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Reduced Muscle Mass Can Predict Risk of Malnutrition, Prolonged Hospital Stay in COPD


Can muscle mass predict whether patients with chronic obstructive pulmonary disease have a longer hospital stay?

A new prospective study is indicating that fat-free mass index (FFMI) and calf circumference (CC) are 2 simple, non-expensive, and non-invasive measures that can reliably predict malnutrition and prolonged length of hospital stay in patients with chronic obstructive pulmonary disease (COPD) experiencing exacerbation.

According to the researchers of the study, there should be consideration for including these 2 measures in nutritional assessment protocols in the pneumology units of hospitals.

The study included 176 patients hospitalized between March 2019 and February 2020 with COPD exacerbation, which often worsens changes in nutritional status among these patients because of increasing inflammation. As a result, emphasis is placed on assessing the muscle mass of patients with COPD upon being admitted to the hospital.

“The impact of nutritional status on the general condition of patients with COPD is mainly observed by weight loss and muscle mass depletion,” wrote the researchers of the study, who added, “In malnourished COPD patients, a decline in pulmonary function, acceleration in disease progression, and decline in resistance to infections can be expected, requiring recurrent hospitalizations for exacerbation.”

According to the FFMI measurement, approximately one-third of patients had low muscle mass, and nearly 3 in 4 (70%) patients had low CC. Researchers performed a multivariate analysis, finding that patients with reduced FFMI were 8.8 times more likely to be malnourished than those with normal FFMI, and low CC resulted in patients being 4.6 times more likely to be malnourished than those who were well-nourished.

A third measure, adductor muscle pollicis thickness (AMPT), was not significantly associated with malnutrition.

Based on the subjective global assessment—the method used for nutritional diagnosis—more than half (58.2%) of patients presented with malnutrition. Bivariate analysis showed that patients who were classified as malnourished had were more likely to have both low FFMI and CC compared with well-nourished patients.

Looking at the impact of these 2 factors on clinical outcomes, the researchers observed that having reduced FFMI or CC was associated with a higher risk of prolonged length of hospital stay. However, lower CC was not independently associated with in-hospital death, which occurred in 9.1% of patients.

The researchers did note that the measures have some limitations in clinical practice, writing: “In patients with fluid accumulation, e.g., edema and/or ascites, the muscle mass is overestimated by [bioimpedance analysis], and the FFMI cannot accurately quantify it. The measure of CC is also not reliable in patients with limb edema, and AMPT should not be performed in patients with hand edema.”

They also explained that while reduced muscle mass can identify patients who are at higher risk for presenting with malnutrition, this measure alone likely cannot accurately diagnose malnutrition, as the condition is a combination of various factors, such as weight loss, reduced food intake, gastrointestinal symptoms, and metabolic demand of disease.


Teixeira P, Kowalski V, Valduga K, Araújo B, Silva F. Low muscle mass is a predictor of malnutrition and prolonged hospital stay in patients with acute exacerbation of COPD: a longitudinal study. J Parenter Enter Nutr. Published online August 14, 2020. doi: 10.1002/jpen.1998.

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