Publications

Dual-energy X-ray absorptiometry (DXA) derived measures of lean mass demonstrate strong associations with magnetic resonance imaging (MRI) derived measures of muscle volume (MV) in cross-sectional studies, however, few studies have compared changes in response to an intervention. The purpose of this study was to determine the accuracy of DXA at detecting changes in lean mass, using MRI-derived MV as a reference standard. 10 male and 16 female subjects (29.2 +/- 9.5 years) underwent DXA and MRI scans before and after a 10-week resistance training intervention. DXA thigh lean mass was compared to MRI mid-thigh MV, and percent change in size was compared between MRI and DXA. There was a strong correlation between measures cross-sectionally (r = 0.89) in agreement with previous investigations. However, there was a modest correlation of percentage change over time between methods (r = 0.49). Bland-Altman plots revealed that the amount of random error increased as the magnitude of the change from baseline increased. DXA measures of change in lean mass were modestly associated with MRI measures of change in MV. While there are several advantages to using DXA for the measurement of lean mass, the inability to accurately detect changes over time calls into question its use in clinical trials.

OBJECTIVES: To examine loss of community-dwelling status 9 months after hospitalization for high-acuity emergency general surgery (HA-EGS) disease among older Americans. DESIGN: Retrospective analysis of claims data. SETTING: US communities with Medicare beneficiaries. PARTICIPANTS: Medicare beneficiaries age 65 years or older hospitalized urgently/emergently between January 1, 2015, and March 31, 2015, with a principal diagnosis representing potential life or organ threat (necrotizing soft tissue infections, hernias with gangrene, ischemic enteritis, perforated viscus, toxic colitis or gastroenteritis, peritonitis, intra-abdominal hemorrhage) and an operation of interest on hospital days 1 or 2 (N = 3319). MEASUREMENTS: Demographic characteristics (age, race, and sex), comorbidities, principal diagnosis, complications, and index hospitalization disposition (died; discharged to skilled nursing facility [SNF], long-term acute care [LTAC], rehabilitation, hospice, home (with or without services), or acute care hospital; other) were measured. Survivors of index hospitalization were followed until December 31, 2015, on mortality and community-dwelling status (SNF/LTAC vs not). Descriptive statistics, Kaplan-Meier plots, and chi(2) tests were used to describe and compare the cohort based on disposition. A multivariable logistic regression model, adjusted for age, sex, comorbidities, complications, and discharge disposition, determined independent predictors of loss of community-dwelling status at 9 months. RESULTS: A total of 2922 (88%) survived index hospitalization. Likelihood of discharge to home decreased with increasing age, baseline comorbidities, and in-hospital complications. Overall, 418 (14.3%) HA-EGS survivors died during the follow-up period. Among those alive at 9 months, 10.3% were no longer community dwelling. Initial discharge disposition to any location other than home and three or more surgical complications during index hospitalization were independent predictors of residing in a SNF/LTAC 9 months after surviving HA-EGS. CONCLUSION: Older Americans, known to prioritize living in the community, will experience substantial loss of independence due to HA-EGS. Long-term expectations after surviving HA-EGS must be framed from the perspective of the outcomes that older patients value the most. Further research is needed to examine the quality-of-life burden of EGS survivorship prospectively. J Am Geriatr Soc 67:2289-2297, 2019.

BACKGROUND AND PURPOSE: Muscle weakness predisposes older adults to a fourfold increase in functional limitations and has previously been associated with reduced motor cortex excitability in aging adults. The purpose of this study was to determine whether a single session of anodal transcranial direct current stimulation (tDCS) of the motor cortex would increase elbow flexion muscle strength and electromyographic (EMG) amplitude in very old individuals. METHODS: Eleven very old individuals-85.8 (4.3) years-performed 3 maximal isometric elbow flexion contractions before and after 20 minutes of sham or anodal tDCS on different days. Order of stimulation was randomized, and the study participants and investigators were blinded to condition. In addition, voluntary activation capacity of the elbow flexors was determined by comparing voluntary and electrically evoked forces. RESULTS: Anodal tDCS did not alter muscle strength or EMG activity in comparison to sham stimulation. Elbow flexion voluntary activation capacity was very high among the study participants: 99.3% (1.8%). CONCLUSION: Contrary to our hypothesis, we observed no effect of anodal tDCS and no impairment in elbow flexor voluntary activation capacity in the very old. Whether anodal tDCS would exert a positive effect and support our initial hypothesis in another muscle group that does exhibit impairments in voluntary activation in older adults is a question that is still to be addressed.

