Estimation of total-body and limb muscle mass in hemodialysis patients by using multifrequency bioimpedance spectroscopy

Sociodemographic and clinical factors associated with low muscle mass and composition in people treated with (chemo)radiotherapy for lung cancer

BACKGROUND

This study examined (1) associations between sociodemographic and clinical variables with low muscle mass and radiodensity and their loss relative to treatment commencement in patients with lung cancer; and (2) the magnitude of change in muscle mass and association with treatment outcomes and survival.

METHODS

Prospective study in patients planned for curative (chemo)radiotherapy for lung cancer. Low skeletal muscle mass and radiodensity and muscle loss were determined from pre- and post-treatment computed tomography images. Sociodemographic, clinical, functional, nutritional, physical activity and alternate body composition were assessed pre-treatment. Logistic and linear regression and Fisher's exact tests were used to assess associations between variables and study outcomes. Cox proportional hazards models were fitted to examine associations with survival.

RESULTS

Overall, 53 patients (62.3% male) with a mean age of 69 ± 9.3 years and 54.8% with stage III disease were included. Pre-treatment low calf circumference was associated with pre-treatment low muscle mass (p = 0.006). Higher comorbidity scores pre-treatment were associated with normal muscle radiodensity pre- and post-treatment (p = 0.015, p = 0.027, respectively). Pre-treatment low energy and protein intake were associated with low muscle radiodensity post-treatment. Muscle mass and radiodensity were not associated with survival or treatment outcomes.

CONCLUSIONS

In patients with lung cancer, there is some evidence anthropometric measures of muscle mass are suggestive of low muscle mass pre-radiotherapy, while low energy intake pre-treatment may indicate low muscle radiodensity after treatment. However, these findings are limited by the small sample size and further prospective studies with larger samples are required.

Development and clinical application of bioelectrical impedance analysis method for body composition assessment

Obesity, which is characterized by excessive body fat, increases the risk of chronic diseases, such as type 2 diabetes, cardiovascular diseases, and certain cancers. Sarcopenia, a decline in muscle mass, is also associated with many chronic disorders and is therefore a major concern in aging populations. Body composition analysis is important in the evaluation of obesity and sarcopenia because it provides information about the distribution of body fat and muscle mass. It is also useful for monitoring nutritional status, disease severity, and the effectiveness of interventions, such as exercise, diet, and drugs, and thus helps assess overall health and longevity. Computed tomography, magnetic resonance imaging, and dual-energy X-ray absorptiometry are commonly used for this purpose. However, they have limitations, such as high cost, long measurement time, and radiation exposure. Instead, bioelectrical impedance analysis (BIA), which was introduced several decades ago and has undergone significant technological advancements, can be used. It is easily accessible, affordable, and importantly, poses no radiation risk, making it suitable for use in hospitals, fitness centers, and even at home. Herein, we review the recent technological developments and clinical applications of BIA to provide an updated understanding of BIA technology and its strengths and limitations.

Phase Angle as Surrogate Marker of Muscle Weakness in Kidney Transplant Candidates Referred to Prehabilitation

Phase angle (PhA), a marker of nutritional status obtained by bioelectrical impedance analysis (BIA), is associated with the integrity of cell membranes. Damage to muscle fiber membranes can impact muscle strength, which is related to adverse outcomes in adults with advanced chronic kidney disease (CKD). The main objective of this study was to determine the usefulness of the PhA in identifying muscle weakness in candidates for kidney transplants (KTs). Secondly, it aimed to examine the associations of PhA with other parameters of body composition, exercise performance, and muscle structure. Sensitivity, specificity, and area under the receiver operating characteristics curve were used to evaluate the PhA (index test) as a biomarker of muscle weakness. Muscle strength was estimated with maximal voluntary isometric contraction of the quadriceps (MVCI-Q) of the dominant side. Muscle weakness was defined as MVIC-Q < 40% of body weight. A total of 119 patients were evaluated (mean age 63.7 years, 75.6% men). A phase angle cut-off of 5.1° was identified to classify men with a higher likelihood of having low muscle strength in upper limbs (MVIC-Q 40% of their body weight). Male KT candidates with PhA < 5.1° had poorer exercise capacity, lower muscle strength, less muscle mass, and smaller muscle size. A PhA < 5.1° was significantly associated with an eight-fold higher muscle weakness risk (OR = 8.2, 95%CI 2.3-29.2) in a binary regression model adjusted by age, frailty, and hydration status. Remarkably, PhA is an easily obtainable objective parameter in CKD patients, requiring no volitional effort from the individual. The associations of PhA with aerobic capacity, physical activity, muscle mass, and muscle size underscore its clinical relevance and potential utility in the comprehensive evaluation of these patients.

Combined action observation and mental imagery versus neuromuscular electrical stimulation as novel therapeutics during short-term knee immobilization

Limb immobilization causes rapid declines in muscle strength and mass. Given the role of the nervous system in immobilization-induced weakness, targeted interventions may be able to preserve muscle strength, but not mass, and vice versa. The purpose of this study was to assess the effects of two distinct interventions during 1 week of knee joint immobilization on muscle strength (isometric and concentric isokinetic peak torque), mass (bioimpedance spectroscopy and ultrasonography), and neuromuscular function (transcranial magnetic stimulation and interpolated twitch technique). Thirty-nine healthy, college-aged adults (21 males, 18 females) were randomized into one of four groups: immobilization only (n = 9), immobilization + action observation/mental imagery (AOMI) (n = 10), immobilization + neuromuscular electrical stimulation (NMES) (n = 12), or control group (n = 8). The AOMI group performed daily video observation and mental imagery of knee extensions. The NMES group performed twice daily stimulation of the quadriceps femoris. Based on observed effect sizes, it appears that AOMI shows promise as a means of preserving voluntary strength, which may be modulated by neural adaptations. Strength increased from PRE to POST in the AOMI group, with +7.2% (Cohen's d = 1.018) increase in concentric isokinetic peak torque at 30°/s. However, NMES did not preserve muscle mass. Though preliminary, our findings highlight the specific nature of clinical interventions and suggest that muscle strength can be independently targeted during rehabilitation. This study was prospectively registered: ClinicalTrials.gov NCT05072652.

Sex differences in muscle-quality recovery following one week of knee joint immobilization and subsequent retraining

This manuscript represents the second phase of a clinical trial designed to examine the effects of knee joint immobilization and retraining on muscle strength and mass. In Phase 2, we examined sex differences in the recovery of multiple indices of muscle quality after a resistance training-based rehabilitation program. Following 1 week of immobilization, 27 participants (16 males, 11 females) exhibiting weakness underwent twice weekly resistance training sessions designed to re-strengthen their left knee. Unilateral retraining sessions utilizing leg press, extension, and curl exercises were conducted until participants could reproduce their pre-immobilization knee extension isometric maximal voluntary contraction (MVC) peak torque. Post-immobilization, both sexes demonstrated impaired MVC peak torque (males = -10.8%, females = -15.2%), specific torque (-9.8% vs. -13.1%), echo intensity of the vastus lateralis (+6.9% vs. +5.9%) and rectus femoris (+5.9% vs. +2.1), and extracellular water/intracellular water ratio (+7.8% vs. +9.0%). The number of retraining sessions for peak torque to return to baseline for males (median = 1, mean = 2.13) versus females (median = 2, mean = 2.91) was not significantly different, though the disparity in recovery times may be clinically relevant. Following retraining, specific torque was the only muscle-quality indicator that improved along with MVC peak torque (males = 20.1%, females = 22.4%). Our findings indicate that measures of muscle quality demonstrate divergent recovery rates following immobilization, with muscle mass lagging behind improvements in strength. Greater immobilization-induced strength loss among females suggests that sex-specific rehabilitation efforts may be justified.

Association between sarcopenic obesity and mortality in patients on peritoneal dialysis: a prospective cohort study

Background

Whether sarcopenic obesity had unfavorable effect on survival of peritoneal dialysis (PD) patients is unknown. We aimed to investigate the association between sarcopenic obesity and survival in PD patients.

Methods

This was a prospective observational study. Eligible PD patients from November 2016 to December 2017 were enrolled and followed until August 31, 2023. Sarcopenia was defined following the recommendations of the Asian Working Group for Sarcopenia (AWGS) as low appendicular skeletal muscle mass index (ASMI) and handgrip strength (HGS). Obesity was defined using the percentage of body fat (PBF). Survival analysis was conducted using the Kaplan-Meier and log-rank test. The Cox regression and the cumulative incidence competing risk (CICR) analyzes were used to investigate the association between sarcopenic obesity and all-cause mortality.

Results

A total of 223 patients were enrolled with 133 (59.6%) males, a median age of 57.5 (44.6, 65.7) years, a median dialysis vintage of 20.3 (6.4, 57.7) months and 48 (21.5%) who had comorbid diabetes mellitus. Among them, 46 (20.6%) patients were sarcopenic, and 25 (11.2%) patients were diagnosed with sarcopenic obesity. After followed up for 51.6 (25.6, 73.9) months, the Kaplan-Meier curve showed the sarcopenic obesity (log-rank = 13.527, p < 0.001) group had significant lower survival rate compared to the nonsarcopenic non-obesity group. For multivariate analysis, the CICR method showed patients with sarcopenic obesity had significantly higher mortality rate (HR: 2.190, 95% CI: 1.011-4.743, p = 0.047) compared to those with nonsarcopenic non-obesity.

Conclusion

Sarcopenia is not uncommon in PD patients, with a considerable proportion having sarcopenic obesity. There is a significant association between sarcopenic obesity and an increased risk of mortality in PD patients.

