| dc.description.abstract | Sarcopenia is defined as the age-related loss of muscle mass and function. The purposes of this study were to examine the consistency among the four different sarcopenia classification models and explore new variables to improve sarcopenia classification, to determine the effects of aging on body composition, functionality, muscle quality, handgrip strength, and skeletal muscle index (SMI) and determine the relationships among muscle mass, functionality, mobility, muscle quality, handgrip strength, and SMI. Ninety-one women (age = 68.5 ± 7.9 yrs; height = 162.1 ± 6.5 cm; weight = 64.7 ± 11.1 kg) and 76 men (age = 70.7 ± 6.2 yrs; height = 176.1 ± 6.6 cm; weight = 82.8 ± 10.6 kg) volunteered to participate in one of two separate studies: a two-phase clinical trial (phase one = A08, n=53; phase two = A09, n=54) sponsored by Abbott Nutrition conducted in 2008 and 2009 entitled “Evaluation of AN777 in Elderly Subjects” and a clinical trial (G10, n=60) sponsored by General Nutrition Corporation conducted in 2010 entitled “Effects of Whey Protein Supplementation on body Composition, Muscular Strength, and Mobility in Older Adults” Participants completed body composition, handgrip strength, functionality and mobility, and bench press and leg press 1-repetition maximum (1-RM) strength assessments. A full body dual-energy x-ray absorptiometry (DEXA) scan was completed to assess total body lean mass (LM), total body fat mass (FM), and appendicular lean mass (ALM). Additional calculations included estimated total body skeletal muscle (TBSM), non-skeletal muscle lean mass, and SMI (ALM/ht^2). Handgrip strength was measured as the average of the two highest of three trials using a hand-held digital or hydraulic handgrip dynamometer with their dominant hand. The timed get-up-and-go (TGUG) was performed on a measured and marked 3-meter course using an armless wooden chair and a digital stopwatch. Bench press and leg press strength were assessed using a five-repetition maximum (5-RM) protocol on a standard Olympic bench and 45° hip sled, respectively, 5-RM was then used to estimate 1-RM strength. Participants were classified as sarcopenic or non-sarcopenic using four different cut-off value criteria established by Baumgartner et al. (1998), Delmonico et al. (2007), and two methods by Newman et al. (2003): (a) ALM/ht^2 and (b) residuals method. Handgrip muscle quality (HGMQ), upper- and lower-body muscle quality (UMQ and LMQ, respectively) were also calculated as maximal strength divided by dominant arm muscle mass, total arm muscle mass, or total leg muscle mass, respectively. Fourteen separate two-way analyses of variance (ANOVA) (gender [men vs. women] x age [50s vs. 60s vs. 70s vs. 80s]) were used to analyze LM, FM, ALM, TBSM, handgrip strength, TGUG, SMI, SMI residuals, non-skeletal muscle lean mass, bench press and leg press 1-RM, HGMQ, UMQ, and LMQ. Independent t-tests were used to analyze gender differences amongst all variables and one-way ANOVAs used to analyze differences between age groups (50s: n=20, 60s: n=63, 70s: n=60, and 80s: n=11). In addition, Kendall's W and chi-squared tests were performed along with binary logistic regression to identify the best cut-off values and models in classification of sarcopenia. PASW version 18.0 was used for all statistical analysis (Chicago, Illinois, United States). An alpha of p<0.05 was used to determine statistical significance for all analyses. Independent t-tests indicated that participants were significantly younger in G10 than A08 or A09 (p<0.05) and men were younger than the women in G10 (p<0.05). Men were taller, weighed more, and had lower body fat percentages than women in all studies (p<0.05), with no differences between studies. Using the Baumgartner et al. (1998), Newman et al. (a) (2003), and Delmonico et al. (2007) cut-off values to classify sarcopenia, sarcopenic individuals were significantly older than non-sarcopenic individuals (p<0.05). However, there