Outcomes of Mid-Arm Muscle Area Is a Better Predictor of Mortality Than Body Mass Index in COPD

Normal-Weight

Subject Characteristics

A total of 114 patients with a diagnosis of COPD were studied. Of these, 18 patients (15.8%) were excluded for different reasons: 7 patients (6.1%) with decompensated cor pulmonale, 3 patients (2.6%) with liver cirrhosis, 2 patients (1.7%) with neoplasms, 2 patients (1.7%) due to sustained oral corticosteroid use, 2 patients (1.7%) because of heart failure, 1 patient (0.9%) with chronic renal failure, and another patient (0.9%) due to malabsorption syndrome. A total of 96 patients were therefore finally included (all male; mean age, 69 ± 9 years [± SD]). Table 1 shows the baseline characteristics of these patients.

Univariate Survival Analysis

Table 2 shows the prognostic influence of the variables included in the univariate analysis. Figure 1, in turn, shows the survival curves of the patients by BMI, MAMA, and FFMi groups. Eighteen patients (18.8%) presented BMI < p25. The cumulative survival probabilities after 12, 24, and 36 months in this group were 83.3%, 70.7%, and 61.2%, respectively. The survival curve was significantly lower than in the case of overweight patients (p = 0.021). No significant differences were observed with respect to the group with normal body weight (Fig 1, top, A). Forty-four patients (45.8%) presented MAMA < p25. Survival rates for these patients after 12, 24, and 36 months were 87.9%, 68.6%, and 60.8%, respectively. These figures were very similar to those recorded in the group with BMI p75 died in the course of the 3 years of follow-up. However, no statistically significant differences were reached vs the group with MAMA < p25 (p = 0.098). Seventeen patients (17.7%) presented FFMi < 16 kg/m2. No survival differences were recorded in relation to FFMi (Fig 1, bottom, C). Nevertheless, the patients with low FFMi values tended to exhibit poorer survival.

Normal-Weight or Overweight Patients and MD

Nineteen patient with normal body weight (59.4%) and 9 overweight subjects (19.6%) presented MAMA s p25. Both subgroups showed a poorer prognosis, with a 3.39-fold (95% confidence interval [CI], 1.11 to 10.38) greater mortality risk (p = 0.032) [Fig 2]. Only two patients (3.9%) with MAMA > p25 showed low body weight values. Be slim together with My Canadian Pharmacy.

Colinearity, Interaction, and Confusion Between Variables

Significant colinearity was observed among the three nutritional parameters (BMI, MAMA, and FFMi). BMI presented important correlation to both MAMA (r = 0.69, p < 0.0001) and FFMi (r = 0.89, p < 0.0001). MAMA and FFMi likewise showed good correlation (r = 0.73, p < 0.0001). On jointly evaluating these parameters with the Cox multivariate model in terms of both absolute and dichotomic values, the only predictor showing statistically significant differences was found to be MAMA (Table 3). Colinearity was also observed between BDI and global SGRQ (r = — 0.71, p < 0.0001) and between FEV1 percentage of predicted and FVC percentage of predicted (r = 0.71, p 50% of predicted, the presence of MD exerted no prognostic influence (p = 0.616). However, among the cases with FEV1 < 50% of predicted (GOLD stages III and IV), those presenting MAMA < p25 showed a trend toward poorer survival (p = 0.058) [Fig 3].

Multivariate Survival Analysis

Age, BDI, global SGRQ, comorbidity index, number of hospital admissions in the year prior to nutritional evaluation, Hpost, FEV1 percentage of predicted, Pa02/fraction of inspired oxygen, PaC02, and MAMA were the variables included in the Cox multiple regression test. In this predictive model, MAMA values were analyzed as dichotomic variables ( p25). In the final regression equation, the variables found to be independent indicators of poor prognosis were high Paco2, Hpost, and MAMA < p25 (Table 5).

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Fig1

Figure 1. Kaplan-Meier survival curves in a patient with COPD by BMI (top, A), MAMA (center, B), and FFMi (bottom, C). NS = not significant.

Fig2

Figure 2. Kaplan-Meier survival curves by MAMA in COPD patients with BMI > p25.