Concordance between muscle mass assessed by bioelectrical impedance analysis and by muscle ultrasound: a cross-sectional study in a cohort of patients on chronic hemodialysis

BACKGROUND

Sarcopenia is a common problem in hemodialysis (HD) patients, and it is diagnosed by low muscle mass, strength and/or low physical performance. Muscle ultrasound (US) is a non-invasive portable tool that might be used for assessment of muscle mass. The aim of the current study was to investigate the concordance between muscle US and bioelectrical impedance analysis (BIA) in diagnosis of sarcopenia in HD patients.

METHODS

This cross-sectional study included 41 HD patients. Sarcopenia was diagnosed according to the European Working Group on Sarcopenia in Older People (EWGSOP). The skeletal mass index was measured by BIA and the muscle strength was measured by handgrip strength. Muscle US was used to measure cross-sectional area (CSA) and thickness of quadriceps and biceps muscles.

RESULTS

The current study included 41 patients on HD (25 males), with a mean (SD) age of 44.18 (13.11) years and a median HD duration of 48 months. Sarcopenia was diagnosed in 58.5% of the patients. Patients with sarcopenia had significantly lower quadriceps muscle CSA than those without sarcopenia. The optimal cut-offs of quadriceps muscle CSA for both males and females for the diagnosis of sarcopenia were 2.96 and 2.92 cm2, respectively.

CONCLUSION

Sarcopenia is prevalent among Egyptian HD patients. US on quadriceps muscle CSA could be used for diagnosis of sarcopenia in these patients.

Computed tomography-based abdominal sarcopenic indices and bio-impedance analysis-based skeletal muscle mass index in hemodialyzed patients

BACKGROUND AND AIMS

Information about muscle wasting in hemodialyzed patients evaluated using computed tomography (CT) is limited. The present study aimed to examine the relationships between CT-based abdominal sarcopenic indices and bio-impedance analysis (BIA)-based skeletal muscle mass index (SMMI) in these patients.

METHODS

A total of 100 consecutive maintenance hemodialyzed patients who underwent CT and BIA were included. The psoas muscle index (PMI), paraspinous muscle index (PSMI), and abdominal skeletal muscle index (ASMI) were calculated by adjusting each muscle area to the height square. The psoas muscle thickness per height (PMTH) was measured using a single cross-sectional CT image obtained at the level of the third lumbar vertebra. The relationships between these CT-based sarcopenic indices and the BIA-based SMMI were examined. Moreover, the diagnostic values of these CT-based indices for BIA-defined muscle wasting (defined by the sex-specific SMMI: males, <7.0 kg/m2; females, <5.7 kg/m2) were investigated.

RESULTS

The PMI, PMTH, PSMI, and ASMI were significantly correlated with the SMMI (r = 0.678, 0.760, 0.708, and 0.785, respectively; p < 0.0001 for all). Twenty-eight patients with reduced muscle mass determined by BIA were identified. After age-sex adjustment, a multivariate logistic regression analysis revealed that the C-statistics of the PMI, PMTH, PSMI, and ASMI for the diagnosis of low muscle mass were 0.863 (p = 0.0099), 0.870 (p = 0.013), 0.891 (p = 0.040), and 0.950 (reference), respectively.

CONCLUSIONS

CT-based abdominal sarcopenic indices presented here may be useful for evaluating muscle wasting in hemodialyzed patients; the ASMI may be the most recommended sarcopenic index for such evaluations.

Muscle Mass and Serum Creatinine Concentration by Race and Ethnicity among Hemodialysis Patients

SIGNIFICANCE STATEMENT

Serum creatinine is a product of skeletal muscle metabolism. Differences in serum creatinine concentration between Black and non-Black individuals have been attributed to differences in muscle mass but have not been thoroughly examined. Furthermore, other race and ethnic groups have not been considered. If differences in body composition explain differences in serum concentration by race or ethnicity, then estimates of body composition could be used in eGFR equations rather than race. Adjustment for intracellular water (ICW) as a proxy of muscle mass among patients with kidney failure in whom creatinine clearance should minimally influence serum concentration does not explain race- and ethnicity-dependent differences.

BACKGROUND

Differences in serum creatinine concentration among groups defined by race and ethnicity have been ascribed to differences in muscle mass. We examined differences in serum creatinine by race and ethnicity in a cohort of patients receiving hemodialysis in whom creatinine elimination by the kidney should have little or no effect on serum creatinine concentration and considered whether these differences persisted after adjustment for proxies of muscle mass.

METHODS

We analyzed data from 501 participants in the A Cohort Study to Investigate the Value of Exercise in ESKD/Analyses Designed to Investigate the Paradox of Obesity and Survival in ESKD study who had been receiving hemodialysis for >1 year. We examined the independent associations among race and ethnicity (Black, Asian, non-Hispanic White, and Hispanic), serum creatinine, and ICW (L/m 2 ), a proxy for muscle mass, derived by whole-body multifrequency bioimpedance spectroscopy, using multivariable linear regression with adjustment for several demographic, clinical, and laboratory characteristics. We examined the association of race and ethnicity with serum creatinine concentration with and without adjustment for ICW.

RESULTS

Black, Asian, and Hispanic patients had higher serum creatinine concentrations (+1.68 mg/dl [95% confidence interval (CI), 1.09 to 2.27], +1.61 mg/dl [95% CI, 0.90 to 2.32], and +0.83 [95% CI, 0.08 to 1.57], respectively) than non-Hispanic White patients. Overall, ICW was associated with serum creatinine concentration (0.26 mg/dl per L/m 2 ICW; 95% CI, 0.006 to 0.51) but was not statistically significantly different by race and ethnicity. Black, Asian, and Hispanic race and ethnicity remained significantly associated with serum creatinine concentration after adjustment for ICW.

CONCLUSION

Among patients receiving dialysis, serum creatinine was higher in Black, Asian, and Hispanic patients than in non-Hispanic White patients. Differences in ICW did not explain the differences in serum creatinine concentration across race groups.

Development and validation of a nomogram model for predicting low muscle mass in patients undergoing hemodialysis

BACKGROUND

Muscle mass is important in determining patients' nutritional status. However, measurement of muscle mass requires special equipment that is inconvenient for clinical use. We aimed to develop and validate a nomogram model for predicting low muscle mass in patients undergoing hemodialysis (HD).

METHODS

A total of 346 patients undergoing HD were enrolled and randomly divided into a 70% training set and a 30% validation set. The training set was used to develop the nomogram model, and the validation set was used to validate the developed model. The performance of the nomogram was assessed using the receiver operating characteristic (ROC) curve, a calibration curve, and the Hosmer-Lemeshow test. A decision curve analysis (DCA) was used to evaluate the clinical practicality of the nomogram model.

RESULTS

Age, sex, body mass index (BMI), handgrip strength (HGS), and gait speed (GS) were included in the nomogram for predicting low skeletal muscle mass index (LSMI). The diagnostic nomogram model exhibited good discrimination with an area under the ROC curve (AUC) of 0.906 (95% CI, 0.862-0.940) in the training set and 0.917 (95% CI, 0.846-0.962) in the validation set. The calibration analysis also showed excellent results. The nomogram demonstrated a high net benefit in the clinical decision curve for both sets.

CONCLUSIONS

The prediction model included age, sex, BMI, HGS, and GS, and it can successfully predict the presence of LSMI in patients undergoing HD. This nomogram provides an accurate visual tool for medical staff for prediction, early intervention, and graded management.

Association of appendicular extracellular-to-intracellular water ratio with age, muscle strength, and physical activity in 8,018 community-dwelling middle-aged and older adults

BACKGROUND

The appendicular extracellular-to-intracellular water ratio (Ap ECW/ICW) has recently gained attention as a non-invasive measurable marker of muscle quality. However, there is a lack of basic evidence regarding age-related changes, sex differences, contribution to muscle strength independent of skeletal muscle mass (SMM), and potential improvement through physical activity (PA) in Ap ECW/ICW.

METHODS

This cross-sectional study enrolled 8,018 middle-aged and older Japanese individuals (aged 45-75 years). The Ap ECW/ICW and SMM were measured using segmental bioelectrical impedance spectroscopy. Muscle strength was evaluated by measuring the handgrip strength (HGS) with a dynamometer, and the PA level (PAL) was measured with an accelerometer. We performed a linear regression analysis of the associations of the Ap ECW/ICW with age, HGS, and PAL.

RESULTS

The Ap ECW/ICW increased by 0.019 for men and 0.014 for women per 5-year increase in age (p < 0.001), and the age-related increase was greater in men than in women (p for interaction <0.001). The Ap ECW/ICW was more strongly associated with the HGS than with the SMM in both men and women (p < 0.001). PAL showed a significant inverse association with the Ap ECW/ICW in both men and women (p < 0.001).

CONCLUSIONS

Ap ECW/ICW is higher with age, and it varies by sex. The Ap ECW/ICW may reflect muscle strength more than the SMM, suggesting that the Ap ECW/ICW may be improved by PA. The findings from this study may provide a framework for further Ap ECW/ICW research.

Dose-response relationship between daily step count and prevalence of sarcopenia: A cross-sectional study

OBJECTIVES

Daily step counts are an easy-to-understand indicator of physical activity; however, there is limited evidence regarding the optimal daily step count to prevent sarcopenia. This study examined the dose-response relationship between daily step count and the prevalence of sarcopenia and explored the optimal dose.

DESIGN

Cross-sectional study.

SETTING AND PARTICIPANTS

The study included 7949 community-dwelling middle-aged and older adults (aged 45-74 years) from Japan.

MEASUREMENTS

Skeletal muscle mass (SMM) was assessed using bioelectrical impedance spectroscopy, and muscle strength was quantified through handgrip strength (HGS) measurement. Participants who exhibited both low HGS (men: <28 kg, women: <18 kg) and low SMM (lowest quartile in each sex-specific category) were defined as having sarcopenia. Daily step counts were measured for 10 days using a waist-mounted accelerometer. To examine the association between daily step count and sarcopenia, a multivariate logistic regression analysis was performed, adjusting for potential confounding factors such as age, sex, body mass index, smoking status, alcohol consumption, protein intake, and medical history. The odds ratios (ORs) and confidence intervals (CIs) were calculated based on the daily step counts categorized into quartiles (Q1-Q4). Finally, a restricted cubic spline curve was fitted to further investigate the dose-response relationship between daily step count and sarcopenia.

