The 39 million Americans over the age of 65 accounted for 13% of the United States population in 2008. The absolute and relative number of older adults (age ≥65 years) is starting to rise rapidly as ...the baby boomers begin to turn 65. The prevalence of mobility disability in older (30%) adults is high and is a large public health concern as disability is associated with lower quality of life, higher health care costs, and mortality. There are many reasons for age-related disability, however; the role of changes to skeletal muscle remains unclear. Fatigue is also an independent risk factor for physical disability and is common among older adults. This dissertation aimed to provide novel insight into the association between skeletal muscle energetics, changes in regional body composition and physical function and fatigability in older adults. First, decreases in visceral and intermuscular adipose tissue as well as an increase in muscle density, a marker of intramyocellular fat, following a weight-loss and physical activity intervention, were shown to be related to improved physical performance. Next, mitochondrial function, measured by phosphocreatine recovery (mM ATP/s) in the quadriceps following an exercise-bout using 31P magnetic resonance spectroscopy, was examined in relation to walking performance (time to walk 400m) and perceived performance fatigability (perceived exertion following a 0.67ms treadmill-walk). Mitochondrial function was related to walking performance in higher functioning older adults and older adults who were functionally impaired but able to ambulate 400m without discomfort. Mitochondrial function was also significantly lower in those with high compared to low fatigability. This research provides novel evidence that function can be improved by targeting specific fat depots and mitochondrial function may impact overall function and fatigability. These findings could have large public health implications, as the etiology of age-related disability in regard to skeletal muscle is unclear. The prevalence of disability among older adults is quite high and is associated with increased health care costs and mortality. Clinicians, public health professionals and researchers can use this information to design interventions, treatments and future research studies focused on skeletal muscle to improve function in older adults.
Background Aging is associated with central fat redistribution and skeletal muscle decline, yet the relationships of tissue compartments with heart failure (HF) remain incompletely characterized. We ...assessed the contribution of body composition to incident HF in elders. Methods and Results Participants from 2 older cohorts who completed dual-energy X-ray absorptiometry (DEXA) and, in one cohort, computed tomography were included. We evaluated associations with incident HF for DEXA principal components (PCs) and total lean, appendicular lean, total fat and trunk fat mass; and for computed tomography measures of abdominal visceral and subcutaneous fat, thigh muscle, intermuscular fat area and thigh muscle density. DEXA analysis included 3621, and computed tomography analysis 2332 participants. During median follow-up of 11.8 years, 927 participants developed HF. DEXA principal components showed no relationship with HF. After adjustment for height, weight, and cardiovascular risk factors, total lean mass was near significantly associated with higher HF (hazard ratio HR, 1.25 per SD 1.00-1.56), whereas total fat mass and thigh muscle density were significantly related to lower HF (HR, 0.82 0.68-0.99 and HR, 0.87 0.78-0.97, respectively). Patterns were similar for HF subtypes. The relationships with HF for total lean and fat mass were attenuated after adjusting for intercurrent atrial fibrillation or excluding high natriuretic peptide levels. Conclusions Total lean mass was positively associated, while total fat mass and thigh muscle density were inversely associated, with incident HF. These findings highlight the limitations of DEXA for assessment of HF risk in elders and support the preeminence of computed tomography-measured skeletal muscle quality over mass as a determinant of HF incidence.
BACKGROUND
The Sarcopenia Definitions and Outcomes Consortium (SDOC) is a collaborative initiative seeking to develop and evaluate cut‐points for low muscle strength and lean mass that predict an ...increased risk for slowness (usual walking speed <.8 m/s) among older adults.
OBJECTIVES
The goal of the present study was to provide clinicians and researchers with an understanding of the diagnostic implications of using SDOC variables and cut‐points in mobility‐limited older adults. Using data from older individuals with specific conditions that render them at increased risk for mobility limitation, we evaluated the performance characteristics (ie, sensitivity and specificity) of five putative sarcopenia parameters and then compared these values with previously recommended diagnostic criteria for sarcopenia.
DESIGN
Retrospective analysis of six randomized controlled trials enriched in persons at risk for mobility limitation.
SETTING
National and international geriatric clinical research centers.
PARTICIPANTS
A total of 925 mobility‐limited older adults (≥55 years of age; 58% women) were included in the analysis.
MEASUREMENTS
The prevalence of low muscle strength and lean mass were assessed using five candidate metrics discriminative of slowness. Analyses of sensitivity and specificity were used to compare muscle weakness criteria with published diagnostics for sarcopenia.
RESULTS
Odds ratios (ORs) supported maximal grip strength (Grip max <35.5 and 20.0 in men and women, respectively) as the most discriminative of slowness in both men and women (OR = 3.66 and 3.53, respectively). More men (58%) than women (30%) fell below sex‐specific maximal grip cut‐points. When applying previously recommended sarcopenia component definitions in our population, we found that fewer individuals met those criteria (range = 6%‐32%).
CONCLUSION
A greater number of individuals fall below SDOC Grip max cut‐points compared with previous recommendations. Clinicians and researchers working with older adults may consider these thresholds as an inclusive means to identify candidates for low‐risk lifestyle promyogenic and function‐promoting therapies. J Am Geriatr Soc 68:1445‐1453, 2020.
See related editorial by Cesari et al in this issue
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