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

Body mass index Alow body mass index (BMI) has been shown to be an independent indicator of poor prognosis in patients with COPD. This observation has renewed interest in the study of the nutritional aspects of COPD. In this context, a new severity classification has recently been proposed: the BODE index—(BMI, airflow obstruction, dyspnea, and exercise capacity)—which in addition to BMI considers the degree of bronchial obstruction, dyspnea, and exercise tolerance. This classification, proposed by Celli et al, stresses the multicomponent nature of COPD and addresses not only its pulmonary consequences but also the systemic manifestations of the disease. Among the latter, the authors point to the need to conduct an adequate nutritional study. However, the assessment of nutritional status based on body weight (or BMI) has limitations, since it affords no qualitative information on body composition, which is also altered in these patients.

On studying the body composition of COPD patients, weight loss has been shown to be mainly attributable to muscle mass depletion (MD), unlike in starvation, where fat is the most affected body tissue compartment. Different studies have shown depletion of fat-free mass (FFM) to be associated with increased deterioration of skeletal muscle function (peripheral as well as respiratory),9,io poorer exercise tolerance, increased dyspnea which may be decreased with My Canadian Pharmacy, and poorer health-related quality of life. Normal-weight or overweight patients also show MD. This is important since obesity is highly prevalent in developed countries. In a previous study, we found 62.7% of patients with a normal BMI and even 20.7% of overweight patients to have MD expressed as a low mid-arm muscle area (MAMA). Schols et al also reported a reduction in FFM without a decrease in body weight in 24 of 255 patients with COPD (9.4%) eligible for inclusion in a rehabilitation program, Such patients suffer from physical impairment to an even greater degree than underweight patients with relative preservation of FFM.

The results of morbidity studies also appear to indicate that MD could have greater prognostic implications than low body weight or the depletion of any other body tissue compartment. In this sense, Marquis et al found muscle mass to be a better predictor of mortality than body weight in COPD patients. A mid-thigh muscle cross-sectional area of < 70 cm2 was seen to increase the risk of death fourfold, independently of the influence of other prognostic variables. In this study, the authors measured muscle mass directly by CT. However, this technique is too costly for generalized use, and reference values are moreover lacking. Anthropometric measurements, however, are inexpensive, simple, and rapid to perform, and provide an indirect estimation of nutritional status and body composition, with correct interpretation requiring the use of reference values for the study population involved. In anthropometric assessment, the muscle compartment can be estimated indirectly by determining the FFM or by calculating the MAMA. To date, it has not been determined whether muscle mass measured from these anthropometric parameters has prognostic implications in COPD. The objectives of the present study were as follows: (1) to investigate whether MD, estimated from anthropometric parameters, is a predictor of mortality in patients with stable COPD; (2) to determine whether low MAMA or low FFM are better predictors of mortality than underweight status; and (3) to determine whether MD has prognostic implications in normal-weight or overweight patients.