RESULTS

The prevalence of sarcopenia in the overall participants was 3.3 % (259/7949 participants), with a mean daily step count of 7292 ± 2966 steps. Expressed in quartiles, the mean daily step counts were 3873 ± 935 steps in Q1, 6025 ± 503 steps in Q2, 7942 ± 624 steps in Q3, and 11,328 ± 1912 steps in Q4. The prevalence of sarcopenia in each quartile of daily step count was 4.7 % (93/1987 participants) in Q1, 3.4 % (68/1987 participants) in Q2, 2.7 % (53/1988 participants) in Q3, and 2.3 % (45/1987 participants) in Q4. The ORs and 95 % CIs adjusted for covariates demonstrated a statistically significant inverse association between daily step count and sarcopenia prevalence (P for trend <0.01), as follows: Q1, reference; Q2, 0.79 (95 % CI: 0.55-1.11); Q3, 0.71 (95 % CI: 0.49-1.03); Q4, 0.61 (95 % CI: 0.41-0.90). The restricted cubic spline curve indicated that the ORs leveled off at approximately 8000 steps per day, and no statistically significant decrease in ORs was observed for daily step counts above this threshold.

CONCLUSIONS

The study found a significant inverse association between daily step count and the prevalence of sarcopenia, with the association plateauing when the daily step count exceeded approximately 8000 steps. These findings suggest that 8000 steps per day may be the optimal dose to prevent sarcopenia. Further intervention and longitudinal studies are needed to validate the results.

Low Phase Angle Values Are Associated with Malnutrition according to the Global Leadership Initiative on Malnutrition Criteria in Kidney Transplant Candidates: Preliminary Assessment of Diagnostic Accuracy in the FRAILMar Study

Malnutrition has a negative impact on patients with chronic diseases and its early identification is a priority. The primary objective of this diagnostic accuracy study was to assess the performance of the phase angle (PhA), a bioimpedance analysis (BIA)-derived parameter, for malnutrition screening using the Global Leadership Initiative for Malnutrition (GLIM) criteria as the reference standard in patients with advanced chronic kidney disease (CKD) waiting for kidney transplantation (KT); criteria associated with low PhA in this population were also analyzed. Sensitivity, specificity, accuracy, positive and negative likelihood ratios, predictive values, and area under the receiver operating characteristic curve were calculated for PhA (index test) and compared with GLIM criteria (reference standard). Of 63 patients (62.9 years old; 76.2% men), 22 (34.9%) had malnutrition. The PhA threshold with the highest accuracy was ≤4.85° (sensitivity 72.7%, specificity 65.9%, and positive and negative likelihood ratios 2.13 and 0.41, respectively). A PhA ≤ 4.85° was associated with a 3.5-fold higher malnutrition risk (OR = 3.53 (CI95% 1.0-12.1)). Considering the GLIM criteria as the reference standard, a PhA ≤ 4.85° showed only fair validity for detecting malnutrition, and thus cannot be recommended as a stand-alone screening tool in this population.

Body composition parameters for predicting the efficacy of neoadjuvant chemotherapy with immunotherapy for gastric cancer

BACKGROUND

Immune checkpoint inhibitors are increasingly used in neoadjuvant therapy for locally advanced gastric cancer. However, the effect of body composition on the efficacy of neoadjuvant therapy has not been reported.

METHODS

The computed tomography (CT) images and clinicopathological data of 101 patients with locally advanced gastric cancer who received neoadjuvant chemotherapy combined with immunotherapy (NCI) from 2019 to 2021 were collected. The CT image of L3 vertebral body section was selected, and the body composition before and after the neoadjuvant treatment was calculated using the SliceOmatic software, mainly including skeletal muscle index (SMI), subcutaneous adipose index (SAI), and visceral adipose index (VAI). The relationship between body composition and the efficacy and adverse events of NCI was analyzed.

RESULTS

Of the 101 patients, 81 with evaluable data were included in the analysis. Of the included patients, 77.8% were male; the median age of all the patients was 62 years, and the median neoadjuvant therapy cycle was three. After the neoadjuvant therapy, 62.9% of the tumors were in remission (residual tumor cells ≤ 50%), and 37.1% of the tumors had no remission (residual tumor cells>50%). Moreover, 61.7% of the patients had treatment-related adverse events (TRAEs), and 18.5% had immune-related adverse events (irAEs). After neoadjuvant therapy, the body mass index (from 23 to 22.6 cm2/m2, p=0.042), SAI (from 34.7 to 32.9 cm2/m2, p=0.01) and VAI (from 32.4 to 26.8 cm2/m2, p=0.005) were significantly lower than those before treatment, while the SMI had no significant change (44.7 vs 42.5 cm2/m2, p=0.278). The multivariate logistics regression analysis revealed that low SMI (odds ratio [OR]: 3.23,95% confidence interval [CI]: 1.06-9.81, p=0.047), SMI attenuation (△SMI) ≥ 1.8(OR: 1.45,95%CI: 1.20-3.48, p=0.048), and clinical node positivity (OR: 6.99,95%CI: 2.35-20.82, p=0.001) were independent risk factors for non-remission. Additionally, high SAI is an independent risk factor for irAEs (OR: 14, 95%CI: 1.73-112.7, p=0.013).

CONCLUSION

Low SMI and △SMI≥1.8 are independent risk factors for poor tumor regression in patients with advanced gastric cancer receiving NCI. Patients with a high SAI are more likely to develop irAEs.

Association of the modified creatinine index with muscle strength and mortality in patients undergoing hemodialysis

Background

In the updated consensus, low muscle strength overtook the role of low muscle mass, and probable sarcopenia was diagnosed once low muscle strength was detected. Whether the modified creatinine index (mCI) could identify persons with probable sarcopenia who may be at risk of adverse outcomes remains unknown. We aimed to evaluate the association of the mCI with probable sarcopenia and mortality in patients undergoing hemodialysis.

Methods

In the cross-sectional study (n = 346), univariate and multivariable logistic regression analyses were performed to study the association of mCI with probable sarcopenia. Modified Quantitative Subjective Global Assessment (MQSGA) was used to evaluate the nutritional status. The performance of the mCI value for identifying probable sarcopenia was analyzed using receiver operating characteristic (ROC) curve analysis. The appropriate cutoff points were determined using Youden’s method. In the longitudinal cohort study composed of an independent hemodialysis cohort (n = 218), cox proportional regression models were used to evaluate crude and adjusted hazard ratios and 95% confidence intervals (CIs) of death by mCI and MQSGA.

Results

Cross-sectional results showed that after adjusting for confounders, the association of mCI with low muscle strength remained significant. The area under the curve (AUC) of the mCI to predict probable sarcopenia was 0.804 (95% CI, 0.744–0.863; p < 0.001) for men and 0.787 (95% CI, 0.711–0.864; p < 0.001) for women. The optimal mCI cutoff values were 21.07 mg/kg/d for men and 19.57 mg/kg/d for women, respectively. Longitudinal results showed that compared with those in the high mCI group, subjects in the low mCI group had a higher risk of death for all causes (adjusted HR, 2.51; 95% CI, 1.16–5.41; p = 0.019). Adding the mCI significantly improved the predictive accuracy for death with an increase in C-index from 0.785 to 0.805 (p = 0.026) and improved the net reclassification index (38.6%, p = 0.021), while adding MQSGA did not.

Conclusion

The mCI is a predictor of muscle strength and survival in hemodialysis patients, and is preferable to the MQSGA for predicting death. Assessment of mCI could provide additional predictive and prognostic information to sarcopenia.

Modeling Low Muscle Mass Screening in Hemodialysis Patients

INTRODUCTION

Computed tomography (CT) can accurately measure muscle mass, which is necessary for diagnosing sarcopenia, even in dialysis patients. However, CT-based screening for such patients is challenging, especially considering the availability of equipment within dialysis facilities. We therefore aimed to develop a bedside prediction model for low muscle mass, defined by the psoas muscle mass index (PMI) from CT measurement.

METHODS

Hemodialysis patients (n = 619) who had undergone abdominal CT screening were divided into the development (n = 441) and validation (n = 178) groups. PMI was manually measured using abdominal CT images to diagnose low muscle mass by two independent investigators. The development group's data were used to create a logistic regression model using 42 items extracted from clinical information as predictive variables; variables were selected using the stepwise method. External validity was examined using the validation group's data, and the area under the curve (AUC), sensitivity, and specificity were calculated.

RESULTS

Of all subjects, 226 (37%) were diagnosed with low muscle mass using PMI. A predictive model for low muscle mass was calculated using ten variables: each grip strength, sex, height, dry weight, primary cause of end-stage renal disease, diastolic blood pressure at start of session, pre-dialysis potassium and albumin level, and dialysis water removal in a session. The development group's adjusted AUC, sensitivity, and specificity were 0.81, 60%, and 87%, respectively. The validation group's adjusted AUC, sensitivity, and specificity were 0.73, 64%, and 82%, respectively.

DISCUSSION/CONCLUSION

Our results facilitate skeletal muscle screening in hemodialysis patients, assisting in sarcopenia prophylaxis and intervention decisions.

