Vitamin D Supplementation and Muscle Power, Strength and Physical Performance in Older Adults: A Randomized Controlled Trial.

BACKGROUND: Low 25-hydroxyvitamin D (25[OH]D) concentrations (<30 ng/mL [<50 nmol/L]) have been associated with muscle weakness and impaired physical performance in observational studies. However, the effect of vitamin D supplementation on changes in muscle strength and physical performance in randomized controlled trials has been mixed. OBJECTIVES: To determine the effect of daily vitamin D supplementation on leg power, strength, and physical performance in low-functioning older adults with 25(OH)D concentrations of 18 to <30 ng/mL. METHODS: In this double-blind, randomized controlled trial, 136 low-functioning [Short Physical Performance Battery (SPPB) scores ≤10] adults aged 65-89 y with 25(OH)D concentrations of 18 to <30 ng/mL were randomly assigned to 2000 IU/d vitamin D3 or placebo for 12 mo. Lower-extremity leg power (primary outcome), leg and grip strength, SPPB, timed up and go (TUG), postural sway, and gait velocity and spatiotemporal parameters (secondary outcomes) were assessed at baseline, 4 and 12 mo. A subset (n = 37) also underwent a muscle biopsy at baseline and 4 mo and muscle fiber composition and contractile properties were assessed. RESULTS: Participants' mean ± SD age and SPPB scores at baseline were 73.4 ± 6.3 y and 7.8 ± 1.8, respectively. Mean ± SD 25(OH)D concentrations at baseline and 12 mo were 19.4 ± 4.2 ng/mL and 28.6 ± 6.7 ng/mL in the vitamin D group and 19.9 ± 4.9 ng/mL and 20.2 ± 5.0 ng/mL in the placebo group for a mean ± SE difference of 9.1 ± 1.1 ng/mL (P < 0.0001). However, there were no differences in change in leg power, leg or grip strength, SPPB score, TUG, postural sway, or gait velocity and spatiotemporal parameters by intervention group over 12 mo or muscle fiber composition and contractile properties over 4 mo. CONCLUSIONS: In low-functioning older adults with 25(OH)D concentrations of 18 to <30 ng/mL, randomization to 2000 IU/d vitamin D3 did not result in improvements in leg power, strength, or physical performance or muscle fiber composition and contractile properties. This trial was registered at clinicaltrials.gov as NCT02015611.

Association Between Contrast Sensitivity and Physical Function in Cognitively Healthy Older Adults: The Brain Networks and Mobility Function Study.

BACKGROUND: To evaluate whether contrast sensitivity is associated with lower extremity physical function in cognitively intact older adults. METHODS: Cross-sectional analysis of the relationship of binocular and worse eye log contrast sensitivity (LCS) to expanded Short Physical Performance Battery (eSPPB) and its components (gait speed, narrow walking speed, chair stand pace, and balance) in 192 cognitively healthy older adults. The association of LCS with postural sway and gait was also tested with tasks that further challenged functional reserve. RESULTS: Mean age was 76.4 years with 56% identifying as female and over 98.5% having good corrected visual acuity. Lower LCS was significantly associated with worse performance on the eSPPB, 4-M gait speed, narrow walking speed, and balance time in unadjusted and adjusted models. The relationship between worse eye LCS and larger postural sway was 3 times greater on a foam surface (beta 1.07, 95% CI [0.35, 1.80]) than a firm surface (beta 0.35, 95% CI [0.05, 0.65]), and both were robust to adjustment for confounders; similar findings were observed with binocular LCS. Lower binocular LCS had a greater decremental effect on gait velocity during the fast pace (beta -0.58, 95% CI [-0.90, -0.27]) than the usual pace (Beta -0.39 [-0.63, -0.15]) gait task. CONCLUSIONS: These findings suggest that cognitively unimpaired older adults without significant visual acuity impairment can have subtle preclinical deficits in contrast sensitivity and physical function that could place them at risk of mobility and balance issues. Future studies should determine whether this subset of older adults may benefit from targeted intervention to prevent disability.

