Mobility Disability In Older Adults Research Articles

ESTIMATING THE EFFECTS OF A POTENTIAL VACCINE FOR CYTOMEGALOVIRUS ON DISABILITIES AMONG OLDER ADULTS IN THE US

Abstract Cytomegalovirus (CMV) infection has been identified as contributing to the development several aging-related diseases, such as disabilities. However, the development of CMV vaccines has been slow, particularly of those targeting older individuals. With few studies that have investigated the potential effects of a CMV vaccine on disabilities among older adults, we aim to study such effects on mobility disabilities by tasks. We use longitudinal data from the Health and Retirement Study (HRS) from 2016 to 2020 to quantify what proportion of disabilities could be prevented in the United States with a viable CMV vaccine. The analytic sample includes N=5,855 individuals aged 65 or above. Under the assumption that a hypothetical vaccine would shift CMV levels from seropositive to seronegative, we construct a binary indicator based on the continuous IgG antibody measure of serum CMV. Using a novel logistic regression-based approach that allows adjustment for continuous age, we estimate attributable fractions (AF) to seropositive CMV levels for five dichotomous outcomes about difficulty with activities of daily living (ADLs), including walking across a room, dressing, bathing, eating, getting in and out of bed, and using the toilet, and stratify the analyses by sex and race/ethnicity. The findings will implicate the potential impact of a vaccine for CMV on mobility disability in older adults, laying the groundwork for future studies to examine the impact of vaccines on disabilities at different time points with varying efficacy levels among the elderly.

COGNITIVE RESERVE AND RISK OF MOBILITY DISABILITY IN OLDER ADULTS

Abstract Background Cognitive Reserve (CR) protects against cognitive decline and dementia but its relation to mobility disability has not been established. To address this important gap in the literature, we conducted a longitudinal investigation to test the hypothesis that higher baseline CR was associated with a lower risk of developing mobility disability in older adults. Methods Participants were dementia-free older adults who received a brain magnetic resonance imaging and had gait speed assessments during follow-up. Using the residuals approach, CR was derived from the modified-Mini-Mental Status Examination (3MS) total score by removing variance accounted for by measures of structural brain integrity, education and race. Mobility disability was defined using a validated cutoff score in gait speed of 0.8 m/s. Logistic regression models using General Estimating Equations (GEE) were utilized to examine longitudinal associations between baseline CR and the risk of developing of mobility disability across repeated assessments. Results Of the participants (n=237; mean age=82ys; %female=56%) who were free of mobility disability at baseline, 103 developed mobility disability during follow-up (mean=3.1ys). Higher CR at baseline was associated with lower risk of developing incident mobility/disability [odds ratio (OR)=.819, 0.67 to 0.98, p=.038 (unadjusted); OR=.815, 0.67 to 0.99, p=.04 (adjusted for socio-demographic variables and depression); OR=.819, 0.68 to 0.88, p=.035 (adjusted for illness history); OR=.824, 0.68 to 0.99, p=.045 (adjusted for white matter hyperintensities); OR= .795, 0.65 to 0.95, p=.016 (adjusted falls history)]. Conclusion We provided first evidence that higher CR was associated with lower risk of developing mobilitydisability in older adults.

