Sarcopenia Definition & Outcomes Consortium Defined Low Grip Strength in Two Cross-Sectional, Population-Based Cohorts

BACKGROUND/OBJECTIVES

The extent to which the prevalence of muscle weakness in the US population varies by different putative grip strength constructs developed by the Sarcopenia Definitions and Outcomes Consortium (SDOC) has not been described.

DESIGN

Cross-sectional analysis.

SETTING

Two nationally representative cohorts-2010 and 2012 waves of the Health and Retirement Survey and round 1 (2011) of the National Health and Aging Trends Survey.

PARTICIPANTS

Adults aged 65 years and older (n = 12,984) were included in these analyses.

MEASUREMENTS

We analyzed three constructs of muscle weakness developed by the SDOC, and found to be associated with mobility disability for men and women, respectively: absolute grip strength (<35.5 kg and 20 kg); grip strength standardized to body mass index (<1.05 kg/kg/m² and 0.79 kg/kg/m²); and grip strength standardized to weight (<0.45 kg/kg and 0.337 kg/kg). We estimated the prevalence of muscle weakness defined by each of these constructs in the overall older US population, and by age, sex, race, and ethnicity. We also estimated the sensitivity and specificity of each of the grip strength constructs to discriminate slowness (gait speed <0.8 m/s) in these samples.

RESULTS

The prevalence of muscle weakness ranged from 23% to 61% for men and from 30% to 66% for women, depending on the construct used. There was substantial variation in the prevalence of muscle weakness by race and ethnicity. The sensitivity and specificity of these measures for discriminating slowness varied widely, ranging from 0.30 to 0.92 (sensitivity) and from 0.17 to 0.88 (specificity).

CONCLUSIONS

The prevalence of muscle weakness, defined by the putative SDOC grip strength constructs, depends on the construct of weakness used. J Am Geriatr Soc 68:1438-1444, 2020.

Application of Cut-Points for Low Muscle Strength and Lean Mass in Mobility-Limited Older Adults

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.

Putative Cut-Points in Sarcopenia Components and Incident Adverse Health Outcomes: An SDOC Analysis

OBJECTIVES

Analyses performed by the Sarcopenia Definitions and Outcomes Consortium (SDOC) identified cut-points in several metrics of grip strength for consideration in a definition of sarcopenia. We describe the associations between the SDOC-identified metrics of low grip strength (absolute or standardized to body size/composition); low dual-energy x-ray absorptiometry (DXA) lean mass as previously defined in the literature (appendicular lean mass [ALM]/ht2 ); and slowness (walking speed <.8 m/s) with subsequent adverse outcomes (falls, hip fractures, mobility limitation, and mortality).

DESIGN

Individual-level, sex-stratified pooled analysis. We calculated odds ratios (ORs) or hazard ratios (HRs) for incident falls, mobility limitation, hip fractures, and mortality. Follow-up time ranged from 1 year for falls to 8.8 ± 2.3 years for mortality.

SETTING

Eight prospective observational cohort studies.

PARTICIPANTS

A total of 13,421 community-dwelling men and 4,828 community-dwelling women. MEASUREMENTS Grip strength by hand dynamometry, gait speed, and lean mass by DXA.

RESULTS

Low grip strength (absolute or standardized to body size/composition) was associated with incident outcomes, usually independently of slowness, in both men and women. ORs and HRs generally ranged from 1.2 to 3.0 for those below vs above the cut-point. DXA lean mass was not consistently associated with these outcomes. When considered together, those who had both muscle weakness by absolute grip strength (<35.5 kg in men and <20 kg in women) and slowness were consistently more likely to have a fall, hip fracture, mobility limitation, or die than those without either slowness or muscle weakness.

CONCLUSION

Older men and women with both muscle weakness and slowness have a higher likelihood of adverse health outcomes. These results support the inclusion of grip strength and walking speed as components in a summary definition of sarcopenia. J Am Geriatr Soc 68:1429-1437, 2020.

Sarcopenia Definition: The Position Statements of the Sarcopenia Definition and Outcomes Consortium

OBJECTIVES

To develop an evidence-based definition of sarcopenia that can facilitate identification of older adults at risk for clinically relevant outcomes (eg, self-reported mobility limitation, falls, fractures, and mortality), the Sarcopenia Definition and Outcomes Consortium (SDOC) crafted a set of position statements informed by a literature review and SDOC's analyses of eight epidemiologic studies, six randomized clinical trials, four cohort studies of special populations, and two nationally representative population-based studies.

METHODS

Thirteen position statements related to the putative components of a sarcopenia definition, informed by the SDOC analyses and literature synthesis, were reviewed by an independent international expert panel (panel) iteratively and voted on by the panel during the Sarcopenia Position Statement Conference. Four position statements related to grip strength, three to lean mass derived from dual-energy x-ray absorptiometry (DXA), and four to gait speed; two were summary statements.

