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. 2014 May;69(5):567-75.
doi: 10.1093/gerona/glu023.

Cutpoints for low appendicular lean mass that identify older adults with clinically significant weakness

Peggy M Cawthon  1 , Katherine W Peters, Michelle D Shardell, Robert R McLean, Thuy-Tien L Dam, Anne M Kenny, Maren S Fragala, Tamara B Harris, Douglas P Kiel, Jack M Guralnik, Luigi Ferrucci, Stephen B Kritchevsky, Maria T Vassileva, Stephanie A Studenski, Dawn E Alley
Affiliations

Cutpoints for low appendicular lean mass that identify older adults with clinically significant weakness

Peggy M Cawthon et al. J Gerontol A Biol Sci Med Sci. 2014 May.

Abstract

Background: Low lean mass is potentially clinically important in older persons, but criteria have not been empirically validated. As part of the FNIH (Foundation for the National Institutes of Health) Sarcopenia Project, this analysis sought to identify cutpoints in lean mass by dual-energy x-ray absorptiometry that discriminate the presence or absence of weakness (defined in a previous report in the series as grip strength <26kg in men and <16kg in women).

Methods: In pooled cross-sectional data stratified by sex (7,582 men and 3,688 women), classification and regression tree (CART) analysis was used to derive cutpoints for appendicular lean body mass (ALM) that best discriminated the presence or absence of weakness. Mixed-effects logistic regression was used to quantify the strength of the association between lean mass category and weakness.

Results: In primary analyses, CART models identified cutpoints for low lean mass (ALM <19.75kg in men and <15.02kg in women). Sensitivity analyses using ALM divided by body mass index (BMI: ALMBMI) identified a secondary definition (ALMBMI <0.789 in men and ALMBMI <0.512 in women). As expected, after accounting for study and age, low lean mass (compared with higher lean mass) was associated with weakness by both the primary (men, odds ratio [OR]: 6.9 [95% CI: 5.4, 8.9]; women, OR: 3.6 [95% CI: 2.9, 4.3]) and secondary definitions (men, OR: 4.3 [95% CI: 3.4, 5.5]; women, OR: 2.2 [95% CI: 1.8, 2.8]).

Conclusions: ALM cutpoints derived from a large, diverse sample of older adults identified lean mass thresholds below which older adults had a higher likelihood of weakness.

Keywords: Cutpoints.; Muscle; Sarcopenia.

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Figures

Figure 1.
Figure 1.
Scatterplots and correlation of appendicular lean mass (ALM) or ALM/body mass index (BMI) versus grip strength or walking speed for men and women in the FNIH (Foundation for the National Institutes of Health) Sarcopenia Project.
Figure 2.
Figure 2.
Classification and regression tree models for measures of lean mass, body size, and lean mass standardized to body size discriminating weakness in older men and women in the FNIH (Foundation for the National Institutes of Health) Sarcopenia Project. Model included the following potential discriminators of weakness (grip strength <16kg in women and <26kg in men): ALM (appendicular lean mass), height, weight, height2, total body fat (TBF), BMI (body mass index), ALMheight (ALM/height), ALMweight (ALM/weight), ALMheight2 (ALM/height2), ALMBMI (ALM/BMI), ALMTBF (ALM/TBF), LLMheight (LLM/height; LLM = leg lean mass), LLMweight (LLM/weight), LLMheight2 (LLM/height2), LLMTBF (LLM/TBF), and ALMBMI (LLM/BMI).
Figure 3.
Figure 3.
Classification and regression tree models for ALMBMI and BMI discriminating weakness in older men and women in the FNIH (Foundation for the National Institutes of Health) Sarcopenia Project. Model included ALM and ALMBMI (ALM/BMI) as potential discriminators of weakness (grip strength <16kg in women and <26kg in men). ALM = appendicular lean mass; BMI = body mass index.
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