Mid-arm and calf circumferences are stronger mortality predictors than body mass index for patients with chronic obstructive pulmonary disease

Figures & data

Table 1 Characteristics of patients with COPD (n=104)

Variables	n (%)	Mean (SD)
Age, years		74.2±6.9
Sex
Male	98 (94.2)
Female	6 (5.8)
Smoking status
Nonsmokers	12 (11.5)
Ex-smokers	74 (71.2)
Smokers	18 (17.3)
GOLD stage*
I	13 (12.5)
II	51 (49.0)
III	33 (31.7)
IV	7 (6.7)
FVC, % predicted		76.4±18.9
FEV1, % predicted		58.4±20.3
Comorbidity
No	46 (44.2)
Yes	58 (55.8)
Medication treatment
Bronchodilator use	87 (83.7)
Steroid use	85 (81.7)
Anthropometrics
BMI (kg/m^2)		23.4±3.7
Mid-arm circumference (cm)		26.3±3.2
Calf-circumference (cm)		32.9±3.2
Fat-free mass index (kg/m^2)		17.6±2.2

Notes:

* GOLD stage I, FEV₁ ≥80% predicted; II, <80% FEV₁ ≤50% predicted; III, <50% FEV₁ ≤30% predicted; IV, FEV₁ <30%.

Abbreviations: BMI, body mass index; COPD, chronic obstructive pulmonary disease; FEV₁, forced expiratory volume in 1 second; FVC, forced vital capacity; GOLD, Global Initiative for Chronic Obstructive Lung Disease; SD, standard deviation.

Table 2 Characteristics of patients with COPD stratified by survival (n=104)

Variables	Survived (n=82)	Died* (n=22)	P-value
Age, years	73.8±7.1	75.4±5.9	0.360
Smoking status			0.435
Nonsmokers (n, %)	10 (12.2)	2 (9.1)
Ex-smokers (n, %)	58 (70.7)	16 (72.7)
Smokers (n, %)	14 (17.1)	4 (18.2)
FEV1 (% predicted)	61.4±19.5	47.4±19.6	0.004
COPD severity (n, %)			0.002
GOLD stage I/II	57 (69.5)	7 (31.8)
GOLD stage III/IV	25 (30.5)	15 (68.2)
Comorbidity			0.542
No	46 (44.2)	12 (11.5)
Yes	36 (34.6)	10 (9.6)
Bronchodilator use			0.246
No	15 (18.3)	2 (9.1)
Yes	67 (81.7)	20 (90.9)
Steroid use			0.174
No	17 (20.7)	2 (9.1)
Yes	65 (79.3)	20 (90.9)
Anthropometrics
BMI (kg/m^2)	23.9± 3.5	21.6±3.8	0.008
MAC (cm)	26.8±2.9	24.2±3.7	0.001
CC (cm)	33.4±2.9	30.9±3.8	0.001
FFMI (kg/m^2)	17.8±1.9	16.9±3.2	0.077

Note:

* Died: GOLD stage I (n=3), II (n=4), III (n=12), IV (n=3).

Abbreviations: BMI, body mass index; CC, calf-circumference; COPD, chronic obstructive pulmonary disease; FEV₁, forced expiratory volume 1; FFMI, fat-free mass index; GOLD, Global Initiative for Chronic Obstructive Lung Disease; MAC, mid-arm circumference.

Figure 1 Three-year follow-up survival curves stratified by BMI, MAC, and CC.

Notes: (A) The Kaplan–Meier survival curve based on BMI obtained using the log-rank test (Mantel–Cox) P<0.001. (B) The Kaplan–Meier survival curve based on MAC obtained using the log-rank test (Mantel–Cox) P=0.001. (C) The Kaplan–Meier survival curve based on CC obtained using the log-rank test (Mantel–Cox) P=0.001.
Abbreviations: BMI, body mass index; CC, calf circumference; MAC, mid-arm circumference.

Table 3 Predictors of mortality in patients with COPD based on multivariate Cox regression and the BIC

Variables	Model I		Model II		Model III
	HR (95% CI)	P-value	HR (95% CI)	P-value	HR (95% CI)	P-value
Age (years)
<64	1	0.470	1	0.481		0.279
65–74	3.68 (0.45, 30.01)	0.223	3.56 (0.44, 28.76)	0.233	4.75 (0.56, 40.55)	0.154
≥75	3.64 (0.42, 31.55)	0.242	3.59 (0.42, 30.83)	0.243	6.16 (0.66, 57.38)	0.111
Smoking status
Nonsmokers	1	0.657	1	0.772	1	0.700
Ex-smokers	1.12 (0.13, 9.48)	0.915	1.48 (0.18, 11.94)	0.712	0.93 (0.11, 7.97)	0.944
Smokers	1.79 (0.20, 15.94)	0.600	1.98 (0.23, 17.25)	0.536	1.46 (0.16, 13.19)	0.737
FEV1 (%)	0.97 (0.94, 1.00)	0.033	0.97 (0.94, 0.99)	0.012	0.96 (0.93, 0.99)	0.004
BMI (<21 kg/m^2)	2.78 (1.10, 7.10)	0.031	NA		NA
MAC (<23.5 cm)	NA		3.09 (1.30, 7.38)	0.011	NA
CC (<30 cm)	NA		NA		4.40 (1.82, 10.63)	0.001

Notes: Model I: −2 likelihood log =182.21; adjusted for age, smoking status, FEV₁% (pred), BMI; BIC =−268.30. Model II: −2 likelihood log =180.63; adjusted for age, smoking status, FEV₁% (pred), MAC; BIC =−269.88. Model III: −2 likelihood log =177.30; adjusted for age, smoking status, FEV₁% (pred), CC; BIC =−273.21. Model I BIC difference Model II =1.58; Model I BIC difference Model III =4.91; Model II BIC difference Model III =3.33.

Abbreviations: BIC, Bayesian information criterion; BMI, body mass index; CC, calf-circumference; CI, confidence interval; COPD, chronic obstructive pulmonary disease; FEV₁, forced expiratory volume 1; HR, hazard ratio; MAC, mid-arm circumference; NA, not applicable.