ASSOCIATION OF LIVER STIFFNESS BY TRANSIENT ELASTOGRAPHY WITH MOBILITY DIFFICULTY IN OLDER ADULTS WITH NO CIRRHOSIS

Abstract Growing experience with non-invasive ultrasound transient elastography (TE) offers now a major opportunity to improve understanding about the functional impact of non-advanced, asymptomatic liver dysfunction. We assessed the relationship of liver stiffness measurement (LSM) and controlled attenuation parameter (CAP) obtained by TE, surrogates for liver fibrosis and steatosis, respectively, with mobility difficulty, an early stage of the disablement process. Cross-sectional study utilizing National Health and Nutrition Examination Survey 2017-2018 data. Analytic sample (n=1,203) included participants aged 60 years and older without known cirrhosis with available LSM and CAP. Logistic regression assessed the odds of mobility difficulty (walking ¼ mile or climbing stairs) according to LSM and/or CAP, with adjustment for demographics, diseases, metabolic syndrome, body mass index, aminotransferases, gamma-glutamyl transferases, albumin, and platelets. LSM and CAP were linearly, positively associated with the probability of mobility difficulty. In the fully adjusted model, LSM, though not CAP, remained strongly associated with mobility difficulty. Those with LSM in the top (>7 kilopascals [kPa]) and intermediate quintiles (4-7 KPa) had higher odds of mobility difficulty; i.e., odds ratio (OR): 1.81; 95% confidence interval (CI): 1.15-2.86; p=0.01) and OR:1.45; 95%CI: 1.01-2.08; p=.046), respectively. LSM was independently associated with early mobility disability in older adults without known cirrhosis. A direct effect through sarcopenia promotion pathways might be speculated. Whether TE screening could be useful to identify adults with non-advanced liver fibrosis who might benefit from preventive interventions – e.g., diet and exercise for non-alcoholic fatty liver disease patients vis-à-vis mobility disability prevention remains to be tested.

Cerebral Small Vessel Disease and Gait Speed in Older Adults without Dementia

AbstractBackgroundDisturbances in gait have been found to be predictors of dementia and mobility disability in older adults. The relationship between cerebral small vessel disease (CSVD) and gait speed during simple (normal pace walking; NPW) and complex walking (walking‐while talking; WWT) conditions are not well understood. The current study examined the relationship between CSVD (as assessed as white matter hyperintensities and lacunes), NPW and WWT in older adults without dementia.MethodsNPW and WWT speeds were measured in 113 older adults (46.9% female, 53.1%% male, mean age=78.6±6.3) without dementia enrolled in the LonGenity study. Using an established rating system, white matter hyperintensities (WMH) and lacunes of presumed vascular origin were quantified from Fluid Attenuated Inversion Recovery (FLAIR) images from the same participants. Linear regression models adjusted for age, gender, global health, cohort, and estimated total intracranial volume were used to examine the association between NPW and DTW velocity and markers of CSVD.ResultsNumber of WMH in both the basal ganglia and the temporal lobes were associated with slower NPW velocity in our adjusted models (β=‐3.274 cm/s p=.047, β=‐3.113 cm/s p=.048, respectively). Number of frontal lobe WMH was associated with slower NPW velocity in our unadjusted model (β=‐3.316 cm/s p=.017) but not in the adjusted model (β=‐1.521 cm/s p=.262). WMH were not found to be significantly associated with WWT velocity. Lacunes of presumed vascular origin were not found to be significantly associated with neither NPW or DTW velocity. Significant interactions between measures of CSVD and gender, age, or cohort were not found in our models.ConclusionGait is a complex task requiring the integration of both cognitive and motor function across different brain regions. We find here that higher CSVD burden as measured by the presence of WMH in the basal ganglia and temporal lobes are independently associated with slower normal gait velocity. Interestingly, no such association was seen with WWT, a task requiring a higher cognitive load. Further studies are needed to establish temporality of these lesions with declines in gait velocity. Doing so may show utility of CSVD imaging markers as predictors of gait disturbances and dementia.

P04-12 The efficacy and feasibility of the SPRINTT physical activity intervention in Finland

BackgroundOlder adults with frailty and sarcopenia are at high risk of disability. These older adults get benefit from physical activity. However, it is challenging to get them involved in exercise interventions. The SPRINtT trial has investigated the efficacy and feasibility of a multicomponent intervention in the prevention of mobility disability in older adults with frailty and sarcopenia in 11 European countries, under the coordination of the Università Cattolica del Sacro Cuore, Italy. Altogether 1566 candidates were recruited to the SPRINtT RCT, and 142 of them in Finland.MethodsThe participants (n = 70) completed at least two years of physical activity training. The training was performed at moderate intensity and consisted of walking, strength, balance and flexibility exercises. The participants attended training two times a week at the center with the addition of home-based exercises. The training intensity increased gradually. The primary outcome of mobility disability was operationalized as an inability to complete the 400-m walk test. Secondary outcomes of physical performance were the short physical performance battery (SPPB) and handgrip strength.ResultsThe results of the intervention will be revealed in spring 2020. Participants experienced that their physical performance improved during the follow-up. The physical activity program and the home-based exercises can be performed without any equipment and could, therefore, be easily implemented for practice.ConclusionsThe physical activity intervention was feasible and could be further recommended for older people with sarcopenia and physical frailty if the final results support these experiences.