Guidance for assessment of the muscle mass phenotypic criterion for the Global Leadership Initiative on Malnutrition diagnosis of malnutrition

The Global Leadership Initiative on Malnutrition (GLIM) provides consensus criteria for the diagnosis of malnutrition that can be widely applied. The GLIM approach is based on the assessment of three phenotypic (weight loss, low body mass index, and low skeletal muscle mass) and two etiologic (low food intake and presence of disease with systemic inflammation) criteria, with diagnosis confirmed by any combination of one phenotypic and one etiologic criterion fulfilled. Assessment of muscle mass is less commonly performed than other phenotypic malnutrition criteria, and its interpretation may be less straightforward, particularly in settings that lack access to skilled clinical nutrition practitioners and/or to body composition methodologies. In order to promote the widespread assessment of skeletal muscle mass as an integral part of the GLIM diagnosis of malnutrition, the GLIM consortium appointed a working group to provide consensus-based guidance on assessment of skeletal muscle mass. When such methods and skills are available, quantitative assessment of muscle mass should be measured or estimated using dual-energy x-ray absorptiometry, computerized tomography, or bioelectrical impedance analysis. For settings where these resources are not available, then the use of anthropometric measures and physical examination are also endorsed. Validated ethnic- and sex-specific cutoff values for each measurement and tool are recommended when available. Measurement of skeletal muscle function is not advised as surrogate measurement of muscle mass. However, once malnutrition is diagnosed, skeletal muscle function should be investigated as a relevant component of sarcopenia and for complete nutrition assessment of persons with malnutrition.

Membrane capacitance and characteristic frequency are associated with contractile properties of skeletal muscle

The cell membrane capacitance (Cm) and characteristic frequencies (fc) of tissues can be obtained using segmental bioelectrical impedance spectroscopy (S-BIS). Higher Cm and lower fc are associated with a larger surface area of skeletal muscle fibers with T-tubules in the tissues. Muscle fiber membrane is one of the major physiological factors that influence surface electromyograms (EMGs) as well as the number of recruited motor units so that the amplitude of surface EMG may be correlated with Cm and fc. The aim of the current study was to examine the association of fc or Cm in the lower leg with contractile and neuromuscular properties in the plantar flexors. We analyzed data from 59 participants (29 women) aged 21-83 years. The Cm, fc, and intracellular water (ICW) in the lower leg were obtained using S-BIS. We measured electrical-evoked torque, maximal voluntary contraction (MVC) torque, and amplitude of EMG normalized by the M wave during MVC contraction. The high Cm group had a significantly lower fc and significantly higher MVC torque, estimated maximum torque, twitch torque, and root mean square (RMS) of EMG normalized by the M wave (EMG:M) in the musculus triceps surae compared to the low Cm group (P < 0.05). Cm was positively and fc was negatively correlated with the nRMS of EMG:M in the triceps surae (P < 0.05). S-BIS recordings can be used to detect changes in skeletal muscle membrane capacitance, which may provide insights into the number of T-tubules. The muscle capacitance measured with S-BIS can be predictive of muscle force generation.

The importance of muscle mass in predicting intradialytic hypotension in patients undergoing maintenance hemodialysis

Background

Patients undergoing hemodialysis are susceptible to sarcopenia. As intracellular reservoirs of water, skeletal muscles are important contributors to intradialytic hypotension. This study was designed to determine the role of skeletal muscle mass in intradialytic hypotension.

Methods

In a cross-sectional study, the body composition of 177 patients was measured immediately after hemodialysis using bioelectrical impedance analysis. The parameters measured were skeletal muscle mass, intracellular and extracellular water contents, total body water, and cell-membrane functionality (in phase angle at 50 kHz). Data from laboratory tests, chest radiography, measurements of handgrip strength and mid-arm circumference, and questionnaires were collected. The main outcome was intradialytic hypotension, defined as more than two episodes of hypotension (systolic blood pressure of <90 mmHg) with intervention over the 3 months following enrollment. Logistic regression models including each parameter related to sarcopenia were compared with a clinical model.

Results

Patients with a low ratio of skeletal muscle mass to dry body weight (SMM/WT) had a higher rate of intradialytic hypotension (41%). Most low-SMM/WT patients were female, obese, diabetic, and had a lower handgrip strength compared with the other patients. In the high-SMM/WT group, the risk of intradialytic hypotension was lower, with an odds ratio of 0.08 (95% confidence interval [CI], 0.02-0.28) and adjusted odds ratio of 0.06 (95% CI, 0.01-0.29).

Conclusion

Measurement and maintenance of skeletal muscle can help prevent intradialytic hypotension in frail patients undergoing hemodialysis.

Guidance for assessment of the muscle mass phenotypic criterion for the Global Leadership Initiative on Malnutrition (GLIM) diagnosis of malnutrition

The Global Leadership Initiative on Malnutrition (GLIM) provides consensus criteria for the diagnosis of malnutrition that can be widely applied. The GLIM approach is based on the assessment of three phenotypic (weight loss, low body mass index, and low skeletal muscle mass) and two etiologic (low food intake and presence of disease with systemic inflammation) criteria, with diagnosis confirmed by any combination of one phenotypic and one etiologic criterion fulfilled. Assessment of muscle mass is less commonly performed than other phenotypic malnutrition criteria, and its interpretation may be less straightforward, particularly in settings that lack access to skilled clinical nutrition practitioners and/or to body composition methodologies. In order to promote the widespread assessment of skeletal muscle mass as an integral part of the GLIM diagnosis of malnutrition, the GLIM consortium appointed a working group to provide consensus-based guidance on assessment of skeletal muscle mass. When such methods and skills are available, quantitative assessment of muscle mass should be measured or estimated using dual-energy x-ray absorptiometry, computerized tomography, or bioelectrical impedance analysis. For settings where these resources are not available, then the use of anthropometric measures and physical examination are also endorsed. Validated ethnic- and sex-specific cutoff values for each measurement and tool are recommended when available. Measurement of skeletal muscle function is not advised as surrogate measurement of muscle mass. However, once malnutrition is diagnosed, skeletal muscle function should be investigated as a relevant component of sarcopenia and for complete nutrition assessment of persons with malnutrition.

Longitudinal Assessment of Body Composition and Its Association With Survival Among Participants of the ACTIVE/ADIPOSE Study

OBJECTIVES

The importance of muscle wasting as a predictor of mortality in the hemodialysis population is not clear. Lack of association of muscle mass with survival in some studies could be related to reliance on single measures or to incorporation of excess extracellular water (ECW) into estimates of muscle mass. We examined changes in body composition over a 2-year period and the association of body composition with survival.

DESIGN AND METHODS

We analyzed data from 325 adults receiving hemodialysis in the Bay Area. We estimated ECW, intracellular water (ICW), and fat mass by whole-body bioimpedance spectroscopy (BIS) at 0, 12, and 24 months from enrollment. We used linear mixed modeling to examine changes in body mass index and BIS-derived estimates of body composition and Cox modeling with BIS-derived estimates as time-varying independent variables to examine associations between body composition and survival in multivariable analyses.

RESULTS

Body mass index declined over time. Considering individual components of body composition, ICW declined (-0.09 kg/m² per year, 95% confidence interval -0.14 to -0.04), but fat mass and ECW did not change significantly. There were 120 deaths over a median of 5.2 years. The relationship between ICW and mortality was not linear such that the association was steeper at low values of ICW, whereas higher ICW was associated with better survival that was relatively stable above 9 kg/m2. Higher ECW was associated with higher mortality, and fat mass was not associated with survival. These associations were independent of markers of inflammation and nutritional status.

CONCLUSIONS

ICW declined over 2 years in this cohort, whereas fat mass and ECW remained relatively stable. Higher ICW was associated with better survival, but higher fat mass was not. Higher ECW was associated with worse survival. These results suggest that muscle mass may predict survival among patients on hemodialysis.

Supportive Effects of Online Hemodiafiltration Therapy on the Nutritional State and Lipid Profile in Very Elderly Dialysis Patients

INTRODUCTION

Online hemodiafiltration (HDF) therapy has been recognized as one of the potential dialysis modalities. However, the long-term effects of online HDF therapy on very elderly dialysis patients older than 75 years have yet to be fully elucidated.

METHODS

Seventy-four very elderly patients older than 75 years undergoing maintenance dialysis therapy were studied retrospectively. Twenty-four (mean ± SE, 81.5 ± 1.0 years) were treated by predilution online HDF, and fifty (81.2 ± 0.6 years) were treated by conventional hemodialysis (HD) for 3 years. Laboratory data related to the nutritional state and lipid profile were collected. Body composition was measured by a bioelectrical impedance method.

RESULTS

Dry weight and body mass index decreased in HD patients (2.9%, p = 0.003 and 3.1%, p = 0.001, respectively), while no significant changes were found in online HDF patients. Serum albumin levels reduced in both HD and online HDF groups (3.5%, p = 0.003 and 2.9%, p = 0.026, respectively). The geriatric nutritional risk index decreased in HD patients (3.0%, p < 0.001), while no significant change was shown in online HDF patients. Body composition analysis demonstrated a significant decrease in intracellular water and increases in extracellular water and edema ratio in both groups. Fat mass and %fat showed significant decreases in HD patients (8.1%, p = 0.003 and 7.3%, p = 0.003, respectively), but no significant changes in online HDF patients. Among laboratory data, serum high-density lipoprotein cholesterol levels did not change in HD patients. However, the levels elevated significantly (10.6%, p = 0.03) in online HDF patients.

DISCUSSION/CONCLUSION

These results indicated that the time-dependent deterioration of the nutritional state in very elderly dialysis patients was inevitable; however, such deterioration was not prominent in online HDF patients. Moreover, the lipid profile showed unique changes in online HDF patients. In order to treat very elderly dialysis patients, online HDF should preferentially be taken into consideration because the maintenance of general condition seems to be a practical goal against the natural time-dependent deterioration.

Sarcopenia and Frailty: Challenges in Mainstream Nephrology Practice

Sarcopenia and frailty are prevalent in the chronic kidney disease (CKD) population. Sarcopenia is characterised by the loss of muscle mass and function, while frailty is defined as a multi-system impairment associated with increased vulnerability to stressors. There is substantial overlap between the 2 conditions, particularly with regards to physical aspects: low grip strength, gait speed and low muscle mass. Both sarcopenia and frailty have been associated with a wide range of adverse health outcomes. Although there is no recommended pharmacological treatment as yet, it is widely accepted that exercise training and nutritional supplementation are the key interventions to maintain skeletal muscle mass and strength. This review aims to present a comprehensive overview of sarcopenia and frailty in patients with CKD.

