Inflammatory response and body composition in chronic obstructive pulmonary disease

Weight loss in chronic obstructive airways disease (COPD) is associated with an increased energy cost of breathing. To determine an association between body composition and the inflammatory response we studied 80 clinically stable patients. Body composition was determined anthropometrically and skeletal muscle mass was determined as the creatinine-height index (CHI). Forty patients had their nitrogen balance determined. Circulating concentrations of interleukin 6 (IL-6), tumor necrosis factor alpha (TNF-alpha), and their soluble receptors were determined for 68 patients. Body mass index (BMI) was normal (> 20 kg/m(2)) in 55 patients, of whom 17 (31%) had a low CHI (< 80% predicted). A reduced CHI was associated with increased circulating levels of IL-6 (p = 0.001), TNF-alpha (p = 0.032) and their soluble receptors IL-6sr (p = 0.002), TNF-alpha sr1 (p = 0.03), and TNF-alpha sr2 (p = 0.001). Patients with a normal BMI and low CHI had inflammatory mediator levels similar to patients with a low BMI and CHI; both were significantly greater than in those with a normal BMI and CHI. Nitrogen balance was similar between normal and low CHI groups, although nitrogen excretion was significantly increased in the low CHI group. Skeletal muscle loss in COPD is probably multifactorial in origin, but our data suggest a link with systemic inflammation, even when weight loss is inapparent.