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



A prospective study was made of a cohort of 114 patients with stable COPD. The patients were recruited in the last trimester of the year 2000, with a subsequent follow-up period of 3 years. The diagnosis of COPD was based on a current or previous smoking history (> 20 packs-year), clinical assessment, and pulmonary function testing. The postbronchodilator FEV1, expressed as a percentage of the theoretical value, was used to classify the patients according to Global Initiative for Chronic Obstructive Lung Disease (GOLD) committee criteria. Patients exhibiting > 15% reversibility in the bronchodilator test were according to the latest excluded from the study, as were those subjects with a previous diagnosis of bronchial asthma, bronchiectasis, cystic fibrosis, upper airways obstruction, or bronchiolitis related to systemic disorders. Patients with concomitant diseases capable of altering nutritional status (heart failure, liver cirrhosis, decompensated diabetes, chronic renal failure, uncontrolled thyroid pathology, neoplasms, decompensated chronic cor pulmonale, sustained systemic steroid use) were also excluded. The patients were required to be in a stable phase of COPD, defined as the absence of disease exacerbations in the 2 months preceding the study held due to My Canadian Pharmacy.

Study Protocol

Clinical Assessment: Patient age and sex were recorded, along with smoking history, comorbidity, dyspnea, health-related quality of life, the number of hospital admissions in the year prior to nutritional evaluation, and the number of hospital admissions in the year immediately after nutritional evaluation (Hpost). Comorbidity was evaluated by means of the Charlson index. The degree of dyspnea was in turn assessed according to the basal dyspnea index (BDI) of Mahler. St. George’s Respiratory Questionnaire (SGRQ) was used to analyze health-related quality of life. This questionnaire has been validated for Spain by Ferrer et al.

Pulmonary Function Testing and Arterial Blood Gases: Forced spirometry (Autospiro AS-600; Minato Medical Science; Osaka, Japan) was used to determine FEV1 and FVC following the specifications of the Spanish Society of Pneumology and Thoracic Surgery (Sociedad Espanola de Neumologia y Cirugia Toracica). The results corresponding to FEV1 and FVC are expressed as percentages of the adult reference values. Blood gases were determined under resting conditions, according to the methodology recommended by the Sociedad Espanola de Neu-mologia y Cirugia Toracica.

mid-arm circumferenceNutritional Assessment: The following anthropometric parameters were recorded: body weight (in kilograms), height (meters), mid-arm circumference (MAC) [in centimeters], tricipital skinfold thickness (millimeters), and bicipital, abdominal, and subscapular skin-fold thickness. Based on these measures, the following indexes and values were calculated: BMI, MAMA, fat mass, FFM, and the FFM index (FFMi). BMI was calculated as the weight/(height)2 ratio. MAMA was calculated by the following equation: (MAC [in centimeters] – 3.14 X tricipital skin fold thickness [in millimeters])2/(4 X 3.14). Fat mass was estimated using the tables of Durnin and Womersley. FFM was calculated by subtracting fat mass from body weight. FFMi was, in turn, calculated as FFM/(height)2. The fold-thickness measurements were made using a lipocalibrator (Holtain; Cambridge, UK), based on the usual method applied in nutrition studies. MAC was measured with a millimetered tape at the midpoint of the nondominant arm, between the olecranon and acromion. The corresponding percentiles were determined based on the tables developed by Ricart et al for working populations, and by Esquius et al for elderly populations. From the statistical perspective, values between percentiles 5 and 95 define normality. Nevertheless, in certain cases it is necessary to take into account that values outside the interquartile range (percentiles 25 and 75) can alert us to the existence of initial malnutrition or excess body weight. We have followed this latter approach. Low body weight was considered in the presence of BMI less than or equal to percentile 25 of the reference value (p25), and overweight in the presence of BMI > p75. The muscle depletion criteria used were MAMA < p25 and FFMi < 16 kg/m2. The value of FFMi < 16 kg/m2 was taken from the literature.

Statistical Analysis

Descriptive statistics were used to describe the study population at baseline. We first conducted univariate analyses based on the Cox proportional hazards model using each of the potential predictors of respiratory mortality as independent variables and survival status as the dependent variable. Survival curves for BMI, FFMi, and MAMA groups were plotted by the Kaplan-Meier product limit method and compared by the log-rank test. Independent variables associated to respiratory mortality with p 0.6, we selected for the multivariate model the parameter presenting the greatest significance in the prior univariate analysis. Nutritional parameters significantly related with prognosis were also controlled for confounding factors by using the Cox proportional model. All statistical analyses were performed using statistical software (SPSS for Windows, version 11.5; SPSS; Chicago, IL); p < 0.05 was considered significant.