The determinants of dyspnoea evaluated by the mMRC scale: The French Palomb cohort

Dyspnoea is a major symptom in COPD patients, but the determinants that could be associated with a higher dyspnoea mMRC score in COPD patients remain unclear. Our research aimed to study the determinants of dyspnoea at the threshold of 1, 2, 3 and 4 mMRC.

Diagnosis of COPD was made using spirometry with post-bronchodilator FEV₁FVC<70%. An online questionnaire has been employed by pulmonologists to recruit COPD patients. The following variables were collected: age, gender, BMI, FEV₁, RV, IC, TLC, FRC, mMRC, frequency of exacerbations and comorbidities. The LASSO was used to select the variables associated with the mMRC dyspnoea scale in a subgroup (who had no missing IC, RV and FRC values) of 421 COPD patients defined by the previously mentioned variables.

One thousand nine hundred and sevety-three patients (65.3% males, average age=66±10, 38% current smokers) were included. Dyspnoea was correlated with a low FEV₁ and with the number of exacerbations in the past 12 months. Multivariate analysis showed that the determinants of dyspnoea(mMRC≥2) are: FEV₁: OR=3.71[2.86-4.82]; anxiety: OR=2.52[1.82-3.47]; cough: OR=1.94[1.57-2.40]; bronchiectasis: OR=1.84[1.03-3.29]; age: OR=1.80[1.45-2.24]; hyperinflation (RV/TLC): OR=1.68[1.34-2.11]; ischemic cardiopathy: OR=1.63[1.22-2.18]; hypertension: OR=1.52[1.21-1.91]; exacerbations (≥2): OR=1.41[1.10-1.81]; women: OR=1.39[1.10-1.74] and overweight: OR=1.33[1.06-1.67]. The subgroup analysis showed that: FEV₁: OR=3.47[1.96-6.12]; exacerbations (≥2) OR=2.31[1.33-4.17] and hyperinflation (IC/TLC) OR=0.57[0.35-0.85] were associated with higher dyspnoea (mMRC≥2).

Our results showed that dyspnoea is related to the severity of airflow limitation, gender, exacerbations, comorbidities and hyperinflation.