RESULTS

The SDOC analyses identified grip strength, either absolute or scaled to measures of body size, as an important discriminator of slowness. Both low grip strength and low usual gait speed independently predicted falls, self-reported mobility limitation, hip fractures, and mortality in community-dwelling older adults. Lean mass measured by DXA was not associated with incident adverse health-related outcomes in community-dwelling older adults with or without adjustment for body size.

CONCLUSION

The panel agreed that both weakness defined by low grip strength and slowness defined by low usual gait speed should be included in the definition of sarcopenia. These position statements offer a rational basis for an evidence-based definition of sarcopenia. The analyses that informed these position statements are summarized in this article and discussed in accompanying articles in this issue of the journal. J Am Geriatr Soc 68:1410-1418, 2020.

Identification of Sarcopenia Components That Discriminate Slow Walking Speed: A Pooled Data Analysis

BACKGROUND

The Sarcopenia Definitions and Outcomes Consortium (SDOC) sought to identify cut points for muscle strength and body composition measures derived from dual-energy x-ray absorptiometry (DXA) that discriminate older adults with slow walking speed. This article presents the core analyses used to guide the SDOC position statements.

DESIGN

Cross-sectional data analyses of pooled data.

SETTING

University-based research assessment centers.

PARTICIPANTS

Community-dwelling men (n = 13,652) and women: (n = 5,115) with information on lean mass by DXA, grip strength (GR), and walking speed.

MEASUREMENTS

Thirty-five candidate sarcopenia variables were entered into sex-stratified classification and regression tree (CART) models to agnostically choose variables and cut points that discriminate slow walkers (<0.80 m/s). Models with alternative walking speed outcomes were also evaluated (<0.60 and <1.0 m/s and walking speed treated continuously).

RESULTS

CART models identified GR/body mass index (GRBMI) and GR/total body fat (GRTBF) as the primary discriminating variables for slowness in men and women, respectively. Men with GRBMI of 1.05 kg/kg/m2 or less were approximately four times more likely to be slow walkers than those with GRBMI of greater than 1.05 kg/kg/m2 . Women with GRTBF of less than 0.65 kg/kg were twice as likely to be slow walkers than women with GRTBF of 0.65 kg/kg or greater. Models with alternative walking speed outcomes selected only functions of GR as primary discriminators of slowness in both men and women. DXA-derived lean mass measures did not consistently discriminate slow walkers.

CONCLUSION

GR with and without adjustments for body size and composition consistently discriminated older adults with slowness. CART models did not select DXA-based lean mass as a primary discriminator of slowness. These results were presented to an SDOC Consensus Panel, who used them and other information to develop the SDOC Position Statements. J Am Geriatr Soc 68:1419-1428, 2020.

Application of Selected Muscle Strength and Body Mass Cut Points for the Diagnosis of Sarcopenia in Men and Women With or at Risk for HIV Infection

BACKGROUND

Persons with HIV may experience greater mobility limitations than uninfected populations. Accurate tools are needed to identify persons at greatest risk of decline. We evaluated the performance of novel muscle weakness metrics (grip, grip/body mass index [BMI], grip/weight, grip/total body fat, grip/arm lean mass) and association with slowness and falls in older persons with or at risk for HIV infection as part of the work of the Sarcopenia Definitions and Outcomes Consortium (SDOC).

METHODS

We assessed the prevalence of sarcopenia among 398 men (200 HIV+, 198 HIV-) from the Multicenter AIDS Cohort Study and 247 women (162 HIV+, 85 HIV-) from the Women's Interagency HIV Study using previously validated muscle weakness metrics discriminative of slowness. Sensitivity and specificity were used to compare new muscle weakness and slowness criteria to previously proposed sarcopenia definitions.

RESULTS

The prevalence of muscle weakness ranged from 16% to 66% among men and 0% to 47% among women. Grip/BMI was associated with slowness among men with HIV only. Grip/BMI had low sensitivity (25%-30%) with moderate to high specificity (68%-89%) for discriminating of slowness; all proposed metrics had poor performance in the discrimination of slowness (area under the curve [AUC] < 0.62) or fall status (AUC < 0.56). The combination of muscle weakness and slowness was not significantly associated with falls (p ≥ .36), with a low sensitivity in identifying those sustaining one or more falls (sensitivity ≤ 16%).

DISCUSSION

Clinical utility of new sarcopenia metrics for identification of slowness or falls in men and women with or at risk for HIV is limited, given their low sensitivity.

A Case for Promoting Movement Medicine: Preventing Disability in the LIFE Randomized Controlled Trial

BACKGROUND

The movement profile of older adults with compromised function is unknown, as is the relationship between these profiles and the development of major mobility disability (MMD)-a critical clinical outcome. We first describe the dimensions of movement in older adults with compromised function and then examine whether these dimensions predict the onset of MMD.

