Development of a Novel Accelerometry-Based Performance Fatigability Measure for Older Adults.

INTRODUCTION: Efforts to study performance fatigability have been limited because of measurement constrains. Accelerometry and advanced statistical methods may enable us to quantify performance fatigability more granularly via objective detection of performance decline. Thus, we developed the Pittsburgh Performance Fatigability Index (PPFI) using triaxial raw accelerations from wrist-worn accelerometer from two in-laboratory 400-m walks. METHODS: Sixty-three older adults from our cross-sectional study (mean age, 78 yr; 56% women; 88% White) completed fast-paced ( n = 59) and/or usual-paced 400-m walks ( n = 56) with valid accelerometer data. Participants wore ActiGraph GT3X+ accelerometers (The ActiGraph LLC, Pensacola, FL) on nondominant wrist during the walking task. Triaxial raw accelerations from accelerometers were used to compute PPFI, which quantifies percentage of area under the observed gait cadence-versus-time trajectory during a 400-m walk to a hypothetical area that would be produced if the participant sustained maximal cadence throughout the entire walk. RESULTS: Higher PPFI scores (higher score = greater fatigability) correlated with worse physical function, slower chair stands speed and gait speed, worse cardiorespiratory fitness and mobility, and lower leg peak power (| ρ | = 0.36-0.61 from fast-paced and | ρ | = 0.28-0.67 from usual-paced walks, all P < 0.05). PPFI scores from both walks remained associated with chair stands speed, gait speed, fitness, and mobility, after adjustment for sex, age, race, weight, height, and smoking status; PPFI scores from the fast-paced walk were associated with leg peak power. CONCLUSIONS: Our findings revealed that the objective PPFI is a sensitive measure of performance fatigability for older adults and can serve as a risk assessment tool or outcome measure in future studies and clinical practice.

Sarcopenia Characteristics Are Associated with Incident Mobility Limitations in African Caribbean Men: The Tobago Longitudinal Study of Aging.

BACKGROUND: Sarcopenia varies by ethnicity, and has a major impact on health in older adults. However, little is known about sarcopenia characteristics in African ancestry populations outside the United States. We examined sarcopenia characteristics in 2,142 African Caribbean men aged 59.0 ± 10.4 years (range: 40-92 years) in Tobago, and their association with incident mobility limitations in those aged 55+ (n = 738). METHODS: Body mass index (BMI), grip strength, dual-x-ray absorptiometry (DXA) appendicular lean mass (ALM), and self-reported mobility limitations were measured at baseline, and 6 years later. Change in sarcopenia characteristics, including grip strength, grip strength/BMI, ALMBMI, and ALM/ht2, were determined. Foundations for the National Institutes of Health Sarcopenia Project (FNIH) and European Working Group for Sarcopenia in Older People 2 (EWGSOP2) cut-points were also examined. Odds ratios (OR) and 95% confidence intervals (CI) for mobility limitation were calculated using multivariable linear regression models adjusted for covariates. RESULTS: Overall, sarcopenia prevalence was quite low using the FNIH (0.3%) and EWGSOP2 (0.6%) operational cut-points, but was higher in those aged 75+ (2.1% [FNIH] and 3.7% [EWGSOP2]). Prevalence was also higher when based on "weakness", versus "low ALM." When sarcopenia markers were examined separately, baseline levels, but not changes, were associated with incident mobility limitations. Baseline grip strength/BMI was a particularly strong risk factor for incident mobility limitations (OR per SD: 0.50; 95% CI: 0.37-0.68). CONCLUSIONS: Our findings suggest that grip strength normalized to body mass, measured at one time point, may be a particularly useful phenotype for identifying African Caribbean men at risk for future mobility limitations.

Body Composition Remodeling and Incident Mobility Limitations in African Ancestry Men.

BACKGROUND: Mobility limitations are common, with higher prevalence in African Americans compared with whites, and are associated with disability, institutionalization, and death. Aging is associated with losses of lean mass and a shift to central adiposity, which are more pronounced in African Americans. We aimed to examine the association of body composition remodeling with incident mobility limitations in older men of African ancestry. METHODS: Seven-year changes in body composition were measured using peripheral quantitative computed tomography (pQCT) of the calf and whole-body dual x-ray absorptiometry (DXA) in 505 African ancestry men aged ≥60 years and free of self-reported mobility limitations at baseline. Self-reported incident mobility limitations were assessed at 7-year follow-up. Odds of developing mobility limitations associated with baseline and change in body composition were quantified using separate logistic regression models. RESULTS: Seventy-five men (14.9%) developed incident mobility limitations over 6.2 ± 0.6 years. Baseline body composition was not associated with incident mobility limitations. After adjustment for covariates, gaining total and intermuscular fat were associated with incident mobility limitations (odds ratio [OR]: 1.60; 95% confidence interval [CI]: 1.21-2.13; OR: 1.51; 95% CI: 1.18-1.94). Changes in DXA lean mass were not related to mobility limitations; however, maintaining pQCT calf muscle area was protective against mobility limitations (OR: 0.65; 95% CI: 0.48-0.87). CONCLUSIONS: Increases in body fat, and particularly intermuscular fat, and decreases in calf skeletal muscle area were associated with a higher risk of developing mobility limitations. Our findings emphasize the importance of body composition remodeling in the development of mobility limitations among African ancestry men.