Effect of exercise modality and weight loss on changes in muscle and bone quality in older adults with obesity.

BACKGROUND: Little is known about the effect of exercise modality during a dietary weight loss program on muscle size and quality, as measured by computed tomography (CT). Even less is known about how CT-derived changes in muscle track with changes in volumetric bone mineral density (vBMD) and bone strength. METHODS: Older adults (66 ± 5 years, 64 % women) were randomized to 18-months of diet-induced weight loss (WL), WL with aerobic training (WL + AT), or WL with resistance training (WL + RT). CT-derived muscle area, radio-attenuation and intermuscular fat percentage at the trunk and mid-thigh were determined at baseline (n = 55) and 18-month follow-up (n = 22-34), and changes were adjusted for sex, baseline value, and weight lost. Lumbar spine and hip vBMD and finite element-derived bone strength were also measured. RESULTS: After adjustment for the weight lost, muscle area losses at the trunk were -7.82 cm2 [-12.30, -3.35] for WL, -7.72 cm2 [-11.36, -4.07] for WL + AT, and -5.14 cm2 [-8.65, -1.63] for WL + RT (p < 0.001 for group differences). At the mid-thigh, decreases were -6.20 cm2 [-10.39, -2.02] for WL, -7.84 cm2 [-11.19, -4.48] for WL + AT, and -0.60 cm2 [-4.14, 2.94] for WL + RT; this difference between WL + AT and WL + RT was significant in post-hoc testing (p = 0.01). Change in trunk muscle radio-attenuation was positively associated with change in lumbar bone strength (r = 0.41, p = 0.04). CONCLUSIONS: WL + RT better preserved muscle area and improved muscle quality more consistently than WL + AT or WL alone. More research is needed to characterize the associations between muscle and bone quality in older adults undertaking weight loss interventions.

Factors associated with falls in older adults: A secondary analysis of a 12-month randomized controlled trial.

PURPOSE: While identifying older adults at risk for falls is important, fall prediction models have had limited success, in part because of a poor understanding of which physical function measures to include. The purpose of this secondary analysis was to determine physical function measures that are associated with future falls in older adults. METHODS: In a 12-month trial comparing Vitamin D3 supplementation versus placebo on neuromuscular function, 124 older adults completed physical function measures at baseline, including the Short Physical Performance Battery (SPPB), Timed Up and Go, tests of leg strength and power, standing balance on a force plate with firm and foam surfaces, and walking over an instrumented walkway. Falls were recorded with monthly diaries over 12 months and categorized as no falls vs. one or more falls. Univariate and multivariable logistic regression adjusting for demographics, treatment assignment, depression, and prescription medications were conducted to examine the association between each physical function measure and future falls. Models were additionally adjusted for fall history. RESULTS: 61 participants sustained one or more falls. In univariate analysis, white race, depression, fall history, SPPB, and postural stability on foam were significantly associated with future falls. In multivariable analysis, fall history (OR (95% CI): 3.20 (1.42-7.43)), SPPB (0.80 (0.62-1.01)), and postural stability on foam (3.01 (1.18, 8.45)) were each significantly associated with future falls. After adjusting for fall history, only postural stability on foam was significantly associated with falls. CONCLUSIONS: When developing fall prediction models, fall history, the SPPB, and postural stability when standing on foam should be considered.

Dietary Weight Loss, Exercise, and Inflammation in Older Adults with Overweight or Obesity and Cardiometabolic Disease.