OBJECTIVES: Impairments in specific tasks that are necessary for independent living may identify future self-care limitations, and the use of time-varying covariates can better capture the fluidity in functional capacity trajectories over time. The purpose of this study was to determine the associations between individual instrumental activities of daily living (IADL) impairments and time to activities of daily living (ADL) disability for middle-aged and older adults in the United States. DESIGN: Longitudinal panel. SETTING: Detailed interviews that included physical, biological, and psychosocial measures were completed in person. The core interview was typically completed over the telephone. PARTICIPANTS: A nationally representative sample of 15,336 adults aged at least 50 years from the 2006 wave of the Health and Retirement Study was followed for 8 years. MEASURES: Ability to perform IADL and ADL were self-reported at each wave. Separate covariate-adjusted Cox models were used to examine the time-varying associations between individual IADL impairments and time to ADL disability. RESULTS: The presence of each IADL impairment was associated with a higher hazard ratio for an ADL disability for the following functions: 2.52 [95% confidence interval (CI) 2.35, 2.70] for grocery shopping, 1.91 (CI 1.77, 2.06) for preparing hot meals, 1.55 (CI 1.37, 1.76) for taking medications, 1.48 (CI 1.36, 1.61) for managing money, 1.41 (CI 1.27, 1.57) for using a telephone, and 1.38 (CI 1.29, 1.48) for using a map. CONCLUSIONS/IMPLICATIONS: Our findings provide insights into the disabling process by revealing how impairments in each IADL are differentially associated with time to ADL disability. Interventions aiming to retain function during aging should be informed by fluctuations in IADL performance and how specific IADL impairments may exacerbate functional capacity declines more so than others.

BACKGROUND: Measures of handgrip strength may show promise for detecting cognitive erosion during aging. OBJECTIVE: To determine the associations between lower handgrip strength and poorer cognitive functioning for aging Americans. METHODS: There were 13,828 participants aged at least 50 years from the 2006 wave of the Health and Retirement Study included and followed biennially for 8 years. Handgrip strength was assessed with a hand-held dynamometer and cognitive functioning was assessed with a modified version of the Mini-Mental State Examination. Participants aged 65 years with scores 7- 11 had a mild cognitive impairment, /=65 years with scores 8- 10 had a mild cognitive impairment,

OBJECTIVES: The primary purpose of this study was to determine the time-varying associations between decreased handgrip strength (HGS) and individual instrumental activities of daily living (IADL) impairments for a nationally-representative sample of aging adults in the United States. DESIGN: Longitudinal-Panel. SETTING: Detailed interviews were completed in person and core interviews were typically completed over the telephone. PARTICIPANTS: A total of 15,336 participants aged at least 50 years who participated in the 2006 wave of the Health and Retirement Study were followed biennially for 8-years. MEASUREMENTS: A hand-held dynamometer assessed HGS and performance in IADLs were self-reported. RESULTS: Every 5-kilogram decrease in HGS was associated with an increased odds ratio for the following IADL impairments: 1.11 (95% confidence interval (CI): 1.09, 1.13) for using a map, 1.10 (CI: 1.07, 1.12) for grocery shopping, 1.09 (CI: 1.05, 1.14) for taking medications, 1.07 (CI: 1.05, 1.09) for preparing hot meals, 1.06 (CI: 1.04, 1.08) for managing money, and 1.05 (CI: 1.02, 1.09) for using a telephone. CONCLUSIONS: Decreased HGS was associated with each IADL impairment, and slightly different associations were observed in individual IADL tasks for aging adults in the United States. Our findings suggest that decreased HGS, which is reflective of reduced function of the neuromuscular system, is associated with diminished performance in autonomous living tasks during aging. Losses in HGS may lead to the development of an IADL impairment. Therefore, health-care providers working with aging adults should utilize measures of HGS as a screening tool for identifying future deficits in neuromuscular functioning. Interventions designed to preserve IADLs in aging adults should also include measures of HGS for detecting early changes in IADL capacity, and intervening at the onset of HGS declines may help aging adults retain their ability to live autonomously.