METHODS

Older adults at risk for MMD (N = 1,022, mean age = 78.7 years) were randomized to receive a structured physical activity intervention or health education control. We assessed MMD in 6-month intervals (average follow-up of 2.2 years until incident MMD), with activity assessed at baseline, 6-, 12- and 24-month follow-up via accelerometry.

RESULTS

A principal components analysis of 11 accelerometer-derived metrics yielded three components representing lifestyle movement (LM), extended bouts of moderate-to-vigorous physical activity (MVPA), and stationary body posture. LM accounted for the greatest proportion of variance in movement (53%). Within health education, both baseline LM (HR = 0.74; 95% CI 0.62 to 0.88) and moderate-to-vigorous physical activity (HR = 0.69; 95% CI 0.54 to 0.87) were associated with MMD, whereas only LM was associated with MMD within physical activity (HR = 0.74; 95% CI 0.61 to 0.89). There were similar nonlinear relationships present for LM in both physical activity and health education (p < .04), whereby risk for MMD was lower among individuals with higher levels of LM.

CONCLUSIONS

Both LM and moderate-to-vigorous physical activity should be central in treatment regimens for older adults at risk for MMD.

TRIAL REGISTRATION

clinicaltrials.gov Identifier NCT01072500.

The Enabling Reduction of Low-Grade Inflammation in Seniors (ENRGISE) Pilot Study: Screening Methods and Recruitment Results

BACKGROUND

The Enabling Reduction of Low-grade Inflammation in Seniors (ENRGISE) Pilot Study is a multicenter randomized clinical trial examining the feasibility of testing whether omega-3 fish oil (ω-3) and the angiotensin receptor blocker losartan alone or in combination can reduce inflammation and improve walking speed in older adults with mobility impairment. We describe recruitment methods and results.

METHODS

Eligible participants were 70 years and older, had elevated interleukin-6 levels (2.5-30 pg/mL) and mobility impairment.

RESULTS

Of those who responded to recruitment, 83% responded to mailings. A total of 5,424 telephone screens were completed; of these, 2,011 (37.1%) were eligible for further screening. The most common reasons for ineligibility at the telephone screens were lack of mobility impairment or use of angiotensin receptor blockers or angiotensin-converting enzyme inhibitors (n=1.789). Of the 1,305 initial screening visits, 1,087 participants had slow gait speed (<1 m/s). Of these, 701 (64%) had elevated interleukin-6 and were eligible for second screening visits. Of the 582 second screening visits, 335 (57.6%) were eligible to be randomized. A total of 289 participants (96% of goal) were randomized: 180 in the ω-3 stratum (240% of goal); 43 in the losartan (57% of goal), and 66 in the combination (44% of goal). The telephone screen and first screening visit to randomization ratio was 19 to 1 and 4.5 to 1, respectively. The estimated cost of recruitment per randomized participant was $1,782.

CONCLUSION

Recruitment for ω-3 exceeded goals, but goals for the losartan and combination strata were not met due to the high proportion of participants taking angiotensin receptor blockers or angiotensin-converting enzyme inhibitors.

Establishing the Link Between Lean Mass and Grip Strength Cut Points With Mobility Disability and Other Health Outcomes: Proceedings of the Sarcopenia Definition and Outcomes Consortium Conference

BACKGROUND

Lack of consensus on how to diagnose sarcopenia has limited the ability to diagnose this condition and hindered drug development. The Sarcopenia Definitions and Outcomes Consortium (SDOC) was formed to develop evidence-based diagnostic cut points for lean mass and/or muscle strength that identify people at increased risk of mobility disability. We describe here the proceedings of a meeting of SDOC and other experts to discuss strategic considerations in the development of evidence-based sarcopenia definition.

METHODS

Presentations and panel discussions reviewed the usefulness of sarcopenia as a biomarker, the analytical approach used by SDOC to establish cut points, and preliminary findings, and provided strategic direction to develop an evidence-based definition of sarcopenia.

RESULTS

The SDOC assembled data from eight epidemiological cohorts consisting of 18,831 participants, clinical populations from 10 randomized trials and observational studies, and 2 nationally representative cohorts. In preliminary assessments, grip strength or grip strength divided by body mass index was identified as discriminators of risk for mobility disability (walking speed <0.8 m/s), whereas dual-energy X-ray absorptiometry-derived lean mass measures were not good discriminators of mobility disability. Candidate definitions based on grip strength variables were associated with increased risk of mortality, falls, mobility disability, and instrumental activities of daily living disability. The prevalence of low grip strength increased with age. The attendees recommended the establishment of an International Expert Panel to review a series of position statements on sarcopenia definition that are informed by the findings of the SDOC analyses and synthesis of literature.

CONCLUSIONS

International consensus on an evidence-based definition of sarcopenia is needed. Grip strength-absolute or adjusted for body mass index-is an important discriminator of mobility disability and other endpoints. Additional research is needed to develop a predictive risk model that takes into account sarcopenia components as well as age, sex, race, and comorbidities.