OBJECTIVE: This study aimed to examine exercise modality during weight loss on change in inflammation among older adults with overweight or obesity and cardiometabolic disease. METHODS: A total of 222 older adults with a mean (SD) age of 66.9 (4.7) years and a mean (SD) BMI of 33.5 (3.5) kg/m2 were randomized to weight loss (WL; n = 68), WL plus aerobic training (WL + AT; n = 79), or WL plus resistance training (WL + RT; n = 75) for 18 months. C-reactive protein (CRP) and interleukin-6 were measured at baseline, 6 months, and 18 months. RESULTS: All groups lost significant weight from baseline to 18 months, with average adjusted changes of -5.5% for WL, -9.0% for WL + AT, and -10.1% for WL + RT. WL + RT and WL + AT lost significantly more weight than WL (P < 0.05). At 18 months, CRP values in WL + RT were significantly lower than WL (2.25 pg/mL vs. 3.38 pg/mL; P = 0.004). The only difference in interleukin-6 was that at 18 months, WL + RT was lower than WL + AT (2.32 pg/mL vs. 2.75 pg/mL; P = 0.03). CONCLUSIONS: The addition of RT during WL was more effective at reducing levels of CRP than WL. Although results were in the expected direction, there was no difference in CRP between WL and WL + AT.

Effect of Weight Change Following Intentional Weight Loss on Bone Health in Older Adults with Obesity.

OBJECTIVE: This study aimed to examine change in bone mineral density (BMD) and trabecular bone score among older adult weight regainers (WR) and weight maintainers (WM). METHODS: Observational data come from 77 older adults (mean age: 67 [SD 5] years; 69% women; 70% white) with obesity (mean BMI: 33.6 [SD 3.7] kg/m2 ) who lost weight during an 18-month weight loss intervention. Total body mass and body composition, along with regional (total hip, femoral neck, lumbar spine) BMD and trabecular bone score, were measured at baseline, 18 months, and 30 months. WR (n = 36) and WM (n = 41) categories were defined as a ≥ 5% or < 5% weight gain from 18 to 30 months, respectively. RESULTS: Among skeletal indices, only total hip BMD was significantly reduced during the 18-month intervention period in both WRs (-3.9%; 95% CI: -5.8% to -2.0%) and WMs (-2.4%; 95% CI: -4.3% to -0.5%; P = 0.07). After adjustment for relevant baseline covariates and weight change from 0 to 18 months, 30-month change in total hip BMD was -2.6% (95% CI: -4.3% to -0.9%) and -3.9% (95% CI: -5.7% to -2.1%) among WRs and WMs, respectively (P = 0.07). CONCLUSIONS: Loss of hip BMD persists in the year after a weight loss intervention among older adults with obesity, regardless of weight regain status.

The Virtual Short Physical Performance Battery: Psychometric Properties and Validation in Older Adults With Multiple Sclerosis.

Background: There are increasing numbers of older adults with multiple sclerosis (MS) who undergo declines in physical function that require attention of clinicians and researchers. Objective and perceived measures of disablement feasible for clinical and residential settings, such as the Short Physical Performance Battery and its virtual counterpart (vSPPB), are critical for defining the degree of disablement. Objective: We evaluated the psychometric properties and validity of the vSPPB as a measure of perceived lower extremity physical function in older adults with MS (age ≥60 years). Method: The sample included 35 older adults with MS and 35 age- and sex-matched healthy controls (age ≥60 years) who completed a battery of assessments, including the vSPPB. Results: The vSPPB performed satisfactorily in older adults with MS regarding data quality, scaling assumptions, and acceptability (i.e., psychometrics). The vSPPB further demonstrated criterion, known-groups, convergent, and discriminant construct validity. Conclusion: This report provides evidence for the validity of vSPPB scores as a measure of perceived lower extremity physical function in older adults with MS.

Prediction of lumbar vertebral body compressive strength of overweight and obese older adults using morphed subject-specific finite-element models to evaluate the effects of weight loss.