Fig3

Figure 3. Kaplan-Meier survival curves by MAMA in COPD patients with FEV1 < 50% of predicted.

Table 1—Baseline Characteristics of the Patients (n = 96)

Parameters Data
Age, yr 69 ± 9
BMI, kg/m2 28.5 ± 5.4
FFM, kg 52.5 ± 12.2
MAMA, cm2 49.5 ± 12.3
Charlson index
0 54 (56.3)
1 31 (32.3)
>2 11 (11.5)
FEVb L 1.10 ± 0.54
FEVb % predicted! 44.2 ± 18.5
Stage I 6 (6.2)
Stage II 23 (24.0)
Stage III 48 (50.0)
Stage IV 19 (19.8)
FVC, L 2.07 ± 0.63
FVC, % predicted 64.5 ± 17.5
Pao2, mm Hg 65.8 ± 12.2
Paco2, mm Hg 43.8 ± 6.9
Mortality 24 (25.0)
Respiratory disease 19 (19.8)
Cardiovascular disease 2(2.1)
Cerebrovascular disease 1 (1.0)
Cancer 1 (1.0)
Not known 1 (1.0)

Table 2—Predictors of Mortality: Univariate Analys

Predictors Hazard

Ratio95% CIp ValueAge, yr1.050.99-1.110.062Current smoking1.120.38-3.300.834Smoking history (pack-years)1.000.98-1.010.620BDI (total)0.830.681.020.079Functional impairment0.700.45-1.080.109Magnitude task0.530.28-1.030.060Magnitude exertion0.650.35-1.200.173Global SGRQ1.031.00-1.050.028Symptoms1.020.99-1.040.117Activity1.021.00-1.040.049Impact1.021.00-1.040.034Comorbidity index1.451.05-2.000.025Hospital admissions   Before nutrition assesment1.441.111.860.006After nutrition asessment6.802.58-17.950.000BMI, kg/m20.930.85-1.020.131BMI<p252.030.77-5.350.147FFMi, kg/m20.950.85-1.060.352FFMi s 16 kg/m21.760.63-4.900.280MAMA, cm20.950.91-0.990.016MAMA s p253.771.36-10.470.011FEV1 after-bronchodilation, %0.940.90-0.990.009GOLD stages  0.111I-II1.00  III5.730.73-44.860.096IV9.371.12-78.120.039FEVj and MAMA  0.091FEVj > 50% and MAMA > p25   FEVj > 50% and MAMA s p250.00 0.987FEV1 s 50% and MAMA > p252.790.31-25.030.359FEV1 s 50% and MAMA s p258.031.04-61.890.045FVC, %0.990.96-1.020.566Pao2, mm Hg0.970.92-1.010.167Pao2/fraction of inspired oxygen0.990.98-0.990.032Paco2, mm Hg1.061.011.120.029

Table 3—Predictors of Mortality, Including Only Nutritional Parameters: Multivariate Analysis

Variables Hazard Ratio 95% CI p Value
Absolute values
BMI 0.93 0.78-1.12 0.469
MAMA 0.91 0.84-0.98 0.022
FFMi 1.24 0.96-1.60 0.093
Dichotomic variables
BMI<p25 1.19 0.34-4.13 0.780
MAMA s p25 3.68 1.22-11.09 0.021
FFMi s 16 kg/m2 0.88 0.24-3.19 0.845

Table 4—Prognostic Effect of Muscle Depletion (MAMA < p25) After Controlling for Confounding Factors

Variables Hazard Ratio 95% CI p Value
Adjusted by admissions
MAMA s p25 2.83 1.01-7.97 0.048
Hpost 5.73 2.15-15.29 0.000
Adjusted by FEV1
MAMA s p25 2.45 0.84-7.10 0.099
FEV1, % predicted 0.95 0.91-0.99 0.026

Table 5—Predictors of Mortality: Stepwise Multivariate Analysis

Variables Hazard Ratio 95% CI p Value
Hospital admissions after nutrition assessment 4.63 1.69-12.66 0.005
Paco2, mm Hg 1.08 1.02-1.15 0.003
MAMA < p25 3.78 1.18-12.11 0.025