Estimating thigh skeletal muscle volume using multi-frequency segmental-bioelectrical impedance analysis

Background

The primary aim of this study was to investigate whether using the extracellular water/intracellular water (ECW/ICW) index and phase angle combined with segmental-bioimpedance analysis (BIA) improved the model fitting of skeletal muscle volume (SMV) estimation. The secondary aim was to compare the accuracy of segmental-BIA with that of ultrasound for estimating the quadriceps SMV measured with MRI.

Methods

Seventeen young men (mean age, 23.8 ± 3.3 years) participated in the study. The T-1 weighted images of thigh muscles were obtained using a 1.5 T magnetic resonance imaging (MRI) scanner. Thigh and quadriceps SMVs were calculated as the sum of the products of anatomical cross-sectional area and slice thickness of 6 mm across all slices. Segmental-BIA was applied to the thigh region, and data on the 50-kHz bioelectrical impedance (BI) index, ICW index, ECW/ICW index, and phase angle were obtained. The muscle thickness index was calculated as the product of the mid-thigh muscle thickness, determined using ultrasound, and thigh length. The standard error of estimate (SEE) of the regression equation was calculated to determine the model fitting of SMV estimation and converted to %SEE by dividing the SEE values by the mean SMV.

Results

Multiple regression analysis indicated that the combination of 50-kHz BI and the ECW/ICW index or phase angle was a significant predictor when estimating thigh SMV (SEE = 7.9 and 8.1%, respectively), but were lower than the simple linear regression (SEE = 9.4%). The ICW index alone improved the model fitting for the estimation equation (SEE = 7.6%). The model fitting of the quadriceps SMV with the 50-kHz BI or ICW index was similar to that with the skeletal muscle thickness index measured using ultrasound (SEE = 10.8, 9.6 and 9.7%, respectively).

Conclusions

Combining the traditionally used 50-kHz BI index with the ECW/ICW index and phase angle can improve the model fitting of estimated SMV measured with MRI. We also showed that the model suitability of SMV estimation using segmental-BIA was equivalent to that on using ultrasound. These data indicate that segmental-BIA may be a useful and cost-effective alternative to the gold standard MRI for estimating SMV.

Association between habitual coffee consumption and skeletal muscle mass in middle-aged and older Japanese people

AIMS

Coffee consumption has been suggested, in animal studies, to inhibit the progression of sarcopenia, possibly through its anti-inflammatory effects; however, few studies have been carried out in humans. We aimed to examine whether coffee consumption was related to indicators of sarcopenia in a Japanese population, and whether the association was mediated by reduced inflammation.

METHODS

This study was a cross-sectional design. Participants were community residents (n = 6369) aged 45-74 years. We measured skeletal muscle mass index (SMI; kg/m² ) by a bioelectrical impedance method, and grip strength with a Smedley-type dynamometer. Habitual coffee consumption was assessed by a self-administered questionnaire. Serum high-sensitivity C-reactive protein was measured as an inflammatory marker. The association between habitual coffee consumption and SMI or grip strength was analyzed with a linear regression model adjusted for covariates.

RESULTS

A significant positive association was found between coffee consumption and SMI (men: β = 0.023; P_trend  = 0.004, women: β = 0.011; P_trend  = 0.012). Further adjustment for high-sensitivity C-reactive protein did not materially alter the results (men: β = 0.023; P_trend  = 0.005, women: β = 0.009; P_trend  = 0.024). The relationship between coffee consumption and grip strength did not reach statistical significance; however, a positive trend was observed (men: β = 0.208; P_trend  = 0.085, women: β = 0.092; P_trend  = 0.167).

CONCLUSIONS

We found that coffee consumption was positively associated with SMI independently of inflammation in middle-aged and older Japanese people. Reduced inflammation by coffee does not seem to be an important mediator, and further investigations are required to explore the mechanisms of this association. Geriatr Gerontol Int 2021; 21: 950-958.

One-year intradialytic leg exercises with resistance bands and fat mass increase in elderly hemodialysis patients: a retrospective study

Background

Intradialytic exercises are recommended to be available as a treatment for enhancing physical functioning. However, there have been few reports which evaluated the results of long-term mild intradialytic exercises in elderly patients. The purpose of this study is to investigate the changes in body weight, body composition, and laboratory data in elderly hemodialysis patients after 1-year intradialytic leg exercises with resistance bands.

Methods

A retrospective study. Twenty-one outpatients, aged 65 or older (mean ± SD, 75.2 ± 5.1 years), received intradialytic leg exercises with resistance bands for a year were analyzed. The values of dry weight, body composition, and laboratory data were collected from the year-ago period, at baseline and 1 year after baseline. Fat and muscle mass were evaluated by using a multi-frequency bioimpedance device.

Results

Physical performance changed and body weight increased after 1-year resistance band exercises. However, the participants gained fat mass, not muscle mass. Although the changes in biochemical data related to protein intake were equivocal, triglyceride levels increased significantly after 1-year exercises. An elevation in serum creatinine levels was observed, even if solute clearance increased significantly.

Conclusions

One-year intradialytic leg exercises with resistance bands may have a potential clinical benefit for body mass index even in elderly hemodialysis patients. However, optimal dietary modification is needed to achieve a balanced increase of muscle and fat mass. An increase of serum creatinine levels does not always mean muscle mass hypertrophy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s41100-021-00341-z.

Development and validation of bioimpedance prediction equations for fat-free mass in unilateral male amputees

Background

Metabolic disease due to increased fat mass is observed in amputees (APTs), thereby restricting their activity. Systemic health management with periodic body composition (BC) testing is essential for healthy living. Bioelectrical impedance analysis (BIA) is a non-invasive and low-cost method to test BC; however, the APTs are classified as being exempted in the BIA.

Objective

To develop segmental estimated regression equations (sEREs) for determining the fat-free mass (FFM, kg) suitable for APTs and improve the accuracy and validity of the sERE.

Methods

Seventy-five male APTs participated in this cross-sectional study. Multiple regression analysis was performed to develop highly accurate sEREs of BIA based on independent variables derived from anthropometric measurements, dual-energy X-ray absorptiometry (DXA), and BIA parameters. The difference in validity between the predicted DXA and sum of the segmentally-predicted FFM values by sEREs (Sum_sEREs) values was evaluated using bivariate linear regression analysis and the Bland–Altman plot.

Results

The coefficient of determination (R²) and total error (TE) between DXA and Sum_sEREs were 71% and 5.4 (kg) in the cross-validation analysis.

Conclusions

We confirmed the possibility of evaluating the FFM of APTs through the sEREs developed in this study. We also identified several independent variables that should be considered while developing such sEREs. Further studies are required to determine the validity of our sEREs and the most appropriate BIA frequencies for measuring FFM in APTs.

QT Prolongation in Dialysis Patients: An Epidemiological Study with a Focus on Malnutrition

BACKGROUND/AIMS

QT prolongation is a known risk factor for ventricular fibrillation and ventricular tachycardia. Therefore, more refined management is necessary to reduce sudden cardiac death secondary to such arrhythmias.

METHODS

Electrocardiographic findings were reviewed in 224 patients, and the associations of QT prolongation with various clinical parameters were examined, including the nutritional state. Correlations were also examined between QT prolongation and body composition measurements determined by multifrequency bioelectrical impedance analysis.

RESULTS

Prolongation of the corrected QT (QTc) interval over 0.44 s was seen in 140 patients (62.5%). QT prolongation was independent of age and dialysis therapy duration and was more frequent in diabetics (70.1%) than in nondiabetics (54.2%, p = 0.014) and more frequent in women (78.8%) than in men (53.5%, p < 0.001). Serum levels of albumin (p < 0.001) and Cr (p < 0.001) and the Geriatric Nutritional Risk Index (GNRI, p < 0.001) were negatively correlated with QTc interval; no significant correlation was noted with total protein, urea nitrogen, or uric acid. Negative correlations with QTc interval were found for BMI(p < 0.01), percent total body water (%TBW; p < 0.05), and percent intracellular water (%ICW; p < 0.01) but not with the percent extracellular water/TBW ratio or edema ratio. The longer the QTc interval, the lower the fat-free mass (FFM; p < 0.01) and muscle mass (MM; p < 0.01), but there was no significant correlation with percent fat.

CONCLUSION

These results suggest that QT prolongation is a common complication and is more frequent in women and diabetic patients. The decreases in serum albumin and Cr levels, GNRI, BMI, %TBW, %ICW, FFM, and MM together coincided with malnutrition and thus suggest a close relationship of QT prolongation with malnutrition. Management of QT prolongation may be achieved better in the future by understanding these biochemical and biophysical changes, particularly those regarding malnutrition.

Comparison of Body Composition Monitor and InBody 720 Bioimpedance Devices for Body Composition Estimation in Hemodialysis Patients and Healthy Controls

Bioelectric impedance devices have become a standard of care not only for peritoneal dialysis but also for hemodialysis patients. We compared the most important body composition variables (extracellular water, intracellular water, total body water and fat mass) measured with the multifrequency bioelectric impedance device InBody 720 (MF-BIA) and bioimpedance spectroscopy body composition monitor Fresenius (BIS BCM) in hemodialysis patients (n = 51, 175.1 + 7.8 cm, 82.2 + 15.2 kg) and healthy controls (n = 51, 175.1 + 7.6 cm, 82.3 + 15.3 kg). The MF-BIA InBody 720 device compared to the BIS BCM device showed significantly larger total body water and intracellular water estimates and significantly smaller extracellular water and body fat estimates in hemodialysis patients (p < 0.001). These differences (p < 0.001) were similar in the cohort of healthy controls; moreover, we observed high correlations in all variables between the hemodialysis patients and the healthy controls (0.80–0.95, p < 0.001). The mean relative differences in the order of 8% were lower for extracellular water and total body fat, but the limits of agreement were still wide enough to be clinically significant. We conclude that the results of the measurements with InBody 720 and BCM Fresenius cannot be used interchangeably. Physicians and nutritionists involved in the care of hemodialysis patients should be aware of this discrepancy between the two devices and should try to use the same device to track the body in their hemodialysis population in a longitudinal direction.