BACKGROUND: Diet and exercise can promote weight loss in older adults; however, there is potential to increase fracture risk due to loss of bone mineral density (BMD) known to accompany weight loss. Weight loss effects on measures of bone quality and strength are currently unknown. AIMS: The purpose of this study is to develop subject-specific finite-element (FE) models of the lumbar spine and study the effect of intentional weight loss on bone strength in a pilot data set. METHODS: Computed tomography (CT) scans of the lumbar spine of 30 overweight and obese (mean BMI = 29.7 ± 3.9 kg/m2), older adults (mean age = 65.9 ± 4.6 years) undergoing an 18-month intentional weight loss intervention were obtained at baseline and post-intervention. Measures of volumetric BMD (vBMD) and variable cortical thickness were derived from each subject CT scan. Development of the subject-specific FE models of the lumbar spine involved model morphing techniques to accelerate the development of the models. vBMD-derived material properties and cortical thickness measures were directly mapped to baseline and post-intervention models. Bone strength was estimated through simulation of a quasi-static uniaxial compression test. RESULTS: From baseline to 18-month post-weight loss intervention, there were statistically significant decreases in estimated bone strength (6.5% decrease; p < 0.05). Adjusting for baseline bone measures and gender revealed no statistically significant correlations between weight change and change in vBMD, cortical thickness, or bone strength. CONCLUSION: Integration of CT-based measures and FE models with conventional areal BMD can improve the understanding of the effects of intentional weight loss on bone health.

Relationship of Physical Function to Single Muscle Fiber Contractility in Older Adults: Effects of Resistance Training With and Without Caloric Restriction.

BACKGROUND: Previous studies support beneficial effects of both resistance exercise training (RT) and caloric restriction (CR) on skeletal muscle strength and physical performance. The goal of this study was to determine the effects of adding CR to RT on single-muscle fiber contractility responses to RT in older overweight and obese adults. METHODS: We analyzed contractile properties in 1,253 single myofiber from muscle biopsies of the vastus lateralis, as well as physical performance and thigh muscle volume, in 31 older (65-80 years), overweight or obese (body mass index = 27-35 kg/m2) men (n = 19) and women (n = 12) who were randomly assigned to a standardized, progressive RT intervention with CR (RT+CR; n = 15) or without CR (RT; n = 16) for 5 months. RESULTS: Both interventions evoked an increase in force normalized to cross-sectional area (CSA), in type-I and type-II fibers and knee extensor quality. However, these improvements were not different between intervention groups. In the RT group, changes in total thigh fat volume inversely correlated with changes in type-II fiber force (r = -.691; p = .019). Within the RT+CR group, changes in gait speed correlated positively with changes in type-I fiber CSA (r = .561; p = .030). In addition, increases in type-I normalized fiber force were related to decreases in thigh intermuscular fat volume (r = -0.539; p = .038). CONCLUSION: Single muscle fiber force and knee extensor quality improve with RT and RT+CR; however, CR does not enhance improvements in single muscle fiber contractility or whole muscle in response to RT in older overweight and obese men and women.

Effect of Hospitalizations on Physical Activity Patterns in Mobility-Limited Older Adults.

OBJECTIVES: To evaluate the effect of hospitalizations on patterns of sedentary and physical activity time in mobility-limited older adults randomized to structured physical activity or health education. DESIGN: Secondary analysis of investigator-blinded, parallel-group, randomized trial conducted at 8 U.S. centers between February 2010 and December 2013. PARTICIPANTS: Sedentary men and women aged 70 to 89 at baseline who wore a hip-fitted accelerometer 7 consecutive days at baseline and 6, 12, and 24 months after randomization (N=1,341). MEASUREMENTS: Participants were randomized to a physical activity (PA; n = 669) intervention that included aerobic, resistance, and flexibility training or to a health education (HE; n = 672) intervention that consisted of workshops on older adult health and light upper-extremity stretching. Accelerometer patterns were characterized as bouts of sedentary (<100 counts/min; ≥1, ≥10, ≥30, ≥60 minute lengths) and activity (≥100 counts/min; ≥1, ≥2, ≥5, ≥10 minute lengths) time. Each participant was categorized as having 0, 1 to 3, or 4 or more cumulative hospital days before each accelerometer assessment. RESULTS: Hospitalization increased sedentary time similarly in both intervention groups (8 min/d for 1-3 cumulative hospital days and 16 min/d for ≥4 cumulative hospital days). Hospitalization was also associated with less physical activity time across all bouts of less than 10 minutes (≥1: -7 min/d for 1-3 cumulative hospital days, -16 min/d for ≥4 cumulative hospital days; ≥2: -5 min/d for 1-3 cumulative hospital days, -11 min/d for ≥4 cumulative hospital days; ≥5: -3 min/d for 1-3 cumulative hospital days, -4 min/d for ≥4 cumulative hospital days). There was no evidence of recovery to prehospitalization levels (time effect p >.41). PA participants had less sedentary time in bouts of less than 30 minutes than HE participants (-8 to -10 min/d) and more total activity (+3 to +6 min/d), although hospital-related changes were similar between the intervention groups (interaction effect p >.26). CONCLUSION: Participating in a PA intervention before hospitalization had expected benefits, but participants remained susceptible to hospitalization's detrimental effects on their daily activity levels. There was no evidence of better activity recovery after hospitalization. J Am Geriatr Soc 67:261-268, 2019.