Long-term rates of change in musculoskeletal aging and body composition: findings from the Health, Aging and Body Composition Study

Musculoskeletal disorders are common among older people. Preventive strategies require understanding of age-related changes in strength, function and body composition, including how they interrelate. We have described, and examined associations between, 9-year changes in these parameters among 2917 Health, Aging and Body Composition Study participants (aged 70-79 years). Appendicular lean mass (ALM), whole body fat mass and total hip BMD were ascertained using DXA; muscle strength by grip dynamometry; and muscle function by gait speed. For each characteristic annualised percentage changes were calculated; measures of conditional change (independent of baseline) were derived and their interrelationships were examined using Pearson correlations; proportion of variance at 9-year follow-up explained by baseline level was estimated; and mean trajectories in relation to age were estimated using linear mixed models. Analyses were stratified by sex. Median [lower quartile, upper quartile] annual percentage declines were grip strength (1.5 [0.0, 2.9]), gait speed (2.0 [0.6, 3.7]), ALM (0.7 [0.1, 1.4]), fat mass (0.4 [- 1.1, 1.9]) and hip BMD (0.5 [0.0, 1.1]). Declines were linear for ALM and accelerated over time for other characteristics. Most conditional change measures were positively correlated, most strongly between ALM, fat mass and hip BMD (r > 0.28). Proportion of variation at follow-up explained by baseline was lower for grip strength and gait speed (39-52%) than other characteristics (69-86%). Strength and function declined more rapidly, and were less correlated between baseline and follow-up, than measures of body composition. Therefore, broader intervention strategies to prevent loss of strength and function in later life are required as those targeting body composition alone may be insufficient.

Application of SDOC Cut Points for Low Muscle Strength for Recovery of Walking Speed After Hip Fracture

BACKGROUND

Sarcopenia is often conceptualized as a precursor to loss of mobility, but its effect on recovery of mobility after a hip fracture is unknown. We determined the prevalence of low muscle strength (weakness) after hip fracture using putative sarcopenia metrics (absolute grip strength, and grip strength normalized to body mass index, total body fat, arm lean mass, and weight) identified by the Sarcopenia Definitions and Outcomes Consortium (SDOC).

METHODS

We examined two well-characterized hip fracture cohorts of community-dwelling older adults from the Baltimore Hip Studies (BHS). The prevalence of muscle weakness was assessed using the SDOC cut points compared to published definitions at 2 and 6 months postfracture. We assessed associations of 2-month weakness with 6-month walking speed <0.6 m/s and calculated the sensitivity and specificity in predicting lack of meaningful change in walking speed (change < 0.1 m/s) at 6 months.

RESULTS

Two hundred and forty-six participants (192 women; 54 men) were included; mean (SD) age of 81 (8) for women and 78 (7) for men. At 2 months, 91% women and 78% men exhibited slow walking speed (< 0.6 m/s). SDOC grip strength standardized by weight (<0.34 kg women, <0.45 kg men) was the most prevalent measure of weakness in men (74%) and women (79%) and provided high sensitivity in men (86%) and women (84%) predicting lack of meaningful change in walking speed at 6 months, although specificity was poor to moderate.

CONCLUSIONS

SDOC cut points for grip strength standardized to weight provided consistent indication of poor walking speed performance post-hip fracture.

Rationale and study design for lifestyle intervention in preparation for pregnancy (LIPP): A randomized controlled trial

INTRODUCTION

Maternal obesity increases neonatal risk for obesity and metabolic syndrome later in life. Prior attempts to break this intergenerational obesity cycle by limiting excessive gestational weight gain have failed to reduce neonatal adiposity. Alternatively, pre-conception lifestyle interventions may improve the in utero metabolic milieu during early pregnancy leading to improved fetal outcomes. This randomized controlled trial (RCT) is evaluating whether a lifestyle intervention to reduce weight and improve maternal metabolism in preparation for pregnancy (LIPP) attenuates neonatal adiposity, compared to standard medical advice.

MATERIAL AND METHODS

Overweight/class 1 obese women after a previous pregnancy, ~12 weeks postpartum, preparing for a subsequent pregnancy, will be block randomized (1:1) to either LIPP or standard of care in a parallel design. Randomization is stratified by lactation status and overweight vs. class 1 obesity. The LIPP program consists of intensive short-term weight loss followed by weight maintenance until conception using supervised exercise and a low glycemic Mediterranean diet.

PRIMARY OUTCOMES

Group differences in neonatal adiposity at birth assessed by PEA POD and placental mitochondrial lipid metabolism.

SECONDARY OUTCOMES

Group differences in maternal pregravid and gestational body composition, insulin sensitivity, β-cell function, fasting metabolic and inflammatory biomarkers, and overall quality of life. Exploratory outcomes include umbilical cord blood insulin resistance, lipid profile and inflammation.