Correlates and Consequences of High Serum Irisin Concentration in Patients on Hemodialysis: A Longitudinal Analysis

OBJECTIVE

Irisin is a hormone released by muscle in response to exercise that acts on white adipose cells to stimulate browning of adipose tissue. We aimed to examine irisin correlates and consequences of irisin in patients receiving hemodialysis.

DESIGN AND METHODS

A prospective cohort study was conducted using data from 749 prevalent patients receiving hemodialysis. Multivariable linear regression and multivariable generalized estimating equations were used to determine correlates of baseline and change in serum irisin concentration. Proportional hazards (Cox) regression was used to assess the association between serum irisin concentration and time to death.

RESULTS

Age and body mass index were inversely associated with baseline and change in serum irisin concentration. Lower muscle mass as estimated by serum creatinine concentration was associated with lower irisin concentration (-1.38% per mg/dL (95% confidence interval [CI]: -2.45, -0.21) and with a 0.72% decrease in irisin concentration (95% CI: -1.48, -0.04) from baseline to 12 months. Each 50% higher serum interleukin-6 (IL-6) concentration was associated with 1.52% higher serum irisin concentration (95% CI: 0.38, 2.66) at baseline and an increase of 1.04% in irisin concentration over 1 year (95% CI: 0.47, 1.61). Irisin concentration at baseline was associated with higher hazard of death (hazards ratio: 1.45, 95% CI: 1.05 2.00); an increase in irisin concentration over 1 year was associated with a higher hazard of death (hazards ratio: 1.34, 95% CI: 1.01, 1.79). In formal mediation analysis, serum IL-6 was a mediator in the association between serum irisin and mortality.

CONCLUSIONS

Lower serum creatinine (reflecting lower muscle mass) and higher serum IL-6 were associated with higher serum irisin concentrations. Higher serum irisin concentrations were associated with higher mortality, which may be mediated by inflammation.

Muscle mass assessment in renal disease: the role of imaging techniques

Muscle wasting is a frequent finding in patients with chronic kidney disease (CKD), especially in those with end-stage kidney disease (ESKD) on chronic dialysis. Muscle wasting in CKD is a main feature of malnutrition, and results principally from a vast array of metabolic derangements typical of the syndrome, that converge in determining reduced protein synthesis and accelerated protein catabolism. In this clinical setting, muscle wasting is also frequently associated with disability, frailty, infections, depression, worsened quality of life and increased mortality. On these grounds, the evaluation of nutritional status is crucial for an adequate management of renal patients, and consists of a comprehensive assessment allowing for the identification of malnourished patients and patients at nutritional risk. It is based essentially on the assessment of the extent and trend of body weight loss, as well as of spontaneous dietary intake. Another key component of this evaluation is the determination of body composition, which, depending on the selected method among several ones available, can identify accurately patients with decreased muscle mass. The choice will depend on the availability and ease of application of a specific technique in clinical practice based on local experience, staff resources and good repeatability over time. Surrogate methods, such as anthropometry and bioimpedance analysis (BIA), represent the most readily available techniques. Other methods based on imaging modalities [dual-energy X-ray absorptiometry (DXA), magnetic resonance imaging (MRI), and whole body computed tomography (CT)] are considered to be the "gold standard" reference methods for muscle mass evaluation, but their use is mainly confined to research purposes. New imaging modalities, such as segmental CT scan and muscle ultrasound have been proposed in recent years. Particularly, ultrasound is a promising technique in this field, as it is commonly available for bedside evaluation of renal patients in nephrology wards. However, more data are needed before a routine use of ultrasound for muscle mass evaluation can be recommended in clinical practice.

Body composition is prognostic and predictive of ipilimumab activity in metastatic melanoma

BACKGROUND

Body composition is minimally investigated in an immunotherapy era. Specific body composition signals such as myosteatosis may reflect aspects of patients' immunology and thereby their ability to respond to immunotherapies. Ipilimumab is a key checkpoint inhibitor in metastatic melanoma. As an antibody, it may also be more accurately dosed using body composition parameters rather than weight alone. This retrospective study aimed to investigate body composition-based dosing and outcomes.

METHODS

Pretreatment computed tomography images from metastatic melanoma, ipilimumab-treated patients from 2009 to 2014 were used to measure myosteatosis [skeletal muscle radiographic density or SMD, in Hounsfield units (HU)] and surface area (cm² ) as previously described. Cut point analysis determined whether a level of ipilimumab dose and myosteatosis demonstrated differences in progression-free (PFS) and overall survival (OS). Secondary endpoints included objective response rates and toxicities.

RESULTS

Of 121 identified, 97 patients were evaluable. Baseline demographics included 56 years median age, 60% male participants, and 23.7% with BRAF mutations. SMD analysis identified cut-offs of SMD < 42 in those with BMI < 25 kg/m² and <20 HU in those with BMI ≥ 25 kg/m² , respectively. Low SMD patients had poorer median PFS [2.4 vs. 2.7 months, hazard ratio (HR) 1.76, P = 0.008] and OS (5.4 vs. 17.5 months, HR 2.47, P = 0.001), which remained significant in multivariate modelling. High SMD patients had more immune-related adverse events, better objective response rates (17.9 vs. 3.3%, P = 0.051), and lower baseline neutrophil-to-lymphocyte ratio (21 vs. 39%, P = 0.049). Separately, patients receiving <2.03 mg/cm² had improved median PFS (3.0 vs. 2.6 months, HR 1.88, P = 0.02) and OS (14.9 vs. 5.7 months, HR 1.98, P = 0.01).

CONCLUSIONS

Low SMD and receiving >2.03 mg/cm² are prognostic of poorer melanoma outcomes post ipilimumab. SMD may identify patients with flawed immunology and predict who may better respond to such therapy. Ipilimumab dosing by skeletal muscle index stands in contrast to weight-based dosing and may demonstrate a more accurate method of antibody dosing.

Low testosterone is associated with frailty, muscle wasting and physical dysfunction among men receiving hemodialysis: a longitudinal analysis

BACKGROUND

Despite the high prevalence of frailty among patients receiving hemodialysis, few preventable or treatable contributing causes have been identified. Hypogonadism is also common in this population and low serum testosterone concentrations share several clinical phenotypes with frailty. We hypothesized that low serum testosterone concentrations would be associated with frailty and several of its individual components.

METHODS

We used data from 440 men from A Cohort Study To Investigate the Value of Exercise in ESRD/Analysis Designed to Investigate the Paradox of Obesity and Survival in ESRD, a longitudinal study that recruited participants from 14 dialysis centers in Atlanta, GA and the San Francisco, CA Bay Area from 2009 to 2011. We assessed frailty using the Fried Frailty Phenotype. We examined the association between free testosterone (as a continuous and dichotomous variable) and frailty, individual frailty components, sarcopenia, lower extremity function and muscle mass estimation by creatinine and body impedance spectroscopy over 12 months using generalized estimating equations.

RESULTS

The mean age was 56.1 ± 14.2 years and 27% were white. A 50% lower concentration of free testosterone was associated with 1.40-fold higher odds of being frail [95% confidence interval (CI) 1.05-1.53] and 1.40-fold higher odds of becoming frail over 12 months (95% CI 1.07-1.73). This association was mainly due to an association with two components of frailty: grip strength and gait speed. In addition, 50% lower free testosterone concentration was associated with a 1.55-fold higher odds of having sarcopenia (95% CI 1.09-2.02) and 1.72-fold higher odds for developing sarcopenia (95% CI 1.13-2.33) as well as with lower muscle mass and a decrease in muscle mass over 12 months as estimated by serum creatinine and by bioelectrical impedance spectroscopy.

CONCLUSION

Serum free testosterone concentration was associated with frailty, physical function, sarcopenia and muscle mass as well as with changes in these outcomes over 12 months. Testosterone replacement may be a feasible therapeutic target toward prevention of frailty, although clinical trials are needed to test this possibility.

Effect of a pedometer-based walking intervention on body composition in patients with ESRD: a randomized controlled trial

BACKGROUND

A randomized trial of a pedometer-based intervention with weekly activity goals led to a modest increase in step count among dialysis patients. In a secondary analysis, we investigated the effect of this intervention on body composition.

METHODS

Sixty dialysis patients were randomized to standard care or a 6-month program consisting of 3 months of pedometers and weekly step count targets and 3 months of post-intervention follow-up. We obtained bioelectrical impedance spectroscopy (BIS) data on 54 of these patients (28 control, 26 intervention) and used linear mixed-modeling (adjusted for sex and dialysis modality) to estimate differences in change in total-body muscle mass (TBMM) adjusted for height2, fat mass (kg), and body mass index (BMI) (kg/m2) between control and intervention groups.

RESULTS

The median age of participants was 57.5 years (53-66), and 76% were men. At baseline, there was no significant difference between groups in age, BMI, race, or body composition, but there were more men in the intervention group. After 3 months, patients in the intervention group increased their average daily steps by 2414 (95% CI 1047, 3782) more than controls (p < 0.001), but there were no significant differences in body composition. However, at 6 months, participants in the intervention had a significantly greater increase from baseline in TBMM of 0.7 kg/m2 (95% CI 0.3, 1.13), decrease in fat mass (- 4.3 kg [95% CI -7.1, - 1.5]) and decrease in BMI (- 1.0 kg/m2 [95% CI -1.8, - 0.2]) relative to controls. In post-hoc analysis, each increase of 1000 steps from 0 to 3 months was associated with a 0.3 kg decrease in fat mass (95% CI 0.05, 0.5) from 0 to 6 months, but there was no dose-response relationship with TBMM/ht2 or BMI.