Multicomponent intervention to prevent mobility disability in frail older adults: randomised controlled trial (SPRINTT project)

ObjectiveTo determine whether a multicomponent intervention based on physical activity with technological support and nutritional counselling prevents mobility disability in older adults with physical frailty and sarcopenia.DesignEvaluator blinded, randomised controlled...

A Physical Therapy Mobility Checkup for Older Adults: Feasibility and Participant Preferences From a Discrete Choice Experiment.

Physical performance measures, like walking speed, identify and predict preclinical mobility disability but are rarely used in routine medical care. A preventive model of care called Mobility Checkup is being designed to reduce mobility disability in older adults. This study had two purposes: 1) determine feasibility and outcomes of the Mobility Checkup, and 2) identify preferences of older adults regarding this model of care using a discrete choice experiment. Adults over 55 years of age were recruited from the community. In the study's first phase, participants completed a Mobility Checkup, with feasibility evaluated using 6 criteria. In the second phase, a new sample of older adults (>55 years old) were educated about the Mobility Checkup and then completed a discrete choice experiment to determine their preferences regarding 4 attributes of this care model: cost, visit duration, desired education topic, and style of educational graphic. Each study phase was completed by 31 participants. Of the 6 feasibility criteria, 5 were met. Visit duration exceeded the 60-minute criteria for 13 of the 31 participants. Still, 91% of participants were very satisfied with the Mobility Checkup. Ability to transition positions identified preclinical mobility disability most frequently. A 30-minute visit with no out-of-pocket cost was deemed preferred. Older adults value knowing what physical performance measurements predict about their general health. Transitions should be evaluated as part of a Mobility Checkup for older adults. Clearly conveyed cost of health care service is important to older adult consumers.

Racial Differences in the Effect of HIV Status on Motor and Pulmonary Function and Mobility Disability in Older Adults.

Older Black adults face a disproportionate burden of HIV prevalence, but less is known about racial disparities in age-related outcomes in HIV. We assessed the effect of HIV status and race on motor and pulmonary function, as well as how they contribute to mobility disability. Community-based study; Chicago, IL METHODS: Participants were 363 community-dwelling adults age ≥ 50years, 48% living with HIV, and 68% Black. Participants with HIV were recruited from a specialty HIV clinic, and participants without HIV (comparable on key demographic, lifestyle, and behavioral characteristics) were recruited from the community.Measures included motor function summarized by 10 motor performance measures, pulmonary function summarized by 3 measures assessed using handheld spirometry, and self-reported mobility disability. In fully adjusted linear models, HIV was associated with better motor (β = 9.35, p < 0.001) and pulmonary function (β = 16.34, p < 0.001). For pulmonary function, the effect of HIV status was moderated by race (interaction between Black race and HIV status: β = - 11.66, p = 0.02), indicating that better pulmonary function among participants with HIV was less evident among Black participants. In fully adjusted models, odds of mobility disability did not differ by race, HIV status, or pulmonary function; better motor function was associated with lower odds of mobility disability (OR = 0.91 per 1-point higher, 95% CI 0.88-0.93). Better motor and pulmonary function exhibited by participants with HIV could reflect access to medical care. Racial differences in lung function among participants with HIV indicate potential disparities in prevention or treatment of pulmonary disease or underlying risk factors.

Cognitive Function and Whole-Brain MRI Metrics Are Not Associated with Mobility in Older Adults with Multiple Sclerosis.