STUDY DESIGN: Between-session reliability of a magnetic resonance imaging (MRI) based experimental technique to quantify lumbar inter-vertebral motion in humans. PURPOSE: We have developed a novel, dynamic, MRI-based approach for quantifying in vivo lumbar inter-vertebral motion. In this study, we present the protocol's reliability results to quantify inter-vertebral spine motion. OVERVIEW OF LITERATURE: Morphometric studies on intervertebral displacements using static, supine MRI and quantification of dynamic spine motion using different X-ray based radiography techniques are commonly found in the literature. However, reliability testing of techniques assessing real-time lumbar intervertebral motion using weight-bearing MRI has rarely been reported. METHODS: Ten adults without a history of back pain performed a side-bending task on two separate occasions, inside an open-MRI, in a weight-bearing, upright position. The images were acquired during the task using a dynamic magnetic resonance (MR) sequence. The MRI imaging space was externally calibrated before the study to recreate the imaging volume for subsequent use in an animation software. The dynamic MR images were processed to create side-bending movement animations in the virtual environment. Participant-specific three-dimensional models were manually superimposed over vertebral image silhouettes in a sequence of image frames, representing the motion trials. Inter-vertebral axes and translation and rotational displacements of vertebrae were quantified using the animation software. RESULTS: Quantification of inter-vertebral rotations and translations shows high reliability. Between-session reliability results yielded high values for the intra-class correlation coefficient (0.86-0.93), coefficient of variation (13.3%-16.04%), and Pearson's correlation coefficients (0.89-0.98). CONCLUSIONS: This technique may be developed further to improve its speed and accuracy for diagnostic applications, to study in vivo spine stability, and to assess outcomes of surgical and non-surgical interventions applied to manage pathological spine motion.

BACKGROUND: Motoric cognitive risk (MCR) syndrome is characterized by slow gait and memory complaints that could be used to predict an increased risk of dementia. This study aims to determine the MCR syndrome and its risk factors among low-income (B40) older adults in Malaysia. METHODS: Data from TUA cohort study involving 1366 older adults (aged 60 years and above) categorized as low-income were analysed, for risk of MCR syndrome based on defined criteria. Chi-square analysis and independent t test were employed to examine differences in socioeconomic, demographic, chronic diseases and lifestyle factors between MCR and non-MCR groups. Risk factors of MCR syndrome were determined using hierarchical logistic regression. RESULTS: A total of 3.4% of participants fulfilled the criteria of MCR syndrome. Majority of them were female (74.5%, p = 0.001), single/widow/widower/divorced (55.3%, p = 0.002), living in rural area (72.3%, p = 0.011), older age (72.74 +/- 7.08 year old, p 0.001) and had lower years of education (3.26 +/- 2.91 years, p = 0.001) than non-MCR group. After adjustment for age, gender and years of education, participants living in rural area (Adjusted OR = 2.19, 95% CI = 1.10-4.35, p = 0.026), with obesity (Adjusted OR = 3.82, 95% CI = 1.70-8.57, p = 0.001), diabetes (Adjusted OR = 2.04, 95% CI = 1.01-4.11, p = 0.046), heart disease (Adjusted OR = 2.50, 95% CI = 1.00-6.20, p = 0.049) and cancer (Adjusted OR = 6.57, 95% CI = 1.18-36.65, p = 0.032) were associated with increased risk of MCR syndrome. CONCLUSION: Only 3.4% of older adults from low-income group were identified as having MCR syndrome. Women, those living in rural areas, had obesity, diabetes, heart disease and cancer were more likely to have MCR syndrome. Further investigation on MCR as a predementia syndrome will help in development of preventive strategies and interventions to reduce the growing burden of dementia, especially among individuals with low socioeconomic status.

The capacity to move is essential for independence and declines with age. Limitations in mobility impact  35% of adults over 70 and the majority of adults over 85. These limitations are highly associated with disability, dependency, and survival. More than 25-years ago the term "sarcopenia" was coined to highlight the age-related loss of muscle mass and strength with the assumption being that sarcopenia led to limitations in mobility. However, contrary to expectations, recent findings clearly indicate these variables only modestly explain limitations in mobility. One likely reason the current sarcopenia variables of muscle mass and strength do not discriminate, or predict, mobility limitations well is because they are heavily influenced by musculoskeletal mechanisms and do not incorporate measures reflective of the central neural control of mobility. Unfortunately, the precise central neural changes associated with aging that lead to decreased mobility are poorly understood. This knowledge gap has hampered the development of effective interventions for mobility limitations and the subsequent reduction of major functional disability for older adults. Here, we discuss the potential role of the motor control circuit of the dorsal basal ganglia as well as dopaminergic function in age-related reductions in mobility.

This cross-sectional study compares voluntary neural activation of lower extremity muscles in clinically weak older adults vs stronger older adults.