Cut-off Values for Lower Limb Muscle Thickness to Detect Low Muscle Mass for Sarcopenia in Older Adults

Figures & data

Table 1 Characteristics of Study Participants

	Male				Female
	Younger (n = 31)	Older (n = 64)	P value	(%)	Younger (n = 28)	Older (n = 140)	P value	(%)
Age (years)	22.9 ± 3.3	76.9 ± 6.4			21.6 ± 1.9	74.7 ± 5.0
Height (cm)	172.6 ± 5.2	164.0 ± 6.3	< 0.001		158.9 ± 5.5	152.4 ± 5.9	< 0.001
Weight (kg)	65.5 ± 7.9	60.6 ± 8.4	0.007		53.3 ± 5.3	50.6 ± 7.7	0.029
BMI (kg/m^2)	22.0 ± 2.4	22.5 ± 2.8	0.389		21.1 ± 2.3	21.8 ± 2.9	0.227
SMI (kg/m^2)	8.35 ± 0.79	7.65 ± 0.86	< 0.001	−8.3	6.86 ± 0.56	6.15 ± 0.60	< 0.001	−10.3
RF MT (cm)	2.52 ± 0.33	1.69 ± 0.34	< 0.001	−32.7	2.03 ± 0.31	1.54 ± 0.29	< 0.001	−24.1
VI MT (cm)	1.82 ± 0.35	1.22 ± 0.27	< 0.001	−33.0	1.49 ± 0.34	0.99 ± 0.30	< 0.001	−33.6
QF MT (cm)	4.34 ± 0.59	2.91 ± 0.50	< 0.001	−32.8	3.52 ± 0.59	2.53 ± 0.44	< 0.001	−28.2
GM MT (cm)	2.05 ± 0.32	1.59 ± 0.27	< 0.001	−22.6	1.83 ± 0.20	1.53 ± 0.24	< 0.001	−16.4
Sol MT (cm)	4.42 ± 0.44	4.27 ± 0.49	0.123	−3.5	4.03 ± 0.34	3.90 ± 0.48	0.092	−3.3
TS MT (cm)	6.48 ± 0.58	5.86 ± 0.61	< 0.001	−9.6	5.87 ± 0.45	5.44 ± 0.57	< 0.001	−7.4
MT sum (cm)	10.82 ± 0.98	8.77 ± 1.00	< 0.001	−19.0	9.39 ± 0.95	7.96 ± 0.81	< 0.001	−15.2

Notes: Percentage indicates the ratio between older and younger adults, calculated using the equation: [mean value of older adults – mean value of younger adults] ×100/mean value of younger adults.

Abbreviations: BMI, body mass index; SMI, skeletal muscle mass index; RF, rectus femoris; MT, muscle thickness; VI, vastus intermedius; QF, quadriceps femoris; GM, medial head of gastrocnemius; Sol, soleus; TS, triceps surae; MT sum, sum of MT of QF and TS.

Table 2 Comparison of Older Adults with and without Low SMI and ROC Analysis for Low SMI