DISCUSSION

This RCT will determine the efficacy of maternal weight loss prior to pregnancy on reducing neonatal adiposity. Findings may change standard obstetrical care by providing Level 1 evidence on lifestyle interventions improving neonatal outcomes for women planning for pregnancy.

CLINICAL TRIAL REGISTRATION

NCT03146156.

Comparative Effects of Angiotensin-Converting Enzyme Inhibitors and Angiotensin Receptor Blockers on Response to a Physical Activity Intervention in Older Adults: Results From the Lifestyle Interventions and Independence for Elders Study

BACKGROUND

Angiotensin-converting enzyme inhibitors (ACEis) and angiotensin receptor blockers (ARBs) may protect against aging-related decline. This study directly compared ACEis and ARBs on associations with risk of mobility disability in older adults when combined with a physical activity intervention.

METHODS

This was a secondary analysis of the Lifestyle Interventions and Independence for Elders (LIFE) trial. Participants aged 70-89 years were randomized to a physical activity or health education intervention. Outcomes included incident and persistent major mobility disability, injurious falls, short physical performance battery, and gait speed. For this analysis, only participants who reported ACEi or ARB use at baseline were included. Baseline differences between ACEi and ARB groups were adjusted for using inverse probability of treatment weights. Weighted Cox proportional hazard models and analysis of covariance models were used to evaluate the independent effects of medications and interaction effects with the intervention on each outcome.

RESULTS

Of 1,635 participants in the Lifestyle Interventions and Independence for Elders study, 796 used either an ACEi (496, 62.3%) or ARB (300, 37.7%). Compared with ACEi users, ARB users had 28% lower risk (hazard ratio [HR] = 0.72 [0.60-0.85]) of incident major mobility disability and 35% (HR = 0.65 [0.52-0.82]) lower risk of persistent major mobility disability whereas no interaction between medication use and intervention was observed. Risk of injurious falls and changes in short physical performance battery or gait speed were not different between ARB and ACEi users.

CONCLUSIONS

These results suggest that ARBs may protect from major mobility disability by other mechanisms than improving physical performance.

Circulating Interleukin-6 Is Associated with Skeletal Muscle Strength, Quality, and Functional Adaptation with Exercise Training in Mobility-Limited Older Adults

BACKGROUND

Human aging is characterized by a chronic, low-grade inflammation suspected to contribute to reductions in skeletal muscle size, strength, and function. Inflammatory cytokines, such as interleukin-6 (IL-6), may play a role in the reduced skeletal muscle adaptive response seen in older individuals.

OBJECTIVES

To investigate relationships between circulating IL-6, skeletal muscle health and exercise adaptation in mobility-limited older adults.

DESIGN

Randomized controlled trial.

SETTING

Exercise laboratory on the Health Sciences campus of an urban university.

PARTICIPANTS

99 mobility-limited (Short Physical Performance Battery (SPPB) ≤9) older adults.

INTERVENTION

6-month structured physical activity with or without a protein and vitamin D nutritional supplement.

MEASUREMENTS

Circulating IL-6, skeletal muscle size, composition (percent normal density muscle tissue), strength, power, and specific force (strength/CSA) as well as physical function (gait speed, stair climb time, SPPB-score) were measured pre- and post-intervention.

RESULTS

At baseline, Spearman's correlations demonstrated an inverse relationship (P<0.05) between circulating IL-6 and thigh muscle composition (r = -0.201), strength (r = -0.311), power (r = -0.210), and specific force (r = -0.248), and positive association between IL-6 and stair climb time (r = 0.256; P<0.05). Although the training program did not affect circulating IL-6 levels (P=0.69), reductions in IL-6 were associated with gait speed improvements (r = -0.487; P<0.05) in "higher" IL-6 individuals (>1.36 pg/ml). Moreover, baseline IL-6 was inversely associated (P<0.05) with gains in appendicular lean mass and improvements in SPPB score (r = -0.211 and -0.237, respectively).

CONCLUSIONS

These findings implicate age-related increases in circulating IL-6 as an important contributor to declines in skeletal muscle strength, quality, function, and training-mediated adaptation. Given the pervasive nature of inflammation among older adults, novel therapeutic strategies to reduce IL-6 as a means of preserving skeletal muscle health are enticing.