Performance criteria for generating predictive optimal control simulations of bicycle pedaling.

The purpose of this study was to identify one or more performance-based criteria that may be used to generate predictive optimal control simulations of submaximal pedaling. Two-legged pedaling simulations were generated based on minimizing muscle activation, muscle stress, metabolic energy, time derivative of muscle force, and minimizing metabolic energy while pedaling smoothly. The simulations based on minimizing muscle activation and muscle stress most closely matched experimental pedaling data, with the activation criterion better matching experimental muscle activation timing. We conclude that predictive simulations of submaximal pedaling may be generated using a cost function based on minimizing muscle activation.

Modeling a rotator cuff tear: Individualized shoulder muscle forces influence glenohumeral joint contact force predictions.

BACKGROUND: Rotator cuff tears in older individuals may result in decreased muscle forces and changes to force distribution across the glenohumeral joint. Reduced muscle forces may impact functional task performance, altering glenohumeral joint contact forces, potentially contributing to instability or joint damage risk. Our objective was to evaluate the influence of rotator cuff muscle force distribution on glenohumeral joint contact force during functional pull and axilla wash tasks using individualized computational models. METHODS: Fourteen older individuals (age 63.4 yrs. (SD 1.8)) were studied; 7 with rotator cuff tear, 7 matched controls. Muscle volume measurements were used to scale a nominal upper limb model's muscle forces to develop individualized models and perform dynamic simulations of movement tracking participant-derived kinematics. Peak resultant glenohumeral joint contact force, and direction and magnitude of force components were compared between groups using ANCOVA. FINDINGS: Results show individualized muscle force distributions for rotator cuff tear participants had reduced peak resultant joint contact force for pull and axilla wash (P ≤ 0.0456), with smaller compressive components of peak resultant force for pull (P = 0.0248). Peak forces for pull were within the glenoid. For axilla wash, peak joint contact was directed near/outside the glenoid rim for three participants; predictions required individualized muscle forces since nominal muscle forces did not affect joint force location. INTERPRETATION: Older adults with rotator cuff tear had smaller peak resultant and compressive forces, possibly indicating increased instability or secondary joint damage risk. Outcomes suggest predicted joint contact force following rotator cuff tear is sensitive to including individualized muscle forces.

Self-Reported Physical Function As a Predictor of Hospitalization in the Lifestyle Interventions and Independence for Elders Study.

