV + DM compared to people with BPPV only. Of importance, we found that people with BPPV+DM do respond well to treatment maneuvers with significant improvements in symptoms, mobility, and balance, and do not require additional treatment maneuvers, when compared to people with BPPV. Although our results did not fully support our central hypothesis, it provides valuable information. This body of work emphasizes the need for early diagnosis and prompt treatment of vestibular dysfunction in individuals with BPPV+DM. Future studies examining falls in people with BPPV+DM considering the influence of other diabetic complications, will help elucidate the relationship between diabetic complications and fall risk

Differences between risk factors for falling in homebound diabetics and non-diabetics

The purpose of this study was to identify the differences in fall risk factors between diabetic and non-diabetic homebound adults in a population identified at high risk for falls. The sample compared 210 non-diabetic homebound adults to 74 diabetic homebound adults. Five research hypotheses supported this study. It was hypothesized that, 1) incidence and severity of somatosensory changes in the feet of diabetics surpassed that of non-diabetics; 2) incidence of lower leg and foot pain in diabetics surpassed that of non-diabetics; 3) deficits in sensory integration would be greater in diabetics than non-diabetics; 4) balance deficits were more evident in diabetics and non-diabetics; and 5) fear of falling was more prominent in diabetics than in non-diabetics. An one-way ANOVA showed a significant difference in sensation between groups, with diabetics reporting less sensation than non-diabetics in all age categories. A small effect size limited external validity. No other significant differences emerged for the other fall risk factors. Gender and age category failed to influence differences between diagnostic groups

Plantar Pressure, Cutaneous Sensation and Stochastic Resonance: An Examination of Factors Influencing the Control and Perception of Posture

The goal of this dissertation was to understand how people control posture in the context of sensory loss. To do so we explored three potential influences on the detection of external information and how they relate to the control of posture and perception of body orientation: 1) does changing posture alter the forces under the foot, and do these changes impact the ability to detect external vibrations? 2) Does decreasing the temperature of the foot influence the ability to detect external vibrations, the perception of body orientation, and the control of posture? And 3) does stochastic resonance (SR) improve the perception of body orientation and the control of posture when the sensory thresholds are elevated to clinical levels through cooling of the feet? The results of the experiments indicate that: 1) increasing the pressure under the feet, elicited by changes in posture, elevates the cutaneous sensory threshold, and that the forefoot appears to be more sensitive than the rearfoot to changes in weighting; 2) decreasing the temperature of the skin elevates cutaneous sensory thresholds, and impacts postural control by constraining the fluctuations of the medial-lateral center of pressure; and 3) applying SR to the soles of the feet improves the ability to perceive body position, with greater amounts of skin cooling resulting in greater improvements in postural performance due to SR. This dissertation demonstrates that decreasing plantar loading lowers cutaneous sensory thresholds, indicating that the changes in postural fluctuations frequently observed among those with clinical sensory loss may serve as a mechanism that allows for improved access to external information if they prove to reduce the pressure under sensory impaired portions of the feet. Additionally, we add to the growing body of literature identifying SR as a means to improve postural performance when cutaneous sensory function is impaired. From a clinical perspective, the results presented here indicate that aids designed to apply SR to the soles of the feet, as a means to improve posture and gait, should modulate their signal such that they apply a signal amplitude appropriate to the amount of loading the foot experiences

Understanding standing

Research objectives. Psychophysical acceleration threshold is a tool for detecting deficits in dynamic postural control. Our lab has shown differences in the acceleration threshold among young adults, elderly adults, and elderly adults with diabetes. Electromyography, Semmes-Weinstein monofilaments, and hearing tests investigate the underlying physiological mechanisms for the detriments in postural control. Due to peri-sway perturbations, the motion of a person\u27s sway affects the signal to noise ratio for perturbed stance. Since increases in sway range accompany postural instabilities, sway entrainment will allow us to investigate changes in acceleration threshold at different points in sway. The center of pressure, observed for entrainment, only changes due to rotations about joints, specifically the ankle. The current method to model rotation about the ankle is a single orthogonal joint, and therefore inaccurate. Methods. The SLIP-FALLS-STEPm Platform has lead to the ability to accurately measure and observe interactions in the range of postural sway. The combination of the platform with other testing modalities such as camera tracking systems, force mats, and accelerometers will allow for a comprehensive testing scheme. The new scheme can be combined with the induced sway produced by a sub-threshold sinusoidal entrainment process. The nonorthogonal modelling is programmed in Matlab®. Results. For constant displacements, anterior accelerations thresholds via two-alternate forced choice (2AFC) showed differences in postural stability in mature, diabetic individuals with peripheral neuropathy (DPN) and those who are neurally intact (DNI) compared to healthy mature adults (HMA), which corresponded with previous results of lateral perturbations. Both DNI and DPN had significantly higher thresholds for acceleration via 2AFC than HMA at 1 and 4 mm displacements (p \u3c 0.01 and p Conclusion. The anterior acceleration thresholds show that peripheral neuropathy is not the sole cause for postural instability with diabetes. The ability to control the motion of sway will allow us to describe acceleration threshold throughout the range of sway. With a realistic ankle model, we will be able to better simulate postural dynamics

Is postural stability compromised in women with urinary incontinence?