ICFSR Task Force Perspective on Biomarkers for Sarcopenia and Frailty

Biomarkers of frailty and sarcopenia are essential to advance the understanding of these conditions of aging and develop new diagnostic tools and effective treatments. The International Conference on Frailty and Sarcopenia Research (ICFSR) Task Force - a group of academic and industry scientists from around the world -- met in February 2019 to discuss the current state of biomarker development for frailty and sarcopenia. The D3Cr dilution method, which assesses creatinine excretion as a biochemical measure of muscle mass, was suggested as a more accurate measure of functional muscle mass than assessment by dual energy x-ray absorptiometry (DXA). Proposed biomarkers of frailty include markers of inflammation, the hypothalamic-pituitary-adrenal (HPA) axis response to stress, altered glucose insulin dynamics, endocrine dysregulation, aging, and others, acknowledging the complex multisystem etiology that contributes to frailty. Lack of clarity regarding a regulatory pathway for biomarker development has hindered progress; however, there are currently several international efforts to develop such biomarkers as tools to improve the treatment of individuals presenting these conditions.

Impact and Lessons From the Lifestyle Interventions and Independence for Elders (LIFE) Clinical Trials of Physical Activity to Prevent Mobility Disability

BACKGROUND

Walking independently is basic to human functioning. The Lifestyle Interventions and Independence for Elders (LIFE) studies were developed to assess whether initiating physical activity could prevent major mobility disability (MMD) in sedentary older adults.

METHODS

We review the development and selected findings of the LIFE studies from 2000 through 2019, including the planning phase, the LIFE-Pilot Study, and the LIFE Study.

RESULTS

The planning phase and the LIFE-Pilot provided key information for the successful implementation of the LIFE Study. The LIFE Study, involving 1635 participants randomized at eight sites throughout the United States, showed that compared with health education, the physical activity program reduced the risk of the primary outcome of MMD (inability to walk 400 m: hazard ratio = 0.82; 95% confidence interval = 0.69-0.98; P = .03), and that the intervention was cost-effective. There were no significant effects on cognitive outcomes, cardiovascular events, or serious fall injuries. In addition, the LIFE studies provided relevant findings on a broad range of other outcomes, including health, frailty, behavioral outcomes, biomarkers, and imaging. To date, the LIFE studies have generated a legacy of 109 peer-reviewed publications, 19 ancillary studies, and 38 independently funded grants and clinical trials, and advanced the development of 59 early career scientists. Data and biological samples of the LIFE Study are now publicly available from a repository sponsored by the National Institute on Aging (https://agingresearchbiobank.nia.nih.gov).

CONCLUSIONS

The LIFE studies generated a wealth of important scientific findings and accelerated research in geriatrics and gerontology, benefiting the research community, trainees, clinicians, policy makers, and the general public. J Am Geriatr Soc 68:872-881, 2020.

Associations of physical activity in detailed intensity ranges with body composition and physical function. a cross-sectional study among sedentary older adults

BACKGROUND

Physical activity is crucial to maintain older adults' health and functioning, but the health benefits of particular activity intensities remain unclear. The aim of this cross-sectional study was to peruse the distribution of physical activity, and to investigate the associations of particular physical activity intensities with body composition and physical function among older adults.

METHODS

The sample comprised of 293 community-dwelling sedentary or at most moderately active older adults (42% men, mean age 74 ± 4 years). Physical activity was measured with a hip-worn tri-axial accelerometer over seven consecutive days, and investigated in detailed intensity range and in categories of sedentary, light and moderate-to-vigorous activity. Fat percent and appendicular lean mass were measured with DXA. Physical function was assessed by six-minutes walking test (6-min walk), maximal walking speed over 10 m (10-m walk) and Short Physical Performance Battery (SPPB). Associations were estimated with partial correlation adjusted for sex and age.

RESULTS

Participants spent on average 602 min per day sedentary, 210 min in light activity and 32 min in moderate-to-vigorous activity. Light and moderate-to-vigorous activity were negatively associated with fat percent (r = - 0.360 and r = - 0.384, respectively, p < 0.001 for both), and positively with SPPB, 10-m walk and 6-min walk results (r = 0.145-0.279, p < 0.01, for light and r = 0.220-0.465, p < 0.001, for moderate-to-vigorous activity). In detailed investigation of the intensity range, associations of physical activity with fat percent, 6-min walk and 10-m walk were statistically significant from very light intensity activity onward, whereas significant associations between physical activity and SPPB were observed mostly at higher end of the intensity range. Sedentary time was positively associated with fat percent (r = 0.251, p < 0.001) and negatively with 6-min walk (r = - 0.170, p < 0.01).

CONCLUSION

Perusing the physical activity intensity range revealed that, among community-dwelling sedentary or at most moderately active older adults, physical activity of any intensity was positively associated with lower fat percent and higher walking speed over long and short distances. These findings provide additional evidence of the importance of encouraging older adults to engage in physical activity of any intensity. More intervention studies are required to confirm the health benefits of light-intensity activity.