	t-test			ROC Analysis
	Low SMI	Normal SMI	P value	AUC	P value	Cut-off (cm)	Sensitivity	Specificity
A. males
Subjects (n)	13	51
Age (years)	79.2 ± 6.9	76.3 ± 6.2	0.190
Height (cm)	163.5 ± 6.7	164.1 ± 6.3	0.796
Weight (kg)	53.6 ± 8.2	62.4 ± 7.6	0.002
BMI (kg/m^2)	20.1 ± 2.5	23.1 ± 2.6	0.001
SMI (kg/m^2)	6.65 ± 0.34	7.91 ± 0.76	< 0.001
RF MT (cm)	1.45 ± 0.28	1.76 ± 0.33	0.003	0.775	0.002	1.51	0.692	0.837
VI MT (cm)	1.10 ± 0.20	1.26 ± 0.28	0.030	0.673	0.056	1.15	0.692	0.673
QF MT (cm)	2.55 ± 0.36	3.01 ± 0.49	0.001	0.777	0.002	2.88	0.923	0.571
GM MT (cm)	1.39 ± 0.16	1.64 ± 0.27	< 0.001	0.799	0.001	1.53	0.846	0.633
Sol MT (cm)	3.92 ± 0.42	4.36 ± 0.47	0.004	0.779	0.002	4.16	0.769	0.653
TS MT (cm)	5.31 ± 0.46	6.00 ± 0.57	< 0.001	0.836	< 0.001	5.67	0.846	0.735
MT sum (cm)	7.86 ± 0.78	9.02 ± 0.91	< 0.001	0.849	< 0.001	8.48	0.923	0.723
B. females
Subjects (n)	30	110
Age (years)	76.3 ± 4.9	74.2 ± 5.0	0.049
Height (cm)	154.1 ± 6.6	151.9 ± 5.6	0.099
Weight (kg)	45.4 ± 5.7	52.0 ± 7.6	< 0.001
BMI (kg/m^2)	19.1 ± 2.0	22.5 ± 2.7	< 0.001
SMI (kg/m^2)	5.37 ± 0.27	6.36 ± 0.48	< 0.001
RF MT (cm)	1.42 ± 0.29	1.57 ± 0.29	0.015	0.654	0.010	1.43	0.600	0.670
VI MT (cm)	0.83 ± 0.21	1.04 ± 0.30	< 0.001	0.710	< 0.001	0.91	0.667	0.642
QF MT (cm)	2.25 ± 0.38	2.61 ± 0.42	< 0.001	0.745	< 0.001	2.34	0.667	0.752
GM MT (cm)	1.37 ± 0.21	1.58 ± 0.22	< 0.001	0.748	< 0.001	1.42	0.700	0.764
Sol MT (cm)	3.73 ± 0.45	3.95 ± 0.47	0.022	0.645	0.015	3.75	0.600	0.664
TS MT (cm)	5.10 ± 0.53	5.53 ± 0.55	< 0.001	0.727	< 0.001	5.37	0.700	0.636
MT sum (cm)	7.35 0±.69	8.13 ± 0.77	< 0.001	0.776	< 0.001	7.62	0.667	0.761

Abbreviations: SMI, skeletal muscle mass index; ROC, receiver operating characteristic; BMI, body mass index; RF, rectus femoris; MT, muscle thickness; VI, vastus intermedius; QF, quadriceps femoris; GM, medial head of gastrocnemius; Sol, soleus; TS, triceps surae; MT sum, sum of MT of QF and TS.

Figure 1 Receiver operating characteristic curve analysis of MT for predicting low SMI. (A) males. AUC: 0.836, cut-off value: 5.67 cm. (B) females. AUC: 0.748, cut-off value: 1.42 cm.

Abbreviations: MT, muscle thickness; SMI, skeletal muscle mass index; AUC, area under the curve; TS, triceps surae; GM, medial head of gastrocnemius.

Table 3 Cut-off Values of MT Based on 2 SD Below the Young Adult Means for Corresponding Muscles

	Males		Females
	Cut-Off (cm)	Prevalence of Low Muscle Mass (%)	Cut-Off (cm)	Prevalence of Low Muscle Mass (%)
RF MT	1.85	69.4	1.42	36.7
VI MT	1.13	35.5	0.81	25.9
QF MT	3.17	72.6	2.34	33.8
GM MT	1.41	25.8	1.44	35.7
Sol MT	3.55	4.8	3.34	12.1
TS MT	5.32	19.4	4.96	22.9
MT sum	8.86	60.0	7.49	28.1
SMI		20.3		21.4

Abbreviations: MT, muscle thickness; SD, standard deviation RF, rectus femoris; VI, vastus intermedius; QF, quadriceps femoris; GM, medial head of gastrocnemius; Sol, soleus; TS, triceps surae; MT sum, sum of MT of QF and TS; SMI, skeletal muscle mass index.