OBJECTIVES: To explore whether baseline scores on the Mobility Assessment Tool-short form (MAT-sf), a brief, animated, computer-based means of assessing mobility that predicts mobility disability, are associated with number of hospitalizations and time to first hospitalization over a median follow-up of 2.7 years. DESIGN: Post hoc analysis of prospectively gathered data from the Lifestyle Interventions and Independence for Elders (LIFE) Study, a randomized clinical trial of lifestyle interventions to preserve mobility in older adults. SETTING: Eight U.S. academic medical centers. PARTICIPANTS: Of 1,635 sedentary community-dwelling older adults enrolled in LIFE, 1,574 completed baseline physical function screening including the MAT-sf, with baseline scores ranging from 30.2 (low function) to 69.8 (high function) on a scale from 30 to 80. MEASUREMENTS: Number of hospitalizations and time to first hospitalization, adjusted for age, sex, race, living alone, clinical site, baseline comorbidities, number of prescription medications, and cognition. RESULTS: Of the 1,557 participants with data regarding hospitalization status, 726 (47%) had at least 1 hospitalization; 78% of these had 1 or 2 hospitalizations. For every 10-point lower MAT-sf score, the rate of all hospitalizations was 19% higher in those with lower scores (adjusted rate ratio=1.20, 95% confidence interval (CI)=1.08-1.32, p<.001). Lower baseline MAT-sf scores were also associated with greater risk of first hospitalization (adjusted hazard ratio=1.20, 95% CI=1.09-1.32, p<.01, per 10-point lower MAT-sf score). CONCLUSION: Low MAT-sf scores identify older adults at risk of hospitalization; further study is needed to test interventions to reduce hospitalizations in these individuals.

Effect of Exercise Modality During Weight Loss on Bone Health in Older Adults With Obesity and Cardiovascular Disease or Metabolic Syndrome: A Randomized Controlled Trial.

The objective of this study was to determine the ability of either aerobic or resistance training to counter weight-loss-associated bone loss in older adults. There were 187 older adults (67 years, 70% women, 64% white) with obesity (BMI = 34.5 ± 3.7 kg/m2 ) and cardiovascular disease and/or metabolic syndrome who were randomized to participate in an 18-month, community-based trial, with a follow-up assessment at 30 months. Intervention arms included: weight loss alone (WL; 7% to 10% baseline weight), WL plus aerobic training (WL + AT), and WL plus resistance training (WL + RT), as well as DXA-acquired total hip, femoral neck, and lumbar spine areal bone mineral density (aBMD), and trabecular bone score (TBS). Biomarkers of bone turnover (procollagen type 1 N-terminal propeptide, C-terminal telopeptide of type 1 collagen) were measured at baseline, 6, 18, and 30 (aBMD and TBS only) months. CT-acquired hip and spine volumetric BMD (vBMD), cortical thickness, and bone strength were measured in a subset at baseline (n = 55) and 18 months. Total hip aBMD was reduced by 2% in all groups at 18 months, with a primary analysis showing no significant treatment effects for any DXA, biomarker, or CT outcome. After adjustment for WL and follow-up at 30 months, secondary analyses revealed that total hip [-0.018 (-0.023 to -0.012) g/cm2 versus -0.025 (-0.031 to -0.019) g/cm2 ; p = 0.05] and femoral neck [-0.01 (-0.009 to 0.008) g/cm2 versus -0.011 (-0.020 to -0.002) g/cm2 ; p = 0.06] aBMD estimates were modestly attenuated in the WL + RT group compared with the WL group. Additionally, lumbar spine aBMD was increased in the WL [0.015 (0.007 to 0.024) g/cm2 ] and the WL + RT [0.009 (0.000 to 0.017) g/cm2 ] groups compared with the WL + AT [-0.003 (-0.012 to 0.005)g/cm2 ] group; both p ≤ 0.01. Community-based exercise does not prevent bone loss during active WL in older adults; however, adding RT may help minimize long-term hip bone loss. © 2018 American Society for Bone and Mineral Research.

Self-reported mobility as a preoperative risk assessment tool in older surgical patients compared to the American College of Surgeons National Surgical Quality Improvement Program.