Due to advances in disease-modifying medications and earlier management of comorbidities, adults with multiple sclerosis (MS) are living longer, and this coincides with the aging of the general population. One major problem among older adults with and without MS is limited mobility, a consequence of aging that often negatively affects quality of life. Identifying factors that contribute to mobility disability is needed to develop targeted rehabilitation approaches. This study examined cognitive processing speed and global brain atrophy as factors that may contribute to mobility disability in older adults with and without MS. Older adults (≥55 years) with MS (n = 31) and age- and sex-matched controls (n = 22) completed measures of mobility (Short Physical Performance Battery) and cognitive processing speed (Symbol Digit Modalities Test) and underwent an MRI to obtain whole-brain metrics (gray matter volume, white matter volume, ventricular volume) as markers of atrophy. Mobility was significantly worse in the MS group than in the control group (p = 0.004). Spearman correlations indicated that neither cognitive processing speed (MS: rs = 0.26; Control: rs = 0.08) nor markers of global brain atrophy (MS: rs range = −0.30 to −0.06; Control: rs range = −0.40 to 0.16) were significantly associated with mobility in either group. Other factors such as subcortical gray matter structures, functional connectivity, exercise/physical activity, and cardiovascular fitness should be examined as factors that may influence mobility in aging adults with and without MS.

A random forest method with feature selection for developing medical prediction models with clustered and longitudinal data

BackgroundMachine learning methodologies are gaining popularity for developing medical prediction models for datasets with a large number of predictors, particularly in the setting of clustered and longitudinal data. Binary Mixed Model (BiMM) forest is a promising machine learning algorithm which may be applied to develop prediction models for clustered and longitudinal binary outcomes. Although machine learning methods for clustered and longitudinal methods such as BiMM forest exist, feature selection has not been analyzed via data simulations. Feature selection improves the practicality and ease of use of prediction models for clinicians by reducing the burden of data collection. Thus, feature selection procedures are not only beneficial, but are often necessary for development of medical prediction models. In this study, we aim to assess feature selection within the BiMM forest setting for modeling clustered and longitudinal binary outcomes. MethodsWe conducted a simulation study to compare BiMM forest with feature selection (backward elimination or stepwise selection) to standard generalized linear mixed model feature selection methods (shrinkage and backward elimination). We also evaluated feature selection methods to develop models predicting mobility disability in older adults using the Health, Aging and Body Composition Study dataset as an example utilization of the proposed methodology. ResultsBiMM forest with backward elimination generally offered higher computational efficiency, similar or higher predictive performance (accuracy and area under the receiver operating curve), and similar or higher ability to identify correct features compared to linear methods for the different simulated scenarios. For predicting mobility disability in older adults, methods generally performed similarly in terms of accuracy, area under the receiver operating curve, and specificity; however, BiMM forest with backward elimination had the highest sensitivity. ConclusionsThis study is novel because it is the first investigation of feature selection for developing random forest prediction models for clustered and longitudinal binary outcomes. Results from the simulation study reveal that BiMM forest with backward elimination has the highest accuracy (performance and identification of correct features) and lowest computation time compared to other feature selection methods in some scenarios and similar performance in other scenarios. Many informatics datasets have clustered and longitudinal outcomes and results from this study suggest that BiMM forest with backward elimination may be beneficial for developing medical prediction models.

Three-Year, Postintervention, Follow-up Comparison of Health Care Resource Utilization and Costs in the Lifestyle Interventions and Independence for Elders (LIFE) Study.

The Lifestyle Interventions and Independence for Elders (LIFE) Study physical activity (PA) intervention was found to be cost-effective compared to health education (HE). However, long-term effects postintervention are unknown. This was a secondary analysis of LIFE Study data linked to Medicare claims data (2014-2016). Participants were linked via Social Security Numbers to Medicare claims data. Utilization and cost variables were analyzed using generalized linear models with negative binomial and Tweedie distributions. Unadjusted means and 95% confidence intervals were compared by year and overall stratified. Each model compared PA versus HE and adjusted for other baseline characteristics and stratified by study site. Additional models were stratified by baseline physical functioning assessment scores. Of the 1,635 LIFE Study participants, 804 (53.5%) were linked to Medicare claims with an average of 33 months of follow-up time during the 3-year data linkage period. Mean outpatient (6.6 vs 6.8), inpatient (0.40 vs 0.40), and other utilization metrics were similar between PA and HE groups. Costs were also similar for each group and each type of service, for example, outpatient: $2,070 versus $2,093 and inpatient: $4,704 versus $4,792. Regression results indicated no statistically significant differences between PA and HE groups. While the LIFE Study demonstrated that PA reduced mobility disability in older adults and was cost-effective, it did not appear to affect long-term health care utilization costs posttrial. These findings suggest that it remains challenging to affect long-term health care costs using PA interventions effects.