CONCLUSION

A pedometer-based intervention resulted in greater decreases in fat mass with relative preservation of muscle mass, leading to a greater decrease in BMI over time compared with patients not in the intervention. These differences were driven as much by worsening in the control group as by improvement in the intervention group. Step counts had a dose-response relationship with decrease in fat mass.

TRIAL REGISTRATION

ClinicalTrials.gov (NCT02623348). 02 December 2015.

Acute effect of multiple sets of fatiguing resistance exercise on muscle thickness, echo intensity, and extracellular-to-intracellular water ratio

Resistance exercise (RE) causes an acute increase of the muscle thickness (MT) considered to relate to an increase in tissue water content. Segmental bioelectrical impedance spectroscopy (S-BIS) is a tool used to noninvasively assess intra- and extra-cellular water (ICW and ECW, respectively) of a given limb segment. The purpose of the present study was to examine the change of MT, ultrasound echo intensity (EI), ICW, and ECW after 3 sets of exhaustive RE. Eighteen untrained young males (age, 25.4 ± 4.1 years) performed RE consisting of 3 sets of knee extension concentric and eccentric contractions with 80% of 1-repetition maximum to failure. The MT and EI of the quadriceps measured by ultrasonography, and ECW/ICW ratio of the thigh assessed by S-BIS before (baseline) and after each set of RE (PostEx1, 2, and 3). The changes (Δ) in MT, EI, and ECW/ICW ratio were calculated as values of PostEx minus baseline values. The values of MT, EI, and ECW/ICW ratio at PostEx3 were significantly higher than baseline (effect size: MT, 1.11; EI, 0.47; and ECW/ICW ratio, 0.45). In addition, ΔMT was significantly and moderately correlated with ΔECW/ICW ratio (r = 0.61). Integrated data showed weak but significant correlation between ΔEI and ΔECW/ICW ratio as well (r = 0.31). The present results suggest multiple sets of exhaustive knee extension RE induce the acute increase of EI and ECW/ICW ratio as well as MT. The acute increase of muscle size after exercise can be at least partly explained by relative ECW increase.

Hyperhomocysteinemia Associated with Low Muscle Mass, Muscle Function in Elderly Hemodialysis Patients: An Analysis of Multiple Dialysis Centers

Background

The hyperhomocysteinemia was with high prevalence and has been considered as a risk factor for cardiovascular disease in hemodialysis patients. These patients also experienced a high risk of muscle wasting caused by the comorbidity, malnutrition, and low physical activity. We investigated the associations of homocysteinemia with muscle mass, muscle function in elderly hemodialysis patients.

Methods

A clinical cross-sectional study was conducted on 138 hemodialysis patients aged 65 years and above in seven hospital-based hemodialysis centers in Taiwan. The data on anthropometry, laboratory, and 3-day dietary intake was examined. The skeletal muscle mass (SMM) was measured by the bioelectrical impedance analysis; the SMM was adjusted by height or weight as SMM_Ht2 (kg/m²) and SMM_Wt (%). Muscle function was defined as handgrip strength (HGS) (kg) measured by handgrip dynamometer. Statistical analyses were conducted using simple regression and multivariable stepwise regression analysis.

Results

In the total sample, 74.6 % of hemodialysis patients were hyperhomocysteinemia (≥ 15 μmol/L). The means of SMM_Ht2, SMM_Wt, arm lean mass, hand grip strength, and muscle quality were 8.7 ± 1.2, 37.7 ± 5.6, 1.7 ± 0.5, 21.1 ± 7.4, and 10.0 ± 3.0, respectively. The multivariable stepwise regression analysis showed that homocysteinemia level was significantly inversely associated with SMM_Wt (B-coeff. = -0.03, p = 0.02) in hemodialysis patients above 65 years old, but not with muscle function.

Conclusions

Hyperhomocysteinemia is common and associated with decreased muscle mass in the elderly hemodialysis patients. Future studies are suggested to explore the impact of the homocysteine-lowering therapy on muscle decline.

Physical Processes in Polymeric Filters Used for Dialysis

The key physical processes in polymeric filters used for the blood purification include transport across the capillary wall and the interaction of blood cells with the polymer membrane surface. Theoretical modeling of membrane transport is an important tool which provides researchers with a quantification of the complex phenomena involved in dialysis. In the paper, we present a dense review of the most successful theoretical approaches to the description of transport across the polymeric membrane wall as well as the cell⁻polymer surface interaction, and refer to the corresponding experimental methods while studying these phenomena in dialyzing filters.

The associations of fat tissue and muscle mass indices with all-cause mortality in patients undergoing hemodialysis

Protein-energy wasting, which involves loss of fat and muscle mass, is prevalent and is associated with mortality in hemodialysis (HD) patients. We investigated the associations of fat tissue and muscle mass indices with all-cause mortality in HD patients. The study included 162 patients undergoing HD. The fat tissue index (FTI) and skeletal muscle mass index (SMI), which represent respective tissue masses normalized to height squared, were measured by bioimpedance analysis after dialysis. Patients were divided into the following four groups according to the medians of FTI and SMI values: group 1 (G1), lower FTI and lower SMI; G2, higher FTI and lower SMI; G3, lower FTI and higher SMI; and G4, higher FTI and higher SMI. The associations of the FTI, SMI, and body mass index (BMI) with all-cause mortality were evaluated. During a median follow-up of 2.5 years, 29 patients died. The 5-year survival rates were 48.6%, 76.1%, 95.7%, and 87.4% in the G1, G2, G3, and G4 groups, respectively (P = 0.0002). The adjusted hazard ratio values were 0.34 (95% confidence interval [CI] 0.10–0.95, P = 0.040) for G2 vs. G1, 0.13 (95%CI 0.01–0.69, P = 0.013) for G3 vs. G1, and 0.25 (95%CI 0.07–0.72, P = 0.0092) for G4 vs. G1, respectively. With regard to model discrimination, on adding both FTI and SMI to a model with established risk factors, the C-index increased significantly when compared with the value for a model with BMI (0.763 vs. 0.740, P = 0.016). Higher FTI and/or higher SMI values were independently associated with reduced risks of all-cause mortality in HD patients. Moreover, the combination of the FTI and SMI may more accurately predict all-cause mortality when compared with BMI. Therefore, these body composition indicators should be evaluated simultaneously in this population.

The effect of dulaglutide on body composition in type 2 diabetes mellitus patients on hemodialysis

AIMS

To evaluate the effect of dulaglutide on body composition in type 2 diabetes mellitus (T2DM) patients undergoing hemodialysis (HD).

METHODS

Twenty-one T2DM patients on HD, who had been treated with insulin and newly added teneligliptin (N = 10) or dulaglutide (N = 11), were enrolled. Body composition changes, such as fat mass (FM) and skeletal muscle mass (SMM), glycated albumin (GA), and insulin doses were compared before and after six months of treatment with teneligliptin or dulaglutide.

RESULTS

The percentage changes of GA and insulin doses were comparable between the teneliglipin and dulaglutide groups. Conversely, although FM and SMM did not change in the teneligliptin group (from 15.7 kg to 14.1 kg, P = 0.63 and 18.6 kg to 18.9 kg, P = 0.16, respectively), those in the dulaglutide group significantly decreased (from 21.9 kg to 18.9 kg, P = 0.037 and 21.0 kg to 20.2 kg, P = 0.011, respectively).

CONCLUSIONS

Six months of dulaglutide treatment significantly reduced not only FM but also SMM, although changes in GA and insulin doses were comparable with those in the teneligliptin group. Dulaglutide may have the effect of promoting sarcopenia; therefore, it may be carefully used in T2DM patients on HD.

Is 3-Carboxy-4-methyl-5-propyl-2-furanpropionate (CMPF) a Clinically Relevant Uremic Toxin in Haemodialysis Patients?

3-Carboxy-4-methyl-5-propyl-2-furanpropionate (CMPF) is a metabolite of furan fatty acid and a marker of fish oil intake. CMPF is described as a protein-bound uremic toxin and interacts with free oxygen radicals, which can induce cell damages. However, the clinical consequences of CMPF accumulation in haemodialysis patients remain poorly documented. The aims of this study are to investigate potential association between CMPF levels and (i) biochemical and nutritional parameters; (ii) cardiovascular events and (iii) mortality. Two hundred and fifty-two patients undergoing maintenance haemodialysis were included. Routine clinical biochemistry tests and assay for CMPF by HPLC technique were performed at the inclusion. Body composition parameters were measured using a bioimpedance spectroscopy method. The enrolled patients were prospectively monitored for cardiovascular events and mortality. CMPF level was positively correlated with nutritional parameters and lean mass and is significantly higher in patients without protein-energy wasting. However, the multivariate linear regression analysis indicated that CMPF level was not independently associated with albumin, prealbumin, creatinemia and body mass index. Elevated serum CMPF was not associated with mortality and cardiovascular morbidity. Our results indicate that CMPF is not a relevant uremic toxin in haemodialysis and in contrast could be a marker of healthy diet and omega 3 intakes.

Frailty and the Quality of Life in Hemodialysis Patients: The Importance of Waist Circumference

OBJECTIVE

Frailty among the end-stage renal disease (ESRD) population is highly prevalent and has been associated with mortality. Little is known about the relation of different aspects of body composition, a modifiable risk factor, with the risk of frailty in ESRD population.