BACKGROUND: The American College of Surgeons National Surgical Quality Improvement Program (NSQIP®) developed a surgical risk calculator using data from 1.4 million patients and including 1557 unique Current Procedural Terminology (CPT) codes. Although this calculator demonstrated excellent performance in predicting postoperative mortality, morbidity, and six surgical complications, it was not developed specifically for use in older surgical patients who have worse surgical outcomes and additional unique risk factors compared to younger adults. We aimed to test the ability of a simple self-reported mobility tool to predict postoperative outcomes in the older surgical population compared to the NSQIP. METHODS: We used data from a prospective cohort study that enrolled 197 older surgical patients (≥ 69 years) undergoing various elective surgeries and assessed 30-day surgical outcomes. Statistical models included data from the Mobility Assessment Tool-short form (MAT-sf) alone, covariates alone, and MAT-sf data and covariates. We used leave-one-out (LOO) cross-validation of the models within our cohort and compared their performance for predicting postoperative outcomes against the NSQIP calculator based on receiver operating characteristic area under the curve (ROC AUC). RESULTS: Patients with poor self-reported mobility experienced higher rates of postoperative complications and nursing home placement. There was no difference in performance between any of our models and the NSQIP calculator (p > 0.1), with AUC between 0.604 and 0.697 for predicting postoperative complications and 0.653 and 0.760 for predicting nursing home placement. All models also predicted a length of stay (LOS) similar to the actual LOS. CONCLUSION: Mobility assessment alone using MAT-sf can predict postoperative complications, nursing home placement, and LOS for older surgical patients, with accuracy comparable to that of the NSQIP calculator. The simplicity of this noninvasive risk assessment tool makes it an attractive alternative to the NSQIP calculator that requires 20 patient predictors and the planned procedure, or CPT code to predict the chance that patients will have 15 different adverse outcomes following surgery.

Self- vs proxy-reported mobility using the mobility assessment tool-short form in elderly preoperative patients.

BACKGROUND: Mobility is fundamental to maintenance of an independent lifestyle and can predict clinical outcomes after health events among older individuals. However, certain clinical situations do not accommodate physical or self-assessments. This investigation examines whether proxy-reported assessments of function using the Mobility Assessment Tool-short (MAT-sf) form is a reliable alternative. METHODS: Sixty-six older persons (≥ age 70) and their proxies were enrolled. Proxies rated patients' mobility using the MAT-sf as did the patients. RESULTS: The mean age of patients was 78.4 yr. (±6.2); 44% were female and 86% were white. Spouses made up 55% of the proxies, while 39% were children/in-laws. The correlation coefficient between patient and proxy MAT-sf scores was 0.81 (p < 0.01); a comparison of the slope of the regression line relating patient- and proxy-reported MAT-sf to a line of identity showed disagreement (p < 0.01), with proxy reports underreporting patient responses by 8.3% in lower mobility patients. The intra-class correlation characterizing agreement between repeated proxy reports 0.81. CONCLUSION: Proxy reports of mobility in older patients have good reliability. However, in patients with poor mobility, the proxies tend to report a lower mobility than the patients.

Gait Speed and Mobility Disability: Revisiting Meaningful Levels in Diverse Clinical Populations.

OBJECTIVES: To investigate the heterogeneity of clinically meaningful levels of gait speed relative to self-reported mobility disability (SR-MD). DESIGN: Five longitudinal studies with older adults in different health states (onset of acute event, presence of chronic condition, sedentary, community living) were used to explore the relationship between gait speed and SR-MD. SETTING: Lifestyle Interventions and Independence for Elders Pilot (LIFE-P), LIFE, Trial of Angiotensin-Converting Enzyme Inhibition and Novel Cardiovascular Risk Factors (TRAIN), Baltimore Hip Fracture Study (BHS2), Invecchiare in Chianti (InCHIANTI). PARTICIPANTS: Individuals aged 65 and older (N=3,540): sedentary, community dwelling (LIFE-P/LIFE), with hip fracture (BHS2), random population-based sample (InCHIANTI), high cardiovascular risk (TRAIN). MEASUREMENTS: Usual-pace gait speed across 3 to 4 m and SR-MD, defined as inability to walk approximately 1 block or climb 1 flight of stairs. RESULTS: The mean gait speed of participants without SR-MD was greater than 1.0 m/s in InCHIANTI and TRAIN, 0.79 m/s in LIFE-P/LIFE, and 0.46 m/sec in BHS2. Of individuals with SR-MD, mean gait speed was 0.08 m/s slower in LIFE-P/LIFE, 0.19 m/s slower in TRAIN, 0.22 m/s slower in BHS2, and 0.36 m/s slower in InCHIANTI. The optimal gait speed cutpoint for minimizing SR-MD misclassification rates ranged from 0.3 m/s in BHS2 to 1.0 m/s in TRAIN. In longitudinal analyses, development of SR-MD was dependent on initial gait speed and change in gait speed (p<.001). CONCLUSION: The relationship between absolute levels of gait speed and SR-MD may be context specific, and there may be variations between populations. Across diverse clinical populations, clinical interpretations of how change in usual pace gait speed relates to development of SR-MD depend on where on the gait speed continuum change occurs.