Association of Fish Oil and Physical Activity on Mobility Disability in Older Adults.

This study aimed to examine whether long-term fish oil (FO) supplementation is associated with a lower risk of mobility disability and enhances benefits of physical activity (PA). A total of 1635 sedentary adults age 70 to 89 yr from the Lifestyle Interventions and Independence for Elders single-blinded randomized, multicenter clinical trial, which compared a structured PA program to a health education program. Primary outcome was incident major mobility disability (MMD), defined by loss of ability to walk 400 m, measured every 6 months for an average of 2.6 yr. Secondary outcomes included persistent mobility disability, Short Physical Performance Battery, 400-m walk speed, and grip strength. A third of participants reported using FO at baseline (456 (28%); mean age, 78.5 yr; 70.5% women). MMD was experienced by 131 participants (28.7%) in the FO group and 405 (34.4%) participants in the nonuser group. After adjusting for confounders, FO supplementation was associated with a lower risk (HR, 0.78; 95% confidence interval (CI), 0.64-0.96) of incident MMD. However, there was no interaction (P = 0.19) between FO supplementation and PA intervention for MMD. For the secondary outcome of persistent mobility disability, the intervention association differed by supplementation (P = 0.002) with PA intervention associations of (HR, 1.36; 95% CI, 0.83-2.23) for users and (HR, 0.61; 95% CI, 0.46-0.81) for nonusers. Changes in physical performance outcomes were not modified by baseline FO supplementation or combination with PA. FO supplementation was associated with a lower risk of MMD in low to moderate functioning older adults. However, supplementation did not enhance the benefit of PA on risk of mobility disability. These results are hypothesis generating and need to be confirmed in randomized trials.

Effect of Gastric Acid Suppressants on Response to a Physical Activity Intervention and Major Mobility Disability in Older Adults: Results from the Lifestyle Interventions for Elders (LIFE) Study.

Proton pump inhibitors (PPIs) and histamine2 receptor antagonists (H2 RAs) are associated with pharmacologic effects that may be detrimental to mobility and response to physical activity. Mobility disability and injurious fall outcomes in PPI and H2 RA users were compared with nonusers in this secondary analysis of data from the Lifestyle Interventions for Elders (LIFE) study. Participants ages 70-89years were randomized to a physical activity (PA) or successful aging intervention and evaluated by medication use. Confounders included baseline demographic characteristics, physical function, cognitive function, sleep quality, and acid reflux symptoms that were adjusted via propensity score weighting. Outcomes were incident and persistent major mobility disability (MMD and pMMD) and injurious falls. Weighted proportional hazard models evaluated independent and interaction effects of PPIs and H2 RAs. No interaction was found between PPIs and H2 RAs and the PA intervention. Drug use associations were significant for H2 RAs (hazard ratio [HR] 1.74 [95% confidence interval [CI] 1.12-2.68]) and PPIs (HR 1.32 [95% CI 1.02-1.70]) compared with nonusers for pMMD. PPIs were associated with increased injurious falls compared with nonusers (HR 1.44 [95% CI 1.06-1.96]). Pooling of data from the H2 RA and PPI exposure groups showed a 26% increase in MMD (HR 1.26 [95% CI 1.07-1.48]), a 44% increase in pMMD (HR 1.44 [95% CI 1.16-1.77]), and a 48% increase in injurious falls (HR 1.48 [95% CI 1.15-1.91]) compared with nonusers. All direct comparisons between PPIs and H2 RAs were nonsignificant. Compared with nonusers, participants using either PPIs or H2 RAs had an increased risk of MMD, pMMD, and injurious falls. It is not known if these effects are related to the individual pharmacology of each medication, reduced acid secretion, or the underlying disease state. Further study is required to determine causality.

Cognitive Function as a Predictor of Major Mobility Disability in Older Adults: Results From the LIFE Study.