AGS and NIA Bench-to Bedside Conference Summary: Osteoporosis and Soft Tissue (Muscle and Fat) Disorders

This report summarizes the presentations and recommendations of the eleventh annual American Geriatrics Society and National Institute on Aging research conference, "Osteoporosis and Soft Tissue (Muscle/Fat) Disorders," on March 11-12, 2019, in Bethesda, Maryland. Falls, fractures, and sarcopenia have a major impact on health in older adults, and they are interconnected by known risk factors. The link between osteoporosis, which is common in older adults, and the risk of falls is well known. Sarcopenia, the age-related decline in skeletal muscle mass and function, is also associated with an increased risk of falls and fractures because it reduces strength and leads to functional limitations. In addition to increasing the risk of falls, sarcopenia and osteoporosis can lead to frailty, reduced quality of life, morbidity, and mortality. The conference highlighted the impact of bone and soft tissue disorders on quality of life, morbidity, and mortality in older adults. Presenters described factors that contribute to these disorders; health disparities experienced by various subpopulations; and promising biological, pharmacologic, and behavioral interventions to prevent or treat these disorders. The workshop identified many research gaps and questions along with research recommendations that have the potential to enhance the prospect of healthy aging and improved quality of life for older adults. J Am Geriatr Soc 68:31-38, 2019.

Impact of Baseline Fatigue on a Physical Activity Intervention to Prevent Mobility Disability

OBJECTIVES

Our aim was to examine the impacts of baseline fatigue on the effectiveness of a physical activity (PA) intervention to prevent major mobility disability (MMD) and persistent major mobility disability (PMMD) in participants from the Lifestyle Interventions and Independence for Elders (LIFE) study.

DESIGN

Prospective cohort of individuals aged 65 years or older undergoing structured PA intervention or health education (HE) for a mean of 2.6 years.

SETTING

LIFE was a multicenter eight-site randomized trial that compared the efficacy of a structured PA intervention with an HE program in reducing the incidence of MMD.

PARTICIPANTS

Study participants (N = 1591) at baseline were 78.9 ± 5.2 years of age, with low PA and at risk for mobility impairment.

MEASUREMENTS

Self-reported fatigue was assessed using the modified trait version of the Exercise-Induced Feelings Inventory, a six-question scale rating energy levels in the past week. Responses ranged from 0 (none of the time) to 5 (all of the time). Total score was calculated by averaging across questions; baseline fatigue was based on the median split: 2 or higher = more fatigue (N = 856) and lower than 2 = less fatigue (N = 735). Participants performed a usual-paced 400-m walk every 6 months. We defined incident MMD as the inability to walk 400-m at follow-up visits; PMMD was defined as two consecutive walk failures. Cox proportional hazard models quantified the risk of MMD and PMMD in PA vs HE stratified by baseline fatigue adjusted for covariates.

RESULTS

Among those with higher baseline fatigue, PA participants had a 29% and 40% lower risk of MMD and PMMD, respectively, over the trial compared with HE (hazard ratio [HR] for MMD = .71; 95% confidence interval [CI] = .57-.90; P = .004) and PMMD (HR = .60; 95% CI = .44-.82; P = .001). For those with lower baseline fatigue, no group differences in MMD (P = .36) or PMMD (P = .82) were found. Results of baseline fatigue by intervention interaction was MMD (P = .18) and PMMD (P = .05).

CONCLUSION

A long-term moderate intensity PA intervention was particularly effective at preserving mobility in older adults with higher levels of baseline fatigue. J Am Geriatr Soc 68:619-624, 2020.

Association between Pre-Intervention Physical Activity Level and Treatment Response to Exercise Therapy in Persons with Knee Osteoarthritis - An Exploratory Study

Objective

Examine whether pre‐intervention physical activity (PA) level is associated with achieving a positive treatment response of pain and/or function improvement after a 12‐week exercise intervention in participants with knee osteoarthritis (OA).

Methods

We performed a secondary analysis of a randomized, single‐blind comparative effectiveness trial showing similar treatment effects between Tai Chi mind‐body exercise and standard physical therapy intervention for knee OA. Baseline PA was assessed by a Community Healthy Activities Model Program for Seniors (CHAMPS) questionnaire and, in a subsample, by tri‐axial accelerometers. The Outcome Measures in Rheumatoid Arthritis Clinical Trials–Osteoarthritis Research Society International (OMERACT‐OARSI) dichotomous responder criteria was used for clinically meaningful improvement at follow‐up. Associations between baseline self‐reported PA by the CHAMPS questionnaire and outcomes of responders vs. nonresponders (reference group) were assessed using logistic regressions, adjusting for demographic covariates. We compared objectively measured PA by accelerometry between responders vs. nonresponders using Wilcoxon tests.

Results

Our sample consisted of 166 participants with knee OA who completed both baseline and 12‐week postintervention evaluations: mean age 60.7 year (SD 10.5), body mass index 32.4 kg/m² (6.9), 119 (72%) women, and 138 (83%) OMERACT‐OARSI responders. Neither time spent in total PA [odds ratio (OR) 1.00; 95% confidence interval (CI) 0.96, 1.03] nor time in moderate‐to‐vigorous PA (OR 1.01; 95% CI 0.93, 1.09) at pre‐intervention were associated with being a responder. Similar findings were observed in 42 accelerometry sub‐cohort participants.

