Development and Validation of Estimation Equations for Appendicular Skeletal Muscle Mass in Chinese Community-Dwelling Older Adults

Figures & data

Table 1 Characteristics of Participants in the Development and Validation Groups

	Total Men/Women	Development Group		Validation Group
		Men	Women	Men	Women
n	690/847	489	587	201	260
Age, years	72.39 ± 5.63	72.22±5.53*	72.56 ± 5.87*	73.43 ± 5.65	71.52 ± 5.09
Height, m	1.60 ± 0.08	1.66±0.06	1.55 ± 0.06	1.67 ± 0.06	1.55 ± 0.05
Weight, kg	60.76 ± 10.23	65.73±9.60	56.77 ± 9.19	66.31 ± 8.83	56.15 ± 8.19
BMI, kg/m²	23.67 ± 3.17	23.68±2.96	23.66 ± 3.46	23.91 ± 2.92	23.48 ± 3.01
Upper arm circumference, cm	27.47 ± 2.65	27.48±2.45	27.30 ± 2.85	27.79 ± 2.25	27.58 ± 2.82
Calf circumference, cm	34.37 ± 2.74	35.21±2.59	33.72 ± 2.78	35.13 ± 2.44	33.70 ± 2.62
Handgrip strength, kg	24.81 ± 7.97	31.07 ± 6.83	19.75 ± 4.45	31.59 ± 6.16	19.31 ± 4.16
Walk speed, m/s	1.01 ± 0.20	1.03 ± 0.20*	0.95 ± 0.20*	1.09 ± 0.18	1.04 ± 0.19
ASM by BIA, kg	18.07 ± 4.37	21.95 ± 3.24	14.91 ± 2.00	22.04 ± 3.00	14.85 ± 1.92

Note: *P<0.05 vs men/women in the validation group.

Abbreviation: BMI, body mass index.

Table 2 Pearson’s Correlation Coefficients of Anthropometric and Physical Function Parameters with BIA-Measured ASM

	ASM, kg
	Development Group (n = 1076)		Validation Group (n = 461)
	r	P value	r	P value
Age, years	−0.197	<0.001	−0.015	0.746
Height, cm	0.791	<0.001	0.792	<0.001
Weight, kg	0.792	<0.001	0.808	<0.001
BMI, kg/m²	0.368	<0.001	0.386	<0.001
Upper arm circumference, cm	0.401	<0.001	0.389	<0.001
Calf circumference, cm	0.651	<0.001	0.599	<0.001
Handgrip strength, kg	0.753	<0.001	0.754	<0.001
Walk speed, m/s	0.269	<0.001	0.160	<0.001

Abbreviations: BMI, body mass index; ASM, appendicular skeletal muscle mass; BIA, bioelectrical impedance analysis.

Table 3 BIA-Measured ASM Estimating Equations Deduced from Age, Anthropometric and Physical Function Parameters (n = 1076)

Equation		r	Adjusted R²	SEE (kg)	P value
No. 1		0.941	0.885	1.4855	<0.001
No. 2		0.947	0.897	1.4072	<0.001
No. 3		0.954	0.909	1.3227	<0.001
No. 4		0.954	0.911	1.3110	<0.001
No. 5		0.955	0.911	1.3050	<0.001
No. 6		0.955	0.912	1.2973	<0.001
No. 7		0.956	0.913	1.2894	<0.001
No. 8		0.956	0.914	1.2826	<0.001
No. 9		0.956	0.914	1.2793	<0.001

Abbreviations: ASM, appendicular skeletal muscle mass; BIA, bioelectrical impedance analysis; r, correlation coefficient; R², coefficient of determination; SEE, standard error of the estimate.

Table 4 Comparison of the Estimated ASMs with BIA-Measured ASM (n = 461)

	Mean ± SD	t^a	P	ICC
ASM4, kg	17.95±4.11	0.568	0.570	0.950
ASM5, kg	17.89±4.10	1.503	0.133	0.949
ASM8, kg	17.91±4.12	0.617	0.537	0.955
ASM9, kg	17.83±4.12	2.217	0.027	0.950

Note: ^aPaired-samples t-test.

Abbreviations: SD, standard deviation; ICC, intraclass correlation coefficient; ASM4, 5, 8, 9: the results deduced from the equations of No. 4, 5, 8, 9 in Table 3 respectively.

Figure 1 Correlation between Estimated ASMs by the Equations and BIA-measured ASM in the Validation Group. (A) Correlation between ASM4 and BIA-measured ASM. (B) Correlation between ASM5 and BIA-measured ASM. (C) Correlation between ASM8 and BIA-measured ASM. (D) Correlation between ASM9 and BIA-measured ASM.

Abbreviations: ASM, appendicular skeletal muscle mass; BIA, bioelectrical impedance analysis; r, correlation coefficient; ASM4, 5, 8, 9, the results deduced from the equations of No. 4, 5, 8, 9 in Table 3 respectively.

Table 5 The Bland-Altman Plot of the Estimated ASMs with Different Equations (n=461)

	Mean Difference	95%LoA
ASM4, kg	0	−2.70~2.60
ASM5, kg	−0.10	−2.70~2.50
ASM8, kg	0	−2.60~2.60
ASM9, kg	−0.10	−2.70~2.50

Abbreviations: LOA, limits of agreement; ASM, appendicular skeletal muscle mass; ASM4, 5, 8, 9, the results deduced from the equations of No. 4, 5, 8, 9 in Table 3 respectively.

Figure 2 Bland-Altman plots of estimated ASMs and BIA-measured ASM in the validation group. (A) Bland-Altman plots of ASM4 and BIA-measured ASM. (B) Bland-Altman plots of ASM5 and BIA-measured ASM. (C) Bland-Altman plots of ASM8 and BIA-measured ASM. (D) Bland-Altman plots of ASM9 and BIA-measured ASM.

Note: Dotted horizontal lines represent the mean difference and limits of agreement defined as the mean difference ± 1.96SD.

Abbreviations: ASM, appendicular skeletal muscle mass; BIA, bioelectrical impedance analysis; SD, standard deviation; ASM4, 5, 8, 9, the results deduced from the equations of No. 4, 5, 8, 9 in Table 3 respectively.