Obesity Impact on Dyspnea in COPD Patients

The role of obesity on dyspnea in chronic obstructive pulmonary disease (COPD) patients remains unclear. We aimed to provide an assessment of dyspnea in COPD patients according to their Body Mass Index (BMI) and to investigate the impact of obesity on dyspnea according to COPD severity.

One hundred and twenty seven COPD patients with BMI ≥ 18.5 kg/m² (63% male, median (interquartile range) post bronchodilator forced expiratory volume of 1 second (post BD FEV₁) at 51 (34-66) % pred) were consecutively included. Dyspnea was assessed by mMRC (Modified medical research council) scale. Lung function tests were recorded, and emphysema was quantified on CT-scan (computed tomography-scan).

Twenty-five percent of the patients were obese (BMI ≥ 30kg/m²), 66% of patients experienced disabling dyspnea (mMRC ≥ 2). mMRC scores did not differ depending on BMI categories (2 (1-3) for normal weight, 2 (1-3) 1 for overweight and 2 (1-3) for obese patients; p = 0.71). Increased mMRC scores (0-1 versus 2-3 versus 4) were associated with decreased post BD-FEV₁ (p < 0.01), higher static lung hyperinflation (inspiratory capacity/total lung capacity (IC/TLC), p < 0.01), reduced DLCO (p < 0.01) and higher emphysema scores (p < 0.01). Obese patients had reduced static lung hyperinflation (IC/TLC p < 0.01) and lower emphysema scores (p < 0.01) than non-obese patients. mMRC score increased with GOLD grades (1-2 versus 3-4) in non-obese patients but not in obese patients, in association with a trend towards reduced static lung hyperinflation and lower emphysema scores.

By contrast with non-obese patients, dyspnea did not increase with spirometric GOLD grades in obese patients. This might be explained by a reduced lung hyperinflation related to the mechanical effects of obesity and a less severe emphysema in severe COPD patients with obesity.