Background and ObjectivesMany cross-sectional studies have confirmed a link between gait speed and cognitive function. However, it is unknown whether cognitive function plays a role in the onset of major mobility disability (MMD) and if the effects are independent of physical function. This study examined cognitive and physical function as predictors of MMD across an average of 2.6 years of follow-up in community-dwelling older adults with compromised mobility.Research Design and MethodData were collected from 1,635 participants in the Lifestyle Interventions and Independence for Elders (LIFE) study ages 70–89 years free of MMD at baseline. MMD was assessed every 6 months and defined as the inability to walk 400 m in ≤15 min without assistance or sitting. Cognitive function was assessed at baseline, 18 months, and 24 months using a cognitive battery categorized into four domains: global cognitive function, processing speed, verbal memory, and executive function.ResultsAcross the study duration of 2.6 years, 536 participants (32.8%) developed MMD. Cox Proportional Hazard models indicated a protective relationship for higher baseline processing speed (Hazard Ratio [HR] per standard deviation: 0.86, p = .006), executive function (HR: 0.86, p = .002), and global cognition (HR: 0.85, p = .001) on incidence of MMD adjusted for demographics, intervention, and comorbidities. Results were not significant after adjustment for gait speed. In adjusted longitudinal models, a positive change in processing speed was significantly associated with reduced risk of MMD (HR: 0.52, p < .001) while other domains were not.Discussion and ImplicationsIn the LIFE study, processing speed at baseline and follow-up was a significant predictor of subsequent MMD although the observed association may be explained by physical function as reflected in gait speed. More studies are needed to understand how cognitive function, alone and in combination with physical function, influences risk of MMD.

Abdominal Obesity and Mobility Disability in Older Adults: A 4-Year Follow-Up the International Mobility in Aging Study.

Abdominal obesity is related to the disability process in older adults, however, little is known about this relationship when adjusted for important confounders such as depression and physical performance measures in a diverse international aged population. To explore the longitudinal relationship between abdominal obesity and mobility disability controlling for physical performance and depression. Longitudinal observational study using data from the International Mobility in Aging Study (IMIAS) Study. 1104 out of 2002 older adults aged 64-74 years old free of mobility disability at baseline (2012) and then reassessed in 2016. Mobility disability was defined as reporting difficulty in walking 400 m or climbing stairs. Activities of daily living (ADL) disability was based on any self-reported difficulty in five mobility-related ADLs. Abdominal obesity was defined as waist circumference ≥ 88cm for women or ≥ 102 cm for men. Four meters gait speed, handgrip strength and depressive symptoms (CES-D) were assessed. Generalized Estimating Equations (GEE) and multinomial regressions were used to estimate associations between disability and abdominal obesity. 1104 free of disability participants were followed over 4 years, the mean age was 68.9 (±2.9) years among men and 68.7 (±2.6) years among women. Prevalence and incidence rates of mobility disability varied widely across research site and sex. The longitudinal associations between mobility disability and abdominal obesity remained significant even when adjusted by depressive symptoms, handgrip strength, gait speed, age, sex, education and research site. Participants with abdominal obesity had higher mobility disability (OR=1.68, 95% CI 1.23-1.76, p-value=0.01) and also increased risk for ADL disability (OR: 1.47, 95% CI 1.23-1.76, p-value=0.01). Abdominal obesity in baseline was also predictor of mobility disability in 2016 (OR: 1.93, 95% CI 1.17-3.17, p-value <0.01) but not for ADL disability (OR: 1.59, 95% CI 0.93-2.71, p-value =0.09) with accounting mortality. Abdominal obesity is associated longitudinally and predicts mobility disability, even over a short period (4 years) in community-dwelling older adults from different epidemiological contexts.

Translating the Lifestyle Interventions and Independence for Elders Clinical Trial to Older Adults in a Real-World Community-Based Setting.

