Determinants of BMI in patients with COPD

Objective: COPD is characterized by significant chronic inflammation that is evident not only in the pulmonary compartment but also in the circulation. Peripheral blood features of COPD include markers of oxidative stress and altered circulating levels of inflammatory mediators and acute-phase proteins. The presence of a systemic inflammatory response may influence quality of life by giving rise to weight loss, muscle wasting and tissue depletion. The aim of the present study was to evaluate the determinants of body mass and the value of serum tumour necrosis factor alpha (TNF-alpha) as a marker of weight loss in COPD patients, and to correlate this with the burden of oxidative stress as measured by serum malonyldialdehyde (MDA) levels. Methodology: Fifty-two male COPD patients (mean age 62.55 +/- 6.81 years) were studied. After anthropometric measurements and standard spirometry, serum TNF-alpha concentration was measured by enzyme-linked immunosorbent assay using an hTNF-alpha kit, and MDA was studied spectrophotometrically using the Yoshioka-Kawada method. Results: The mean BMI was 24.82 +/- 3.46. BMI was lower than normal (< 19) in six patients. Mean serum TNF-alpha concentration was 14.99 +/- 8.98 pg/mL and MDA was 0.93 +/- 0.13 nmol/L. There was no significant correlation between serum MDA and TNF concentrations (P = 0.140). Serum TNF-alpha and MDA concentrations were not correlated with severity of airflow obstruction or degree of hypoxaemia (P > 0.05 for all). BMI was negatively correlated with burden of smoking (pack-years) (r = -0.392, P = 0.004); but not with pulmonary function, degree of hypoxaemia, serum TNF-alpha or MDA levels. BMI was significantly lower in current smokers than ex-smokers (P = 0.041); however, serum MDA and TNF levels were similar in both groups. Conclusion: The results of this study indicate that body mass is related to smoking status (both pack-years and continuance of smoking) in COPD; however, serum TNF-alpha concentration does not seem to be a good marker of weight loss in these patients.