Maintenance of Physical Function 1 Year After Exercise Intervention in At-Risk Older Adults: Follow-up From the LIFE Study.

Background: Structured physical activity interventions delay the onset of disability for at-risk older adults. However, it is not known if at-risk older adults continue to participate in physical activity or maintain mobility benefits after cessation of structured intervention. Methods: One thousand six hundred and thirty-five sedentary men and women aged 70-89 years with Short Physical Performance Battery (SPPB) scores of 9 or less and able to walk 400 m were randomized to a structured, moderate-intensity physical activity (PA) program consisting of center-based (twice/week) and home-based (three to four times per week) aerobic, resistance, and flexibility training or a health education (HE) program combined with upper extremity stretching. Results: Most of the participants (88% of HE and 87% of PA) returned for a follow-up visit (POST) 1 year after cessation of formal intervention. The HE group reported about 1-hour less activity per week than the PA group at end of intervention (LAST TRIAL; -68.9; 95% confidence interval [CI] = -86.5 to -51.3) but similar weekly activity at POST (-13.5; 95% CI = -29.5 to 2.47). SPPB did not differ between the two groups at LAST TRIAL (-0.06; 95% CI = -0.31 to 0.19) nor POST (-0.18; 95% CI = -0.45 to 0.088). Conclusions: Although sedentary at-risk older adults increased their physical activity during a structured physical activity intervention, they did not continue at this level following the cessation of intervention. Future exercise interventions need to include novel methods to support older adults in continued physical activity following structured interventions.

Evaluating Accelerometry Thresholds for Detecting Changes in Levels of Moderate Physical Activity and Resulting Major Mobility Disability.

Background: An important decision with accelerometry is the threshold in counts per minute (CPM) used to define moderate to vigorous physical activity (MVPA). We explore the ability of different thresholds to track changes in MVPA due to a physical activity (PA) intervention among older adults with compromised function: 760 CPM, 1,041 CPM, and an individualized threshold. We also evaluate the ability of change in accelerometry and self-reported PA to attenuate treatment effects on major mobility disability (MMD). Methods: Data from a week of hip worn accelerometers and self-reported PA data (30-day recall) were examined from baseline, 6-, 12-, and 24-months of follow-up on 1,528 older adults. Participants were randomized to either PA or Health Education (HE). MMD was objectively defined by loss of ability to walk 400 m during the follow-up. Results: The three thresholds yielded similar and higher levels of MVPA for PA than HE (p < .001), however, this difference was significantly attenuated in participants with lower levels of physical function. Self-reported PA that captured both walking and strength training totally attenuated the intervention effect for MMD, an 18% reduction to a 3% increase. Accelerometer CPMs showed less attenuation of the intervention effect. Conclusions: Accelerometry assessment within the LIFE study was not sensitive to change in level in physical activity for older adults with very low levels of physical function. A combination of self-report and objective measures are recommended for use in physical activity intervention studies of the elderly; limitations of accelerometry deserve closer attention.