were no age-related differences when using the Newman et al. (b) cut-off values (p>0.05). There were no gender- or age-related differences for TGUG (p>0.05). There was a significant interaction for handgrip strength (p<0.05). Men in their 50s, 60s, and 70s had greater handgrip strength than women (p<0.05), men in their 50s, 60s, and 70s had greater handgrip strength than those in their 80s, and women in their 50s and 60s had greater handgrip strength than those in their 70s and 80s (p<0.05). Men had greater values for ALM, TBSM, LM, non-skeletal muscle LM, bench press and leg press 1-RM, HGMQ, UMQ, LMQ, SMI, or SMI residuals (p<0.05) than women. Men and women in their 50s, 60s, and 70s had significantly greater LM, TBSM, ALM, and LB 1-RM than those in their 80s (p<0.05). Non-skeletal LM was greater for individuals in their 60s than in their 80s (p<0.05). Bench press1-RM was greater for individuals in their 60s than those in their 80s (p<0.05). LMQ was greater for individuals in their 50s than those in their 80s (p<0.05), and SMI was greater for individuals in their 60s than those in their 80s (p<0.05). There were low to moderate positive correlations among UMQ and LMQ (r=0.39) and leg press 1-RM and handgrip strength (r=0.47) in women, UMQ and leg press 1-RM (r=0.48), LMQ and HGMQ (r=0.31), HGMQ and bench press 1-RM (r=0.37), handgrip strength and bench press1-RM (r=0.67), and handgrip strength and leg press 1-RM (r=0.57) in men. Men and women had low to moderate positive correlations among LMQ and handgrip strength (r=0.43 and r=0.32, respectively) and bench press 1-RM (r=0.58 and r=0.49, respectively). There were low to moderate negative correlations among UMQ and TGUG (r= -0.27), age and LMQ (r= -0.35), HGMQ (r= -0.34), and leg press 1-RM (r= -0.46) in women, and age and handgrip strength (r= -0.30 and r= -0.54, respectively) and bench press 1-RM (r= -0.37 and r= -0.28, respectively) in men and women. In men and women, SMI was positively correlated with bench press 1-RM (r=0.59 and r=0.53, respectively), leg press 1-RM (r=0.65 and r=0.61, respectively), handgrip strength (r=0.52 and r=0.37, respectively), LM (r=0.72 and r=0.70, respectively), ALST (r=0.83 and r=0.82, respectively), LMQ (r=0.43 and r=0.36, respectively), and TBSM (r=0.83 and r=0.82, respectively). In women, SMI was positively correlated with FM (r=0.29) and negatively correlated with age (r= -0.37) and negative correlated with TGUG (r= -0.42) in men. The prevalence of sarcopenia ranged from 31-44% in women and was 13% in men based off of the four different cut-off values. To identify which of the four cut-off values would be the most appropriate to adapt as the standard in classifying sarcopenia, Kendall's W and chi-squared tests were performed. The highest agreement in distributions was among Newman et al. (a) (2003) and Delmonico et al. (2007), with 100% agreement (r=1.00, p<0.001), followed by Baumgartner et al. (r=0.760, p<0.001). Exploratory binary logistic regression was calculated to determine if sarcopenia status (sarcopenic vs. non-sarcopenic) could be determined with theory-based predictors (age, gender, LM, handgrip strength, and TGUG). The best predicted probability estimates were derived with Newman et al. (a) (2003) or Delmonico et al. (2007) as the dependent variable in classifying sarcopenia using gender and lean mass as the predicting variables. The results of the present study confirm previous findings that functional strength and muscle quality were negatively correlated with age and that LM and functional strength decreased in the 7th and 8th decades of life. Previous studies have used cut-off values established by Baumgartner et al. (1998), however, using ALM/m^2 and cut-off values established by Newman et al. (a) (2003) or Delmonico et al. (2007) may be more appropriate in classifying sarcopenia. A larger epidemiological database needs to be established in order to generalize the proper cut-off values to the entire elderly population. | |