The Lifestyle Interventions and Independence for Elders (LIFE) clinical trial demonstrated that a structured program of physical activity (PA) reduced mobility-disability in older adults by up to 28%. It remains unknown whether the benefits of LIFE PA can be translated to older adults at risk for mobility-disability in real-world community-based settings. To address this knowledge gap, we conducted the ENhancing independence using Group-based community interventions for healthy AGing in Elders (ENGAGE) pilot study and examined the safety, feasibility, and preliminary effectiveness of translating LIFE PA to a community-based senior center. Forty older adults with severe lower extremity functional limitations (age: 76.9 ± 7.3 years; body mass index: 32.7 ± 8 kg/m2; 85% female; short physical performance battery score: 6.3 ± 2.2) were randomized to 24 weeks of PA or a health education control intervention. Community-based PA was safe (serious adverse events: PA vs health education, 0:2; nonserious adverse events: PA vs health education, 3:1) and participants successfully adhered to the PA intervention (65.2%). Compared to health education, PA participants who attended ≥25% of scheduled visits had meaningful and sustained short physical performance battery improvements at follow-up (between group short physical performance battery score differences: ~0.7 units). ENGAGE has demonstrated the preliminary safety, feasibility, and effectiveness of LIFE PA in a real-world community-based setting. Larger-scale translational studies are needed to further disseminate the benefits of LIFE PA to vulnerable older adults in a variety of community-based settings.

The Effect Of Two Low-dose Strength/Balance Programs On The Physical Function Of Mobility-limited Older Adults

BACKGROUND: Strength and balance training are critical to maintaining physical function and delaying the onset of major mobility disability in older adults (OAs). The minimum amount of this training required to yield clinically meaningful improvements in physical function is not clear. PURPOSE: To evaluate the effect of two low dose strength/balance programs on physical function in mobility-limited OAs. METHODS: Twenty community-dwelling OAs with mobility limitations were randomized to one of two strength/balance doses (n=10/dose), held 3x/week at a local YMCA for 10 wks. Eligible participants were ≥ 65 yrs of age, exhibited mild to moderate mobility impairment (short physical performance battery (SPPB) score of 3-9 out of 12), sedentary (<125 minutes/week of any kind of physical activity, determined by 7-day pre-baseline accelerometry), and had no major medical issues that would preclude exercise. Exercise doses were as follows: Low dose (L): 1 set each of chair stands, hip abduction, step-up and back with head turns, toe raises, and a balance stand). Higher dose (H): 2 sets of the previous mentioned exercises were performed. Each exercise had three variations of difficulty to accommodate different participant abilities and the number of reps were based on an RPE of 7 out of 10. Participants were assessed on SPPB score and 400m walk speed before and after the intervention by individuals blinded to which dose that participant was randomized to. Clinically meaningful improvements were defined as an SPPB improvement of 0.5 points and a 400m walk speed improvement of 0.05 m/sec. Data was analyzed using a t-paired test. Results are expressed as means (+ std deviation). RESULTS: SPPB score improved by 2.5 (+ 1.1) points among the entire cohort (p<0.001). Improvement was significant for each dose alone (L: 1.5 (+ 0.6), p<0.05), (H: 3.0 (+ 0.82), p<0.001). The improvement in SPPB score in the higher dose was significantly different from that observed with the lower dose (p<0.05). There was no significant effect of either dose on 400m walk speed. CONCLUSION: A 10 wk strength/balance program performed 3x/week and consisting of a single set each of select strength/balance exercises was sufficient to elicit clinically meaningful improvements in physical function for OAs with mild to moderate mobility limitations.

Greater Stance Time Variability is Associated with Lower Step Activity in Older Adults