Conclusion

Pre‐intervention PA levels (subjective report or objective measurement) were not associated with individuals achieving favorable treatment outcomes after a 12‐week exercise intervention, which suggests that regardless of pre‐intervention PA level, individuals will likely benefit from structured exercise interventions.

Mitochondrial DNA Sequence Variants Associated With Blood Pressure Among 2 Cohorts of Older Adults

Background

Age‐related changes in blood pressure are associated with a variety of poor health outcomes. Genetic factors are proposed contributors to age‐related increases in blood pressure, but few genetic loci have been identified. We examined the role of mitochondrial genomic variation in blood pressure by sequencing the mitochondrial genome.

Methods and Results

Mitochondrial DNA (mtDNA) data from 1755 participants from the LIFE (Lifestyle Interventions and Independence for Elders) studies and 788 participants from the Health ABC (Health, Aging, and Body Composition) study were evaluated using replication analysis followed by meta‐analysis. Participants were aged ≥69 years, of diverse racial backgrounds, and assessed for systolic blood pressure (SBP), diastolic blood pressure, and mean arterial pressure. After meta‐analysis across the LIFE and Health ABC studies, statistically significant associations of mtDNA variants with higher SBP (m.3197T>C, 16S rRNA; P=0.0005) and mean arterial pressure (m.15924A>G, t‐RNA‐thr; P=0.004) were identified in white participants. Among black participants, statistically significant associations with higher SBP (m.93A>G, HVII; m.16183A>C, HVI; both P=0.0001) and mean arterial pressure (m.16172T>C, HVI; m.16183A>C, HVI; m.16189T>C, HVI; m.12705C>T; all P's<0.0004) were observed. Significant pooled effects on SBP were observed across all transfer RNA regions (P=0.0056) in white participants. The individual and aggregate variant results are statistically significant after multiple comparisons adjustment for the number of mtDNA variants and mitochondrial regions examined.

Conclusions

These results suggest that mtDNA‐encoded variants are associated with variation in SBP and mean arterial pressure among older adults. These results may help identify mitochondrial activities to explain differences in blood pressure in older adults and generate new hypotheses surrounding mtDNA variation and the regulation of blood pressure.

Clinical Trial Registration

URL: http://www.ClinicalTrials.gov. Unique identifiers: NCT01072500 and NCT00116194.

Muscle strength is increased in mice that are colonized with microbiota from high-functioning older adults

Evidence in support of a gut-muscle axis has been reported in rodents, but studies in older adult humans are limited. Accordingly, the primary goals of the present study were to compare gut microbiome composition in older adults that differed in terms of the percentage of whole body lean mass and physical functioning (high-functioning, HF, n = 18; low-functioning, LF, n = 11), and to evaluate the causative role of the gut microbiome on these variables by transferring fecal samples from older adults into germ-free mice. Family-level Prevotellaceae, genus-level Prevotella and Barnesiella, and the bacterial species Barnesiella intestinihominis were higher in HF older adults at the initial study visit, at a 1-month follow-up visit, in HF human fecal donors, and in HF-colonized mice, when compared with their LF counterparts. Grip strength was significantly increased by 6.4% in HF-, when compared with LF-colonized mice. In contrast, despite significant differences for the percentage of whole body lean mass and physical functioning when comparing the human fecal donors, the percentage of whole body lean mass and treadmill endurance capacity were not different when comparing human microbiome-containing mice. In sum, these data suggest a role for gut bacteria on the maintenance of muscle strength, but argue against a role for gut bacteria on the maintenance of the percentage of whole body lean mass or endurance capacity, findings that collectively add to elucidation of the gut-muscle axis in older adults.

The clinical impact and biological mechanisms of skeletal muscle aging

Skeletal muscle is a highly plastic tissue that remarkably adapts to diverse stimuli including exercise, injury, disuse, and, as discussed here, aging. Humans achieve peak skeletal muscle mass and strength in mid-life and then experience a progressive decline of up to 50% by the ninth decade. The loss of muscle mass and function with aging is a phenomenon termed sarcopenia. It is evidenced by the loss and atrophy of muscle fibers and the concomitant accretion of fat and fibrous tissue. Sarcopenia has been recognized as a key driver of limitations in physical function and mobility, but is perhaps less appreciated for its role in age-related metabolic dysfunction and loss of organismal resilience. Similar to other tissues, muscle is prone to multiple forms of age-related molecular and cellular damage, including disrupted protein turnover, impaired regenerative capacity, cellular senescence, and mitochondrial dysfunction. The objective of this review is to highlight the clinical consequences of skeletal muscle aging, and provide insights into potential biological mechanisms. In light of population aging, strategies to improve muscle health in older adults promise to have a profound public health impact.