Women with urinary incontinence (UI) have an increased risk of falling compared to their age-matched peers without UI. Due to the anatomical location of the pelvic floor muscles, they are suspected to contribute to the maintenance of postural stability during everyday activities. Women with UI have weak or dysfunctional pelvic floor muscles. The purpose of this study was to determine if women with UI, specifically stress, urge, and mixed UI, have deficits in postural stability during static tasks and in response to postural perturbations of the support surface.;Methods: To measure static stability, 14 women (7 with UI: age 51.75 +/- 17.85 yrs, height 164.94 +/- 5.40 cm, mass 79.38 +/- 19.45 kg, number of falls 0.714 +/- 1.89, number of pregnancies 1.29 +/- 0.76 and 7 controls: age 51.71 +/- 18.20 yrs, height 163.29 +/- 6.64 cm, mass 60.47 +/- 8.32 kg, number of falls 0.00 +/- 0.00, number of pregnancies 1.29 +/- 0.76) stood quietly on a force plate with their eyes open and then eyes closed. These same women had their dynamic stability measured by undergoing perturbations of the force plate in both the toes up and toes down directions. A two-factor MANOVA (group x eyes open/closed) was performed on the following static variables: anterioposterior sway, mediolateral sway, length of the path of the center of pressure (COP), sway velocity in quiet stance, and elliptical sway area. Another two-factor MANOVA (group x toes up/down) was performed on the following dynamic variables: initial sway, total sway, and sway velocity. The alpha value for all statistical analyses was 0.05.;Results: No differences in the static stability variables of anterioposterior sway, mediolateral sway, length of the path of COP, sway velocity in quiet stance, and elliptical sway area were seen between groups. Results of the dynamic stability assessment revealed that the UI group had significantly less initial sway (p=0.006), total sway (p=0.008), and sway velocity (p=0.001) compared to the controls.;Conclusion: Women with UI have less COP movement in response to postural perturbations compared to an age and parity-matched control group. Further studies are needed to determine muscular compensations and co-contractions that may be contributing to this response

Postural Stability in Unilateral Transtibial Amputees Using Two Suspension Systems: SmartpuckTM vs Lock and Pin

The number of individuals with lower limb amputation is growing. Individuals with transtibial amputation (TTA) face an increased risk of falling. Center of pressure (COP) is measured during quiet stance to assess postural stability and fall risk. The purpose of the present study was to examine postural stability of individuals with TTA using two suspension systems: SmartPuck™ (PUCK) and lock and pin (PIN). Four participants with TTA (71.34 ± 41.52 kg, 1.39 ± 0.08 m; 49.2 ± 27.79 years, K3 - K4) performed 30 seconds of quiet standing for four different conditions with each suspension system: (a) rigid surface eyes open (RSEO), (b) rigid surface eyes closed (RSEC), (c) compliant surface eyes open (CSEO), and (d) compliant surface eyes closed (CSEC). Center of pressure and vertical ground reaction forces (GRF) (1000 Hz) were collected using two force plates (AMTI, Watertown, MA). Throughout the four conditions, significant interlimb differences were observed in mean resultant velocity, mean AP velocity, 95% CE area, sway area, and %BWT, demonstrating greater reliance of the intact limb. As conditions increased in difficulty, more interlimb differences in measures of postural stability were present, demonstrating increased reliance of the intact limb when stability is challenged. No significant differences were found in either limb between PUCK and PIN suspensions. However, trends demonstrating increased control of postural stability were observed with PUCK suspension in the RSEO, RSEC, and CSEO conditions. Conversely, trends in measures of postural stability in the CSEC condition suggest increased stability with PIN suspension. As vision was removed and the standing surface was manipulated, participants demonstrated loss of control of postural stability, or instability. Confidence in the significance of the results is low due to the small number of individuals who participated in the study. Considering the direct relationship between instability and increased fall risk, it is important to identify whether different prosthesis designs can aid in postural steadiness. Further research with more participants is needed to understand the differences in postural stability caused by suspension systems