Previous research has shown that older adults with greater gait variability are at a higher risk for falling. Falls increase fear of falling and may subsequently result in mobility disability manifesting as decreased physical activity. Physical activity is commonly gauged from continuous step activity monitoring. While decreased step activity has been associated with impaired gait, the associations between gait variability and step activity are not understood. PURPOSE: To examine the relationship between gait variability and step activity in older adults. METHODS: Spatiotemporal gait parameters were recorded for 19 healthy older adults (mean age 74.5 ± 6.3 years; 9 males/ 10 females) walking at a normal walking speed across a GAITRite walkway for 5 trials. Step activity (# of steps) was collected using a research-grade step activity monitor for 7 consecutive days. Average number of steps for the 7 days was used. Coefficient of variation (defined as % of SD over mean) of gait speed, stride length, step width, swing time, stance time and double support time were calculated. Pearson’s and Spearman’s correlation coefficients were used based on normality to determine the relationship between gait variability and step activity. RESULTS: Stance time variability showed significant moderate inverse correlation with step activity (rho = -0.482, p = 0.036). Swing time variability showed moderate inverse correlation with step activity with a trend towards significance (r = -0.451, p = 0.052). Variability of gait speed (rho = -0.349, p = 0.143), stride length (r = -0.3, p = 0.212), step width (rho = -0.088, p = 0.721), and double support time (rho = -0.249, p = 0.304) showed weak inverse but not significant correlation with step activity. CONCLUSION: In general, gait variability seems to be inversely related to step activity in older adults meaning those with greater gait variability showed lower step activity. In particular, stance time variability has earlier shown to be critical in identifying older adults with mobility disability and those older adults at risk for future disability. Our finding of decreased step activity in those older adults with increased stance time variability suggests that step activity monitoring could provide surrogate and complimentary measures to identify mobility disability in older adults.

Metabolites Associated With Risk of Developing Mobility Disability in the Health, Aging and Body Composition Study.

Metabolic pathways that give rise to functional decline and mobility disability in older adults are incompletely understood. To identify metabolic perturbations that may affect functional decline, nontargeted metabolomics was used to measure 350 metabolites in baseline plasma from 313 black men in the Health ABC Study (median age 74 years). Usual gait speed was measured over 20 m. Cross-sectional relationships between gait speed and metabolites were explored with partial correlations adjusted for age, study site, and smoking status. Risk of incident mobility disability (two consecutive reports of severe difficulty walking quarter mile or climb 10 stairs) over 13 years of follow-up was explored with Cox regression models among 307 men who were initially free of mobility disability. Significance was determined at p ≤ .01 and q (false discovery rate) ≤ 0.30. Two metabolites were correlated with gait speed: salicylurate (r = -.19) and 2-hydroxyglutarate (r = -.18). Metabolites of amino acids and amino acid degradation (indoxy sulfate; hazard ratio [HR] = 1.48, 95% confidence interval [CI] = 1.09-2.03, symmetric dimethylarginine; HR = 3.58, 95% CI = 1.57-8.15, N-carbamoyl beta-alanine; HR = 1.91, 95% CI = 1.16-3.14, quinolinate; HR = 2.56, 95% CI = 1.65-3.96) and metabolites related to kidney function (aforementioned symmetric dimethylarginine and indoxy sulfate as well as creatinine; HR = 5.91, 95% CI = 2.06-16.9, inositol; HR = 2.70, 95% CI = 1.47-4.97) were among the 23 metabolites associated with incident mobility disability. This study highlights the potential role of amino acid derivatives and products and kidney function early in the development of mobility disability and suggests metabolic profiles could help identify individuals at risk of functional decline.

Exercise's effect on mobility disability in older adults with and without obesity: The LIFE study randomized clinical trial.

ObjectiveSome data suggests that obesity blunts the benefits of exercise on mobility in older adults. We tested the homogeneity of the effect of a physical activity intervention on major mobility disability across baseline obesity classifications in the Lifestyle Interventions and Independence for Elders (LIFE) Study. LIFE randomized 1,635 sedentary men and women 70–89 years to a moderate intensity physical activity (PA) or health education (HE) program.MethodsMajor mobility disability (MMD), defined as the inability to walk 400m, was determined over an average follow up of 2.6 years. Participants were divided into 4 subgroups: 1) non-obese (BMI < 30 kg/m2; n=437); 2) non-obese with high waist circumference (WC >102 cm [men], >88 cm [women]; n=434); 3) class 1 obesity (30 kg/m2 ≤ BMI < 35 kg/m2; n=430); and 4) class 2+ obesity (BMI ≥ 35 kg/m2; n=312). Cox proportional hazard modeling was used to test an obesity by intervention interaction.ResultsThe PA intervention had the largest benefit in participants with class 2+ obesity (HR 0.69, 95% CI 0.48, 0.98). However, there was no statistically significant difference in benefit across obesity categories.ConclusionA structured PA program reduced the risk of MMD even in older adults with extreme obesity.