DESIGN AND METHODS

One hundred and fifty-one patients including 85 men and 66 women, aged ≥18 years with ESRD who had been receiving conventional maintenance hemodialysis (HD) for at least 3 months were included. Body fat and muscle mass from both bioimpedance spectroscopy and skin-fold thickness and waist circumference as a surrogate of abdominal obesity were measured. Frailty was defined based on Fried's criteria. Health-related quality of life was collected using the RAND version of the Kidney Disease Quality of Life (KDQOL-36) Survey.

RESULTS

We performed single and multiple predictor logistic regression analyses to determine factors associated with frailty. After adjustment for age, sex, and comorbidities, fat mass (both by bioimpedance spectroscopy and anthropometry) and waist circumference, but not muscle mass remained the main predictors of frailty. The odds ratio of frailty in the third tertile compared with the first was 4.97 (1.70-14.55) and 3.84 (1.39-10.61) for fat mass and waist circumference, respectively (P for trends for both <.05). The scores of physical health and kidney disease effect component of quality of life were lower in frail compared with nonfrail patients (40.7 ± 9.2 vs. 33.7 ± 10.2, P < .01 and 66.8 ± 22.4 vs. 51.6 ± 25.7, P < .05 for physical health and effects of disease, respectively).

CONCLUSIONS

Frailty, which is associated with poor outcomes in chronic HD patients, is common and predicted by fat mass and waist circumference but not by body mass index and muscle mass. Interventions to modify abdominal obesity, reflected by waist circumference, could potentially lower the incidence of frailty and hence improve the quality of life in the HD population.

Effect of Change in Fluid Status Evaluated by Bioimpedance Techniques on Body Composition in Hemodialysis Patients

OBJECTIVE

This prospective study uses calf bioimpedance spectroscopy (cBIS) to guide the attainment of dry weight (DW_cBIS) in chronic hemodialysis (HD) patients. The primary aim of this study was to evaluate whether body composition is altered when fluid status is reduced to DW_cBIS.

METHODS

Target post-HD weight was gradually reduced from baseline (BL) until DW_cBIS was achieved. DW_cBIS was defined as the presence of both flattening of the curve of extracellular resistance and the attainment calf normalized resistivity in the normal range during the dialysis treatment. Extracellular volume (ECV), intracellular volume, and total body water (TBW) were measured using whole body BIS (Hydra 4200). Fluid overload, lean body mass, and fat mass were calculated according to a body composition model.

RESULTS

Seventy-three patients enrolled and 60 completed the study (55 ± 13 years, 49% male). Twenty-eight patients (25% diabetes) achieved DW_cBIS, whereas 32 patients (47% diabetes) did not. Number of treatment measurements were 16 ± 10 and 12 ± 13 studies per patient in the DW_cBIS and non-DW_cBIS groups, respectively. Although significant decreases in body weight and ECV were observed, lean body mass and FM did not differ significantly in both groups from BL to the end of study. ECV, ECV/TBW, and fluid overload were higher in the non-DW_cBIS than in the DW_cBIS group both at BL and at the end of study. Ratios of intradialytic changes in calf normalized resistivity, ECV, and ECV/TBW to ultrafiltration volume were significantly lower in diabetic than in non-diabetic patients.

CONCLUSIONS

This study shows that decreasing fluid status by gradual reduction of post-HD weight in both DW_cBIS and Non-DW_cBIS groups did not affect body composition significantly over a period of about 4 weeks.

Associations of Body Mass Index and Body Fat With Markers of Inflammation and Nutrition Among Patients Receiving Hemodialysis

BACKGROUND

Understanding the extent to which visceral and subcutaneous body fat are associated with markers of nutrition and inflammation in patients on dialysis therapy could shed light on the obesity paradox and the biology of subcutaneous fat.

STUDY DESIGN

Cross-sectional.

SETTING & PARTICIPANTS

609 adults receiving hemodialysis who participated in the ACTIVE/ADIPOSE Study.

PREDICTORS

Body mass index (BMI), waist circumference, and bioelectrical impedance spectroscopy-derived estimates of percent body fat.

OUTCOMES

C-Reactive protein (CRP), interleukin 6 (IL-6), prealbumin, albumin, leptin, and adiponectin concentrations.

MEASUREMENTS

We performed linear regression analyses to examine the extent to which proxies of visceral and subcutaneous fat were associated with inflammation, nutrition, and adiposity-related hormones.

RESULTS

BMI was directly associated with markers of inflammation (standardized estimate for ln[CRP in mg/L]: 0.30 [95% CI, 0.22-0.38] per 10kg/m²; for ln[IL-6 in pg/mL]: 0.10 [95% CI, 0.02-0.18] per 10kg/m²), but was not associated with markers of nutrition. BMI was also inversely associated with adiponectin and directly associated with leptin. With waist circumference and percent body fat (as a proxy of visceral and subcutaneous fat, respectively) modeled together, waist circumference was associated with markers of inflammation (standardized estimate for ln[CRP in mg/L]: 0.21 [95% CI, 0.09-0.34] per 10cm; for ln[IL-6 in pg/mL]: 0.18 [95% CI, 0.07-0.29] per 10cm), whereas percent body fat was not associated with CRP (standardized estimate for ln[CRP in mg/L]: 0.03 [95% CI, -0.10 to 0.15] per 1%) and was inversely associated with IL-6 (standardized estimate for ln[IL-6 in pg/mL]: -0.15 [95% CI, -0.27 to -0.02] per 1%). In addition, waist circumference was inversely associated with prealbumin and albumin (standardized estimates of -0.12 [95% CI, -0.23 to -0.02] mg/dL per 10cm and -0.17 [95% CI, -0.28 to -0.06] g/dL per 10cm, respectively), and percent body fat was directly associated with prealbumin and albumin (0.20 [95% CI, 0.07-0.32] mg/dL and 0.15 [95% CI, 0.02-0.28] g/dL per 1%, respectively). Higher waist circumference was associated indirectly with adiponectin and directly with leptin concentrations.

LIMITATIONS

Although the observed associations implicate visceral fat as the cause of inflammation, it cannot be determined in this cross-sectional study.

CONCLUSIONS

Proxies of visceral and subcutaneous fat appear to have opposing associations with biomarkers of inflammation and nutrition. Subcutaneous fat may be an indicator of nutritional status, and visceral fat, an indicator of inflammation.

The Extracellular to Intracellular Water Ratio in Upper Legs is Negatively Associated With Skeletal Muscle Strength and Gait Speed in Older People

Skeletal muscles contain a large volume of water that is classified into intracellular (ICW) and extracellular (ECW) water fractions. Nuclear magnetic resonance-based biomarkers suggest that increased water T2 heterogeneities, as well as elevated water T2 relaxation in the quadriceps occurs in the elderly when compared with young adults. However, nuclear magnetic resonance is difficult to apply to a large-scale study or a clinical setting for sarcopenia and frailty screening. Segmental bioelectrical impedance spectroscopy is a unique tool used to assess the segmental ratio of ECW/ICW in the limbs. We evaluated 405 community-living people aged between 65 and 90 years. ECW and ICW in the upper legs were assessed by segmental bioelectrical impedance spectroscopy. Isometric knee extension strength, gait speed, and skeletal muscle mass were measured. Thigh ECW/ICW was negatively correlated with knee extension strength and gait speed (r = -.617 and -.431, respectively, p < .001) and increased with age (p < .001). Thigh ECW/ICW was a significant predictor of knee extension strength and gait speed independent of age, sex, body mass index, and skeletal muscle mass. Relative expansion of ECW against ICW in the thigh muscles is a factor in decreased muscle quality and a biomarker of muscle aging.

Developing and Validating an Age-Independent Equation Using Multi-Frequency Bioelectrical Impedance Analysis for Estimation of Appendicular Skeletal Muscle Mass and Establishing a Cutoff for Sarcopenia

Background: Appendicular skeletal muscle (or lean) mass (ALM) estimated using dual-energy X-ray absorptiometry (DXA) is considered to be a preferred method for sarcopenia studies. However, DXA is expensive, has limited portability, and requires radiation exposure. Bioelectrical impedance analysis (BIA) is inexpensive, easy to use, and portable; thus BIA might be useful in sarcopenia investigations. However, a large variety of models have been commercially supplied by different companies, and for most consumer products, the equations estimating ALM are not disclosed. It is therefore difficult to use these equations for research purposes. In particular, the BIA equation is often age-dependent, which leads to fundamental difficulty in examining age-related ALM loss. The aims of the current study were as follows: (1) to develop and validate an equation to estimate ALM using multi-frequency BIA (MF-BIA) based on theoretical models, and (2) to establish sarcopenia cutoff values using the equation for the Japanese population. Methods: We measured height (Ht), weight, and ALM obtained using DXA and a standing-posture 8-electrode MF-BIA (5, 50, 250 kHz) in 756 Japanese individuals aged 18 to 86-years-old (222 men and 301 women as developing equation group and 97 men and 136 women as a cross validation group). The traditional impedance index (Ht²/Z₅₀) and impedance ratio of high and low frequency (Z₂₅₀/Z₅) of hand to foot values were calculated. Multiple regression analyses were conducted with ALM as dependent variable in men and women separately. Results: We created the following equations: ALM = (0.6947 × (Ht²/Z₅₀)) + (-55.24 × (Z₂₅₀/Z₅)) + (-10,940 × (1/Z₅₀)) + 51.33 for men, and ALM = (0.6144 × (Ht²/Z₅₀)) + (-36.61 × (Z₂₅₀/Z₅)) + (-9332 × (1/Z₅₀)) + 37.91 for women. Additionally, we conducted measurements in 1624 men and 1368 women aged 18 to 40 years to establish sarcopenia cutoff values in the Japanese population. The mean values minus 2 standard deviations of the skeletal muscle mass index (ALM/Ht²) in these participants were 6.8 and 5.7 kg/m² in men and women, respectively. Conclusion: The current study established and validated a theoretical and age-independent equation using MF-BIA to estimate ALM and provided reasonable sarcopenia cutoff values.